china 1000kv

INV ITEDP A P E R

Ultra High VoltageTransmission in China:Developments, Current Statusand Future ProspectsUHV systems are being developed to meet the need for transmission of greater amounts

of power over longer distance and at lower costs.

By Daochun Huang, Student Member IEEE, Yinbiao Shu, Jiangjun Ruan, and Yi Hu

ABSTRACT | The developments and current status of ultra high

voltage (UHV) alternating current (AC) and direct current (DC)

transmission in China were reviewed in this paper. The UHV

transmission historical developments in the past twenty years;

the demand of development UHV transmission; the research

results of the UHV key technologies including electromagnetic

environment, over-voltage and insulation coordination, light-

ning performance, live-line working and equipment manufac-

ture recent years in China; the design parameters and

construction of UHV AC, UHV DC test and demonstration trans-

mission lines, UHV AC, DC test bases and state grid simulation

center were introduced. The suggestions at the aspects of UHV

transmission future design, construction, commercial opera-

tion and maintenance were simply presented and discussed.

The review and discussion are important for the safe and

reliable operation of UHV grid in China and can be a reference

for other countries that want to develop UHV AC and DC

transmission.

KEYWORDS | Alternating current (AC); direct current (DC);

electromagnetic environment; equipment manufacture;

lightning performance; live-line working; operation and

maintenance; over-voltage and insulation coordination;

simulation center; test and demonstration transmission

line; UHV AC test base; UHV DC test base; ultra high

voltage (UHV)

NOMENCLATURE AND ABBREVIATION

ABB Asea Brown Boveri Ltd.

AC Alternating Current.

ACSR Aluminium Conductor Steel Reinforced.

AEP American Electric Power Company.AIS Automatic Identification System.

AN Audible Noise.

ASEA Allmanna Svenska Elektriska Aktiebolaget.

BPA Bonneville Power Administration.

CEPRI China Electric Power Research Institute.

CEPEL Centro de Pesquisas de Energia Eletrica.

CESI Centro Elettrotecnico Sperimentale Italiano.

CRIEPI Central Research Institute of Electric PowerIndustry.

CSG China Southern Power Grid.

CT Current Transformer.

CVT Capacitor Voltage Transformer.

DC Direct Current.

DS Disconnecting Switch.

EGM Electric-Geometry Model.

EHV Extra High Voltage.EMTP-RV Electromagnetic Transient Program-

Restructured Version.

ENEL Ente Nazionale Energia Elettrica.

Manuscript received December 12, 2007; revised October 6, 2008.

Current version published April 1, 2009.

D. Huang and J. Ruan are with the School of Electrical Engineering, Wuhan University,

Wuhan, Hubei 430072, China (e-mail: [email protected]; [email protected]).

Y. Shu is with the State Grid Corporation of China (SGCC), Beijing 100031, China

(e-mail: [email protected]).

Y. Hu is with the State Grid Electric Power Research Institute of SGCC, Wuhan,

Hubei 430074, China (e-mail: [email protected]).

Digital Object Identifier: 10.1109/JPROC.2009.2013613

Vol. 97, No. 3, March 2009 | Proceedings of the IEEE 5550018-9219/$25.00 �2009 IEEE

EPCRI Beijing Electric Power Construction ResearchInstitute.

EPRI Electric Power Research Institute.

ES Earthing Switch.

ESDD Equivalent Salt Deposit Density.

GE General Electric Company.

GIS Gas Insulated Switchgear.

HGIS Hybrid Gas Insulated Switchgear.

IREQ Hydro-Quebec Institute of Research.MOA Metal Oxide Arrester.

NSDD Non-soluble Deposit Density.

OFAF Oil Forced Air Forced.

PSCAD/

EMTDC

Power Systems Computer Aided Design/

Electro-Magnetic Transient in DC system.

RI Radio Interference.

SIR Silicone Rubber.

RTDS Real-Time Digital Simulator.SGCC State Grid Corporation of China.

TEPCO Tokyo Electric Power Company.

TOV Temporary power frequency over-voltage.

TRV Transient Recovery Voltage.

TVI Television Interference.

UHV Ultra High Voltage.

VFTO Very Fast Front Over-voltage.

VT Voltage Transformer.WHVRI Wuhan High Voltage Research Institute.

XECRI Xi’an Electro-Ceramic Research Institute.

YEPRI Yunnan Electric Power Research Institute.

I . INTRODUCTION

Over the past 100 years, the development of electric power

transmission always focused on the theme of improvingtransfer capacity and reducing transmission cost. Raising

voltage level is the most efficient way to improve trans-

mission power. The electric power transmission at 1000 kV

and above AC voltages is known as UHV AC transmission,

and the voltages at above �600 kV DC are known as

UHV DC transmission [1]–[5]. Especially, 1000 kV AC

and �800 kV DC are UHV AC and UHV DC transmission

voltages in China, respectively [6], [7].In order to meet the growing of power load, to carry out

long distance and bulk capacity power transmission, Russia

(the former USSR), Japan, the United States of America

(USA), Italy, Canada, Brazil began study on the UHV

transmission relevant technologies in 1960’s and 1970’s

[1]–[5]. Wuhan High Voltage Research Institute (WHVRI)

of State Grid Corporation of China (SGCC), China Electric

Power Research Institute (CEPRI), Beijing Electric PowerConstruction Research Institute (EPCRI) of SGCC and

some universities in China began study on the UHV AC

transmission technologies in 1986 [8]. China [6]–[8],

India [8], [9] and Southern Africa [8], [10] began study on

the UHV DC transmission technologies in recent years.

Many research works such as line parameters (conductors,

towers, insulators, etc.), effects on environment, lightning

performance, over-voltage and insulation coordination,live-line working, equipment manufacture etc., have been

carried out to discuss UHV AC transmission in the range of

1000–1500 kV and UHV DC transmission at the voltages of

�800 kV and above.

The research results indicate that UHV transmission

lines can transmit large block of electric energy over a long

distance; reduce number of circuit lines and right-of-way,

lower electric energy loss, etc. Especially, the UHV ACtransmission suits to interconnect large power grid; the

UHV DC alternative of voltages above�600 kV (UHV DC)

can be economically attractive for very long distance and

high capacity transmission. The obtained results demon-

strate that there is no insurmountable technical obstacle in

the design and construction of UHV transmission; and the

UHV transmission is presently available and awaiting

commercial applications. CIGRE working group 38-04evaluated the UHV technique and conclusions were drawn

that the application of UHV AC transmission technology

was fully developed and�800 kV UHV DC was technically

feasible [1]–[5], [7]–[10].

The UHV transmission research activities and achieve-

ments of China in the past twenty years, including the

UHV AC, UHV DC test and demonstration lines, test

bases, etc., the future prospects of UHV transmission inChina are introduced in this paper.

II . UHV TRANSMISSION RESEARCHHISTORICAL AND BACKGROUND

The UHV AC and DC transmission and transformation

development history and research background in Russia

(the former USSR), Japan, USA, Italy, Canada, Brazil,China and other countries are introduced in this section.

Rapid load growth in the 1960’s and the prospects of

continued load growth in future several decades were the

driving forces for research and development of UHV AC

power transmission lines at voltages above 1000 kV. Even

as the first transmission lines at 500 and 750 kV were

being built and operated in the 1960’s, there was a

heightened interest in developing the next higher trans-mission voltages in the so called UHV range of 1000 to

1500 kV AC and above�600 kV DC. In order to gather the

vast amount of technical information necessary to design

transmission lines above 1000 kV AC and above �600 kV,

research and test facilities were built in several countries

in the 1970’s and the following about thirty years.

Information on the progress of UHV technology research

works with focus on UHV system planning, performanceand reliability aspects, UHV transmission lines, UHV

substations and equipment, UHV testing facilities and new

technologies that carried out in Russia (The Former

USSR), Japan, the USA, Italy, Canada, Brazil, India, France

were presented in three excellent CIGRE Working Group

(WG) reports WG 31.04 1983 [1]; WG 38.04 1988 [3];

WG 38.04 1994 [4] and two overview papers [2], [5].

Huang et al. : Ultra High Voltage Transmission in China: Developments, Current Status and Future Prospects

556 Proceedings of the IEEE | Vol. 97, No. 3, March 2009

A. Russia (The Former USSR)In 1970’s, in order to satisfy the need of strengthening

the electrical links between integrated power systems, as

well as the need for transfer large quantities of power over

long distances, USSR had an in-depth study on the insu-

lation system, line and equipment of UHV AC transmis-

sion at voltages in the range of 1150 to 1500 kV.

A circuit of three phases 1.17 km long 1150 kV test line

was constructed at the Bely Rast Substation. Test data wereobtained on the corona performance of conductor bundles.

Tests of the air insulation, insulation of equipment, studies

of switching over-voltage, audible noise (AN), radio inter-

ference (RI), electric fields in a substation, and installa-

tion, operation and maintenance of equipment were also

carried out.

2362 km 1150 kV AC transmission lines were con-

structed successively in USSR from the end of 1980’s to thebeginning of 1990’s. Three substations and two segments

were put into service, but the line, after a few years of

operation at the design voltage of 1150 kV, has been oper-

ated at the lower level of 500 kV [4], [5].

In the end of 1970’s, USSR also practiced �750 kV DC

project (6000 MW and 2414 km). The main equipment

passed the type test and 1090 km transmission lines were

constructed. Most earthwork and equipment installationin converter stations at the both ends of the line were

completed.

B. JapanJapan began study on UHV transmission technology in

1973. The need for overcoming stability problems of the

existing 500 kV network and obviating the problems of

excessive short-circuit currents led to the consideration oftransmission above 1000 kV to overlay the existing net-

work. And UHV research was carried out at Central Re-

search Institute of Electric Power Industry (CRIEPI),

Tokyo Electric Power Company (TEPCO), and the NGK

Insulator Company.

Testing facilities of CRIEPI have a UHV fog chamber

for testing of polluted insulators, a facility for insulator

testing under continuous energized with phase-to-groundvoltages up to 900 kV, a corona cage used for AN test,

and a double-circuit 600 m long test line of voltage

1000 kV AC (convertible to a �500 to �650 kV DC).

On the UHV test line, the behavior of 8-, 10-, and

12-conductor bundles and towers under strong wind and

earthquake were investigated. Construction and mainte-

nance techniques, AN, RI and television interference (TVI),

as well as studies of the effects of electric fields were alsoinvestigated.

Takaishiyama test line of TEPCO has two spans with

10 Aluminium Conductor Steel Reinforced (ACSR)

conductor bundles. Research and development work for

mechanical performance of bundled conductor and

insulator assemblies, such as galloping and icing, were

carried out on the test line.

RI and AN tests on insulator assemblies under pollutedconditions were performed with corona testing equipment

and the 1000 kV pollution testing equipment constructed

at NGK high voltage laboratory. A significant amount of

information was obtained on the withstand voltages of

contaminated and snow-covered insulator strings.

TEPCO began construct the 1000 kV transmission

project in 1988, and Sin-Haruna UHV equipment test

field was constructed in 1996, the construction of 427 km,1000 kV double-circuit transmission line on the same

tower was completed in 1999 [5], but the line has been

operated at 500 kV since it was energized, and is planned

to be upgraded to 1000 kV AC around 2015.

C. The USAThe USA began study on UHV transmission technol-

ogies in 1967, the purpose of the new transmission systemswas to transmit large blocks of power, improve system

stability, and reduce environmental impact.

In the USA, UHV studies were conducted at the

General Electric Company (GE), the Electric Power

Research Institute (EPRI), the American Electric Power

Company (AEP), and the Bonneville Power Administration

(BPA). Research works of AC and DC environment tests,

AC line and DC line tests in the same corridor, etc., werecarried out.

Three separate research and test facilities were built to

evaluate the technical feasibility of transmission lines

above 1000 kV: 1) the GE/EPRI Project UHV comprises a

three-phase experimental line, a test cage, and a pollution

chamber. The facilities have the capability of testing the

corona performance of conductor bundles, withstand

strength of air clearances and the pollution performanceof line and station insulators; 2) the AEP/ASEA test

station, jointly operated by AEP and the ASEA (combined

to a part of ABB since 1988) company of Sweden, locates

near South Bend, Indiana, has the capability of testing

single-phase conductor bundles at voltages corresponding

to transmission system voltages up to, and even beyond

1500 kV, but now this UHV AC test facility has been

decommissioned; 3) at BPA, a full-scale three-phase,1200 kV prototype test line, near Lyons, Oregon, was

used to evaluate the long-term corona performance of an

8-conductor bundle. In addition, the facility at Carey High

Voltage Laboratory was used for studies on air insulation,

while conductor vibration and galloping studies were

carried out at the Moro mechanical test line.

In 1967, a research program to study on overhead

transmission lines with voltages of 1000 to 1500 kV wasinitiated at GE’s Project UHV research facility located in

Lenox, Massachusetts. A single-phase experimental line

consisting of three spans each 305 m long, a station with a

UHV transformer manufactured by ASEA (rated voltage at

420/835/1785 kV, three-phase equivalents, and 333 MVA)

and two test cages, each cage is 30.5 m long. The cages

have a square section and the dimensions could vary


Vol. 97, No. 3, March 2009 | Proceedings of the IEEE 557

between 6.1 m � 6.1 m and 9.1 m � 9.1 m, were used toevaluate the corona performance of large conductor

bundles. In 1974, a new three-year program to construct

and operate a three-phase test line in the range of 1000 to

1500 kV was started by the EPRI. The single-phase test line

was expanded to three-phase operation with the addition

of two UHV transformers, surge arresters, coupling capa-

citors, and associated equipment. The three-phase UHV

test line was 523 m long and test voltages up to 1500 kVphase-to-phase were utilized.

At Project UHV, extensive switching impulse tests on

many different types of line and substation equipment

were performed and power frequency tests on contami-

nated insulators were performed at UHV voltages. The AN,

RI, corona loss, TVI, electric field at ground level, and

ozone generation of 11 different conductor bundles with

subconductor diameters in the range of 33–56 mm and thenumber of subconductors in the range of 6–16 were

measured. The facilities at Project UHV were also used for

HVDC research later. New equipment had been installed

as part of this project to make possible a comprehensive

research program with test voltage up to �1500 kV.

Data on the corona performance, including AN,

RI, TVI, and corona loss of several bundles, with up to

18 subconductors, were obtained at the AEP/ASEA UHVProject test station. In addition, ASEA had performed

developmental testing to determine and verify the

insulation design of UHV equipment. Research on the

GIS equipment had been conducted for support insulators,

entrance bushings, and on the effects of varying gas quality

and pressure.

At BPA, extensive research and development on UHV

transmission have been conducted at the test facility atLyons, Oregon, and the mechanical test line at Moro,

Oregon. The Lyons UHV test facility consists of a 2.1 km

three-phase, 1200 kV line, has been used for electrical

studies. The test line at Moro has been used for structural

and mechanical studies without voltage. Investigations at

Lyons and Moro have been supported with tests and

studies in the BPA laboratories.

Studies of corona performance on conductors, insula-tors, and hardware fittings had been carried out both in the

BPA’s Carey Laboratory and on the Lyons 1200 kV test

line. Long term AN, RI, TVI, corona loss, and ozone gen-

eration for 7- and 8-conductor bundles of 41 mm diameter

subconductor have been investigated. Mechanical and

structural tests including studies of line loadings (wind and

ice load), conductor motion (aeolian vibration, subconduc-

tor oscillation, and galloping), switching surge withstandstrength of air gaps, pollution performance characteristics

of ceramic and nonceramic insulator strings, have been

performed in the BPA’s Mangan mechanical-electrical

laboratory and at the Moro mechanical test line.

In addition, other studies include studies of substation

noise and electric fields; and evaluation of the perfor-

mance of transformers, arresters, and SF6 equipment.

Between 1982 and 1985, EPRI (USA) with CEPEL/ELETROBRAS (Brazil) studied the critical problems in

developing HVDC converter station equipment for volt-

ages in the range of �600 to �1200 kV. The conclusion

was that converter stations at voltage �800 kV DC was

technically feasible.

D. ItalyIn the middle of 1970’s, Italy began study on UHV

transmission technology, and the purpose was to transmit

large blocks of power from large power generation faci-

lities to the load centers far away. The UHV transmission

studies were carried out in Italy at several testing stations

and laboratories.

At the Suvereto 1000 kV Project, a 1 km long test line

was used for air insulation and corona studies; a 40 m

outdoor test cage was also used for corona studies. Switch-ing impulse behavior of air clearances, behavior of surface

insulation of UHV system in polluted atmosphere,

performance of SF6 insulation, and development of non-

conventional insulators were carried out. Studies on the

interference levels produced by UHV insulators and

fittings were also carried out.

A test line at Pradarena Pass was used for icing and

wind loading studies in winter and vibration, sub-spangalloping, and spacer performance studies in summer.

Studies on air insulation and performance of polluted in-

sulators were carried out at the CESI laboratories in Milan.

The researches generated a large amount of data for

determining phase-to-ground and phase-to-phase air

clearances, selecting ceramic and non-ceramic insulator

strings, and selecting conductor bundles for a 1050 kV

prototype transmission line. The test data were also used inthe development of vibration dampers, spacers, and non-

conventional tower structures and foundations for 1050 kV

transmission lines.

A �700 kV generator was used for the dielectric tests

of UHV DC insulation. A test plant was also used for the

functional tests of thyristor modules of converter valves.

E. CanadaIn Canada, the need for transmission systems above

1000 kV was foreseen in the provinces of British Columbia

and Quebec to bring large blocks of power from remote

hydro-electric projects to the load centers.

The main research and test facilities for studies at

system voltages up to 1500 kV were located at the HV

laboratory of Hydro-Quebec Institute of Research (IREQ).

The test facilities at IREQ comprising a large indoor high-voltage laboratory, with capabilities for air insulation

studies on tower window mockups for system voltages up

to 1500 kV, a large pollution chamber for studies on

insulators, and an outdoor experimental line and test cages

were used for the corona test of conductor bundles for AC

systems up to 1500 kV and DC systems up to 1200 kV.

IREQ also studied the corona, electric field, and ion



current performance of DC transmission lines in the rangeof �600 to �1200 kV. Phase-to-ground and phase-to-

phase air insulation tests on line and substation config-

urations at IREQ provided a large amount of data necessary

for determining air clearances for transmission lines and

substations at system voltages of 1200 and 1500 kV.

A test line was also built at Magdalen Islands to study

vibration performance of 6 and 12 conductor bundles and

development of spacer dampers.

F. BrazilThe purpose for research on transmission lines above

1000 kV in Brazil was the need for transmitting a block

of power on the order of 20 000 MW from the Amazon

Basin to the load centers at distances in the range of

1500–2500 km.

Research and test facilities were built at the researchinstitute CEPEL in Adrianopolis, Brazil. A 360 m long test

line and a 7.5 m � 7.5 m test cage were installed and used

to conduct research for AC transmission systems up to

1500 kV and DC systems up to �1000 kV. In addition to a

large indoor high voltage laboratory for tests on equip-

ment, the facilities at CEPEL include an outdoor area

where full-scale or mockup transmission towers can be

tested for air insulation clearances and an outdoorexperimental line and test cages for corona studies.

Since 1978, Brazil has been associated with ENEL, in

Italy, B.C. HYFRO, in Canada, for a joint UHV AC research

and development program.

Basic research in HVDC �800 kV systems in 1987–

1995 was carried out and some equipment were designed

and manufactured in Brazil. Since then design work has

continued within ABB (combined of ASEA/Sweden andBBC Brown Boveri/Switzerland since 1988). Several

studies and meetings confirmed that �800 kV HVDC is

a feasible voltage level [5].

The Itaipu �600 kV, 6300 MW transmission line is

operating at �600 kV since 1984, Brazil, which is the

highest voltage and capacity DC transmission system in the

world, and the design and implementation of this project

was a joint effort of ASEA/Sweden and ASEA/Brazil.

G. ChinaWHVRI, CEPRI, EPCRI of SGCC and some universities

began study on the UHV transmission technology in 1986.

Since 1986 [8], the UHV transmission research was

included in the mega-projects of Scientific Research for

7th Five-Year plan, 8th Five-Year plan and 10th Five-Year

plan in China. Some subject researches had beendeveloped, including the prophase research of UHV AC

transmission (1986–1990) structured by Importance

Project Ministry of State Council; demonstration on long

distance transmission and voltage level (1990–1995)

structured by Importance Project Ministry of State

Council; the feasibility study on 1000 kV AC transmission

(1990–1995) and the prophase demonstration on UHV AC

transmission (1997–1999) structured by Ministry ofScience and Technology of China; UHV AC test line

(1994–1996), the effects on environment of UHV AC

transmission line (1997–1999) and the generation of long-

front switching wave by using power frequency test

equipment (1997–1999) structured by Ministry of Power

Industry of China; the background factor of UHV AC

transmission technology development (1998–2000) and

external insulation characteristics of UHV AC transmis-sion line (1999–2001) structured by State Power Corpo-

ration; higher voltage level application in Southern Power

Grid (2003–2004) structured by China Southern Power

Grid Corporation (CSG); the economical feasibility study

on 1000 kV AC transmission (2003–2004) structured by

SGCC.

Test facilities of WHVRI of SGCC comprising a

450 m � 120 m outdoor test yard, a 5.4 MV, 530 kJimpulse generator, a 24 m� 24 m� 26 m artificial pol-

lution chamber with a 800 kV (phase-earth) rated voltage

wall bushing, a 3 � 750 kV, 4 A transformer cascade

(Fig. 1), 2250 kVA regulator, 7500 kVA synchronous

generation voltage regulation unit; and a 1000 kV 200 m

long test line (Fig. 2) that was constructed at WHVRI of

SGCC in 1994.

Test facilities of CEPRI comprising a 6 MV, 300 kJimpulse generator and a transformer cascade. A tower test

site was constructed at ECPRI of SGCC in 2004.

China, Brazil, India and South-Africa began study on

the UHV DC transmission technologies at the voltage of

�800 kV and above in recent years [6], [9]–[11].

From the above review of UHV AC and DC develop-

ment in China and other countries, the conclusion can be

drawn that, although the technical feasibility is approved,there is no practical transmission systems at the voltages of

1000 kV AC, �800 kV DC and above being operated at the

present time [5].

Fig. 1. 2250 kV power frequency AC test transformer at WHVRI

(3 � 750 kV, 4 A transformer cascade).



III . GOALS OF THE UHV SYSTEMDESIGN AND RESEARCHBACKGROUND IN CHINA

The need of UHV AC and DC power transmission in Chinaand recent important innovations and progresses are

introduced in this section.

A. The Demand and Goals Analysis of UHVTransmission in China

In the past 20 years, the power industry in China has

been developing very fast. Both the installed capacity and

the total power consumptions in China has been thesecond largest one in the world since 1996 [12]. By 2005,

the installed capacity reached 512 GW, and the annual

growth rate is higher than 10%. China is now building a

well-off society in an all-round way, and the GDP should

be increased from USD 1653 billion by 2004 to USD

4000 billion by 2020. Strengthening the power supply is

one of the reliable guarantees to attain the above economic

objective. A huge installed capacity is indispensable tomeet the rapid load growth in the coming years. By

2010, it is expected that the total installed capacity will be

900 GW, the power consumption be 4200 TWh per year.

By 2020, it is expected that the total installed capacity will

be 1400–1600 GW, and 1300 GW at least, the power

consumption be 7000–8000 TWh per year [13]. Because

the present power system could not meet the future power

transmission needs of China, developing a 1000 kV ACnetwork supported by a series of �800 kV DC transmis-

sion projects is needed urgently.

1) The Excellent Characteristics of UHV Transmission: The

UHV transmission has obvious advantages of improving

transmission capacity, increasing power transmission dis-

tance, reducing line losses, lowering project investment,

saving line corridors.

a) Increase transmission capacity: The UHV transmis-sion can increase the transmission capacity. The natural

transmission capacity of a 1000 kV AC circuit is about 5 GW,

and that is approximately 4–5 times that of a 500 kV AC

transmission line. A circuit �800 kV DC transmission line

has the capacity of 6.4 GW, which is 2.1 times that of a

�500 kV DC power line.

b) Increase transmission distance: The UHV transmis-

sion could increase the economic power transmissiondistance. A 1000 kV AC line can economically transmit

power distances of 1000 km to 2000 km. A �800 kV DC

power line can economically transmit power over dis-

tances of 2000 km to 3000 km. A �800 kV DC power line

is economical than 1000 kV AC line when the transmission

distance is longer than 1200 km [13].

c) Reduce transmission loss: If the conductor cross-

section and transmission power are regard as constant, theresistance losses of a 1000 kV AC power line is 25% that of

the 500 kV AC power line. The resistance loss of �800 kV

DC transmission line is about 39% that of a comparable

�500 kV DC line.

d) Reduce cost: At the same conditions, the resistance

loss of the 1000 kV AC line is only 1/4 of the 500 kV AC

line, and the project investment, etc. can be saved. The

cost per unit of transmission capacity of 1000 kV AC and�800 kV DC transmission scheme are 73% and 72% that

of 500 kV AC and �500 kV DC schemes, respectively.

e) Reduce land requirements: UHV transmission has

obvious advantages in reducing the land occupation of the

line. A 1000 kV AC power line saves 50% to 66% of the

corridor area required by 500 kV AC lines in transmitting

the same capacity. A �800 kV DC line would save 23% of

the corridor area required by a 500 kV DC lines intransmitting the same capacity.

2) The Need of Bulk Power Transmissiona) Power demands increase rapidly with fast economic

growth: At present, China is in a critical period to build the

well-off society. The industrialization and urbanization

keep speeding up and the demand for electric power keeps

growing. The whole society power consumption has beenannually increasing at more than 10% in the past four years.

According to the national economic and social develop-

ment plan, by 2020, the total installed capacity is predicted

to be 1300 GW at least, the power consumption be 7000–

8000 TWh per year. Hence, the national power grid faces

a big challenge to ensure the safe and reliable supply of

the bulk electric power transmission [13].

b) Imbalance distribution of energy resources and loads:The distribution of generation energy resources and power

demands in China differs sharply from place to place [12].

In China, the resources of hydro-power and coal are the

main power generation resources. The proven amount of

the coal resource is over 1000 billion tons among which

more than 2/3 are in north and northwest China including

Shanxi province and the Inner Mongolian Autonomous

Fig. 2. UHV AC test line section at WHVRI.



Region. The exploitable capacity of hydro resource is over400 GW among which more than 3/4, such as Jinsha River,

Yalong River, Daduhe River and Lancang River are in

southwest region including Sichuan province, Yunnan

province and the Tibet Autonomous Region. However,

more than 2/3 energy demand is in the relative developed

central and eastern region.

The important energy bases are always 800–3000 km

away from the load centers. Because of the high pressureon environment protection, high cost of transportation and

limited land resources, the east region is no longer suitable

for the building of large-scale coal power plant. To meet

the continuous increasing demand for electricity, it is

necessary to optimize the energy resources allocation

nationwide and transmit power in a trans-region, cross-

drainage area, long distance and large scale manner by the

construction of strong electric grid.The power grid backbones consisting of 500 kV AC and

�500 kV DC now in China are difficult to overcome the

problems of imbalance distribution of energy sources and

loads for the following reasons: without enough substation

sites and line corridors; short circuit currents beyond

standards at heavy loaded areas; difficulties in coal

transportation; weak basis for power grids security; heavy

pressure on environmental protection.Because of insufficient ability in power transmission

and short circuit current exceeds the breaking capability of

circuit breaker; the present 500 kV AC and �500 kV DC

grid is hard to meet the future development needs. Espe-

cially, 12 hydro-power plants were planned to be built in

the trunk stream of the Jinsha River, including the hydro-

power plants designed in Yalong River and Daduhe River.

The area of the Jinsha River will have 100 GW installedcapacity, which accounts for 25% of all exploitable hydro-

power in China. The installed capacity of prophase I pro-

ject for the lower reaches of the Jinsha River will be about

18.6 GW, even which is 0.4 GW more than that of the

Three Gorges project. These hydro-power bases with large

installed capacity scale are concentrated and remote from

load centers with distance of more than 1000 km with

limited line corridors. Hence, UHV DC transmission is re-quired to transmit hydro-power out. Therefore it is urgent

to develop a UHV electric grid with strong ability for

resources allocation and build an electric power highway.

3) The Need of National Power Grid Development: China

has six regional grids: the North China Grid, Northeast

Grid, Central China Grid, East China Grid, Northwest Grid

and South China Grid. For the most part, interconnectionbetween these grids has been accomplished. Because of the

insufficient long-term investment, power grid develop-

ment in China lagged behind, and resulted in a very weak

grid structure. The ability of grid to optimize the resources

allocation cannot be brought into play. Its ability to resist

accidents and risks is not strong; and the risk of large area

blackout always exists.

The construction of the UHV grid, namely 1000 kV ACand �800 kV DC, can effectively solve the safety and

stability problems caused by the present insufficient ability

of 500 kV AC and�500 kV DC grid, optimize the layout of

electric power and obviously improve the safe and reliable

operation.

UHV AC transmission system is flexible for transmis-

sion, interchange and distribution of power on the strong

power grids. The UHV AC transmission is oriented tonetwork configuration of higher voltage level and bulk

power transmission between regions. While �800 kV DC

transmission is oriented to long distance electric power

send-out from large hydro-power bases.

For the proposed UHV synchronized network connect-

ing North, East and Central China, the total installed

capacity will exceed 700 GW by 2020. Power system sim-

ulation shows that the stability level will be high enough totransmit bulk power while protecting the system from high

current faults. In case of a bipolar failure of �800 kV or a

single transmission corridor failure of UHV AC, the system

will be capable of maintaining system stability without

experiencing serious low-frequency oscillation.

B. Important Innovations and ProgressIn order to build a strong and reliable national grid

and meet the load growth, construction of UHV backbone

transmission network comprising 1000 kV AC and

�800 kV DC transmission projects was proposed by SGCC

and CSG [6]–[8].

Although a large amount of research and test data are

obtained from the different facilities around the world, the

situation of China is different from other countries,

especially high altitude and heavy pollution, hence, manytechnical problems relevant UHV transmission and

transformation need to be discussed [14].

The SGCC started study on key technologies of UHV

including power system analysis of UHV AC and DC

transmission, construction and test, engineering design,

manufacture of main equipment, etc., at the end of 2004

[6]; the CSG started do that at 2003 [8]; many other

enterprises concern UHV transmission also research, de-sign and manufacture the UHV equipment actively; the

UHV research works are promoted greatly and many

valuable achievements for the development of the UHV

transmission have been achieved [7].

Important innovations and progress have been

achieved in the following aspects:

1) Made a systematic demonstration of the necessity

and feasibility of UHV transmission and revealedthe objective necessity of transformation for

Chinese grid development pattern and large scale

development of the UHV transmission.

2) The key technologies like voltage standards, over-

voltage and insulation coordination, electromag-

netic environment, live-line working, etc., have

been carefully and systematically studied based on



the 1000 kV AC and �800 kV DC powertransmission and transformation projects. The

recent research developments of 1000 kV AC and

�800 kV DC transmission and transformation key

technologies in China will be introduced in detail

in the following sections.

3) The 1000 kV AC and �800 kV DC tests and

demonstration project were approved and the

project design were completed, and are underconstruction at the present.

4) The UHV AC and DC test bases were energized,

and the state grid simulation center is under

construction.

5) The UHV equipment research was fully promoted.

A whole technology specification was formed and

conceptual design of the equipment was complet-

ed, and some equipment was successfully devel-oped, this will be introduced in the following

section of equipment manufacturing.

6) The UHV grid plan was formed and a scheme was

proposed to build the north, central and east

China UHV AC synchronous electric grid and

realize large capacity transmission with super long

distance through UHV DC.

C. UHV AC and DC Key Technologies Researchesand Achievements

More than 2000 academicians, experts and engineers

from various consulting organizations, scientific research

institutions, universities and engineering and equipment

manufacturing organizations to make a in depth research

and repeated evaluations on more than 100 key technical

problems of UHV transmission. Lots of researches havebeen carried out for over-voltage and insulation coordina-

tion, live-line working, lightning performance, electro-

magnetic environment (AN, RI, and TVI, effects of electric

field and magnetic field on human bodies under UHV AC

and DC transmission lines) of 1000 kV AC and �800 kV

DC transmission and transformation projects.

1) Voltage Standards: 1000 kV AC and �800 kV DC arethe voltage level of UHV transmission in China.

2) Over-Voltage and Insulation Coordination: The external

insulation discharge characteristics of power frequency,

switching impulse and lighting impulse on AC transmis-

sion and substation equipment air clearances, heat stable

extending radius flexible bundle conductor (bus), bundle

conductor, tubular bus were carried out by mimic realconfiguration test on UHV transmission line [15], [16].

The relationship curves between air clearances and dis-

charge voltage had been obtained by switching impulse,

lightning impulse and power frequency voltage tests.

The front time of switching impulse test voltage is

1000 �s, which is close to the switching over-voltage of

real transmission line. The selection of air clearance under

operation voltage considers the maximum operating volt-age; the maximum wind speed happened once in 100 years;

the rate of flashover is 0.13%. The minimum operating

frequency voltage air clearance for altitudes 500 m,

1000 m, and 2000 m requires 2.7 m, 2.9 m, and 3.1 m

respectively. The selection of air clearance under switch-

ing voltage considers the 1.7 p.u. of maximum statistic 2%

over-voltage level along the line; the influence of the mul-

tiply clearance connected in parallel on flashover voltage;the ratio of flashover is 0.13%. The minimum switching

voltage air clearance for altitude 500 m, 1000 m, and

2000 m requires 6.7 m, 7.2 m, and 7.7 m for middle phase,

respectively. For side phase it requires 5.9 m, 6.2 m, and

6.4 m, respectively. The air clearance of side phase is

controlled by operating voltage and the air clearance of

middle phase is controlled by switching voltage impulse

voltage. The lightning impulse voltage does not control thedistance of tower air clearance. The requirement of air

clearance under lightning impulse voltage can not be spe-

cified [17]. The tests figures are shown in Fig. 3.

The switching impulse discharge characteristic curve of

1000 kV AC substation equipment air clearance was

studied at WHVRI of the SGCC [18]. Two sets of impulse

voltage generators, whose voltages are 5400 kV and

3000 kV respectively, are used conjointly in the experi-ments. By adjusting the time delay unit to make the two

impulse generators in synchronism, The test used up and

down method to obtain the discharge characteristic curve

under switching impulse between the ring phases, the

tubular bus phases and the 4 multiple conductor phases

which have 5–9 m distance.

Over-voltage and insulation coordination of 1000 kV

AC transmission line, substation (or switch station) andthe equipment were studied [19]. High voltage shunt reac-

tor configuration was proposed when avoidance of non-

complete phases’ power frequency resonant over-voltage,

limitation of over-voltage level and reduction of number of

spare high voltage shunt reactor were considered. power

frequency Temporary Over-voltage (TOV), secondary arc

current and recovery voltage, parameter choice of MOA,

switching over-voltage (including energized and single-phase energized unloaded line over-voltage, ground fault

over-voltage and clearing short-circuit faults switching

Fig. 3. UHV AC phase to tower air clearance tests at

WHVRI outdoor test yard.



over-voltage), Gas Insulated Switchgear (GIS) isolatorswitching over-voltage, circuit breaker Transient Recovery

Voltage (TRV), DC component decayed time constant of

short-circuit current cleared by circuit breaker were

studied. Air clearances choice of UHV transmission line

tower under working voltage, lightning impulse and

switching impulse voltage, air clearances distance choice

of substation and switch station as well as the choice of

UHV equipment insulation level of Jindongnan-Nanyang-Jingmen transmission line had been carried out. The Very

Fast Front Over-voltage (VFTO) of GIS and Hybrid Gas

Insulated Switchgear (HGIS) substation of Jindongnan-

Nanyang-Jingmen UHV AC demonstration line was

calculated [20]. The Jindongnan GIS VFTO produced by

disconnector switching on and off can be up to 2795 kV

(3.11 p.u.), and 500 � switching on and off parallel re-

sistance installed on the disconnector can limit the VFTOto about 1008 kV (1.12 p.u.). The VFTO of a transformer in

GIS substation is not high when the transformer is con-

nected to GIS by overhead line. The maximum VFTO of

Jingmen HGIS substation is 2.16 p.u. of all kind of con-

nection and operation modes.

The UHV transmission research results in China indi-

cate that long air clearance switching impulse discharge

voltage is influenced greatly by the shape of electrodes[22]. In all kinds of shape electrodes, the discharge voltage

of pole-plate air clearance is the lowest, and its saturation

trend is obvious. Whereas, the switching impulse dis-

charge characteristics of conductors to tower air clearance

in transmission line are influenced by the type of con-

ductors, hardware fittings configuration, type of insulators,

framework of tower, width, etc.; and its clearance coeffi-

cient is obvious bigger than that of pole-plate air clearance.Hence, the switching impulse discharge characteristics of

UHV AC transmission line have no obvious saturation. The

tower head dimension of UHV AC transmission line is

proposed based on large amount of 1 : 1 true type testing

in China.

Power frequency voltage withstands performance tests

were carried out on artificially polluted insulator string

with real model arrangement. Influence of high altitude oninsulator pollution withstands voltage, influence of NSDD

on insulator, influence of different pollution accumulation

on pollution withstand voltage and the correction coeffi-

cient of different pollution accumulation had been ob-

tained by tests and studies. The results show that U50% of

insulator string rise nonlinearly with string length [21].

The linearly analogous U50% is 1.6%–10.2% higher than

tested one. The U50% of different type insulator string iscorrelated to ESDD with negative exponential power of

�0:202 � �0:195. The U50% values are also correlated

with NSDD with negative exponential power of about

�0.1341. Under the same test conditions, the U50% of

single string of double-shed insulator is about 5% higher

than that of normal insulator, the U50% of double string of

normal insulators is about 6% lower than that of single

string, and that of V string is 4% � 13% higher than that ofsingle string [23].

The effects of high altitude, contamination, ice-

covered, snow-covered, acid rain and acid fog on discharge

characteristics of insulators for UHV DC transmission lines

as well as the discharge characteristics of long air clearance

under high altitude were expounded and discussed in China

[24]. Icing flashover performance tests of short samples of

two different type of silicone rubber (SIR) composite longrod insulators intended for UHV AC transmission lines

were carried out. Ice thickness, pollution severity on the

surface of insulators before ice accretion, atmospheric

pressure, and shed profiles were also considered [25].

The discussion meeting for the first draft of 1000 kV AC

transmission system over-voltage and insulation coordina-

tion guide was hold on November 10th, 2007 at Wuhan,

China; and the amendatory advices were proposed.The causes and characteristics of the over-voltage of

�800 kV UHV DC transmission system was investigated

under operation and fault conditions by a complete simu-

lation model of PSCAD/EMTDC, and the factors which

influence the over-voltage level [26].

�800 kV DC transmission tower head air clearance

switching impulse and 50% lightning impulse breakdown

voltage tests were carried out at outdoor test yard ofCEPRI of SGCC [27]. It was found that the air clearance of

�800 kV DC transmission tower head should not less than

6.1 m; the 2000 m altitude correction coefficient for air

clearance switching impulse breakdown voltage was 1.13;

and the influence of barrier that shorter than 2 m can be in

the DC field air clearance design of converter station.

�800 kV DC and the insulation coordination were also

studied and the values of AC and DC equipment switchingimpulse insulation level and lightning insulation level

were proposed [28].

Preliminary recommendations on the decisive parame-

ters of suitable shed profiles and a test method for station

composite insulators were discussed at Tsinghua Univer-

sity on November, 22nd 2005 [29], with a group of invited

experts on external insulation from Beijing Wanglian

HVDC Engineering Technology of SGCC, TechnologyResearch Center of CSG, CEPRI, Xi’an Electro-Ceramic

Research Institute (XECRI), Tsinghua University, ABB

HVDC Sweden, and ABB Corporate Research in China.

Flashover performances of three kinds of composite

insulators were studied at the high voltage test base of

Yunan Electric Power Research Institute (YEPRI) by

Graduate School at Shenzhen, Tsinghua University. It

was found that the DC flashover voltage was influenced byshed profiles, and the flashover voltage can be increased

20% by reasonable optimization of shed profiles [30].

The artificial pollution flashover performance of the

short samples of one kind FXBW-�800/400 DC SIR

composite long rod insulator was investigated in the

multifunction artificial climate chamber (a diameter of

7.8 m and a height of 11.6 m) in the High Voltage and



Insulation Technological Laboratory of Chongqing Uni-versity [31], [32]. The effects of pollution and high altitude

on the flashover performance were analyzed. The expo-

nent characterizing the influence of Equivalent Salt Depo-

sit Density (ESDD) on the flashover voltage was related

with the profile and the material of the insulator shed. The

values of the samples’ exponents vary between 0.24 and

0.30, which were smaller than those of porcelain or glass

cap-and-pin insulators, namely, the influence of the pollu-tion on the composite long rod insulators was less, rela-

tively. The best ratio of the leakage distance to the arcing

distance was about 3.35. The exponent characterizing the

influence of air pressure on the flashover voltage is related

with the profile and the material of the insulator shed

and the pollution severity; the values of the samples’

exponents vary between 0.6 and 0.8, which are larger than

those of porcelain or glass cap-and-pin insulators. There-fore, the DC composite insulator used in high altitude

regions should have enough arcing distance. If FXBW-

�800/400 DC SIR composite long rod insulator is selected

for the �800 kV UHV DC transmission lines, the basic

arcing distance should be no less than 8.16 m and the basic

leakage distance no less than 30.2 m.

It was reported in [33] that 64 units 210 kN cap and pin

insulators can be used for �800 kV I insulator string inlight pollution level according to the principle of same

creepage distance, and 67 units 210 kN cap and pin insu-

lators can be used according to principle of the same

spacing height. If composite insulator is used, the spacing

height and creepage distance are suggested to be 80%

length of 210 kN cap and pin insulators. The external

insulation arrangement design in much light pollution

level should be same as light pollution class.The configuration scheme of lightning arrester protec-

tion for �800 kV converter station, the principle of insu-

lation coordination and over-voltage protection strategy

for converter station were analyzed; the parameters and

characteristic of lightning arresters were calculated; after

analyzing the over-voltage protection for equipment and

insulation level of equipment in detail, the discharge

voltage of air clearances in converter station was givenpreliminarily [34].

3) Live Line Working: The live line working research

works for 1000 kV AC transmission line were firstly and

systematically carried out in China at WHVRI of the SGCC

[35]–[38]. The research results indicate that the live line

working of 1000 kV AC transmission line in China is fea-

sible and safe [22].The minimum approach distance and combined

clearance at different system over-voltage level, altitude

above sea level, working conditions, on side phase, middle

phase and tension string were studied respectively [35].

Power frequency breakdown test, power frequency

withstand voltage test and switching impulse flashover test

of portable protective clearances were carried out. The

maximum portable protective clearances correlated to dif-ferent altitude were calculated according to the test re-

sults. Various actual work conditions were simulated in

1 : 1 tower window, and the switching impulse discharge

test concerning insulation matching between portable

protective clearances and working clearance was carried

out by up and down method. The research results indicate

that insulated tools made in China can satisfy the

requirement of 1000 kV AC transmission line liveworking [36].

Suitable full set shielding clothes were also developed,

and then characteristics of material that the shielding

clothes made of and the ready-to-wear were tested in ac-

cordance with national standards of China live line

working. Measuring of electrical field intensity in and

outside of shielding clothes at different part of body while

climbing tower and during equal-potential process, theelectric field intensity inside the screening shielding

clothes were 0.4–10 kV/m, 8.4–137 kV/m inside the

mask, and the current through the body of equipotential

operator was 32 �A [38]. The arc test and impulse current

measuring while during equal-potential process were also

carried out. The tests results indicate that the shielding

clothes developed have good performances on electrical

field shielding, current splitting and voltage sharing, thusmeets the requirements for the safety protection [37].

4) Lightning Performance: Lightning performance of UHV

AC transmission line and lightning invaded wave over-

voltage of UHV substations were studied. The measures to

improve shielding performance were recommended [39].

The shielding performance of ground lines and back

flashover were studied at CEPRI of SGCC. The shieldingangles of typical UHV AC towers in China were

recommended [40].

Some special design problems on direct lightning

stroke shielding of 1000 kV AC substation were calculated

and discussed. Lighting invaded wave protection of typical

substations was also simulated to suggest the number and

location of MOA in substation. For different station oper-

ating conditions, the safety operation guideline was calcu-lated. According to the calculation results, the MOA

installation schemes were put forward for ensuring safety

operation of every station in 1500–2000 years [41].

The striking distance factor for high tower was studied.

The results showed that the striking distance factor ð�Þwould reduce with the height ðHÞ of tower increasing, and

the value of lightning current did not affect the striking

distance factor. The relation equation between � andH : � ¼ 1:18� H=108:69 was proposed, and then the

striking distance factor was introduced to the improved

electric-geometry model (EGM) to analyze the lightning

protection performance of shielding failure for UHV

transmission line [42].

The lightning performance of Yun-Guang �800 kV

UHV DC transmission line was also analyzed [43], [44].



5) Electromagnetic Environment: The electromagneticenvironment for 1000 kV AC power transmission line such

as power frequency electric field, power frequency mag-

netic field, RI and AN were studied [45]–[49]. �800 kV

DC ion flow density, combined field strength at ground

surface, RI and AN were also studied. And the recom-

mended control criteria were proposed. The control

criteria can be satisfied by using multi-bundled and large

section conductors and increasing the lowest phase con-ductor to the ground surface [50]–[52]. Based on the

control criteria, the 6� 720 mm2 conductors can be used

when the transmission capacity is 6400 MW, 45 cm bundle

spacing can be used; 6� 800 mm2 conductors can be used

when the altitude is above 2600 m, however, the

6� 720 mm2 conductors can still be used when the dis-

tance between the two poles increased properly [53].

The tests for critical corona onset voltage of the heat-resistant diameter expanded flexible conductor, the bundle

conductor and the tubular bus bar, the visible corona onset

voltage of typical grading ring for transmission line and

insulator strings were carried out by using UHV test line

section of WHVRI [54]. The relationship between corona

voltage and the height of conductors; the minimum of the

grading ring’s diameter was also achieved.

6) Relay Protection: The development of a test environ-

ment based on a Real-Time Digital Simulator (RTDS) of a

UHV power system model and the results of testing a

distance relay using the model was presented [55]. The

conclusion that the protective zone will be enlarged in the

UHV system with shunt reactor compensation and reduced

without the compensation was drawn. The suggestion that

new protective algorithms should be developed andexamined was proposed.

The control and protection system differences between

UHV DC project and conventional HVDC project as well

as the special requirements of UHV DC project were anal-

yzed [56]. The integral structure, control strategy, hier-

archy of the structure and redundancy, distribution of

control functions and configuration of the protection, etc.

of the control and protection system, were carried out.Then a possible integral scheme of control and protection

system for UHV DC project was put forward. Simulation

results show that the proposed control strategy can com-

pletely satisfy the requirement of the design for HVDC

power transmission system, the faulty 12-pulse converters

can be reliably deblocked to ensure continuous operation

of UHV DC system [57]–[59].

A novel transient based protection for �800 kV DCtransmission lines was proposed based on a �800 kV DC

bipolar model that was built with the PSCAD/EMTDC

software [60]. Wavelet-multiresolution signal decomposi-

tion technique was applied to analyze the transient volt-

ages. Based on spectral energy distribution of transient

voltages, the criteria were presented to distinguish the

�800 kV line faults from other transient phenomena.

Some new protection principles and actions, whichinclude a criteria of differential current between bi-pole

under bipolar operation mode and an action of switching to

metallic return mode under unipolar operation mode, in the

bi-pole area of �800 kV DC system was put forward [61].

7) Sharing Earth Electrodes: Sharing earth electrode was

firstly proposed in China to make it easier to choose the

electrode sites for the close distance between multi-converter stations, the technical and economic feasibility

were studied thoroughly and approved [62]–[66].

The different operation modes of the UHV DC system

sharing earth electrode from the aspect of power system

stable operation were discussed [62]. Two UHV DC

system rectifiers and inverters sharing earth electrodes

were studied respectively by electromagnetic transient

analysis software EMTP-RV. The influence on the normaloperation of UHV DC system sharing earth electrode was

simulated and analyzed. The merits and demerits of

sharing earth electrode were also summarized in detail.

The analysis of the choice of burial depth and the ef-

fects on step voltage, earth resistance and current density

caused by multi-ring electrodes with equal or unequal

depth were studied [65]. The conclusions was drawn that

the maximum depth of electrodes buried in soil should becontrolled less than 4 m; the position of inner rings has

little influence on the running parameters; the model of

triple concentric-ring electrodes laid with different depth

in the upper soils with a smaller resistivity could be more

economical in the investments on the premise that all

parameters are within their permissible running limits.

The feasibility of sharing earth electrodes by two or three

converter stations was also validated.

8) Tower and Truss Tests: EPCRI of SGCC has built the

aeolian vibration laboratory, stranded wire fatigue labora-

tory, heavy current laboratory, mechanical property labo-

ratory and transmission line galloping laboratory,

electrical and mechanical performance tests of conductor

and fittings for 1000 kV transmission line can be carried

out with the testing facilities.Tower test station of EPCRI of SGCC has the test

capability of 1000 kV single circuit tower, 750 kV double

circuit tower and 500 kV multi-circuit towers. The

maximum height of test tower is 100 m; the maximum

span of tested tower foot is 30 m; the maximum uplifting

force per tower leg is 10000 kN; the over-turn torque is

bigger than 240000 kN �m.

a) ZM2 straight tower strength tests: Strength tests ofthe first UHV true type ZM2 straight tower in China under

fourteen working conditions were successfully carried out

from September 28th to October 2nd, 2006 in the tower

test station of EPCRI.

The head of the ZM2 straight tower is cat head shape,

the nominal tower height is 59 m, the total tower height is

79.3 m, the root span is 16.66 m, and the weight is 59 t.



High strength Q420 steel is used in the main part of towerbody and lower bent arm [67].

The tests under fourteen working conditions, including

the wire breakage fault working condition, installing

working condition, normal operation working condition,

etc., were carried to test the stress characteristics of truss

member, stress transfer relationship between truss mem-

bers and the reasonability of joint structure.

The 60� strong wind overload test, testing the ultimatebearing capacity of tower under strong wind, was carried

out on October 2nd, 2006. The testing load was increased

from 0 to 100% design load, and then was increased step

by step according to 5% design load. The fracture pheno-

mena was occurred on the tower when the testing load was

increased from 120% to 125% design load, then the tower

fell down. This was identical with the design and calcu-

lated results.b) Transformation truss 1 : 2 model strength tests:

Transformation truss 1 : 2 model (Fig. 4) true type strength

tests of 1000 kV AC test and demonstration project were

successfully carried out from April 15th to April 18th, 2007.

The height of the outlet line beam is 27.5 m, the height

of bus-bar beam is 19 m, and the horizontal span is 7.5 m.

The testing transformation truss is made up of steel pipe,

and the maximum design withstand wind velocity is 25 m/s.c) SZ1 straight tower strength tests: UHV true type SZ1

straight tower strength tests (Fig. 5) were successfully

carried out on August 17th, 2007 in the tower test station

of EPCRI. This SZ1 tower is made up of Q460 high

strength steel, and this is the first time use of Q460 high

strength steel in power transmission tower.

The test results can supply reliable parameters for UHV

tower design and operation in China.The research and development of the UHV transmis-

sion technology and equipment development has been put

into the 2006–2010 national economic and social develop-

ment program, the national middle and long term tech-

nology development program and the key task of nation’s

rejuvenating equipment manufacturing industry in China.

IV. EQUIPMENT MANUFACTURING

Research institutions and equipment manufacturers con-

duct in-depth investigations on the design and manufac-

ture of UHV equipment. Over the past several years, great

breakthroughs have been made in the development and

manufacture of UHV equipment. Performance of equip-

ment test, equipment research, development and manu-

facture of 1000 kV AC and �800 kV DC transmission and

transformation projects have been carried out [68].

A. UHV AC Equipment Manufacture

1) Transformer: One type of UHV AC oil-immersed

250 MVA/1200 kV testing power transformer which can be

used in UHV test was developed; another type of UHV AC

oil-immersed 610 MVA/1700 kV testing power transformer

passed all the type tests successfully on July 8th, 2007.The first unit of 1000 kV/1000 MVA UHV AC trans-

former in the world passed the long time induced voltage

(with partial discharge measurement) test on June 30th,

2008. And the normal test, switching impulse test and

lightning impulse test of this type transformer had been

passed before.

The rated power of ODFPS-1000 MVA/1050 kV

transformer, used in China UHV transmission project, is1000/1000/334 MVA; the rated voltage ratio is 1050=

ffiffiffi

3p

=525=

ffiffiffi

3p

=110 kV; The voltage regulation mode is neutral

Variable Flux Voltage Variation (VFVV) [69], [70].

2) Reactor: The 1100 kV/240 MVar reactor passed all

the test items on February, 13th, 2008. The 1100 kV/

320 MVar reactor, the biggest capacity reactor in theFig. 4. Transformation truss strength tests of 1000 kV AC test

and demonstration project (1 : 2 model).

Fig. 5. SZ1 straight tower strength tests.



world, passed all the test items on March 9th, 2008.Configuration of twin columns for improving the magnetic

leakage distribution was adopted.

BKD-200 MVar/1100kV UHV shunt reactor passed all

the test items on May 18th, 2008. The reliability of insu-

lation was improved by application of unique connection

and winding insulation configuration.

Especially, the partial discharge, temperature rising,

noise and vibration of these three types reactor all reachedthe advanced level in the world.

3) Circuit Breaker: The technique of 550 kV single-break

arc chamber with independent intellectual property right

had been achieved. Based on two 550 kV single-break arc

chamber series, internationally advanced 1100 kV double-

break circuit breaker can be developed.

All the type tests of one typical type of 1100 kV circuitbreaker, which has double-break chamber, closing resistor

and capacitor are paralleled for each break chamber, each

phase has a hydraulic operating mechanism, will be

finished in 2008.

LW10-1100 kV SF6 circuit breaker was also developed.

4) Switch: Prototypes of 1100 kV disconnecting switch

(DS) and earthing switch (ES) in China were assembledand tested.

The insulation level of one typical type 1100 kV/63 kA

ES developed in China has the technical characteristics

that the lightning impulse voltage is 2680 kV; the switch-

ing impulse voltage is 1860 kV; and the power frequency

withstand voltage is 1230 kV.

5) Bushing: The bushing of 1100 kV capacitivetransformer/reactor were successfully developed in

February, 2008.

The technical parameters of one typical type 1100 kV

bushing developed in China are: the rated voltage is

1100 kV; the rated current is 2000 A; the lightning impulse

withstand voltage is 2400 kV; the switching impulse with-

stand voltage is 1960/1800 kV; and the power frequency

withstand voltage is 1200 kV (5 min) [71].1100 kV OIP type condenser bushing developed in

China is with porcelain insulator, and the tan � � 0:4%;

the partial discharge G 10 pC under 1100 kV voltage.

6) Insulators: Normal type porcelain insulator, normal

type glass insulator, double-shed porcelain insulator and

tri-shed porcelain insulator were developed and manufac-

tured. 1000 kV composite insulators were successfully dev-eloped and the main parameters are given in Table 1 [72].

The technical parameters of typical 1100 kV post insu-

lators made in China are: the lightning impulse withstand

voltage is 2550 kV; the switching impulse withstand volt-

age is 1800 kV; the power frequency wet withstand voltage

is 1100 kV; and the bend failing load is 12.5 kN and 16 kN

respectively.

7) Arrester: The technical parameters of one typical

1000 kV arrester are: the maximum current non-uniform

coefficient in multi-columns of disks is 5%; the maximum

potential distribution non-uniform coefficient is 1.17 (with

grading capacitor configuration); the energy absorption

capability is 40 MJ; and the 4/10 �s withstands impulse

current is 4 � 100 kA.

The developed high capacity resistance piece cancompletely satisfy the requirements with enough margin

for 1000 kV UHV AC GIS and porcelain-clad metal oxide

arrester. The porcelain-clad arrester was the initiate pro-

duct on the world. Three GIS and twelve porcelain-clad

metal oxide arresters had been assembled and tested on

August 8th, 2008 and before [73], [74].

8) Current Transformer, Voltage Transformer: CurrentTransformer (CT) and Voltage Transformer (VT) were also

developed.

The developed typical 1000 kV Capacitor Voltage

Transformer (CVT) has the technical characteristics of

that the tan � � 0:07%; the partial discharge level � 3 pC;

and the excellent anti-corrosion performance. All the test

items had been passed before December 2006 [75].

Eighteen 1000 kV CVTs of 1000 kV Jindongnan-Nanyang-Jingmen test and demonstration line were

successfully passed the on-site experiments from

September 22nd to October 8th, 2008.

9) Fittings: The UHV AC transmission line hardware

fittings include: grading ring, yoke plate, spacer, suspen-

sion hardware fittings, tension hardware fittings, jumper

line hardware fittings, protection hardware fittings, anti-galloping device, vibration damper etc. were developed by

some corporations in China. The performance testing of

some hardware fittings had been carried out at WHVRI of

SGCC (Fig. 6).

10) HGIS: The first 1100 kV HGIS, developed with the

cooperation of ABB had been successfully manufactured in

June, 2008.

Table 1 Typical Dimensions and Mechanical-Electrical

Characteristics of 1000 kV AC Composite Insulators



B. UHV DC Equipment Manufacture

1) Converter Transformer: The parameters of developed

ZZDFPZ-321100/500 kV converter transformer are:

�ð400þ 400Þ kV DC rectifier, the rated power is

321.1 MVA; the rated voltage is 530=ffiffiffi

3p

=170:3=ffiffiffi

3p

kV;

the impedance is 18%.Line side insulation level: the lightning impulse with-

stand voltage (full wave) is 1550 kV; the switching impulse

withstand voltage is 1175 kV; the power frequency with-

stand voltage is 680 kV.

Valve side insulation level: the lightning impulse with-

stand voltage (full wave) is 1800 kV; the switching impulse

withstand voltage is 1600 kV; the power frequency with-

stand voltage is 921 kV; the applied DC withstand voltageis 1271 kV (120 min).

2) Converter Valve: The preliminary research and

development of �800 kV converter valves had been

carried out actively based on the �500 kV converter valve

technologies and has obtained the intermediate achieve-

ments as follows: the electrical design of the valve section;

the mechanical components design of the valve section;the thermal design of the valve section; the technical spe-

cification of valve-based electronic equipment (VBE).

3) Smoothing Reactor: Technical parameters of manu-

factured �800 kV dry type smoothing reactor are: the

rated voltage is 800 kV; the rated current is 4000 A; the

inductance is 75 mH; the lightning impulse withstand

voltage (full wave) is 2100 kV; and the applied DC with-stand voltage is 960 kV (120 min).

Technical parameters of another type�800 kV/4000 A

smoothing reactor primary layout are: the rated DC cur-

rent is 4296 A; the rated inductance is 75 mH; the insu-

lating thermal endurance grade of turn insulation is H, and

holistic insulation is F; the temperature rise of average is79 K, and the hotspot is 90 K; the dry-arcing distance on

coil surface is 4300 mm; the lightning impulse withstand

voltage is 1225 kV (between terminals); the switching im-

pulse withstand voltage is 1005 kV (between terminals);

the diameter is 5000 mm.

4) Thyristor: Through technology import and domestic

innovation, the prototype of 6 inch ultra high powerelectric triggered thyristors for UHV DC applications had

been independently developed, which is under perfection

through tests and studies.

The developed prototype of 6 inch thyristor

(KPE4000-80), has the excellent technical characteristics:

outstanding dynamic performance; advanced electron

irradiation technology; evaporation of thick aluminum

layer technology; unique chip packaging technology; thedesign of explosion-proof packages.

5 inch thyristor module for UHV DC transmission

was also developed, and its rated current is 3125 A. The

thyristor module passed the routine test according to the

test specification of the thyristor valve. The test results

meet the requirements of �800 kV UHV DC thyristor

valve [76].

5) Insulators: �800 kV DC composite insulators were also

successfully developed [77]. 16 kinds of different shed

structure �800 kV DC composite insulators sample were

manufactured and large amount of optimal DC pollution

flashover tests were carried out by Shenzhen Graduate School

of Tsinghua University in the Extra High Voltage (EHV) test

base of Yunnan Electric Power Research Institute (YEPRI).

The most optimal structural parameters of DC compositeinsulator were achieved and the pollution withstand charac-

teristic of composite insulator was improved. The main

parameters of two typical �800 kV composite insulators are

given in Table 2 [72].

The composite post insulators with porcelain core for

�800 kV DC system were developed and passed all the

23 type test items [78].

Fig. 6. Performance test of some UHV hardware fittings at

WHVRI outdoor test yard.

Table 2 Typical Dimensions and Mechanical-Electrical

Characteristics of �800 kV DC Composite Insulators



V. UHV AC DESIGN AND TEST SYSTEMS

According to the research of Chinese actual conditions,

the technical problems in 1000 kV UHV AC powertransmission projects, including the problems of over-

voltage and insulation, external insulation characteristics,

electromagnetic environment, the UHV equipment man-

ufacture and test are still not solved well.

UHV AC demonstration line and test bases are the first

UHV transmission and transformation projects in China.

The line has the abilities to validate the prophase research

achievements in China, the performance and reliability ofthe transmission and transformation equipment, improve

the power equipment level in China. However, the line

should have the ability of normal transmission power.

Hence, the demonstration lines have the functions of de-

monstration, test and commercial operation.

The UHV AC test base can solve the problems and offer

the UHV AC demonstration projects first class test and

measurement platform. The UHV AC key technologiesresearch achievements can be directly used in the con-

struction of UHV AC test base, hence, the former research

achievements can be validated, the UHV equipment can be

developed, tested, and applied, the research achievements

can be further completed with the application of equip-

ment in test bases [79], [80].

A. Jindongnan-Nanyang-Jingmen UHV AC Testand Demonstration Line

The Jindongnan-Nanyang-Jingmen 1000 kV AC test

and demonstration project, sponsored by SGCC, laid

foundation in Changzhi city of Shanxi Province, China

on August 19th, 2006. The demonstration line, which is

about 645 km long, has the functions of demonstration,test and commercial operation, and will be put into

operation in the end of 2008 [22], [85].

1) The Output Scale and Scheme of the Project: The rated

voltage of Jindongnan-Nanyang-Jingmen 1000 kV AC test

and demonstration project is 1000 kV, the highest oper-

ating voltage is 1100 kV, the rated current is 4 kA, and the

rated transmission power is 5 GW.The test and demonstration project comprises three

substations and two segments of transmission lines. It starts

from Jindongnan substation in Changzhi city of Shanxi

Province, via Nanyang switching station in Nanyang city of

Henan Province, and ends at Jingmen substation in

Jingmen city of Hubei Province. The total length of

recommended lines is about 645 km (including a large

span of 3.721 km crossing the Yellow River and theother span of 2.956 km crossing the Hanjiang River).

The length of two segments of 1000 kV transmission line

are about 358.43 km and 286.57 km from Jindongnan to

Nanyang and from Nanyang to Jingmen respectively.

Single phase transformers of 1000 MVA and single

phase HV shunt reactors of 320 Mvar are firstly developed.

GIS/HGIS and two circuit breakers are applied in electrical

connection scheme. Rated short circuit current at 1000 kVside is selected as 50 kA, and that is 63 kA at 500 kV side.

2) Bundle Conductors, Ground Wires and Tower: The

altitude of areas where transmission lines of UHV AC test

and demonstration project going through does not exceed

1500 m, and 78% region is below 500 m. the pollution

level of most areas is above II level. Jingmen segment is

located at the region where conductors galloping oftenhappen. Transmission lines in Taihang Mountains have

special weather conditions, such as extremely heavy ice

and high velocity wind.

8�LGJ-500/35 or 8�JL/LB1A-500/35 conductor bun-

dles is selected. The spacing is 400 mm, and the circum

circle diameter of conductor bundles is 1045 mm. The

distance of conductor to ground is 22 m in non-residential

area and 27 m in residential area. 8�LGJ-630/45 conduc-tors are used near the macaque national class natural

protection area at Taihang Mountain.

Ground wire is recommended to be OPGW-175 fiber

optic cable or complete aluminum clad steel ground wire

JLB20A-170.

Waist type tangent support tower is adopted in plain

areas and cup shaped tower in mountainous areas, V type

insulator string is adopted in the middle phase and I type inthe outer phases. The recurrence of the maximum wind

velocity is considered to be once in 100 years, the maxi-

mum designed wind velocity is not lower than 27 m/s at

the level of 10 m above ground.

3) Substations and Switching Station: GIS is adopted in

Jindongnan substation. The rated power of autotransform-

er is 3 � (1000/1000/334) MVA with one standby phase.The autotransformer is single-phase, oil immersed, adopt-

ing neutral VFVV mode. There are five 500 kV outlet lines

and one 1000 kV outlet line. The capacity of the shunt

reactor is 3 � 320 Mvar with one standby phase. The

reactance of the neutral-point reactor is from 245 � to

280 �. At present stage, two groups of low voltage shunt

reactors with capacity of 240 Mvar and three groups of

low voltage shunt capacitors with capacity of 240 Mvarare installed at the tertiary side of UHV transformer.

HGIS is adopted in Nanyang switching station. There are

two 1000 kV outlet lines at present stage. Two groups of 3�320 Mvar shunt reactors are installed with reactors. The

reactance of one group of the neutral point reactor is from

327 � to 370 �, and the other one is from 345 � to 370 �.

Jingmen substation adopts HGIS. The rated power of

autotransformer is also 3 � (1000/1000/334) MVA withone standby phase. The autotransformer is single-phase,

oil immersed, adopting neutral VFVV mode. There are two

500 kV outlet lines and one 1000 kV outlet line. One group

of 3 � 320 Mvar shunt reactors are installed with one

standby phase and one group of neutral point reactors. The

reactance of the neutral-point reactor is from 414 � to

440 �. At present stage, two groups of low voltage shunt



reactors with capacity of 240 Mvar and three groups low

voltage shunt capacitors with capacity of 240 Mvar are

installed at the tertiary side of UHV transformer.

4) Electromagnetic Environment: Large section, multi-

conductor bundles are used in UHV AC test and demons-

tration project, and the control criteria of electromagnetic

environment should be identical with that of 750 kV,

500 kV AC transmission project in China. The controlcriteria are shown in Table 3.

5) Over-Voltage and Insulation Coordination: Over-voltage

levels of 1000 kV AC transmission system are shown in

Table 4.

Clearances distance of phase conductors to tower at

different altitude above sea level and the minimumclearances distance design value of substation in 1000 m

altitude area are shown in Tables 5 and 6 respectively.

The region of Jindongnan-Nanyang-Jingmen transmis-

sion line across is II or III pollution level mostly, and a

small part is IV pollution level.

Specific distance of creepage method and pollution

withstand voltage method are applied to select the disk

number of suspension insulator string at different pollutionregions. 300 kN, 400 kN (420 kN) and 550 kN strength

insulators are mainly selected based on the load of con-

ductors. The assemble configurations include: single I string,

double I string, single V string and double V string, and the

included angle is in the range of 80�–110�. The specific

configuration schemes of suspension insulator string below

1000 m altitude above sea level are given in Table 7 [22].

The disk number of tension insulator string should not

consider self clean ability. The specific configuration

schemes of tension insulator string according to the same

rule of suspension insulator string are shown in Table 8 [22].External insulation of outdoor equipment in substations

(switching station) is designed according to III level pol-

lution standards. The insulation level is given in Table 9.

Over-voltage control measures of 1000 kV AC test and

demonstration project are given as follows:

960/720/720/600 Mvar shunt reactors and neutral

grounding reactors are installed. The application of

Table 3 Electromagnetic Environment Control Criteria of 1000 kV

AC Transmission and Demonstration Project

Table 4 Over-Voltage Level of 1000 kV AC Transmission System

Table 5 Clearances Distance of Phase Conductors to Tower at Different

Altitude Above Sea Level (m)

Table 6 Minimum Clearances Distance Design Value of Substation in

1000 m Altitude Area (m)

Table 7 The Configurations of Suspension Insulator String (Single I String,

Double I String, Single V String and Double V String)

Notes: 1) N is the disk number of insulator strings; H is the spacing

height, mm; Cd is the creepage distance, mm. 2) The disk number of

400 kN (420 kN) and 550 kN insulators are corrected according to the

porcelain part length of 300 kN insulators.



controllable HV reactor is planned in future development.

The maximum secondary current can be limited to below

12 A by using neutral small reactor and the single phase

reclosing intermission time can be controlled within 1 s.Using high performance Metal Oxide Arrester (MOA)

with rated voltage of 828 kV, a configuration of four

parallel blocks. Residual voltage under switching impulse

is U2 kA ¼ 1460 kV, and under lightning impulse is

U2 kA ¼ 1620 kV.

Closing resistance of circuit breaker could be selected

in the range of 400–600 �.

High amplitude VFTO appears on the GIS when GISisolating switches switching on and off short lines. The

VFTO can be limited to about 1000 kV by selecting about

500 � switching on and off resistance.

6) Lightning Performance: Cup-shaped tower, negativeprotection angle, and assembling the third ground wire

within Jindongnan-Nanyang-Jingmen inlet and outlet

segment lines 2 km are proposed; cat head tower is used

and ground wires protection angle is smaller than 4� at

plain area when ground surface slope angle is smaller than

20�; cup-shaped tower is used and ground wires protection

angel is smaller than �2� at mountainous area when

ground surface slope angle is bigger than 20�.At the two terminals near the substation, within 2 km

inlet line, negative shielding angle is selected. CVT and

shunt reactor will use the same group of MOA, and one

group of MOA is installed on either buses.

7) The Basic Technical Parameters of Main Equipment:Some basic technical parameters of autotransformer, shunt

reactor and switchgear are given in Tables 10 [69], [70],

11 and 12, respectively.

B. UHV AC Test Base Design and ConstructionThe UHV AC test base, sponsored by the SGCC,

was laid foundation at WHVRI, Wuhan, China, on

October 10th, 2006; and its occupied area is more than

140 000 m2. The UHV AC test base comprises 35 kV

system, 220 kV system and 1000 kV system, and has a

220 kV transformer (220/35) and a set of three 1000 kV

transformers (3 � 40 MVA, 35=ð1200=ffiffiffi

3pÞ, single phase,

double winding autotransformer) made by TBEA

(Shenyang), TWBB (Baoding), and XDXB (Xi’an) respec-tively, and the highest voltage can be up to 1200 kV [80], [81].

Table 8 The Configurations of Tension Insulator String

Notes: 1) N is the disk number of insulator string; Sd is the specific distance

of creepage, mm; Cd is the creepage distance, mm. 2) The values at left of

symbol B/[ are the disk number of insulator string at 1000 m altitude

above sea level, and the values at right of symbol B/[ are the disk number

of insulator string at 1500 m altitude above sea level in pollution region III

and IV.

Table 9 Insulation Level of 1000 kV UHV AC Equipment (kV)

Table 10 Parameters of 1000 kV Autotransformer

Table 11 Parameters of 1000 kV Shunt Reactor



The test base has the capability of 1000 kV substationstructure optimization design, transmission line optimiza-

tion design, electromagnetic environment research and

transmission line operation technology research etc.

The prophase of UHV AC test base has been finished.

1) Parameters and Functions of UHV AC Test Base MainParts: The UHV AC test base mainly comprises 1000 kV AC

single circuit and double-circuit on the same tower testlines, electromagnetic environment laboratory, artifical

environment climate laboratory, and electrical live exam-

ination test yard, UHV corona test cage.

a) UHV AC test lines: The UHV AC test base has a

single circuit 1000 kV AC and a double-circuit on the same

tower 1000 kV AC test lines (Fig. 7); both of the lines

are about 1000 m long. Test lines include the towerconfiguration with single circuit horizontal (for triangle)

and double-circuit vertical configurations. And the lines

have the capability of research on corona performance,

electromagnetic environmental effect, live line working

and characteristics of insulators pollution for UHV lines.

The configuration of tower is tension towerVstraight

towerVstraight tower-tension tower. The conductors’ load

of single circuit test line is designed according to 8�LGJ-630/55, and the tower is designed according to cat head

tower with IVI insulator strings, and now 8�LGJ-500/35

conductors are hung. The conductors load of double-

circuit on the same tower test line is designed according

to 8�LGJ-800/55, and the tower is designed according to

drum type tower, and now 8�LGJ-630/55 conductors are

hung, and 8�LGJ-800/55 conductors could be hung

later. Different section conductors’ electromagneticenvironment and other tests can be carried out [82].

The different phase distance test can be carried out by

using test lines. The I type insulator string can be hung as

normal case, besides, the hanging point position can be

altered þ1 m, þ2 m, �1 m and �2 m respectively. I type

insulator string can also be modeled by changing the

hanging points’ positions, and can satisfy the requirement

of single circuit line with 3V insulator strings anddouble-circuit line with 6V insulator strings respectively.

The distance of conductors and ground surface can be

adjusted by adjusting the length of connection hardware

fittings as well as the length of suspension insulator string.

Hence, electromagnetic environment at different distance

of conductors and ground surface can be carried out [82].

Porcelain, glass and composite insulators are used in

the test lines to examine the operating performance ofdifferent type insulators. 210 kN, 300 kN, 420 kN and

550 kN strength class composite insulators are used; the

disk number of porcelain and glass insulator string is in

the range of 44–62 based on the spacing (170–240 mm)

of insulators; and the number is 44 for 550 kN, 52 for

420 kN, 54 for 400 kN and 62 for 210 kN respectively.

The 1000 kV single circuit test line section was ener-

gized on February 13th, 2007. Then, the electromagneticenvironment parameters of single circuit test line section

and inside substation under light rain were measured on

March 18th, 2007. The measured data indicate that RI

level is in the range of 54–55 dB ð�V/mÞ in fine weather,

and audible noise is in the range of 39–41 dB (A) at 20 m

far away from the single circuit line side phase projection;

and that is 65–67 dB ð�V/mÞ and 53 dB (A) in rain

weather respectively, these are approximately the same asthe research results of UHV AC prophase scientific

research [22], [83].

The 1000 kV double-circuit on the same tower test line

section was energized on June 15th, 2007. The research of

UHV base substation noise level and its improve measures

was carried out. Scientific researchers preliminarily

achieved the practical level of UHV transmission and

Table 12 Parameters of 1100 kV AC Switchgear

Fig. 7. Single and double-circuit test line sections of

UHV AC test base at WHVRI.



transformation electromagnetic environment. The selec-tion of line conductors, substation bus bar and the con-

nection type were confirmed.

b) Electromagnetic environment laboratory: Electro-

magnetic environment laboratory includes a 200 m2

(shielding room is 60 m2) measuring and observing labo-

ratory and a 120 m � 50 m test field. Research of elec-

tromagnetic environmental parameters measurement in

full weather conditions, corona and electromagnetic com-patibility research for UHV lines can be carried out.

c) Environment climate laboratory: Environment cli-

mate laboratory includes a net dimension of �20 m� 25 m

artificial climate chamber (Fig. 8), a 1000 m2 measuring

and controlling and auxiliary rooms, and has 1500 kV AC

and �1000 kV DC power supply. Pollution test, middle and

short gap discharge test, flashover test of icing and ice-

melting insulator string etc. can be carried out undersimulated complex climates and low atmospheric pressure

of high altitude up to 5500 m and low temperature down

to �19�C.

The long insulator string icing flashover tests have been

carried out in the laboratory.

d) Electrical live examination test field: The electrical

strength test of all kind of UHV AC equipment can be carried

out at the electrical live examination test field (Fig. 9).e) Corona test cage: The UHV corona test cage is a rigid

two layer cage, its section is 8 m� 8 m, and its length is 35 m.

The AC voltage can be up to 1500 kV [84]. It has the capability

of testing UHV AC transmission line corona performance and

electromagnetic environment, the AN, RI, and corona loss

with different section, spacing, and 1–12 bundled conductors.

Spray system is equipped and corona performance under

different rain conditions can be carried out.

2) Thirteen World Records of UHV AC Test Base: The UHV

AC test base has thirteen world records aspects:1) the geometrical size adjustability and the optimal

designing and testing capability for UHV test line;

2) the test conditions for the electromagnetic envi-

ronment measurement of single circuit and double-

circuit on the same tower line at the same time;

3) the test conditions of external insulation char-

acteristics under the simulated 5500 m altitude;

4) the pollution test capability of UHV AC full-scaleinsulator strings;

5) the flashover test capability of the icing and ice

melting of UHV long string insulators;

6) the full voltage and full current live examination

field of UHV GIS, HGIS, and AIS equipment;

7) 1000 kV/8 kA SF6 inductive-type up flow

equipment;

8) the voltage level and uncertainty measurement of1000 kV standard voltage transformer;

9) the voltage level and capacity of power frequency

harmonic test devices;

10) the comprehensive parameters and on line moni-

toring function of lightning, pollution, icing and

vibration of test lines;

11) the comprehensive training function and condition

of UHV operation, inspection and live working;12) the full weather electromagnetic environment

monitoring system;

13) the only one 10 m method anechoic chamber that

has EHV power supply in the world.

As an important part of UHV AC transmission demon-

stration project, the research work of UHV AC transmis-

sion and transformation project’s scientific research,

construction and operation will be carried out systemat-ically and comprehensively at UHV AC test base.

VI. UHV DC DESIGN AND TEST SYSTEMS

UHV DC test and demonstration transmission lines design

and construction, UHV DC test bases design and con-struction are introduced in this section.

The technical problems of �800 kV UHV DC power

transmission projects, including the problems of over-voltageFig. 8. Artificial climate laboratory.

Fig. 9. Structural frame of electrical live examination test field.



and insulation, external insulation characteristics, electro-magnetic environment, the UHV equipment manufacture

and test are still not solved well.

UHV DC demonstration lines and test bases are the

first several UHV DC transmission and transformation

projects in China. These lines have the abilities to validate

the prophase research achievements in China, the per-

formance and reliability of the transmission and transfor-

mation equipment, improve the power equipment level inChina. The demonstration lines have the functions of

demonstration, test and commercial operation.

The UHV DC test bases can offer the UHV DC demon-

stration projects first class test and measurement platform.

The UHV DC key technologies research achievements can

be directly used in the construction of UHV DC test bases,

hence, the former research achievements can be validated,

the UHV equipment can be applied and tested, the re-search achievements can be further completed with the

application of equipment in test bases [79], [80].

Yunnan-Guangdong, Sichuan-Shanghai and Sichuan-

Jiangsu�800 kV UHV DC transmission demonstration lines

are being built by CSG and SGCC respectively [85]–[89].

A. Yunnan-Guangdong UHV DC TransmissionDemonstration Line

Yunnan-Guangdong �800 kV DC transmission dem-

onstration line, sponsored by CSG, which is the first

�800 kV DC transmission project, was laid foundation on

December 19th, 2006, Yunnan, China, and started the

construction on March 25th, 2008, The unipolar opera-

tion will be started in 2009, and the bipolar operation

will be started in 2010 [85], [86].

1) The Output Scale and Scheme of the Project: The first

UHV DC transmission demonstration line begins from

Yunnan Chuxiong converter station and ends at

Guangdong Suidong converter station, and the transmis-

sion distance is 1438 km. The rated voltage is �800 kV,

DC rated current is 3125 A, and the proposed capacity is

5.0 GW [89]. This project has seven outlet lines, three lines

to Xiaowan hydro-power station, two lines to Jinanqiaohydro-power station, and two lines to Kunxibei substation.

Hence, this line could meet the power transmission of

Xiaowan, Jinanqiao and other large hydro-power stations.

At receiving end, Suidong converter station is � type

connection with 500 kV AC Zengcheng-Hengli double-

circuit on the same tower line, and two 500 kV AC lines to

Yongxiang substation will be built, AC main transformer

and 220 kV outlet line are also reserved [85], [86].

2) Some Technical Parameters: The scheme of (400 kV þ400 kV) doubles 12-pulse converters in series is used at

sending end and receiving end valves group. 36 converter

transformers with rated voltage�600 kV, and 12 converter

transformers near polar bus with rated voltage �800 kV are

used, and 8 converter transformers are reserved.

Dry-type smoothing reactors are used in this project,and 2 smoothing reactors are a group in series, are equipped

at polar bus of each pole and neutral line respectively.

The valve transformer side bushing and DC wall bush-

ing are mainly depended on the techniques of ABB and

SIEMENS.

B. Sichuan-Shanghai UHV DC TransmissionDemonstration Line

Sichuan-Shanghai �800 kV DC transmission demon-

stration line, sponsored by SGCC, which is the second

�800 kV DC transmission project in China, was laid

foundation on May 21st, 2007, Shanghai, China, and

started the construction on December 21st, 2007, the uni-

polar operation will be started in 2011, bipolar operation

will be started in 2012.

1) The Output Scale and Scheme of the Project: Phase I of

the Jinsha River hydro-power send out project at the

lower reaches of the Jinsha River consists of three bi-

polar UHV DC transmission lines, and rated voltage of

each line is �800 kV. The proposed capacity is 6.4 GW,

and the actual transmission capacity is anticipated to

reach 7.0 GW [89].

The demonstration project is being built to transmitpower from Xiangjiaba hydro-power station, the lowest

power station in Jinsha River lower reaches, to East China,

begins from Sichuan Fulong converter station and ends at

Shanghai Fengxian converter station, and the transmission

distance is about 2034 km.

2) Line External Insulation Design of the Project: The

demonstration project passes across many heavy icingregions such as Wumeng Mountain, Wuling Mountain and

Xuefeng Mountain etc., with complex landform, changing

climates, heavy pollution and heavy icing. The highest

altitude above sea level is about 2300 m. The air gap of

tangent tower with V type insulator string is not less than

6.1 m for �800 kV UHV DC transmission line. The

altitude coefficient of switching impulse flashover voltage

is 1.128 in the area of 2000 m altitude. The number of anti-fog type insulator for single string is not less than 65 units

(I type string) and 56 units (V type string) for single

string in the common pollution area where ESDD is less

than 0.05 mg/cm2. And composite insulators are recom-

mended in the heavy pollution area where ESDD is higher

than 0.1 mg/cm2.

3) Electromagnetic Environment Control Criteria: Thelevel of �800 kV DC transmission line electromagnetic

environment can be limited to the same with that of

operating �500 kV DC transmission project in China by

using large cross-section, multiple-conductor bundles and

increasing the distance of conductor to ground surface.

The control criteria of the �800 kV DC transmission

demonstration line is shown in Table 13.



4) Thyristor and Converter Valve: 6 inch thyristor is pro-

posed to be used in the demonstration line. The research

and development of 6 inch thyristors is of technical andeconomical significance with respect to �800 kV, 6.4 GW

HVDC technologies. Compared with 5 inch thyristor,

6 inch ones have improved short circuit current capa-

bility, which is beneficial to the optimization of HVDC

systems. 6 inch thyristors also have large overload capa-

bility, which can increase the transmission capacity. In

addition, the wider heat-dissipation area is favored to the

design of the cooling systems as well as the stability,reliability, and security of multiple DC lines operating in

parallel. Other advantages include reducing numbers of

thyristors, simplifying valve structure, improving aseis-

matic capability and decreasing valve losses.

Double valves or quadruple valves, which are air insu-

lated, water cooled, are proposed to be applied for the

demonstration line. Each single valve of the 6 inch

thyristor valves has 3 layers, each layer has 60 thyristorconnected in series, with 3 thyristors in redundancy. The

valve margins for switching, lightning and steep front

surge wave are 10%, 10%, 15% respectively.

5) Design of Shared Ground Electrode: The three�800 kV

DC converter stations at output side of Jinsha River are20–40 km apart from each other. The selection of three

ground electrode sites is difficult. Hence, the scheme of

three converter stations sharing ground electrode is pro-

posed after study. Its influence on the safety and reliability

of UHV DC transmission system can be reduced by the

correct selecting of the electrode sites and good design of

the ground electrodes.

The ground electrode lays multi-circles in plane. Thethree UHV DC converter stations share one or two ground

electrodes, which can save about 50 million yuan RMB for

the projects. The design principles of the shared ground

electrode are: the temperature rise is calculated with the

injection current of 4080 A, the step voltage is calculated

with the injection current of 8040 A, and the ground

resistance should be less than 0.6 �.

6) Technical Parameters of Main Equipment: The basictechnical parameters of converter transformer, dry-type

smoothing reactor and converter valve of the demonstra-

tion line are given in Tables 14, 15, and 16, respectively.

7) Eighteen World Records: Sichuan-Shanghai �800 kV

DC demonstration line will have eighteen world records

aspects when its construction is completed:

1) the highest voltage level (�800 kV), the largestrated transmission capacity (6.4 GW), and the

maximum transmission capacity can be 7.0 GW;

2) the largest rated current (4000 A);

3) the longest transmission distance (about 2000 km);

Table 14 Parameters of Converter TransformerTable 13 Electromagnetic Environment Control Criteria of

�800 kV DC Project

Table 15 Parameters of Dry-Type Smoothing Reactor

Table 16 Parameters of Converter Valve



4) the largest unit corridor transmission capability(more than 0.084 GW/m);

5) the highest reliability specification, unipolar out-

rage rate is 2 times/pole � year, bipolar outrage

rate is 0.05 time/year;

6) the lowest transmission loss of unit transmission

capacity � km;

7) the lowest operation and maintenance cost of

unit transmission capacity � km;8) the lowest construction cost of unit transmission

capacity � km;

9) the lowest unit capacity inversion cost converter

station;

10) the least unit capacity inversion occupied area

converter station;

11) the lowest unit capacity inversion loss converter

station;12) the lowest unit capacity inversion operation and

maintenance cost converter station;

13) the largest capacity converter (about 1.75 GW);

14) the first use of electric-triggered 6 inch thyristor;

15) the highest voltage level and single largest capacity

converter transformer (�800 kV, 321.1 MVA);

16) the highest voltage level and the largest rated

current smoothing reactor (�800 kV, 4292 A);17) the first use of three converter stations shared

ground electrodes, the cost is the least;

18) largest rated current ground electrode.

C. Sichuan-Jiangsu UHV DC Transmission LineSichuan-Jiangsu �800 kV DC transmission line

sponsored by SGCC, China, starts from Xichang City,

Sichuang province, ends at Suzhou City, Jiangsu province,which will be the third �800 kV DC transmission project

in China. The transmission capacity is 7.2 GW, and the

transmission distance is about 2095.5 km. This UHV DC

transmission line will be the largest transmission capacity

and longest transmission distance in the world.

This line will use 900 mm2 large section conductors,

the technical parameters were promulgated on June 10th,

2008 by SGCC. It was reported that the use of this typeconductors can reduce corona loss, reduce the horizontal

wind load, reduce the icing horizontal and vertical loads,

and can also reduce the tower weight.

The operation of this line will also be started in 2011.

D. SGCC UHV DC Test BaseThe key technique researches of UHV DC relying on

the UHV DC test base [90], [92].The UHV DC test base, sponsored by the SGCC, was

laid foundation at CEPRI, Beijing, China, on August 10th,

2006; and its occupied area is about 8 hectare. The test

line section of UHV DC test base was completely energized

on June 28th, 2007; and four types of tests were carried

out at UHV DC test base and a series of test data reports

were submitted to SGCC on June 29th, 2007. The voltage

of test line was boosted to�1100 kV on August 16th, 2007,and that was boosted to �1200 kV on September 12th,

2007 successfully. The air clearance of �1100 kV DC

transmission simulated tower window breakdown test was

also successfully carried out with 2400 kV switching

impulse voltage on September 12th, 2007, and the test was

the first creativity in the world.

1) Parameters and Functions of UHV DC Test Base MainParts: The UHV DC test base comprises following parts:

UHV DC test line, outdoor test yard, testing hall, corona

cage, pollution and environment laboratory, electromag-

netic environment simulation yard, arrester and insulator

laboratory [90]–[92].

a) UHV DC test line: The length of UHV DC test line

(Fig. 10) is 1084 m, which is the longest double-circuit test

line in the world, and the test line has 6 towers, includingone terminal tower, one polarity converting tower, two

gantry towers and one anchor tower. The height of gantry

tower is 88 m, and its width is 80 m, it has two layer

adjustable crossbeams, and the test conductors can be

adjusted at horizontal and vertical direction [93].

The UHV DC test line has three spans, and the length

of middle measured span is 300 m. The rated voltage of

DC voltage generator is �1200 kV, and the rated currentis 0.5 A, which is the highest voltage level of DC voltage

generator in China and which could supply bipolar direct

voltage. Three kinds of tower for special use are used at

the origin of the test line, all the tower height is up to

70 m, and the number of the test connection scheme is

more than ten with combination use of three kinds of

tower according to the requirement.

The UHV DC test line can be used to test the elec-tromagnetic environment of double-circuit on the same

tower transmission line, and the highest voltage level can

be up to �1200 kV (Fig. 11). The electromagnetic envi-

ronment test of corona performance, total electric field

intensity, ion current density, RI and AN can be ana-

lyzed. If AC power supply is installed, the research of

Fig. 10. Double-circuit on the same tower test line section of

UHV DC test base at CEPRI.



electromagnetic environment of single circuit AC trans-mission line with horizontal arrangement and triangle

arrangement could be realized. In addition, compact

circuit could also be carried out.

b) Outdoor test yard: The length of the outdoor test

yard is 180 m, and the width is 90 m. Outdoor test yard

occupied area is about 25 km2. The working area of out-

door test yard consists of three parts: impulse and DC test

area, equipment electrical live examination test area andelectromagnetic environment test area. The main equip-

ment consist of a 7.2 MV/480 kJ impulse voltage generator

which includes 24 steps, and the voltage of each step is

300 kV; a 7.2 MV impulse voltage divider (Fig. 12), capa-

citance is 400 pF, which is the first voltage level in the

world, and a 1600 kV DC voltage generator.

There are one gantry tower and two tension tower inthe test yard. The vertical clearance of gantry tower is

60 m, span clearance is 50 m. There are three suspension

points whose suspending weight is 12 ton. It can be used

for suspension and tension insulator string test. The ten-

sion tower, whose height is 45 m, is used for experimental

study about tension insulator string.

Lightning and switching impulse voltage test of DC

insulator string and air gap, live-line working test, light-ning, switching and DC voltage withstand test research to

large-size DC equipment etc. can be carried out at UHV

DC outdoor test yard.

c) Testing hall: The net dimension of the testing hall

is 90 m� 62 m� 50 m, and the electromagnetic shield-

ing effectiveness is 70 dB (0.5 � 1.6 MHz).

The main equipment include: 2 � 750 kV power fre-

quency cascade transformer; �1800 kV DC voltage gen-erator; 6 MV power frequency cascade test transformer.

The electrical performance test of �800 kV DC equip-

ment, such as lighting and switching impulse voltage test,

AC and DC voltage withstand test, partial discharge, visible

corona and RI test. Lightning mechanism and lightning

protection new technology research can be carried out in

the testing hall.

d) Corona cage: The cage is the biggest corona cagein the world, with the size of 70 m long, 22 m wide, and

13 m high [92], and its test voltage can be up to �1200 kV.

Research of UHV DC unipolar and bipolar conductors

corona performance can be carried out in the corona cage,

including RI, AN and corona loss, etc. The cage is equipped

with raining system and spray system; hence it can

simulate the natural conditions such as fog, drizzle,

moderate rain, and downpour [94].e) Pollution and environment laboratory: The pollution

and environment laboratory includes a net dimension of

�20 m� 25 m pollution, icing and low air pressure multi-

function laboratory and a net dimension of 6 m� 6 m �10 m small fog chamber.

The main equipment consists of: 800 kV/6 A test trans-

former;�1000 kV/2A DC voltage generator;�200 kV DC

power supply and other auxiliary equipment.Artificial pollution test, raining test, icing and

corona test for �800 kV insulator and bushing under

normal and low air pressure can be carried out in this

laboratory.

f) Electromagnetic environment simulation yard: The

occupied area of the electromagnetic environment simu-

lation yard is 90 m � 60 m.

The main equipment consists of: a �300 kV/2A DCvoltage generator; a 330 kV three-phase AC transformer;

AC and DC test line sections.

Electromagnetic environment of UHV DC, AC, AC and

DC in the same corridor research can be carried out in the

simulation yard.

The conductor arrangements include: DC polar

conductors can be horizontal and vertical arrangement

Fig. 11. Origin of the test line.

Fig. 12. 7.2 MV/480 kJ impulse voltage generators (left);

7.2 MV impulse voltage divider (right).



for single circuit line and horizontal arrangement fordouble-circuit line. When the AC and DC lines are in the

same corridor, DC polar conductors can be horizontal and

vertical arrangement for single circuit line and horizontal

arrangement for double-circuit line, AC line can be

horizontal and vertical triangle for single circuit and

horizontal arrangement for double-circuit line.

g) Arrester laboratory: The dimension of the arrester

laboratory is 45 m� 30 m� 15 m.The main equipment include: 1/10, 8/20, 4/10, and

30/60 �s impulse current generator; 2 ms square wave

current generator; 4800 kVA/10 kV power frequency

voltage withstand characteristic test equipment; DC back-

to-back aging test equipment; 15 kV accelerated aging

test equipment; 20 kA whole branch residual voltage and

shunt current characteristic test equipment.

ZnO elements, UHV AC and DC arrester research canbe carried out in the arrester laboratory.

h) Insulator laboratory: The dimension of the

insulator laboratory is 45 m� 30 m� 15 m.

The main equipment include: 1200 kV steep front im-

pulse voltage generator; 500 kV power frequency test

transformer; 600 kN thermo mechanical test equipment;

2000 kN, 15 m horizontal type tension machine;

700 kN �m, 14 m flexural-torsional test machine; com-posite integrated mechanical devices; temperature cycling

test equipment; physicochemical test equipment.

Electromechanical performance of porcelain, glass and

composite insulators and bushing can be carried out in

insulator laboratory.

2) Fifteen World Records of UHV DC Test Base: The UHV

DC test base has fifteen aspects of world records:1) UHV DC test line section is 900 m, and the

length is the longest one in the world;

2) the voltage level of UHV DC double-circuit on

the same tower test line is;

3) the EHV/UHV all voltage levels DC test line

section with the widest regulated range of con-

figuration and electrical parameters;

4) the synthetical performance of impulse, powerfrequency and DC test equipment in the testing

hall;

5) electromagnetic shielding performance of same

scale test hall in the world;

6) the artificial environment chamber of pollution,

icing, raining and lower atmospheric pressure,

laboratory;

7) the test ability of the 7.2 MV impulse voltagegenerator;

8) the test ability of DC and impulse voltage combi-

nation for external insulation;

9) the cage is one of the biggest corona cages in the

world;

10) the entire branch arrester lightning impulse resid-

ual voltage test capability of arrester laboratory;

11) the accelerated aging test capability of arresterlaboratory;

12) the ability of UHV DC electromagnetic environ-

ment testing;

13) the ability of UHV AC and DC external insulation

testing;

14) the large electro-hydraulic servo crankle ma-

chine, thermo-mechanic test equipment and

measurement and control system of insulatorlaboratory;

15) the synthetical test capability of UHV DC test base.

As one of the most important parts of UHV DC trans-

mission demonstration project, the research work of UHV

DC transmission and transformation project’s scientific

research, construction and operation will be carried out

systematically and comprehensively at UHV DC test base.

E. CSG UHV DC Test BaseIn order to meet the electromagnetic environment,

internal and external insulation test requirement of high

altitude, icing and heavy pollution characteristics of

southwest China hydro-power send out transmission and

transformation projects, a UHV test base, sponsored by

CSG, was laid foundation on January 3rd, 2008, which is

under construction at about 2100 m high altitudeSongming county, Kunming city, Yunnan Province. This

base will be the highest altitude above sea level in the

world.

The prophase of this UHV test base project construct

�800 kV DC test facilities comprises four parts: UHV DC

and outdoor impulse test yard, UHV DC test line and

electromagnetic environment test yard, UHV pollution

and icing laboratory, UHV equipment long time live-linetest yard. And has the capability of �800 kV DC equip-

ment lightning and switching impulse voltage test, total

electric field intensity, ion current density etc.

The anaphase project of this test base will also install

1000 kV AC test facilities.

VII. STATE GRID SIMULATIONCENTER CONSTRUCTION

The state grid simulation center, sponsored by the SGCC,

laid foundation at CEPRI, Beijing, China, on October 16th,

2006. The construction area of the state grid simulation

center is about 61 km2.

The state grid simulation center consists of three

laboratories: Power System Digital and Analogical Hybrid

Simulation Laboratory, Power System Dynamic SimulationLaboratory, Power System Operation Simulation and

Security Monitoring Laboratory. With the largest scale

power system simulation equipments in Asia, the new state

grid simulation center of SGCC will provide a simulation

research platform for UHV power grid, international power

transmission and other important projects, as well as safety

and stability analysis of large scale power system.



The state grid simulation center will have five aspectsworld records when its construction is completed:

1) the simulation technology level;

2) the scale of simulation system;

3) digital and analogical simulation of backbone na-

tional grid can be carried out, and the simulation

and test ability of large scale power system;

4) the UHV system protection and automatic equip-

ment test can be carried out, and the powersystem dynamic simulation capability;

5) the dynamic security prewarning demonstration

system of large scale power system will be built,

and the simulation capability of power system

operation and control.

VIII . OTHER RELEVANT ACTIVITIES

Some activities relevant UHV transmission and transfor-

mation research in China recent years are shown as below.

A. 2006 International Conference of UHVTransmission Technology

From November 27th to 29th 2006, more than 350

representatives from electric utilities, research institutes,

consulting companies, associations, universities, financialorganizations and equipment manufacturing enterprises

from 19 countries and regions attended 2006 International

Conference of UHV Transmission Technology in Beijing.

The representatives conducted in-depth discussion con-

cerning the challenges faced by electric power industry,

studied the goal and orientation of the electric grid devel-

opment, and exchanged the research result of the UHV

power transmission technology.This conference provides the attendees a valuable op-

portunity to strengthen international cooperation for pro-

moting the more rapid and better development of world’s

UHV transmission. Tackle the key technical obstacles and

promote the rapid development of UHV transmission

technology.

Setting up a communication mechanism for UHV

transmission technology, sharing the experience andknowledge, promoting the research and application of

the UHV transmission technology and dealing with the

challenges faced by the sustainable development of electric

power industry in the new century was proposed.

B. International Symposium on InternationalStandards for Ultra High VoltageTransmission and Transformation

From July 18th to 21st, 2007, more than 320 repre-

sentatives from utilities, transmission system planners and

operators, contractors, equipment manufacturers, transmis-

sion design engineers, research and test laboratories, gov-

ernment regulators and universities from 19 countries and

regions attended 2007 International Symposium on Inter-

national Standards for Ultra High Voltage, Beijing, China.

The symposium was organized by IEC (InternationalElectrotechnical Commission) and CIGRE, hosted by

Chinese national committee of IEC, Chinese national

committee of CIGRE, SGCC, China Electricity council to

discuss the UHV transmission technical development ap-

proach, engineering application of UHV transmission, and

the technical and safety specifications for UHV Standards.

The leading experts joined together to develop

international standards for UHV AC and DC technologyto ensure the safe and efficient use of this technology. All

the experts conducted an in-depth and extensive discus-

sion on the standardization problems, including aspects of

environment, safety, efficiency, etc. The consensus was

reached that the UHV AC and DC technology should be

more mature and to meet the requirement of market, then

forward to international standardization. With the devel-

opment of UHV AC and DC technology in China, India,Brazil, Japan and South Africa, it is necessary to build the

UHV AC and DC technology international standards. At

present, the most chief task is to solve the international

standardization problem of 1100 kV AC system and

�800 kV DC system. All the experts believed that one

special technical committee or working group should be

established to charge for the build of UHV AC and DC

standards.UHV AC and DC standard system was proposed by

CEPRI, China, by combining the development of UHV AC

and DC technology in China and analyzing the standards

built by IEC. The proposed standard system has general

standards, design standards, equipment standards, con-

struction standards, operation and maintenance standards.

IX. FUTURE PROSPECTS OFUHV TRANSMISSION IN CHINA

China developments UHV AC and DC transmission and

transformation for: long-distance transportation of electric

power from remote hydro or thermal electric power bases

to load centers; overlay on an existing EHV transmission

network; and interconnection with another strong power

system.SGCC, the largest electric power provider in China,

will first build a 1000 kV transmission network covering

North and Central China, and then expand it to East

China. SGCC also plans to construct three �800 kV UHV

DC projects for Xiluodu and Xiangjiaba hydro power

station in southwest China, in which two circuits go to East

China and one to central China, the transmission capacity

of each project is 6.4 GW, and it will be available from2011 to 2016; �800 kV UHV DC project from Jingping

hydro power station in southwest China to East China, the

transmission capacity is 6400MW, and it will be available

around 2013; �800 kV UHV DC project for Hulunbeier

coal base, in which one circuit go to Liaoning province in

North-East China, and another to North China, the

transmission capacity of each project is 6.4 GW, and it



will be available from 2015 to 2020. Then the UHV AC andDC hybrid grid that connects the various power source

bases and main load centers is formed. By that time, the

transmission capacity of the AC and DC hybrid system of

UHV grid will be over 200 GW [95], [96].

CSG plans to build two �800 kV UHV DC projects to

transmit the electric power from Yunnan Province to

Guangdong Province, China. The transmission distance is

1438 km and 1500 km respectively; the transmissioncapacity is 5 GW. Five 1000 kV AC transmission projects

will also be built from northwest of Yunnan Province to

Guangdong Province via Guizhou Province, Guangxi

Province by 2030, and the transmission distance is in the

range of 1600–1800 km [95]–[97].

In order to ensure the safe and reliable operation of the

UHV AC and DC transmission and transformation projects,

some design, equipment manufacture, operation and main-tenance technologies on UHV AC and DC transmission and

transformation are necessary to be further studied before

the transmission projects are in operation. Especially the

control and protection of wide area power system.

The control of large scale UHV AC and DC hybrid

power grid is very important [98]–[102]. The require-

ments that the AC channel can take in hand the power

transfer during the period of DC channel fault, DC systemcan be in safe and reliable operation after removing fault at

sending and receiving end, the safe and reliable operation

of multi-terminal DC system should be satisfied.

In China, the dominant oscillation frequency of State

Grid is about 0.15 Hz at present [99]. Weak damping has

become the primary bottleneck limiting the enhancement

of power transfer capabilities [99], [100]. With the devel-

opments and interconnections of regional power gridsafter the UHV AC and DC grid is come into being, the

system scale and inertia increases, and oscillation frequen-

cies of inter-area modes become lower, that is very

dangerous for the safe and reliable operation of power

system, hence power system stability research and con-

troller research is in urgently need of [100]–[102].

Some rare power system failures-blackouts become

catastrophes with severe long-term consequences for thenational economies and population. Recent blackouts in

North America, Europe, Russia, and other countries

require specialists once again to pay closer attention to

the blackout phenomenon [103], [104]. The reasons for

blackout may be conductor contacts with trees, inability of

system operators to visualize events on the system, failure

to operate within known safe limits, ineffective opera-

tional communications and coordination, inadequatetraining of operators to recognize and respond to system

emergencies, and inadequate reactive power resources.Hence, the philosophy of preventing blackouts should be

based on dispatching personnel training, wide area system

visibility, and better computer models for the analysis of

the stability and security of power systems.

X. CONCLUSION

The recent year’s developments and current status ofUHV AC and DC transmission in China are introduced in

this paper. As demonstrated in the preceding sections of

this paper, many achievements have been achieved in

China in the fields of UHV AC and DC key technologies.

Such as fundamental research, system planning, equip-

ment manufacture, equipment performance test, design

and construction of AC and DC test bases, design and

construction of AC and DC demonstration lines, etc.As a new technology for huge capacity and low loss

transmission over long distances, UHV transmission is

indispensable for the power system with a very extensive

service area and bulk power delivery in China in the

future.

The practice of UHV transmission are very necessary;

the safety, economy, reliability and effects on environment

are all needed to be further studied via UHV AC and DCdemonstration projects. The future operating experiences

and test results of demonstration lines, test results of UHV

AC and DC test bases, practical situation in China should

be considered together to decide the future design,

operation and maintenance of UHV AC and DC transmis-

sion and transformation projects.

The research and development of UHV AC and DC

transmission and transformation projects will promote thesustainable development of China’s electric power and energy

industry. Moreover, it will also have an active and far-

reaching influence on the innovation and technology to global

power grid. This stresses that the electrical power industry

faces common global problems and that a global effort,

cooperation, and exchange of the best practices is needed. h

Acknowledgment

The authors gratefully acknowledge the contributions

of SGCC, CSG, WHVRI of SGCC, CEPRI of SGCC, EPCRI

of SGCC, and some UHV equipment manufacturers for the

technical information on their websites. The authors cited

some of the original materials on the websites in preparing

for this paper.

The authors also gratefully acknowledge the CIGRE forsupplying WG 31.04 and WG 38.04 reports freely.

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ABOUT T HE AUTHO RS

Daochun Huang (Student Member, IEEE) was

born in Heilongjiang Province, China in 1976. He

received the B.S. degree from School of Electrical

Engineering, Wuhan University in 2003. Currently,

he is pursuing the Ph.D. degree in transmission

line external insulation and numerical analysis of

electromagnetic field in School of Electrical Engi-

neering, Wuhan University. His major fields of

interests include external insulation of overhead

transmission lines, numerical analysis of electro-

magnetic field and its application in engineering.

Yinbiao Shu was born in Hebei Province, China in

1958. He received the B.S degree from North China

Electric Power University in 1982, M.S. and Ph.D.

degrees from School of Electrical Engineering,

Wuhan University in 2001 and 2007 respectively.

He worked as a visiting scholar at the university of

Strathclyde, UK, in 1989–1990. He has served in

China National Power Dispatching and Communi-

cation Center (CNPDCC) for almost 20 years.

Before shifting from this center, he was chief

engineer of CNPDCC. After this shifting, he was appointed as director

general of Power Grid Construction Department of State Power

Corporation in 2001. He has served in the area of power grid construction

for more than 3 years before appointed to be the assistant to President of

State Grid Corporation of China (SGCC). Now he is vice president of SGCC

and in charge of the UHV transmission and transformation design and

construction of SGCC, China.

Jiangjun Ruan was born in Zhejiang Province,

China in 1968. He received the B.S. and Ph.D.

degrees in electric machine engineering from

Huazhong University of Science & Technology

(HUST) in 1990 and 1995, respectively, and

finished his post-doctoral research in 1998 from

Wuhan University of Hydraulic & Electric Engi-

neering. He is currently a professor of Wuhan

University, Wuhan, Hubei Province, China. His

research interests include electromagnetic field

numerical simulation, electromagnetic compatibility, high voltage engi-

neering, and power quality.

Yi Hu was born in Hubei Province, China in 1955.

He received the B.S. and M.S. degrees from

Huazhong University of Science & Technology

(HUST) in 1982 and China Electric Power Research

Institute in 1985, respectively. His research inter-

ests include high voltage, transmission and live

line working technologies, and focus on the

research of UHV transmission technology in

recent years. Now he is vice president of State

Grid Electric Power Research institute of SGCC

(former WHVRI). He is also a part-time professor of Wuhan University and

Huazhong University of Science & Technology, Wuhan, Hubei Province,

China.



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