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Impacts of High-voltage Shunt Reactor on 750kV

Line Losses

Li Yang1, Liu Wenying1Department of Electrical and Electronic Engineering,

North China Electric Power University,

Changping District, Beijing, 102206, China

Zheng Jingjing2Electric Power Research Institute of Gan Su,

Lan Zhou, Gan Su, 730000, China

AbstractFor the problem of neglecting the shunt reactor active

power loss in calculation of line losses, this paper includes the

shunt reactor losses in line loss and derives the calculation mode

of line loss that includes the shunt reactor loss. According to the

new model, the paper analyzes the influences of high-voltage

shunt reactor on 750 kV line losses and verifies it through the

emulation. The guidance of reducing the 750kV line loss is

proposed at last.

Keywords-high-voltage shunt reactor; active power loss;

750kV transmission line; operation mode

I. INTRODUCTION

According to the Northwest Power Network developmentplan, the interconnection between Northwest Power Networkand Xinjiang power grid started commissioning in lateOctober, 2010. The Northwest Power Network has formed750kV main grid which connects five provinces power grid. Asthe vast Northwest, many transmission lines are longer than200km, so the problem of reactive power and voltage

controlling is outstanding. In order to solve reactive powerbalance and over-voltage problem, the high-pressure shuntreactors are installed in 750kV line

[1-7]. Because the reactor is

made of metal wire and it will consume large amounts of activepower when it was put into operation. And the resistance in750kV line consumes little active power losses. Compared withthe power network up to 500kV, the high-voltage shuntreactors have greater impacts on line loss in the 750kV voltagelevel. So the impacts of high-voltage shunt reactor on 750kVline losses have important significance.

II. THE ACTIVE POWER LOSS OF THE HIGH-VOLTAGE

SHUNT REACTOR

A.

The improved model includs the active power loss of the

shunt reactor

Before doing research on the impacts of high-voltage shuntreactor on 750 kV line losses, the active power loss of the shuntreactor should be determined at first. In 750kV lines, the wiringdiagram of shunt reactor was shown in Fig.1.

Figure 1. The wiring diagram of shunt reactor

Usually the model only considers the compensatedreactance of the shunt reactor, and neglects the active powerlosses in reactors metal wire. In electric power grid lossescomputing guideline, the calculation formula of shunt reactorsactive power loss is:

jf

=3L KU

P PU

2

N

(1)

LP is the active power loss of shunt reactor, KP is the

active power loss of one-phase reactor in the case of rated

voltage and 75, jfU is the operating voltage of the shunt

reactor, and UN

is the rated voltage of the shunt reactor. To

calculate the loss, the shunt reactor model was improved andshown in Fig.2.

Figure 2. The improved shunt reactor model with the active power loss

Z represents the impedance of the transmitting line, GLrepresents the conductance in shunt reactor that consumesactive power, -jBL represents the part that consumes thereactive power in the form of susceptance in shunt reactor. Sothe active power loss of GL is the active power loss of the

reactor. According to the improved model and formula (1), thefollowing formula can be drawn:

= 3L K

G P U2

N (2)

The rated voltage and rated active losses is stipulated in theJB/T 10779-2007 750KV oil-immersed shunt reactor technical

parameters. So from the formula (2), the conductance of the750kV shunt reactor can be calculated. After calculating thevalue of the conductance, the actual active power losses ofshunt reactor in the improved model is:

978-1-4577-0547-2/12/$31.00 2012 IEEE


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2=L jfP GU (3)

From the formula (3), it can be seen that the active powerloss of the shunt reactor is proportional to the square of linevoltage, and has no direct relationship with the transmission

power in lines. When the reactor in operation, the active powerconsumption is inevitable, the higher the voltage level of thereactor is, the greater the active power loss is.

B. The impacts of shunt reactor on line active power loss

After improving the model of shunt reactor as Fig.2, theconductance of shunt reactor could be calculated by formula(2). So the active power loss of shunt reactor in actualoperation could be calculated according to the formula (3). It issupposed that there is a high-voltage shunt reactor at the end ofthe 750kV line. The voltage and power are shown in Fig.3.

jfU

P jQ+

Figure 3. The voltage and power of 750kV line

The total loss of line and shunt reactor is[8]

:

Z LP P P = +

2 22

jf2

jf

Z

P QR GU

U

+= + (4)

P is the total active power loss of the line and the shunt

reactor, ZP is the active power loss of the 750kV line, P and

Q represent active power and the reactive power of the

transmission line respectively, and RZ is the resistance of the750kV line.

By the formula (4) and under the circumstances that thepower of the transmission line is constant, when the operating

voltage is high, ZP is smaller and LP is greater relatively,

however, when the operating voltage is low, ZP is greater

and LP is smaller relatively. Therefore, it is necessary to find

out the operating voltage that makes the minimum total loss ofthe line and the shunt reactor.

When the power of the transmission line is constant, the

formula can be deduced as follow by the formula (4):2 2

2

jf2

jf

Z

P QP R GU

U

+ = +

( )2 22 ZGR P Q + (5)

According to the formula (5), the voltage could becalculated as follow:

2 2

4jfmin Z

P QU R

G

+= (6)

When the jfminU is calculate as formula (6), the minimum

value of P is ( )2 22 ZGR P Q + , at this time jfminU is

only the minimum value in theory, but in power system, lineoperating voltage must be in the allowed voltage range.

III. SIMULATION AND ANALYSIS OF THE EXAMPLE

The simulation uses the Power System Analysis SoftwarePackage version 6.28 developed by China Electric PowerResearch Institute, and flow calculation package is based onGansu Power Grid five typically operation mode data in 2011.According to the high-voltage reactor parameters in GB/T23753-2009 and JB/T 10779-2007

[9-10], the conductance of the

reactor can be calculated. Then the conductance should beconverted to normalized value and put into the simulation

package.

A. The relationship between the loss of 750kV shunt reactorand the operating voltage

In the simulation, selecting the shunt reactor of the singleline from Pingliang to Qianxian in west to east cross-section,the high-voltage shunt reactor at the end of the Qianxian iscalled Qianxian K1. Under the five typically operation mode in2011, the relationship between the active power loss of K1 andline operating voltage is shown in Table 1.

TABLE I. THE ACTIVE POWER LOSS AND VOLTAGE OF SHUNTREACTOR

Shunt

reactor

Operation

modejfU

kV

LP

MW

2L

jf

PU

S

Qianxian

K1

Winter

heavy load778.24 1.28

2.11E-

06

Winter

light load781.72 1.29

2.11E-

06

Early in

this year776.13 1.27

2.11E-

06

Summer

heavy load775.80 1.27

2.11E-

06

Summer

light load793.71 1.33

2.11E-

06

From table 1, it can be seen that the operating voltage and

the active power losses are different in five operation mode, butthe value of

2

L jfP U is a constant, that is the conductance

of the shunt reactor. So from the data in Table 1, it can beconcluded that the active power loss of the shunt reactor is

proportional to the square of line voltage, and theproportionality coefficient is the conductance G in theimproved model of the shunt reactor.


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B. The influence of line operating voltage on shunt reactors

active power loss

We select the single line from Pingliang to Qianxian at the2011 winter heavy load operation mode. The length of the lineis 173km, the resistance of the line is 2.23516 ohms, and the

conductance of the shunt reactor is 2.1110-6 S. At this

operation mode, the power of this transmission line is 742.484+ j218.263MVA. According to the formula (6), the value of

jfminU is calculated as 892.481kV. However, in actual

operation, the operating voltage of 750kV line can not exceed825kV. So in the allowed voltage range, the suitable voltagethat makes the total loss of the line and the shunt reactorminimum is 825kV. The following table lists the losses of lineand shunt reactor when the transmission power of the line is742.484 + j218.263 MVA and the operating voltage isdifferent.

TABLE II. THE LOSS OF THE SHUNT REACTOR AND THE LINEUNDER DIFFERENT VOLTAGE,

Voltage(kV)Line

loss(MW)

Shunt reactor

loss(MW)

Total

loss(MW)750 2.38 1.19 3.57

775 2.23 1.27 3.50

800 2.09 1.35 3.44

825 1.97 1.44 3.40

From the data in Table 2, it can be seen that the higher theoperating voltage is, the smaller the line loss is, and the largerthe shunt reactor loss is. As the voltage increases, the total lossis decreasing. When the operating voltage is 825kV, the totalloss is the smallest. It is the same with the theoreticalconclusions.

However, the operation voltage can not reach 825 kV in

actual operation. The power system is prone to voltage limitviolation and cause accidents. So the operation voltage should

be enhanced in the appropriate range according to actualoperation. Then the total loss of the line and the shunt reactorwill be reduced.

IV. CONCLUSION

Usually in the calculation model of line loss, it does nottake the shunt reactor active power loss into consideration. Inthis paper, from the point view of the reactor loss, the model ofshunt reactor is changed and the active power loss of shuntreactor is taken into account. So the paper researches theinfluence of high-voltage shunt reactor loss on 750kV line loss.Then the paper proposes that the shunt reactor loss has close

relationship with the line voltage and has no direct relationshipwith the transmission power in line. According to the improvedmodel, the most suitable voltage that makes the total loss of theline and the shunt reactor minimum is given. The simulation of750kV line loss in actual operation verifies correctness of theconclusion. At last, the paper proposes guidance to reduce theloss of the 750kV line.

REFERENCES

[1] Zhang Li, Xu Yuqin, Application and development of shunt reactors inEHV and UHV transmission lines, Electric Power AutomationEquipment, vol. 27, pp. 75-78, 2007.

[2] Kang Zhen, Jiang Chaowei, Application of shunt reactor in 750kV

EHV transmission line, Ningxia Electric Power, vol. 2, pp. 8-10, 2008.[3] Huang Mingliang, Study on Connecting System for Laxiwa

Hydropower Station and Construction Schemes of 750kV NorthwestChina Power Grid, Power system Technology, vol. 29, pp. 20-25, 2005.

[4] Li Bin, Li Yongli, He Jiali, Study on the Performance of ProtectiveRelaying and Shunt Reactors of 750 kV Transmission Line,Automation of Electric Power System, vol. 29, pp. 40-44, 2005.

[5] Li Qingwen, Analysis on Vibration-reduction Measures and Results of750 kV Parallel Reactors, Electric Power Construction, vol. 27, pp. 23-25, 2006.

[6] Pan Xiong, Ding Xinliang, Huang Mingliang, Yang Panfeng,Simulation Analysis on Application of Controllable Reactors in 750 kVNorthwest China Power Grid, Automation of Electric Power System,vol. 31, pp. 104-107, 2007.

[7] Wan Qianyun, Zhao Zhiyong, Wan Ying, Power System Operation

Technology, China Electric Power Press, pp. 127-128, 2007

[8] Chen Heng, Power system steady-state analysis, China Electric PowerPress, pp. 73-75, 2007.

[9] Republic of China Machinery Industry Standard JB/T 10779 - 2007750KV oil-immersed shunt reactor technology parameters, MechanicalIndustry Press,2008.

[10] GB/T 23753-2009 330KV and 500KV oil-immersed shunt reactorparameters and technical requirements, China Standards Press,2009.

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