t155 420 - 550 kv gas-insulated substations brochure gb

GRID

T155420 – 550 kV Gas-insulated Substations

The ALSTOM GRID T155 gas-insulated

switchgear (GIS) is ideal for such applica-

tions on 420 and 550 kV networks.

The T155 derives its extensive benefits from

ALSTOM GRID's active involvement in

SF6 switchgear technology for over 44 years,

during which over 20000 GIS bays have

been sold and installed around the world –

to the entire satisfaction of operators.

The T155 is continuously being upgraded,

reliably achieving all guaranteed ratings and

providing state-of-the-art technology.

Customer benefits

• High operational reliability

• Superior availability

• Excellent accessibility

• Modular design

• Increased compactness

Transmission networks are evolving into Smart Grids, integrating multipleenergy sources, optimising energy efficiency, and providing higher reliability andavailability. Alstom Grid T155 GIS offer solutions to face these new challenges.

Sustained improvements ALSTOM anticipates the new requirements

resulting from changing market conditions

and customer priorities.

Research and development continuously

aims at improving the quality, performance

and reliability of products.

Using internationally recognised KEMA,

CESI and CERDA test laboratories, ALSTOM

closely follows-up technological develop-

ments and contributes to the technological

transformations of the future.

The ALSTOM quality-assurance system is

assessed and certified according to ISO 9001

and EN 29001 standards. It is subject

to unceasing improvements and is considered

an essential management tool throughout

the company.

Machining and manufacturing facilities use

the most modern technologies and ensure

the highest quality levels. From receipt of

order to delivery, thorough production and

engineering-flow planning associated with

computerised data-processing ensures that

deadlines and commitments are fully met.

2

Proven design T155 switchgear, based on its proven and

reliable ancestors, provides key customer

benefits. The main implemented tech-

nologies for enclosures, gaskets, insulators

and conductors have been validated by

several decades of field experience.

Optimal solutionsT155 switchgear is optimally suitable for all

types of single-line diagrams, arrangements,

building dimensions, environments and site

constraints.

All components have been designed to give

the T155 the highest flexibility:

• Individual customer solutions

• Clear and simple layouts

• Minimum space requirements

• Reduced substation construction costs.

Reliable operation The T155's reliability can be attributed to

the following reasons:

• Professional experience and training of all

people involved in the industrial process,

from research and development designers

to site installation supervisors

• Minimum number of components and parts

• Field-proven design principles

• Long-term experience – over 44 years

with GIS and over 50 years with circuit

breaker (CB) spring mechanisms

• ISO 9001 certified quality assurance

system

• Comprehensive development and labora-

tory testing.

Life cycle costs are dropped down to the

lowest.

Short manufacturing, installation and commissioningtimesT155 advanced concepts make it possible to

reduce engineering, manufacturing, instal-

lation and commissioning times. Amongst

other reasons for these time reductions, the

following points deserve mentioning:

• Components and arrangements are highly

standardised, thus reducing engineering

lead times

• Support frames are simply bolted to the

concrete slab or floor by means of clas-

sical anchoring bolts, with no need of

embedded sectional rails, thanks to mini-

mum dynamic stresses

• Very little structural steelwork is neces-

sary

Key system advantages

• Proper sizing of transport units allows

convenient handling

• Most low voltage cables are fitted with

plug-in connectors

• Comprehensive factory tests ensure that

equipment is ready-to-operate.

Accessible componentsThe switchgear arrangement and the loca-

tion of the operating mechanisms (circuit-

breakers, disconnectors and earthing

switches) definitely provide the highest

degree of accessibility, thus bringing many

advantages:

• Safe operation

• Easy servicing with no use of heavy

equipment

• Convenient retrofits, changes and further

extensions

• Short dismantling and equipment adjust-

ment times, thanks to busbar coupling

elements.

AdaptabilityNot only is the T155 the ideal product to

design substations according to any single-

line diagram (single busbar, double busbar,

one circuit-breaker and a half, etc.), but it is

also optimal for gas-insulated modules.

OPTIGIM® T155 gas-insulated modules

enable the creation and/or extension of air-

insulated substations with lower space

requirements, while benefitting from safer

and more reliable gas-insulated switchgear.

The T155 GIS is also suitable for future

modications and extensions, thus optimi-

sing capital costs.

1 Circuit breaker

2 Spring-operated mechanism

3 Disconnector

4 High-speed earthing switch

5 Low-speed earthing switch

6 Current transformer

7 Cable connection

GAS-INSULATED SUBSTATIONS T155

3

Adapted aluminium enclosures Enclosures are made of aluminium alloys,

cast or welded, each material being selec ted

for different reasons:

• Low electrical resistance, which mini-

mises touch voltage, creates an efficient

electromagnetic shielding (return current

and primary current are nearly equal) and

reduces resistive losses

• Non-magnetic behaviour which entails

no magnetic losses

• High resistance to corrosion, making it

unnecessary to paint enclosures and

internal surfaces and ensuring long-term

gas tightness and flange-to-flange con-

tact resistance quality (despite there

being no technical need to do so, external

surfaces are painted regardless, for a

long-lasting attractive look)

• Light weight, which makes handling easy,

minimises static loads and reduces civil

works.

Perfect SF6 sealingThe ALSTOM sealing system uses original

patented gaskets, which actually provide

three concentric seals and ensure that sub-

station’s gas leakage rate is less than

0.5% per year.

Safe insulators Conductors and live parts are fitted to cast

epoxy-resin insulators, made of special

high-quality materials and manufactured

in ALSTOM's own workshops. Optimized

shapes and long creepage distances jointly

ensure the highest long-term voltage with-

stand, within resin and gas.

Components

Adequate SF6 accessories Each SF6 compartment has a filling valve,

moisture absorber, safety pressure relief

valve and a temperature-compensated

density switch or sensor. Density thresholds

can be tested without depressurising the

main gas compartment. Digital monitoring

systems offer valuable solutions for SF6

management and trend analysis.

State-of-the-art circuit breaker Each T155 circuit breaker pole is equipped

with its own spring mechanism. Each

pole contains two breaking chambers. The

chambers use high-performance breaking

technology with an optimum combination

of both puffer and thermal effects. The

use of two interrupting units per pole ensures

full compliance with the IEC's latest and

most stringent standards, even for high-level

ratings such as 550 kV and 63 kA. The

circuit breaker has been fully type-tested

under all operating conditions and conse-

quently can be used for all types of networks

and applications.

Grading capacitors ensure uniform voltage

distribution between the interrupting ele-

ments.

Design, manufacture, assembly and

quality control provide the highest levels of

both mechanical and electrical endurance,

which means that no reconditioning is

required before at least 25 years, under

normal operating conditions.

High quality conductors Connecting conductors are made of tubular

aluminium with high-grade, silver-plated

contacts at the ends. The sliding feature

allows thermal expansion without transmit-

ting mechanical stress to insulators.

Specific design provides ample angular

deflection for easier and shorter assembling

or dismantling operations.

Rated voltage kV 420 – 550

Rated frequency Hz 50/60

Rated lightning impulse withstand voltage kV 1425 – 1550

Rated power frequency withstand voltage kV 650 – 710

Rated current for busbars A up to 6300

or feeders A up to 4000

Rated short time current (3 s) kA up to 63

Rated breaking current kA up to 63

Application Indoor/ Outdoor

Other values on request

Design, manufacturing and testing is per-

formed in accordance with most stringent

international standards, ensuring the

highest mechanical withstand and degree

of safety.

Technical data


4

Superior spring mechanisms

ALSTOM’s experience with circuit breaker

spring mechanisms spans over 70 years

and amounts to more than 90000 units

produced – customers have repeatedly

expressed their deep satisfaction with them.

These mechanisms are called full-spring

mechanisms since they have no pressurised

(hydraulic or pneumatic) driving fluid.

Contrary to hydraulic or pneumatic mecha-

nisms (even when the fluid is used for

transmission only), ALSTOM’s spring

mechanisms are not likely to leak, they

forever store their energy and do not prema-

turely age due to frequent motor starts and

pressure top-ups. Operation times do not

depend on temperature and pressure, thus

making the right use of synchronising relays

(see below). The use of a spring mechanism

at such voltages and ratings is only possible

due to ALSTOM's long-term experience in

the fields of spring-operated mechanisms

and circuit breakers.

Control of switching surgesDepending on overhead line (OHL) para-

meters and network ratings, OHL switching

surges may be mitigated by using one or

several of the following means:

• Synchronising relay

• Additional surge arresters

• Insertion closing resistor.

For reactor switching, a synchronising relay

may be associated with the mandatory

surge arresters required for protection of

this sensitive equipment.

Thanks to its spring mechanism, the T155

circuit breaker features perfect timing

stability, a pre-requisite to its association

with a synchronising relay.

Safe disconnectorsAll three disconnector (DS) poles are con-

nected to a common 3-pole electrical

mechanism via a sturdy mechanical linkage.

Clear and safe indication of the main con-

tacts position is provided by a reliable indi-

cator directly fitted to the linkage. This indi-

cator is well-visible from the operating level.

Totally safe insulation between energised

and de-energised sections of the substation

is provided thanks to long gaps between

open contacts and proper dielectric design.

Disconnectors reliably switch capacitive

currents which occur when switchgear sec-

tions are energised or de-energised, as well

as commutation currents caused by busbar

transfers. All performances have been

demonstrated according to the latest appli-

cable standards.

High power earthing switches Earthing switches (ES) may have switching

capabilities or not. Those with these capa-

bilities are fast-operated (high-speed type),

not only on closing but also on opening, by

means of a spring released at the end of

both operations. High-speed ES are there-

fore capable, not only of making the full

short-circuit current, but also of interrupting

(according to most stringent standard spe-

cifications) currents associated with parallel

overhead lines. The latter capability is widely

and reliably achieved thanks to the specific

high-speed opening feature of the T155

earthing switch. Properly selected ES, either

high or low-speed, may be electrically

insulated from the enclosures by removing

an external link, thus conveniently enabling

current or voltage injection tests for timing,

resistance measurement or protection check

purposes.

All three ES poles are connected to a com-

mon 3-pole electrical mechanism via a

sturdy mechanical linkage. The contact

position indicator, which is common to the

three poles of low-speed ES and fitted to

each pole of high-speed ES, is reliable and

clearly visible at operating level.

Field-proven busducts Tens of kilometres of ALSTOM gas-insulated

busducts are installed around the world,

thus demonstrating an unsurpassable field

experience. Not only can these busducts

match all physical constraints, but the GIS

and its high voltage terminations can also

be arranged in the most suitable way.

ALSTOM spring mechanisms have few

moving parts, require almost no maintenance,

need no on-site adjustment and stand

out due to their long service life. Sturdy

design assures superior reliability. Adapted

travel curve and damping entail low dynamic

loads on the floor and adjacent GIS com-

ponents. Therefore, mechanical ageing is

sharply reduced and civil works are less

expensive.


5

Busducts can be installed either above

ground, or in trenches, tunnels, or shafts. This

makes it possible to locate HV substations

within underground power plants for instance,

thus enabling operators to locate step-up

power transformers underground too.

Thermal expansion is dealt with by means

of suitable sliding supports, bellows, special

steel frames, etc.

Customised current and voltage transformersT155 current and/or voltage transformers

are suitable for all protection and metering

purposes and cover a very large range of

ratings. Most often, instrument transformers

are conventional, inductive types.

Non-conventional instru-

ment transformers (NCIT)

can also be provided. The

ALSTOM non-conventio-

nal current transformer

is based on the Rogowski

principle, which avoids

any magnetic saturation

concerns. Thanks to ALSTOM's original

design, even the most demanding metering

ratings, up to 0.2 accuracy class, can be

achieved with very low primary currents.

The non-conventional voltage transformer

is a capacitive-type and may even be com-

bined with the CT. The ALSTOM NCIT deli-

vers standard analog and/or digital signals.

Integrated surge arresters Gas-insulated surge arresters minimise sub-

station footprints, improve equipment

reliability and reduce the number of outdoor

insulators. Thousands of units are installed

in high and extra-high voltage air and

gas-insulated substations. T155 zinc-oxide

resistors have very high ratings which mini-

mise residual voltages, thus perfectly pro-

tecting the equipment and dissipating the

very high energies associated with the

longest lines and cables. Proper grading

of the electrical field inside the enclosure is

achieved with special stress shields. A

leakage current meter and/or a discharge

counter may also be connected.

High-voltage terminationsThe T155 can be directly connected to high

voltage cables, transformers and/or over-

head lines.

Reliable SF6-air bushings The GIS connects to overhead lines by

means of busducts and SF6-air bushings,

the insulator of which, (porcelain or compo-

site) is filled with SF6 at substation rated

pressure. Electric field grading is natural,

based on sole SF6 insulation, which pro-

vides an excellent voltage surge withstand.

This limits the risk of ageing too. A range

of insulators allows external creepage

distances to meet specific customer require-

ments.

Composite insulators are also explosion-

proof and thus bring a valuable safety

feature.

Direct connection to power transformers In order to remove any air-insulated part,

the T155 can be directly connected to

power transformers and reactors by means

of gas-insulated busducts and a specific

enclosure which houses the gas-tight

oil-SF6 bushing. The latter is provided by

the transformer or reactor manufacturer

and must be as per IEC standards. Proper

design easily manages the positioning tole-

rances of the power transformer or reactor.

The transformer or reactor may be discon-

nected from the substation via a removable

connection during GIS high voltage tests.

Standard HV cable connectionA specific enclosure is used to connect the

switchgear to the cable termination, whose

insulator provided by the cable supplier

must be as per IEC standards. Such a ter-

mination fits any type of HV cable, irre-

spective of insulation type (XLPE, paper-oil,

etc.) or conductor section.

The cable can be disconnected from the

switchgear via a removable conductor,

to allow separate GIS and cable high voltage

tests. Tools and testing means for HV cable

testing must be provided by the cable supplier.


6

Condition monitoring

Monitoring Despite its superior reliability, T155 switch-

gear availability can be further enhanced by

means of condition monitoring systems

which have the following features:

• Predictive, instead of preventive mainte-

nance

• Early warnings

• Time-tagged event recording.

SF6 , circuit breaker and partial discharge

monitoring are the most valuable systems.

Precise circuit breaker monitoringCircuit breaker monitoring can be provided

too. Travel curves and electrical wear are

recorded and can report on circuit-breaker

conditions in order to trigger servicing only

when it is strictly necessary.

For both SF6 and CB monitoring, ALSTOM

deploys modular electronic devices, whose

reliability is supported by hundreds of

thousands in operation around the world in

all types of critical industrial processes. These

devices are permanently self-monitoring

and any failure is immediately signalled.

These devices have successfully undergone

extremely severe and extensive qualication

tests. Due to their proximity to high voltage

and high current equipment, electro-

magnetic compatibility (EMC) withstand is

thoroughly checked: not only do these devi-

ces fully comply with the upper class of the

tests (electromagnetic fields, fast transients,

electrostatic discharges, radiated radio

waves, etc.) defined in IEC 1000/EN 61000

standards, but they also experience no

misoperation during the same tests. Display

is provided by user-friendly human-machine

interfaces.

UHF monitoringInternal partial discharges may be signs of

possible problems. It may be therefore

useful to monitor the ultra-high frequency

(UHF) electromagnetic waves generated by

the partial discharges. Associated with the

high voltage tests, this is the most effective

way to ensure full GIS integrity after instal-

lation or heavy maintenance. UHF sensors

transmit electromagnetic waves, the fre-

quency of which may reach 1 GHz. Sensors

(i.e. antennas) are properly located inside

the enclosures. On commissioning staged

and regular inspections, sensors are con-

nected to a portable UHF analyser.

A trained operator may then observe the

signals and determine switchgear status.

A more sophisticated online monitoring

system may also be supplied for more

critical installations, for the permanent

supervision of switchgear dielectric con-

ditions.

remote monitoring communication

communicationwith control equipment

monitoring

gateway

bay

gateway

&

SF6

monitoring

module

condition

monitoring

module(s)

A/D – D/A

converters

digital links

digital positionsensors

digitalSF6

sensorsanalogue sensorson/off

inputson/off

outputs

Control room

LCC

Switchgear

Complete SF6 monitoringApart from the usual density

thresholds (refilling request

and minimum operating

density), ALSTOM SF6 moni-

toring can also provide many

valuable functions:

• Accurate density display

• Filling overpressure alarm

• SF6 liquefaction detection

• Sensor status control

• Early warning

• Calculation of leakage rate

• Internal failure detection

• Historical record.

These functions help

operators to make proper

decisions and dramatically

increase substation

availability.

LAN


7

Assembly & maintenance

Local controlA local control cubicle is generally asso-

ciated to each T155 circuit breaker bay.

This cubicle may provide all or part of the

following functions:

• Control, i.e. means of opening and closing

all switches (circuit breaker, disconnectors

and earthing switches)

• LV supply protection

• Display of switch position

• Alarm display (SF6 thresholds, supply

voltage, etc.)

• Safety electrical interlocks (using CB, DS

and ES auxiliary contacts)

• Current / voltage meters

• Interfacing terminals for remote control.

Reliable type and routine testsType tests are carried out according to

latest IEC standards. For some features, IEC

requirements are even supplemented by

additional tests, or more severe conditions,

to meet ALSTOM’s own superior standards

of quality. Despite our modern workshops,

which include a dustfree assembly hall, the

same rigorous policy is applied for routine

tests. For instance, partial discharge mea-

surement is performed at a much higher

voltage than required by IEC standards.

Simple transport and on-site testsShipping units are filled with SF6 or N2 gas

at a slight overpressure, to prevent moisture

and dust ingress during transport. After site

erection, the equipment undergoes rigorous

inspections to ensure all required perfor-

mances. Site tests include severe resistance

measurements and mechanical and voltage

withstand tests.

Minimal maintenanceThe T155 has a near-zero maintenance

concept – where reliability and availability

mean inspections at distant intervals and

where long life duration for mechanical and

electrical parts is guaranteed. The ALSTOM

Service team remains at the customer’s

disposal for any assistance and service,

however. An inspection and maintenance

plan can also be established to support the

equipment throughout its entire life cycle.

Comprehensive servicesALSTOM provides a global service offer,

supported by local resources:

• Network consulting

• Equipment expertise and diagnosis

• Erection and commissioning supervision

• Maintenance and spare parts management

• Repairs and emergency support

• Renovation and refurbishment

Dedication to customer satisfaction is

ALSTOM’s first guideline to its employees,

a testimony to the will of shapping a better

future.

The implemented technology can be con-

ventional (based on electromechanical

relays) or digital (based on electronic micro-

processors).

The ALSTOM local control cubicle may also

incorporate the bay control unit (BCU) of a

substation digital control system (DCS)

and/or the protection relays themselves.


GRID

Applications

Hybrid module

Displayed OPTIGIM includes

one circuit breaker with:

1 current transformer

1 earthing switch

1 disconnector

1 SF6 -air bushing on both sides.

Length 10 m

Bushing terminal height 7.5 m

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Alstom Grid Worldwide Contact Centre

www.grid.alstom.com/contactcentre/

Tel: +44 (0) 1785 250 070

www.grid.alstom.com

One circuit breaker and a half substation with 4 feeders

Building width 10 m, length 34 m

Double busbar layout with 6 feeders and 1 coupler

Building width 10 m, length 25 m


t155 420 - 550 kv gas-insulated substations brochure gb

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