application of gas-insulated modules (gim) to ehv substations.pdf

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CIGRE 2004 - Application of GIM to EHV substations Page 1 / 10

* [email protected]

Application of gas-insulated modules (GIM) to EHV substations

F. Salamanca, R. Salazar, A. Alcocer T. Millour, Ph. Ponchon*, J.-L. Habert

Red Electrica de Espaa AREVA T & D

Spain Spain & France

Key-words : AIS - GIS - GIM - Hybrid - Gas-insulated module - NSR - HV - EHV

Summary

Electric power transmission and distribution market changes are driving operators to look for more

economical, fast-to-implement, environment-friendly and easy-to-maintain extra-high voltage (EHV)substations (S/S). This search has led to mixed technology substations equipped with gas-insulated

modules (GIM) which, in a modular arrangement, integrate several feeder functions in a compact way

and are connected to air-insulated busbars, instead of traditional air-insulated (AIS) or fully gas-

insulated (GIS) substations. Then, GIM use has been extended to different applications, and to the

highest voltages of transmission networks. This paper presents different GIM applications, their spe-

cific needs and impacts, the solutions proposed for the equipment.

1.Introduction

Since several years, heavy changes of electrical power transmission and distribution market are

driving operators to look, for HV and EHV substations (S/S), for more economical, fast-to-implement,

environment-friendly, reliable and easy-to-maintain solutions.

In several cases, air-insulated substations (AIS) equipped with gas-insulated modules (GIM) have

been selected, up to 550 kV network voltage, instead of AIS with traditional air-insulated switchgear,

and instead of fully gas-insulated (GIS) substations.

This paper presents different categories of GIM application, their specific requirements and impacts,

the solutions proposed for the equipment. Focus is done on a recent 420 kV application.

2.Background

Main advantages of the different substation types, generally agreed, are listed here-after :

GIS :

It is the best solution in terms of compactness and reliability, It is well adapted to stringent environmental constraints such as heavily polluted areas (for in-stance industrial areas or sea shores), low temperatures and icing conditions, strong earthquake with-

stand, It requires light maintenance, It is easy to integrate in locations where visual impact has to be optimised.

Traditional AIS (with separate elements) :

It enables to replace an element from a given supplier by another one from another supplier, It shortens equipment replacement time, It features low initial costs, as far as land costs and civil works remain moderate.

AIS with GIM :

It combines several advantages of both traditional AIS and GIS :

It allows simpler single-line diagrams (SLD), since AIS redundancy level is unnecessary, It needs smaller areas than traditional AIS, It requires much less external insulators than traditional AIS, Like GIS, it solves disconnector ageing under severe ambient conditions, It provides better earthquake withstand, similar to GIS one.

21, rue d'Artois, F-75008 Parishttp://www.cigre.org CIGR

Session 2004B3-215


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Dead-tank circuit-breakers (CB) use gas-insulated technology for circuit-breakers only, with no in-

tegration of feeder components such as disconnectors, earthing switches, voltage transformers, and

therefore cannot be considered as GIM. However, extending with GIM a substation fitted with dead-

tank CB can be easily performed, due to arrangement likeness.

3.General trend

Combination of GIS switchgear and air-insulated busbars is not new : it is used since the beginningof GIS technology, however in rare cases. However, for last 5 years, triggered by deregulation, utilities

have shown an increased interest in innovative S/S solutions. Parallely, optimised GIM solutions have

been designed and proposed by manufacturers.

While market share remains low in comparison with classical AIS & GIS technologies, the result is

an increase of GIM quantities installed all over the world, since yearly average quantity of delivered

GIM is close to 100 modules, with applications at all voltage levels up to 420 and even 550 kV.

It was therefore quite interesting to analyse the applications where GIM is used. We shall first, in

chapter no. 4, look at evolution of specifications towards more functional ones. Then, in chapter no. 5,

will be presented the five main categories of applications. Last, in chapter no. 6, we shall try to explain

why, up to now, GIM technology is not more often used.

4.Evolution of functional specification

4.1.Reliability

Some GIM are in service since more than twenty years, based on GIS technologies which have evi-

denced the highest reliability. However, in a competitive market, operators in electrical power trans-

mission and distribution need to ensure energy delivery to their customers and also to limit their in-

vestments. They are therefore looking for more reliable equipments which allow to decrease the re-

dundancy of functions on the network.

Three main contributions to higher reliability, more and more often specified, are detailed here-

after :

Circuit-breaker spring mechanism : Most recent circuit-breaker interrupting chambers require low

driving energy, thus enabling spring mechanism to be used up to 550 kV and 63 kA. Spring mecha-

nisms provide a superior reliability, confirmed by decades of positive field experience. They also en-

tail very low dynamic loads, and consequently reduce mechanical stresses exerted onto the equipment.

Gas-insulated disconnectors : Such disconnectors are not sensitive to ambient conditions, a crucial

feature when substation is installed in polluted industrial areas, nearby the sea or in cold countries.

Monitoring : Self-monitored digital monitoring system provides trend analysis, early warnings and

on-line display (local and remote). Thus equipment failures may be predicted and maintenance is per-

formed in due time.

4.2.Maintainability and availability

Operators care a lot about outages duration. Maintainability and availability of electrical equipment

are therefore essential. This can be translated into MTTR requirements. GIM, as far as fitted with ade-

quate gas partitioning (segregated disconnectors and buffer compartments) allows to limit the impact

on adjacent feeders in case of failures and during replacement of components, as in AIS.

An efficient monitoring allows to optimise the rate of maintenance, too.4.3.Safety

Like in other domains, there is fortunately a strong and clear request of limitation of physical risk

towards people. Besides basic safety improvement brought by live parts encapsulation, GIM can be

equipped with earthing switches. While low-speed earthing switches are already quite safer than port-

able earthing rods, high-speed earthing switches further cope with misoperations, with no risk for per-

sonal. Last but not least, explosion-proof composite bushings further reduce the injury risk.

4.4.Interchangeability

The need of better global efficiency induces, among other possible improvements, the search for:

Simplification of procurement process, Reduction of engineering cost and time, Decrease of expenses for spares, Cut of time-to-repair.


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Interchangeability, for various SLDs, between elements coming from different suppliers has a very

positive impact in these domains. Standard GIM allows interchangeability, within a given network, for

different SLDs (for instance ring bus and single busbar) and applications (new S/S, extensions), there-

fore facilitating spare parts management and reducing the time to replace a faulty element.

Interchangeability between GIM from different suppliers may be easily guaranteed, by specific ad-

aptation of civil works and/or modules, or by means of versatile interfaces.

5.Main categories of applications

5.1.Standardisation and optimisation of new S/S and/or extensions in large networks

5.1.1.Introduction

Large utilities are managing important networks with many substations. They are deeply interested

in reducing investment and life-cycle costs, through standardisation of engineering and HV equipment.

As far as properly designed, a standard GIM may be easily adapted to different arrangements, as

needed by utilities, with no design change. Consequential standardisation of S/S design, with new sin-

gle-line diagrams, further reduces engineering work. This not only allows to reduce delivery, erection

and commissioning times, but large module quantities allow bulk programs and reduced manufactur-

ing costs.

Life cycle cost comparison is decisive to select the best substation design. However, the most reli-able and simple alternatives, based on GIM technology, have been prejudiced, since this comparison

was most often inadequately done. For instance, due to simplification excess or lack of time, substa-

tion designers have often evaluated solutions figured out for conventional AIS, the only change being

to replace air-insulated equipment by GIM. This is clearly wrong, as a fair comparison demands the

adaptation of both SLD and layouts.

This is due to the fact that GIM equipment does not require, thanks to its higher reliability and com-

pactness, the same redundancy of functions and single-line diagrams as AIS equipment does.

In other words, in order to actually optimise the design, comparison must consider operation, reli-

ability and maintenance features of each technology, and not only replace AIS equipment by GIM.

5.1.2.Red Electrica de Espana (REE) standard substations

5.1.2.1.New substation design

Fig. 1 : Single-line diagram of new standard substation Fig. 2 : Meshed ring layout with segregated phases

GIM application is now reaching 420 and 550 kV voltage levels, too. A typical example in the cate-

gory of application to large network and with standardisation purpose is the case of REE, the utility in

charge of the transmission network in Spain. Further to complete re-engineering of its 400 kV substa-

tion design, after years of standardisation of AIS solutions based on one and a half CB, REE reached

the following conclusions :

GIM higher reliability and compactness allows one and a half CB SLD to be replaced by themeshed ring diagram (see fig. 1) which, despite less equipments, provides greater operation flexibility,


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Most optimised physical layout at 400 kV for meshed ring scheme is the so-called NSR (NewSegregated Ring) arrangement (see fig. 2) which features segregated phases and modular groups di-

rectly connected altogether in order to match the ring layout, consequently avoiding the unnecessary

busbars,

Such NSR provides a complete family of solutions for indoor and outdoor substations which onlydiffer by the way GIM are altogether connected,

The latter not only means less possibilities of failures, but also decreased costs, even more par-ticularly for indoor solutions which require very short gas-insulated busbars,

Proper design and adequate gas partition make possible the safe replacement of any GIM func-tional sub-group (CB, disconnector, instrument transformer) within less than 6 hours, thus adds easier-

than-AIS maintenance capabilities to inherent GIM higher reliability,

GIM allows the use of same technology equipments in all outdoor and indoor substations, whichimplies simpler maintenance and spare parts needs,

Such standardisation provides following main advantages : engineering for each standard new420 kV S/S is reduced, interchangeability between suppliers is kept (specified dimensions on HV and

civil sides), gas-insulated disconnectors are more reliable, maintenance costs are lower, future exten-

sions will be easier.

5.1.2.2.Description of GIMGIM displayed in fig. 3 normally includes all usual functions : circuit-breaker, current transformers,

disconnectors, low-speed earthing switches and SF6-air bushings. Other diagrams are easily matched,

with no design change of standard GIM, just by addition of voltage transformer, earthing switches, etc.

All components fulfil latest IEC standard requirements. For instance, CB complies with most strin-

gent capacitive switching requirements (class C2 very low probability of restrike).

This GIM is designed for voltages up to 550 kV, short-circuit currents up to 63 kA and based on

proven technologies : horizontal CB layout provides better access to components (valves, drives, ),

CB flat-twin arrangement, combined with spring mechanism, drastically reduces stresses on equip-

ment and civil works, composite bushings improves safety.

Horizontal and vertical electrical clearances fully comply with safety requirements, this being man-

datory to work on bushings. Buffer compartments associated with independent compartments for cir-

cuit-breaker and disconnectors gives the possibility of safe disassembling while feeders remain ener-

gised (see fig. 4).

Fig. 3 : View of a 420 / 550 kV GIM

Fig. 4 : Adequate GIM partitioning (thanks to buffer com-

partments, CB may be replaced while both bushings termi-nals remain energised)

Fig. 5 : Complete module, but bushings, is shipped to site

Deformation of steel structure parallelogram shape, together with a special trolley, easily allows to

safely remove and replace components between the two bushings.

Replacement of any component (including the whole module) in less than 6 hours has been tested on

full-size GIM, with following typical time schedule : Installation of tools and SF6 < 1.5 hour, disas-

sembling and reassembling < 2 hours, SF6 filling, LV connection, checks < 2.5 hours.

GIM is 7.5 m high with bushings, only 3.5 m without bushings. Its length is approx. 10 m. Thus, as

shown on fig. 5, modules are transported fully-assembled, including supports but excluding bushings,in order to shorten erection time on site and improve reliability.


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5.1.3.ENEL 170 kV standard substations

A second example for this category is the extension of the italian sub-transmission network. ENEL

utility decided to add a large number of HV to MV S/S within the right-of-way of existing 170 kV

overhead lines and defined two typical "Y" single-line diagrams which may be realised by using only

one GIM, with 1 or 2 CB (see fig. 6).

Fig 6 : The two single line diagrams Fig. 7 : S/S integration within right- Fig. 8 : Type Y2 GIM , with 2 CBof-way of existing overhead line

Two main criteria are in favour of GIM :

Compactness, allowing to use existing overhead line right-of-way for the new S/S (see fig. 7),

A single GIM includes all HV equipment, with up to two CB (see fig. 8).This concept also results from complete reconsideration of network operation : MV equipment re-

mote control and automatic reconfiguration allow to move from a typical "H" S/S, with redundant

power transformer, to "Y1" or "Y2" with redundancy, at the MV level, between two different S/S.

5.2.AIS refurbishment with operational constraints and/or space limitations

Another typical GIM application is the reconstruction of old existing AIS with operational con-

straints and/or space limitations. The new substation has to be built totally or partly beside the existing

one, and at least part of the existing S/S has to remain in operation during erection and commissioning

of the new S/S (or first stage of it).

For this application, there are three main GIM advantages :

compactness allows easier erection beside existing live equipment, air-insulated busbars permit quick connection between two different sections of busbars, or be-

tween modules and busbars,

short erection time reduces the length of the period with reduced operational safety margin (no re-dundancy on transformers or lines, ).

Fig. 9 : Layout of Tully substation switchyard Fig. 10 : View of Tully 145 kV substation with GIM

A typical example is the reconstruction of Powerlink Tully substation located in Queensland, Aus-

tralia. In this area, the 145 kV network comes from the original main transmission networks that were

initially constructed in the various parts of the state in the 1950s, then extended during the 1960s and

1970s. The substations comprising the original nodes of these networks are now approaching the end

of their economic lives. Maintenance costs of the equipment are rising considerably, parts are hard to

obtain, and asset values are low. Powerlink has thus initiated a program to replace a number of suchsubstations in the northern part of the state.


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The rebuilt substation is to have two feeder bays, one additional spare feeder bay, two transformer

bays, and a bus-coupler bay. All the construction is required to remain within the existing property

boundaries. The existing supply to the distribution utility via two transformers is also required to be

maintained at all times, apart from short outages of a single transformer during non-critical periods, to

allow connection of new equipment and disconnection of old equipment.

Preliminary layouts, with conventional AIS clearances, evidenced that some of the works would

overlap the existing equipment area. GIM offered a straightforward, yet flexible, way of building. The

integrated and pre-tested switchgear also offered shorter installation and commissioning times, an im-

portant advantage with tight scheduling. This benefit is further enhanced by the completely pre-tested

secondary system which can be rapidly connected to the primary plant and commissioned.

Intelligent on-line monitoring and diagnosis system is included, which provides extensive switch-

gear condition information, both locally and remotely. Such monitoring, together with the inherent

higher reliability of GIM components, is expected to provide lower overall life cycle cost for the new

substation, compared to a conventional AIS construction.

5.3.Extension of air-insulated S/S with space limitations,

Network natural evolution very often requires feeders addition, to increase transmission capacity, to

improve availability, to reduce constraints on equipment or to improve efficiency. Most frequently

added bays are intended for overhead lines, cables, power transformers, reactors, couplings or bus-ties.More and more often, site available space is not sufficient to add such conventional bays, while GIM

generally allows to add two bays per each spare bay foreseen at the initial AIS.

Fig. 11 : Echalas 420 kV AIS with busbar coupling GIM Fig. 12 : Escombreras 420 kV module installed on site

As a first instance, a coupling bay has been installed by RTE utility at one busbar end of Echalas

420 kV S/S, in France. Since the conventional substation features a segregated-phase busbar arrange-

ment, the new coupling bay has been installed in a narrow corridor, using three single-pole modules at

one end of the existing S/S, as per fig. 11. An AIS coupling bay would have required at least six times

more space.

Fig. 12 shows another REE application of the module concept in case of space limitation, which

consists in the addition of one transformer bay in existing Escombreras substation, which was only

possible by means of GIM.

A third application was carried out by REE utility, too, in Vandellos S/S, in Spain, consisting of a

double busbar, a transfer busbar and 8 bays : 6 lines, 1 coupling and 1 bus transfer. It was necessary to

add two new lines. The extension of this substation was problematic since, at one end, the neighbour-

ing installation (generator bays) belongs to a different owner and, at the other end, there is a steep

slope. Therefore, the only available area for extension was a narrow strip, between the last built bay

and the slope. The present layout is schematised in fig. 13. Being impossible to extend at both ends the

substation by means of conventional equipment, the applied solution was to shift the coupling bay to

one end of the substation and set up the two new line bays in the space left free. The new coupling is

made with GIM equipment in the left narrow space. Eventual layout is thus schematised in fig. 14.


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Fig. 13 : Vandellos SLD before S/S extension Fig. 14 : Vandellos SLD after S/S extension

5.4.New S/S with optimised single-line diagrams and/or layouts.

Initial investment decrease sometimes push utilities to reconsider single-line diagrams and arrange-

ments, with no standardisation purpose. This is quite less valuable than in large networks, since the

cost of the engineering for these new solutions has to be supported by each project.

In many cases, the substation is eventually performed by means of conventional AIS or full-GIS so-

lutions. However some specific applications exist, such application being also for utilities a way to

evaluate new designs.

For instance, in Termobahia S/S (Brazil), instead of a standard single busbar scheme, only 3 GIM

and 2 AIS disconnecting switches were used to build the S/S. This has been made possible by accept-

ing to reduce the number of disconnectors and earthing switches, as shown in fig. 15.

Fig. 15 : Single-line diagram of Termobahia 230 kV S/S Fig. 16 : View of Termobahia substation with GIMInside curved plain lines: GIM

Inside curved dotted lines : cancelled equipmentInside straight broken lines: AIS equipment

In this case, GIM solution was selected for following reasons : reduction of land area, improvement

of equipment reliability, reduction of duration and cost of specification, engineering and procurement

process (each GIM phase has been transported fully assembled).

5.5.Mobile substations

One should not forget that mobile substations, too, are GIM applications concept. Fig. 17 displays a245 kV application in Abu Dhabi, while fig. 18 refers to a Swiss Railways S/S (16 2/3 Hz frequency).

Fig 17 : Mobile 245 kV substation in Abu Dhabi Fig. 18 : Railway (16 2/3 Hz) substation in Switzerland


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6.GIM introduction resistance factors

It has been shown numerous GIM advantages and the main specific categories of application for

which this technology has been satisfactorily implemented.

Considering this, one could expect a greater global market share than stated in chapter 3 (yearly av-

erage quantity of delivered GIM is close to 100 modules). Why isnt it more ?

Following paragraphs try to highlight the main resistance factors to GIM introduction in S/S designand construction, when design does not consider different SLD and scope for different technologies

(AIS-GIM-GIS), this being unreasonable since it results in unnecessary redundancies and costs for

GIM solutions, as already detailed in chapter 5.1.1.

6.1.Lack of reliability incentive

First of all, we must come back to what is mentioned in the 2nd

chapter, titled "background". It exists

a wide range of well-proven AIS, GIS or DT solutions, covering all cases of applications. These solu-

tions are generally recognised as having a high level of reliability and availability, or at least an ac-

ceptable one. Thus no major move comes from this matter.

6.2.Insufficient economical and environmental differentiation

As mentioned in the introduction, main change drivers are economical (investment costs, lead times,

maintenance costs) and sometimes environmental (area, height, visual impact, etc.).Comparison of such impacts for GIM and conventional solutions, performed on a turn-key basis

with same process as a real tender, gives some elements of answer to the here-above question.

Several parameters were considered :

Voltage level : 145, 245 and 420 kV, Single-line diagram : single and double busbar arrangements are considered at 145 kV and

245 kV, double busbar and one and a half circuit-breaker arrangements at 420 kV,

Type of high-voltage interface : different possibilities were considered, depending on voltage.For instance, at 145 kV, one of the considered cases features only cable connections.

Typical solutions only were considered for S/S general arrangement, location of overhead lines gan-

tries, location and size of control building, and so on.

6.2.1.Economical impactAs far as economical criteria are concerned, the best criteria would theoretically be the life cycle cost

one. Despite many general studies have tried to make estimation on these life cycle costs, there is no

full confidence on announced figures. The ground of this is that operation, maintenance and end-of-

life (recycling and disposal) costs are difficult to determine with accuracy, even for technical solutions

which are in operation for a long time. In addition, these costs are deeply depending on internal rules

and organisational structures of the different utilities. Eventually, since short-term results are mainly

considered, the sole initial "investment cost" was selected as economical criteria.

Complete substation turn-key cost was also split down : civil works, switchgear, power transformers

erection, control equipment, etc.

6.2.2.Environmental impact

It is difficult to determine representative criteria for environmental impact of the different solutions.Complete methods exist, taking into account numerous parameters (energy spent during manufac-

turing process, quantities of raw material, etc.). However, not only it is complicate to apply to numer-

ous cases of complete substations, but at the end does not correspond to the Purchasers actual prac-

tice. Finally, the land surface required by the switchyard was selected as environmental criteria.

6.2.3.Results

Part of these results are shown on the following diagram (fig. 19), cost and surface of a 145 kV AIS

being taken as references.

Despite the fact that cost-surface trends clearly appear, it remains difficult to make general conclu-

sions, due to different reasons, among which the main following ones :

Cost of land and civil works can considerably change, from one country to another, and from onesite to another,

Actual arrangement may depend a lot of actual site conditions (ground nature, slope, etc.), Engineering cost may be spread over a single or tens of substations.


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Cost versus surface diagram

with

double busbar 145 kV AIS = 1.00;1.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

Surface (ratio)

AISGIMGIS

145 kV, single busbar

145 kV, double busbar


245 kV, single busbar


Fig. 19 : Comparison diagram, complete turn-key, in some cases of single and double busbar SLD

6.3.Difficult application to double busbar SLD

At transmission voltages, most common single-line diagram is the double busbar one. This is morethe result of habits than the result of technico-economical surveys.

Three main reasons make difficult GIM application to double busbar diagram :

First, SF6-air bushings number is proportionally higher than for single busbar, ring or one and half

circuit-breaker diagrams, thus reducing the economical advantage.

Second, two air insulated busbars require a lot of space, thus reducing the space advantage brought

by GIM in some other arrangements. Interfacing a very compact GIM to large AIS double busbar is

difficult. Solution requires additional post-type insulators, the number of which depends of the con-

nection type (rigid or flexible) and short circuit current. This also reduces GIM cost savings.

Third, an appropriate gas partitioning must be provided in the module, in order to maintain flexibil-

ity and availability advantages of the double busbar system.

At the end, GIM does not appear to be a natural alternative to AIS or GIS for double busbar SLD.

This is confirmed by the fact that very few of the existing GIM have been integrated in double busbarS/S.

6.4.Weight of design and engineering at project and realisation stages

Detailed analysis of the different solutions applicable to a given substation is time-consuming. It is

difficult to distinguish the intrinsic impact of the type of insulation from the impact of single-line dia-

gram, general arrangement and particular site characteristics. Excepted for cases were evident solu-

tions are defined for these parameters, it requires to get offers, for many alternatives, from the differ-

ent companies which may be involved in the whole project. In these conditions, it is also not evident to

have a fair competition on a common technical basis, as naturally imposed by purchasing department.

Moreover, this complex process is very often not compatible with the engineering department load

or the project time schedule. It is therefore quite difficult to justify such extra expense and extra time,

even more for a single S/S.Should this whole process be finally performed, final conclusions of the complete study could be not

clear enough, as illustrated by the above graphic, to impose a natural solution.

Therefore, easiest way is to go directly to well-known solutions allowing to start very quickly the

request for building license, for instance.

At realisation stage, for first substation using a new concept, it is necessary to perform the detailed

engineering, including for instance civil works, cable routings, protections, etc.

Such process requires money and time-consuming engineering capabilities with strong expertise. It

may be profitable only for very large projects or, even better, for many substations within a large

electrical network.

Consequently, only companies able to invest in general studies, for several S/S, can afford such

profitable expenses.


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7.Conclusions

Last years have seen the introduction, in high-voltage and extra-high-voltage networks, of an

AIS / GIS (gas-insulated substation / air-insulated substation) mixed technology, which gains from the

use of GIM (gas-insulated modules).

Analysis undoubtedly shows that GIM is specially suitable for following categories of applications,

at all voltage levels up to 550 kV : Standardisation and optimisation of new S/S and/or extensions in large networks, AIS refurbishment with operational constraints and/or space limitations, Extension of air-insulated S/S with space limitations.

However, while GIM perfectly matches networks and users requirements in previous applications,

this introduction remains moderate, due to several resistance factors, the main one being the wrong re-

placing of AIS equipment by GIM, without substation global approach, i.e. without considering differ-

ent single-line diagram and general arrangement for technologies with different reliabilities.

Despite this, GIM future seems to be insured by AIS refurbishment and extension market which will

mathematically increase with equipment ageing and network reinforcement.

For the global approach market, GIM spreading out depends on large utilities will and capabilities to

set large standardisation programs, in view of cost-killing actions.

8.Bibliography

Hybrid switchgear modules and integrated digital control system offer a flexible and economic solu-

tion for AIS substation refurbishment, by Mark Blundell, Peter Berry, Endre Mikes CEPSI 2000

Environmentally friendly, low cost HV/MV distribution substations using new compact HV and MV

equipment, by V. Colloca, G. Como, F. Pozzana, S. Sciarra, F. Iliceto, C. di Mario, E. Colombo

CICIRED 2001

Influence of electrical arrangement and rated voltages on substation space requirements and total

costs for various gas- and hybrid-insulation solutions, by H. Aeschbach, E. Mikes, Ph. Ponchon, F.

Gallon CIGRE 2002

Application of gas-insulated modules (GIM) to EHV substations, by Ph. Ponchon, M. Bus, J.-L.

Habert, S. Balland MatPost 2003 (2nd

european conference on HV and MV substations equipment)

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