Cigre TB 513

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513

5

Final Report of the 2004 - 2007

International Enquiry on Reliability of

High Voltage Equipment

Part 5 - Gas Insulated Switchgear (GIS)

Working Group

A3.06

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Working Group A3.06

Final Report of the 2004 - 2007 International Enquiry on

Reliability of High Voltage Equipment

Part 5 – Gas Insulated Switchgear (GIS)

Members

M. Runde (NO) Convener, C. E. Sölver (SE) Past Convener, A. Carvalho (BR),

M. L. Cormenzana (ES), H. Furuta (JP), W. Grieshaber (FR), A. Hyrczak (PL), D. Kopejtkova (CZ), J. G. Krone (NL), M. Kudoke (CH), D. Makareinis (DE), J. F. Martins (PT), K. Mestrovic (HR),

I. Ohno (JP), J. Östlund (SE), K.-Y. Park (KR), J. Patel (IN), C. Protze (DE), J. Schmid (DE), J. E. Skog (US), B. Sweeney (UK), F. Waite (UK).

Corresponding Members

B. Bergman (CA), S. Tsukao (JP)

Copyright © 2012

“Ownership of a CIGRE publication, whether in paper form or on electronic support only infers right of use for personal purposes. Are prohibited, except if explicitly agreed by CIGRE, total or partial reproduction of the publication for use other than personal and transfer to a third party; hence circulation on any intranet or other company network is forbidden”.

Disclaimer notice

“CIGRE gives no warranty or assurance about the contents of this publication, nor does it accept any responsibility, as to the accuracy or exhaustiveness of the information. All implied warranties and conditions are excluded to the maximum extent permitted by law”.

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5.1 Common Matters of the 2004-2007 Reliability Survey

The results of the 2004 - 2007 reliability study of high voltage equipment are presented in six Technical Brochures (TBs):

• TB 509 “Final Report of the 2004 - 2007 international enquiry on reliability of high voltage equipment, Part 1 - Summary and General Matters” [1].

• TB 510 “Final Report of the 2004 - 2007 international enquiry on reliability of high voltage equipment, Part 2 - SF6 Circuit Breakers” [2].

• TB 511, “Final Report of the 2004 - 2007 international enquiry on reliability of high voltage equipment, Part 3 - Disconnectors and Earthing Switches”[3]. • TB 512 “Final Report of the 2004 - 2007 international enquiry on reliability of

high voltage equipment, Part 4 - Instrument Transformers” [4]

• TB 513 “Final Report of the 2004 - 2007 international enquiry on reliability of high voltage equipment, Part 5 - Gas Insulated Switchgear” [5].

• TB 514 “Final Report of the 2004 - 2007 international enquiry on reliability of high voltage equipment, Part 6 - GIS practices [6].

TB 509 contains material that concerns the entire work, such as the objectives and scope, description of how the survey was organized, explanations of the statistical methods being applied, suggestions on how utilities can use the results, some general definitions and a short bibliography. In addition, extensive summaries of the most important findings from the different component types are included.

The four component TBs, i.e., no. 510 - 513, contain much more details as they present all results for each component type. This includes tables, figures, and graphs presenting reliability and service experience data and correlations, as well as text with commentaries and discussions. The relevant parts of the questionnaire and the relevant definitions used in the survey are shown in their appendices.

TB 514 presents an overview of utility practices concerning commissioning (high voltage testing) service (monitoring, diagnostics and service problems), major maintenance, extension as well as experience with new technology for gas insulated switchgear (GIS). The information was collected by means of a questionnaire that was circulated together with the reliability enquiry questionnaire. Again, the relevant parts of the questionnaire and the associated definitions are shown in its appendix.

Each TB is a self contained and complete report, but does also form a part of a bigger whole. To simplify cross referencing between the different parts, an overall numbering system that assigns a unique number to all sections, tables and figures is applied. Items in Part 1 are numbered using the format 1.X.X.X, in Part 2 the format is 2.X.X.X, etc. In Part 5 the format is 5.X.X.X.

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5.2 Introduction

5.2.1 History of GIS experience surveys

The 1st_{GIS international survey questionnaire was circulated in 1991 and both users and}

manufacturers were addressed. It collected experience up to 31.12.1990. 109 users from 34 countries and 18 manufacturers from 9 countries responded to the questionnaire. The users’ experience represented 1 817 GIS, 10 531 circuit breaker-bays (bays) and 78 036 CB-bay-years, the manufacturer’s experience represented 4 867 GIS, 24 870 CB-bays and 199 473 CB-bay-years. The questionnaire addressed: general data about GIS installations, factors which contributed to selection of GIS over AIS, adequacy of existing design/production/site test procedures, reliability, availability and maintainability, cause of major failures, future trends/condition monitoring /diagnostics and general open-ended questions. The survey and data analysis were published in [7], [8], [9] and [10] CIGRE papers during 1992 to 1994.

The 2nd GIS international survey questionnaire was circulated five years later, in 1996, with the aim of collecting service experience data available up to 31.12.1995. 80 users from 30 countries responded to the questionnaire. The collected data referred to 2115 GIS installations, 13 696 CB-bays and 118 483 CB-bay-years. In comparison to the 1st questionnaire, the 2nd_{questionnaire was more focused on installation overview and major}

failure statistics (dataset 1) and GIS life cycle issues (dataset 2). Therefore only users were addressed. Besides the general data about GIS installations (similar to data sheet in the first survey) the users were asked to report in dataset 1 the characteristics and service experience (major failures) for each individual GIS from the beginning of their putting into service and in dataset 2 to answer more general questions concerning maintenance, lifetime and environmental aspects independently of the number of installed GIS and voltage level. The survey and data analysis were published in [11], [12] and [13] CIGRE papers during 1998 to 2000.

The 3rd_{GIS international survey questionnaire was circulated in 2003 and collected}

population and failure data in 2004 to 2007. The structure of the questionnaire was as much as useful similar to the 2nd_{survey to enable a comparison. The survey structure is described}

in details in technical brochure [1] and the GIS questionnaire cards and their relevant definitions can be found in Appendix 1 of this brochure.

5.2.2 The 3

rd

GIS experience survey analysis

The below shown analysis follows a structure of the GIS population cards, and GIS failure cards for circuit breakers, disconnectors/earthing switches, instrument transformers and other components in GIS. It uses data from all these five questionnaire cards. As questions and answers in these cards were not identical it was necessary to make their re-coding to get a common platform. The resulting analysis below includes the following:

• Description of the participation in the survey (chapter 5.3)

• Overview of collected GIS service experience distribution (chapter 5.4) • Overview of collected GIS failures distribution (chapter 5.5)

• Calculation of GIS major failure frequencies (chapter 5.6)

• Analysis of collected GIS major and minor failure characteristics (chapter 5.7) • Correlations between prevailing GIS major failure characteristics (chapter 5.8.) • Summary and conclusion

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All chapters below include introduction (description of subchapters), collected data in absolute and relative values, interpretation graphs, comparison with the 2nd_{GIS survey}

results (if applicable) and final summary of findings and their WG’s commentary.

As the failure frequency is concerned there was taken the same unit as in the 2nd_{survey, i.e.}

the failure frequency is described as number of failures per 100 circuit-breaker-bay-years (CB-bay-years). One CB-bay is a 3-phase GIS assembly consisting of one circuit breaker, its associated isolating switches, instrument transformers, interconnecting bus up to and including the line disconnecting switch (if applicable), and section of main bus (if applicable). GIS maintenance card analysis is included in technical brochure [6].

The GIS voltage ranges, i.e. voltage classes, were divided in the questionnaire and are described here as follows:

Expression of a voltage class in the

questionnaire1

Expression of a voltage class in chapter

tables and graphs [kV] Expression of a voltage class in a chapter text

60<= ... <100 kV 60≤ U<100 kV class 1 100<= ... <200 kV 100≤ U<200 kV class 2 200<= ... <300 kV 200≤ U<300 kV class 3 300<= ... <500 kV 300≤ U<500 kV class 4 500<= ... <700 kV 500≤ U<700 kV class 5 >=700 kV ≥ 700 kV class 6

1_{To avoid font compatibility problems when the questionnaire was processed on computers around}

the globe, only simple characters were used. Using "<=" instead of "≤" seemed not to have been misinterpreted by the users.

5.3 Participation in the Survey

Participation in the survey was quite even in individual reference years (i.e. surveyed years from 2004 up to and including 2007) in spite of the fact that some countries and some utilities reported only in some survey years and in the others did not. The same is valid for the reporting of individual GIS substations – in some years specific GISs were reported in some were not. The GIS questionnaire population card requested that one complete GIS was described in one line. In such a case the total number of lines in individual reference years would show the number of reported GIS. Unfortunately many respondents did not follow the instructions and reported each CB-bay in a separate line. If they simultaneously did not mention identical name for the GIS in each line or did not mention the GIS name at all, the database (DB) considered each line as a separate GIS. This problem concerned 23 412 lines with only 1 CB bay reported and 59 lines without any CB- bay (from total of 37 707 DB lines). For this reason it is impossible neither to evaluate number of reported GIS nor to evaluate an average number of CB-bays in one substation. The responses enable only analyses of number of participating countries, number of participating utilities, number of reported CB-bays in individual reference years and number of collected service experience CB-bay-years, i.e. sum of reported CB-bays in all four reference years.

Table 5-1 shows participation of countries and utilities (in brackets), both in individual reference years and in individual GIS voltage classes. The total is not a sum of lines above or to the left as most of countries and many utilities referred about GIS in multiple reference years and in multiple voltage classes.

Table 5-2 shows number of reported GIS population in individual reference years, i.e. number of reported CB-bays. Table 5-3 shows the same distribution but without one and Table 5-4 without two prevailing countries.

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Table 5-1: Number of countries (utilities) participated in GIS survey (absolute)

Voltage class

Number of countries (utilities) contributing to reference year Total number of different countries (utilities) in 4 years 2004 2005 2006 2007 60≤ U<100 kV 6 (15) 5 (14) 5 (14) 5 (14) 6 (15) 100≤ U<200 kV 19 (38) 16 (36) 15 (36) 16 (38) 20 (44) 200≤ U<300 kV 12 (22) 12 (23) 12 (24) 12 (24) 13 (25) 300≤ U<500 kV 14 (24) 11 (21) 13 (22) 13 (22) 16 (26) 500≤ U<700 kV 3 (11) 3 (11) 3 (11) 3 (11) 3 (11) ≥ 700 kV 2 (2) 2 (2) 2 (2) 2 (2) 2 (2) Total number of different countries (utilities) 23 (50) 21 (48) 20 (48) 21 (49) 24 (55)

Table 5-2: Number of GIS population [CB-bays] collected in individual survey years (absolute)

Voltage class

Number of GIS CB/bays population collected in reference year 2004 2005 2006 2007 60≤ U<100 kV 10 047 10 071 10 116 10 170 100≤ U<200 kV 6 144 6 263 6 993 7 002 200≤ U<300 kV 2 005 2 049 2 093 2 160 300≤ U<500 kV 2 560 2 434 2 665 2 672 500≤ U<700 kV 776 797 807 807 ≥ 700 kV 85 85 85 85 Total 21 617 21 699 22 759 22 896

Table 5-3: Number of GIS population [CB-bays] collected in individual survey years – data without one prevailing country (absolute)

Voltage class

Number of GIS CB/bays population collected in reference year 2004 2005 2006 2007 60≤ U<100 kV 43 46 46 46 100≤ U<200 kV 5 662 5 779 6 508 6 502 200≤ U<300 kV 281 313 345 410 300≤ U<500 kV 1 381 1 245 1 476 1 481 500≤ U<700 kV 29 47 47 47 ≥ 700 kV 85 85 85 85 Total 7 481 7 515 8 507 8 571

Table 5-4: Number of GIS population [CB-bays] collected in individual survey years – data without two prevailing countries (absolute)

Voltage class

Number of GIS CB/bays population collected in reference year 2004 2005 2006 2007 60≤ U<100 kV 26 29 29 29 100≤ U<200 kV 945 854 942 936 200≤ U<300 kV 281 313 345 410 300≤ U<500 kV 517 360 399 404 500≤ U<700 kV 29 47 47 47 ≥ 700 kV 48 48 48 48 Total 1 846 1 651 1 810 1 874

As the GIS population card asked for 3-phase data about Gas Insulated Switchgear (GIS) and those parts of hybrid substations made from GIS components all of the above mentioned values are related to 3-phase arrangements.

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Comparison with previous survey

Number of countries (24) as well as number of utilities (55) participating in the 3rd_GIS

experience survey is lower than participation in the 2nd_{survey by 20% for countries (30) and}

31% for utilities (80). Number of referred GIS CB-bays (22 240) is higher than in the 2nd

survey (13 696) by about 60%. This reflects an increasing use of GIS technology.

The utilities, that responded to the 3rd_{survey, are not the same and there is only a certain}

overlap (less than 50%) in both surveys. This makes the comparison of both surveys results problematic. The brochure user is therefore kindly asked to keep this fact in mind when reading the “comparison with previous survey” paragraphs below.

Findings and commentary

The participation of countries and utilities in the four years (2004, 2005, 2006 and 2007) of the survey was quite even. The same is valid for their four years contributions in individual voltage classes. Altogether 24 countries and 55 utilities took part in the survey with an average total population of about 22 240 GIS CB-bays. As shown later in chapter 5.4 the WG A3-06 decided to provide two types of analyses – the first one for all collected data and the second one for all data without countries 14 and 23 data. The reason is to analyze the data without two dominant countries separately to find out if there are any differences.

5.4 GIS Service Experience Distribution

As written in chapter 5.3 a sum of reported CB-bays in individual reference years gives a value of reported GIS service experience, i.e. number of CB-bay-years. The reported service experience population data [CB-bay-years] is analyzed here from the following point of views:

• Country contribution to the survey and GIS voltage class distribution (chapter 5.4.1) • GIS extent distribution (chapter 5.4.2)

• GIS type of enclosure distribution (chapter 5.4.3) • GIS location distribution (chapter 5.4.4)

• GIS age distribution (chapter 5.4.5)

• GIS maintenance practices distribution (chapter 5.4.6)

The reported GIS service experience is a number of three phases CB-Bays.

5.4.1 Country contribution and GIS voltage class service experience

distribution

Country contribution to the survey is shown in Table 5-5. It shows voltage class contributions of the individual countries as well as their contribution to the total. 100% bases are the service experiences of individual voltage classes, and/or total data (last column) cumulated over the 4-year survey period.

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Table 5-5 : GIS service experience country contribution to the survey (absolute and relative values within individual voltage classes)

Country code

GIS Voltage class

Total 60≤U<100 kV (cl.1) 100≤U<200 kV (cl.2) 200≤U<300 kV (cl.3) 300≤U<500 kV (cl.4) 500≤U<700 kV (cl.5) ≥700 kV (cl.6) Number of CB-bay-years [%] Number of CB-bay-years [%] Number of CB-bay-years [%] Number of CB-bay-years [%] Number of CB-bay-years [%] Number of CB-bay-years [%] Number of CB-bay-years [%] 1 72 0,18 136 0,52 96 1,16 216 2,09 0 0 192 56,47 712 0,80 2 0 0 0 0 0 0 24 0,23 0 0 0 0 24 0,03 4 0 0 166 0,63 56 0,67 0 0 0 0 0 0 222 0,25 5 0 0 8 0,03 0 0 0 0 0 0 0 0 8 0,01 7 0 0 95 0,36 0 0 0 0 0 0 0 0 95 0,11 8 0 0 661 2,50 0 0 136 1,32 0 0 0 0 797 0,90 9 0 0 116 0,44 0 0 0 0 0 0 0 0 116 0,13 10 0 0 0 0 12 0,14 0 0 44 1,38 0 0 56 0,06 11 12 0,03 192 0,73 44 0,53 72 0,70 0 0 0 0 320 0,36 12 0 0 24 0,09 81 0,98 12 0,12 0 0 0 0 117 0,13 13 0 0 653 2,47 8 0,10 24 0,23 0 0 0 0 685 0,77 14 40 223 99,55 1 951 7,39 6 958 83,76 4748 45,96 3017 94,67 0 0 56 897 63,95 17 2 0,00 68 0,26 29 0,35 159 1,54 0 0 0 0 258 0,29 18 0 0 32 0,12 13 0,13 0 0 0 0 45 0,05 19 27 0,07 80 0,30 49 0,59 4 0,04 126 3,95 0 0 286 0,32 20 0 0 0 0 0 0 54 0,52 0 0 0 0 54 0,06 21 0 0 528 2,00 100 1,20 554 5,36 0 0 0 0 1182 1,33 22 0 0 31 0,12 0 0 0 0 0 0 0 0 31 0,03 23 68 0,17 20 774 78,68 0 0 3 903 37,78 0 0 148 43,53 24 893 27,98 24 0 0 0 0 762 9,17 288 2,79 0 0 0 0 1 050 1,18 26 0 0 3 0,01 0 0 0 0 0 0 0 0 3 0,00 27 0 0 3 0,01 0 0 0 0 0 0 0 0 3 0,00 28 0 0 324 1,23 52 0,63 116 1,12 0 0 0 0 492 0,55 29 0 0 557 2,11 60 0,72 8 0,08 0 0 0 0 625 0,70 Total 2664 45.41 22548 29.67 9882 9.34 30018 11.61 13128 3.58 2040 0.38 88 971 100,00

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Collected service experience in individual voltage classes is summarized in table 5-6 in absolute numbers and in % (the base is total number of collected service experience). Figure 5-1 shows a graph of absolute values for all data and it compares it with all data without two dominant countries 14 and 23.

Table 5-6: GIS service experience in individual voltage classes (absolute and relative values within total)

Voltage class

All data Data without countries 14 and 23

Number of CB-bay-years % Number of CB-bay-years %

60≤U<100 kV 40 404 45,4 113 1,6 100≤U<200 kV 26 402 29,7 3 677 51,2 200≤U<300 kV 8 307 9,3 1 349 18,8 300≤U<500 kV 10 331 11,6 1 680 23,4 500≤U<700 kV 3 187 3,6 170 2,4 ≥700 kV 340 0,4 192 2,7 Total 88 971 100,0 7 181 100

Figure 5-1: Distribution of GIS service experience absolute values in individual voltage classes

Comparison with previous survey

The 2nd_{GIS experience survey collected service experience, number of major failures, for the}

whole time of the referred GIS’s life. The total collected service experience was therefore higher (118 483 GIS CB-bay-years) than in the 3rd_{survey (88 971 GIS CB-bay-years). In}

spite of that the 3rd_{survey collected experience reached 75% of those from the 2}nd_{survey. In}

the 2nd_{survey there was one dominant country equal to one of the two dominant countries in}

the 3rd_{survey (country 14). The second dominant country (country 23) did not participated in}

the 2nd survey. The 2nd survey results were thus provided for all population and for population without one dominant country to show the GIS performance in Europe and in the rest of the world. For failure frequency calculation in the 2nd survey one more utility data were subtracted. This utility had one of the oldest breaker technology in its GIS with extremely high number of failures. As the voltage class definitions were the same in both surveys it is possible to provide a comparison of collected service experience as shown in table 5-7.

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 Service experince [CB ‐bay ‐years] GIS service experience voltage classes distribution (all data) 60≤U<100 kV 100≤U<200 kV 200≤U<300 kV 300≤U<500 kV 500≤U<700 kV ≥700 kV 0 500 1000 1500 2000 2500 3000 3500 4000 GIS service experience voltage classes distribution (data without countries 14 and 23)

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Table 5-7: Comparison of collected GIS service experience in individual voltage classes in the 2nd and the 3rd GIS surveys (absolute values)

Voltage class

Collected GIS service experience –

2nd survey [CB-bay-years]

3rd survey [CB-bay-years]

All data

All data without

the worst utility country 14 and Data without

the worst utility All data countries 14 and 23Data without

60≤U<100 kV 56 884 56 884 5 114 40 404 113 100≤U<200 kV 34 060 29 415 20 999 26 402 3 677 200≤U<300 kV 16 040 16 040 9 576 8 307 1 349 300≤U<500 kV 6 774 6 371 6 371 10 331 1 680 500≤U<700 kV 4 525 4 525 1 101 3 187 170 ≥700 kV 200 200 200 340 192 Total 118 483 113 435 43 361 88 971 7 181

As the 3rd_{survey experience without two dominant countries (14 and 23) represents only}

15% of comparable collected data in the 2nd_{survey the WG A3-06 decided to provide most of}

the survey comparisons below only for all data. The reader can, if he wishes, find result details for 2nd_{survey without country 14 population in [13].}

Graphical interpretation of all data collected service experience is shown in Fig.5-2.

Figure 5-2: Comparison of total collected GIS service experience in individual voltage classes in the 2nd and the 3rd GIS surveys

The total collected data of service experience in the 2nd_{and the 3}rd_{GIS experience surveys}

in individual voltage classes is comparable and can be used (with restrictions mentioned in 5.3) for their results approximate comparison. An increase of the collected experience has been observed only in voltage class 4.

0 10000 20000 30000 40000 50000 60000 Service experience [CB ‐bay ‐years] Voltage class [kV] Comparison of collected GIS service experience 2nd survey (1995) 3rd survey (2007)

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Findings and commentary

From the above shown tables it is evident that the reported service experience is dominated by countries with codes 14 and 23. Both are countries that are traditionally known of using modern technologies and of applying effective maintenance strategies. Country with code number 14 dominates almost absolutely in voltage class 1 (99,6%) and in voltage class 5 (94,7%). In voltage class 3 it represents 83,8 % of reported service experience. Country with code 23 dominates in voltage class 2 (78,7 %). In class 4 these two countries share the domination by 46% (country 14) and by 37,8% (country 23). Only two countries reported about service experience in class 7. These two countries (country 1 and 23) share the total service experience in class 7 by approximately half and half.

This uneven distribution of service experience shall be kept in mind when reading the rest of the results analysis. If the further analysis was made only for total data the contribution of other countries than 14 and 23 would be suppressed. However it might be interesting to see also the differences between the two prevailing countries and the rest. Therefore the WG decided to provide the analyses of reported service experience data, where appropriate, for total data and for data without the two dominant countries.

The difference is already visible when evaluating the division of the service experience in individual GIS voltage classes in the survey. Evaluating all data, classes 1 (45,5%) and 2 (29,7%) prevail whereas class 4 represents about 12% and the portion of other classes is less than 10%. Evaluating data without countries 14 and 23 the majority of experience lies in class 2 (51%), 3 (19%) and 4 (23%).

5.4.2 GIS extent service experience distribution

The respondents were asked to divide their GIS installations population into the following two categories (for details see Appendix 1 – the questionnaire):

• Fully GIS - substation the bays of which are fully made from GIS technology components. Only external HV connections to overhead or cable lines, or transformers, shunt reactors and capacitors can have external insulation.

• Hybrid GIS - substation the bays of which are made from a mix of GIS and AIS technology components, i.e. in which the CB-bays contains combination of enclosed gas insulated and air insulated parts.

Collected service experiences in individual voltage classes are summarized in table 5-8 for all data and in table 5-9 for all data without countries 14 and 23. The values in both tables are expressed in absolute and in relative values. The calculation bases for relative values are numbers of collected service experiences in individual voltage classes. Figures 5-3 show graphically absolute data in Tables 5-8 and 5-9, i.e. portions of fully GIS and hybrid GIS CB-bays service experiences collected in individual voltage classes.

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Table 5-8 : Distribution of service experience for the two types of GIS installation extent - all data (absolute and relative values within individual voltage classes)

Voltage class

Fully GIS [CB-bay-years] Hybrid GIS [CB-bay-years]

Absolute % Absolute % 60≤U<100 kV 37 819 93,6 2 585 6,4 100≤U<200 kV 25 732 97,5 670 2,5 200≤U<300 kV 7 123 85,7 1 184 14,3 300≤U<500 kV 8 807 85,2 1 524 14,8 500≤U<700 kV 1 890 59,3 1 297 40,7 ≥700 kV 340 100,0 0 0,0 Total 81 711 91,8 7 260 8,2

Table 5-9 : Distribution of service experience for the two types of GIS installation extent - data without countries 14 and 23 (absolute and relative values within individual voltage classes)

Voltage class

Fully GIS [CB-bay-years] Hybrid GIS [CB-bay-years]

Absolute % Absolute % 60≤U<100 kV 113 100,0 0 0,0 100≤U<200 kV 3 398 92,4 279 7,6 200≤U<300 kV 1 266 93,8 83 6,2 300≤U<500 kV 1 469 87,4 211 12,6 500≤U<700 kV 170 100,0 0 0,0 ≥700 kV 192 100,0 0 0,0 Total 6 608 92,0 573 8,0 0 5000 10000 15000 20000 25000 30000 35000 40000 Service experience [CB ‐bay ‐years] Voltage class [kV]

GIS installationextent distribution (all data)

Fully GIS

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Figures 5-3 : Distribution of service experience absolute values for the two types of GIS installation extent

Comparison with previous survey

Comparison with the 2nd_{GIS experience survey is provided in table 5-10 and figures 5-4.}

Table 5-10: Comparison of collected fully and hybrid GIS service experience in individual voltage classes in the 2nd and the 3rd GIS surveys (absolute values)

Voltage class

2nd_{survey [CB-bay-years]} Collected GIS service experience – ₃rd_{survey [CB-bay-years]}

Fully GIS Hybrid GIS Fully GIS Hybrid GIS

60≤U<100 kV 54 452 2 432 37 819 2 585 100≤U<200 kV 31 864 2 196 25 732 670 200≤U<300 kV 15 018 1 022 7 123 1 184 300≤U<500 kV 6 680 94 8 807 1 524 500≤U<700 kV 3 742 783 1 890 1 297 ≥700 kV 200 0 340 0 Total 111 956 6 527 81 711 7 260

Figures 5-4: Comparison of collected fully and hybrid GIS service experience in individual voltage classes in the 2nd and the 3rd GIS surveys

The difference in absolute as well as relative collected service experience between the 2nd

and the 3rd_{surveys is visible namely at hybrid GIS installations. With exception of voltage}

class 2, there is visible an increase in hybrid GIS utilization. 0 500 1000 1500 2000 2500 3000 3500 4000 Service experience [CB ‐bay ‐years] Voltage class [kV] GIS installation extent distribution (data without countries 14 and 23) Fully GIS Hybrid GIS 0 10000 20000 30000 40000 50000 60000 Se rv ic e ex p e ri e n ce [C B ‐ba y‐ ye ar s] Voltage class [kV] Comparison of collected fully GIS service experience 2nd survey (1995) 3rd survey (2007) 0 500 1000 1500 2000 2500 3000 Se rv ic e ex p er ie n ce [C B0 b ay ‐ye a rs] Voltage class [kV] Comparison of collected hybrid GIS service experience 2nd survey (1995) 3rd survey (2007)

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Findings and commentary

Portion of hybrid GIS installations is still relatively small. Hybrid GIS represents only about 8% of all collected data. There is no difference between relative total data and relative data without two dominant countries. However there is a certain trend visible in increasing their portion at higher voltage classes in which mixed technologies (MTS) installation can offer advantages for new installations as well as for upgrading and extensions of existing AIS (for details about comparison of AIS-GIS-MTS features see CIGRE technical brochure [15].

5.4.3 GIS type of enclosure service experience distribution

The respondents were asked to divide their GIS installations population in dependence on number of HV conductors placed in one enclosure into the following two categories (for details see Appendix 1 – the questionnaire):

• Single phase enclosure (1-phase) • Three phase enclosure (3-phase)

They were supposed to indentify these categories separately for busbars and for individual CB-bays.

Collected service experiences in individual voltage classes are summarized in table 5-11 for all data and in table 5-12 for all data without countries 14 and 23. The values in both tables are expressed in absolute and in relative values. The bases for calculations of relative values are numbers of collected service experiences in individual voltage classes.

Table 5-11: Distribution of service experience for the two types of GIS enclosure design - all data (absolute and relative values within individual voltage classes)

Voltage class

Number of bay-years in

CB-bay design of Number of CB-bay-years connected to busbar design of

1-phase 3-phase 1-phase 3-phase

Absolute % Absolute % Absolute % Absolute %

60≤U<100 kV 7 752 19,2 32 652 80,8 15 139 37,5 25 265 62,5 100≤U<200 kV 15 453 58,5 10 949 41,5 2 058 7,8 24 344 92,2 200≤U<300 kV 3 643 43,9 4 664 56,1 3 409 41,0 4 898 59,0 300≤U<500 kV 8 555 82,8 1 776 17,2 4 154 40,2 6 177 59,8 500≤U<700 kV 3 187 100,0 0 0,0 2 233 70,1 954 29,9 ≥700 kV 340 100,0 0 0,0 340 100,0 0 0,0 Total 38 930 43,8 50 041 56,2 27 333 30,7 61 638 69,3

Table 5-12: Distribution of service experience for the two types of GIS enclosure design - data without countries 14 and 23 (absolute and relative values within individual voltage classes)

Voltage class

Number of bay-years in

CB-bay design of Number of CB-bay-years connected to busbar design of

1-phase 3-phase 1-phase 3-phase

60≤U<100 kV 72 63,7 41 36,3 0,0 113 100,0 100≤U<200 kV 1 972 53,6 1 705 46,4 1 445 39,3 2 232 60,7 200≤U<300 kV 1 333 98,8 16 1,2 916 67,9 433 32,1 300≤U<500 kV 1 670 99,4 10 0,6 1 516 90,2 164 9,8 500≤U<700 kV 170 100,0 0 0,0 170 100,0 0 0,0 ≥700 kV 192 100,0 0 0,0 192 100,0 0 0,0 Total 5 409 75,3 1 772 24,7 4 239 59,0 2 942 41,0

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As the questionnaire asked about the design for two separate parts of GIS it was necessary to synthesize the answers to get an overview about the collected service experience of uniform design substations and of combined design substations. The results of this synthesis are shown in table 5-13 for all data and in table 5-14 for all data without countries 14 and 23. The values in both tables are expressed in absolute and in relative values. The bases for calculations of relative values are numbers of collected service experiences in individual voltage classes. Figures 5-5 show graphically absolute data in tables 5-13 and 5-14, i.e. portions of 1-phase, 3-phase and combined GIS CB-bays service experiences in individual voltage classes.

Table 5-13: Distribution of service experience for combinations of the two types of GIS enclosure design - all data (absolute and relative values within individual voltage classes)

Voltage class

Number of CB-bay-years

1-phase GIS 3-phase GIS Busbar 1-phase +

CB-bay 3-phase Busbar 3-phase + CB-bay 1-phase

60≤U<100 kV 3 818 9,4 21 331 52,8 11 321 28,0 3 934 9,7 100≤U<200 kV 1 826 6,9 10 717 40,6 232 0,9 13 627 51,6 200≤U<300 kV 2 664 32,1 3 919 47,2 745 9,0 979 11,8 300≤U<500 kV 4 154 40,2 1 776 17,2 0 0,0 4 401 42,6 500≤U<700 kV 2 233 70,1 0 0,0 0 0,0 954 29,9 ≥700 kV 340 100,0 0 0,0 0 0,0 0 0,0 Total 15 035 16,9 37 743 42,4 12 298 13,8 23 895 26,9

Table 5-14: Distribution of service experience for combinations of the two types of GIS enclosure design - data without countries 14 and 23 (absolute and relative values within individual voltage classes)

Voltage class

1-phase GIS 3-phase GIS Busbar 1-phase +

CB-bay 3-phase Busbar 3-phase + CB-bay 1-phase

60≤U<100 kV 0 0,0 41 36,3 0 0,0 72 63,7 100≤U<200 kV 1 437 39,1 1 705 46,4 8 0,2 535 14,5 200≤U<300 kV 912 67,6 16 1,2 4 0,3 421 31,2 300≤U<500 kV 1 516 90,2 10 0,6 0 0,0 154 9,2 500≤U<700 kV 170 100,0 0 0,0 0 0,0 0 0,0 ≥700 kV 192 100,0 0 0,0 0 0,0 0 0,0 Total 4 227 58,9 1 772 24,7 12 0,2 1 182 16,5 0 5000 10000 15000 20000 25000 Service experience [CB ‐bay ‐years] Voltage class [kV] GIS design distribution (all data) 1‐phase GIS 3‐phase GIS Busbar 1‐phase + CB‐bay 3‐phase Busbar 3‐phase + CB‐bay 1‐phase

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Figures 5-5: Distribution of service experience (absolute values for combinations of the two types of GIS enclosure design]

The further analysis focuses mainly on CB-bays design. The main reason is that the further failure frequency analysis is subsequently made for one CB-bay. This is the same way as made in 1995 in the previous GIS survey. The only place where 1-phase and 3-phase busbar enclosure will be considered will be the analysis of busbar failures itself.

Comparison with previous survey

The 2nd GIS survey questionnaire did not ask a question about the referred GIS an enclosure design.

Findings and commentary

Combination of 1-phase busbars and 3-phase CB-bays appears very seldom in 13,8% of all collected experience (thereof in 28% in voltage class 1) and almost does not exist in other countries than in 14 and 23. Combination of 3-phase busbars and 1-phase CB-bays appears much more frequently and represents 27% in total and 17% in other countries than 14 and 23 collected experience. It can be found with a high portion (30%) even in voltage class 5 GIS. Evaluating the total data this combination seems to be very popular in voltage classes 2 and 4 in which it reaches 52% and 43% of service experience collected in these voltage classes. In countries other than 14 and 23 this design combination is used in voltage classes 1 (64%), 2 (15%), 3 (31%) and 4 (9%).

As unified designs are concerned the single phase GIS appears in all voltage classes- the higher voltage the higher representation. It s representation vary from about 10% at classes 1 and 2 up to nearly a half in voltage classes 3 and 4 and to almost 100% in voltage classes 5 and 6. Countries other than 14 and 23 use single phase GIS design even more frequently and this design prevails starting already voltage class 3. The three phase GIS design can be found up to voltage class 4 and it is used in countries 14 and 23 much more often than in other countries. It prevails in GIS up to voltage class 3, whereas in other counties only up to voltage class 2.

5.4.4 GIS location service experience distribution

The respondents were asked to divide their GIS installations populations into the following categories (for details see Appendix 1 – the questionnaire):

• GIS Indoor Normal (Indoor N) - for normal indoor conditions

• GIS Indoor Special (Indoor S) - for special indoor conditions (e.g. for containerized installations, installations under simple buildings as shelters without heating, altitudes >1000m, etc.)

• GIS Outdoor Normal (Outdoor N) - for normal outdoor conditions 0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 Service experience [CB ‐Bay ‐years] Voltage class [kV] GIS design distribution (data without countries 14 and 23) 1‐phase GIS 3‐phase GIS Busbar 1‐phase + CB‐bay 3‐phase Busbar 3‐phase + CB‐bay 1‐phase

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• GIS Outdoor Special (Outdoor S) - for special outdoor conditions (e.g. for lower ambient temperatures than -40°C, altitudes >1000m, pollution areas III or IV, ice coating >20 mm, direct coastal areas, etc.)

Note: GIS whose only outdoor parts are bushings (SF6/air, SF6/transformer) and/or necessary lengths of connecting busducts are considered as indoor installations.

Collected service experiences in individual voltage classes are summarized in table 5-15 for all data and in table 5-16 for all data without countries 14 and 23. The values in both tables are expressed in absolute and in relative values. The bases for relative values calculations are numbers of collected service experiences in individual voltage classes.

Figures 5-6 show graphically absolute data in tables 5-15 and 5-16, i.e. portions of indoor normal, indoor special, outdoor normal and outdoor special GIS locations CB-bays service experiences in individual voltage classes.

As special installations portions are almost negligible (with exception of voltage class 1 distribution in data without countries 14 and 23) further analysis is made only in the division of Indoor/Outdoor locations. To show the difference between installation habits in all population (dominated by countries 14 and 23) and the rest of the world, table 5-17 shows absolute and relative data and figure 5-7 illustrates relative values of Indoor/Outdoor installations in these two groups of population.

Table 5-15: Distribution of service experience for types of GIS installation locations - all data (absolute and relative values within individual voltage classes)

Voltage class

Indoor N Indoor S Outdoor N Outdoor S

60≤U<100 kV 12 643 31,3 155 0,4 27 462 68,0 144 0,4 100≤U<200 kV 17 458 66,1 24 0,1 8 920 33,8 0 0,0 200≤U<300 kV 2 707 32,6 20 0,2 5 561 66,9 19 0,2 300≤U<500 kV 2 847 27,6 64 0,6 7 396 71,6 24 0,2 500≤U<700 kV 336 10,5 9 0,3 2 830 88,8 12 0,4 ≥700 kV 192 56,5 0 0,0 148 43,5 0 0,0 Total 36 183 40,7 272 0,3 52 317 58,8 199 0,2

Table 5-16: Distribution of service experience for types of GIS installation locations - data without countries 14 and 23 (absolute and relative values within individual voltage classes)

Voltage class

Indoor N Indoor S Outdoor N Outdoor S

60≤U<100 kV 74 65,5 27 23,9 12 10,6 0 0,0 100≤U<200 kV 3 397 92,4 24 0,7 256 7,0 0 0,0 200≤U<300 kV 1 282 95,0 7 0,5 60 4,4 0 0,0 300≤U<500 kV 1 263 75,2 64 3,8 329 19,6 24 1,4 500≤U<700 kV 32 18,8 0 0,0 138 81,2 0 0,0 ≥700 kV 192 100,0 0 0,0 0 0,0 0 0,0 Total 6 240 86,9 122 1,7 795 11,1 24 0,3

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Figures 5-6: Distribution of service experience (absolute values for types of GIS installation locations)

Table 5-17: Distribution of service experience for indoor and outdoor GIS installation locations – all data and data without countries 14 and 23 (absolute and relative values within individual voltage classes)

Voltage class

Number of CB-bay-years (all data)

Number of CB-bay-years (data without countries 14 and 23)

Indoor GIS Outdoor GIS Indoor GIS Outdoor GIS

60≤U<100 kV 12 798 31,7 27 606 68,3 101 89,4 12 10,6 100≤U<200 kV 17 482 66,2 8 920 33,8 3 421 93,0 256 7,0 200≤U<300 kV 2 727 32,8 5 580 67,2 1 289 95,6 60 4,4 300≤U<500 kV 2 911 28,2 7 420 71,8 1 327 79,0 353 21,0 500≤U<700 kV 345 10,8 2 842 89,2 32 18,8 138 81,2 ≥700 kV 192 56,5 148 43,5 192 100,0 0 0,0 Total 36 455 41,0 52 516 59,0 6 362 88,6 819 11,4 0 5000 10000 15000 20000 25000 30000 Service experince [CB ‐bay ‐years] Voltage class [kV] GIS location distribution (all data) Indoor N Indoor S Outdoor N Outdoor S 0 500 1000 1500 2000 2500 3000 3500 4000 Service experience [CB ‐bay ‐years] Voltage class [kV] GIS location distribution (data without countries 14 and 23) Indoor N Indoor S Outdoor N Outdoor S

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Figure 5-7: Relative distribution and comparison of service experience for indoor and outdoor GIS installation locations

Comparison with previous survey

The distinction between “normal” and “special” GIS locations was made only in the 3rd

survey. Comparison with the 2nd_{GIS experience survey in categories indoor-outdoor is}

provided in table 5-18 and figure 5-8.

Table 5-18: Comparison of collected indoor and outdoor GIS service experience in individual voltage classes in the 2nd and the 3rd GIS surveys (absolute values)

Voltage class

2nd survey [CB-bay-years] Collected GIS service experience – 3rd survey [CB-bay-years]

Indoor GIS Outdoor GIS Indoor GIS Outdoor GIS

60≤U<100 kV 22 573 34 311 12 798 27 606 100≤U<200 kV 28 173 5 887 17 482 8 920 200≤U<300 kV 9 734 6 306 2 727 5 580 300≤U<500 kV 4 356 2 418 2 911 7 420 500≤U<700 kV 2 044 2 481 345 2 842 ≥700 kV 200 0 192 148 Total 67 080 51 403 36 455 52 516

Figures 5-8: Comparison of collected indoor and outdoor GIS service experience in individual voltage classes in the 2nd and the 3rd GIS surveys

Outdoor GIS experience has relatively increased (in voltage classes 2, 4 and 5 also absolutely) in all voltage classes in the 3rd_{GIS survey compared to the 2}nd_{GIS survey.}

0 10 20 30 40 50 60 70 80 90 100

Indoor (all data) Outdoor (all data) Indoor (data

without 14&23) Outdoor (data without 14&23) Service experience distribution [%] GIS location distribution 60≤U<100 kV 100≤U<200 kV 200≤U<300 kV 300≤U<500 kV 500≤U<700 kV ≥700 kV Total 0 5000 10000 15000 20000 25000 30000 Se rv ic e ex p e ri e n ce [C B ‐ba y‐ ye ar s] Voltage class [kV] Comparison of collected indoor GIS service experience 2nd survey (1995) 3rd survey (2007) 0 5000 10000 15000 20000 25000 30000 35000 40000 Se rv ic e ex p er ien ce [C B 0 b a y ‐ye a rs ] Voltage class [kV] Comparison of collected outdoor GIS service experience 2nd survey (1995) 3rd survey (2007)

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Findings and commentary

Special locations are very rare. They represents only 0,3 % of indoor and 0,2% of outdoor installations. Therefore it is possible to neglect the special conditions in further analysis and to add these installations to only indoor/outdoor categories.

As indoor/outdoor installations are concerned there is a visible difference when evaluating all data and data without countries 14 and 23. Analyzing all data it seems that outdoor installations slightly prevail in higher voltage classes starting voltage class 4. The installations of other voltage classes most probably depend on local needs and not on a general installation policy. The utilities in countries other than 14 and 23 prefer indoor installations at all voltage classes (except class 5) in spite of the fact that size of GIS building or shelter can represent a certain design challenge.

5.4.5 GIS age service experience distribution

As the survey was running in the period of 4 years the reported GIS age overview would be complicated (“floating age”). The age aspect is therefore expressed in another way – in the way of analyzing manufacturing years. In the GIS population failure cards there were identified manufacturing years of individual GIS. In CB and other equipments population cards there were identified only intervals of manufacturing years. The GIS data were therefore also classified into the same intervals to provide the data analysis in the same structure of classes.

Table 5-19 shows a distribution of collected GIS service experience in seven intervals of GIS manufacturing years for all data and in absolute and relative values (100% is number of GIS CB-bays service experience collected within individual voltage classes). Table 5-20 shows the same data but without two dominant countries.

Table 5-19 : Distribution of service experience in seven intervals of GIS manufacturing years - all data (absolute and relative values within individual voltage classes)

Manufacturing

year <100 kV 60≤U <200 kV 100≤U <300 kV 200≤U <500 kV 300≤U <700 kV 500≤U ≥700 kV

abs. % abs. % abs. % abs. % abs. % abs. %

before 1979 2 760 6,8 354 1,3 697 8,4 420 4,1 160 5,0 0 0,0 1979-1983 4 092 10,1 773 2,9 722 8,7 1 153 11,2 574 18,0 0 0,0 1984-1988 8 916 22,1 1 731 6,6 1 590 19,1 1 466 14,2 512 16,1 192 56,5 1989-1993 9 926 24,6 3 532 13,4 1 826 22,0 1 813 17,5 513 16,1 0 0,0 1994-1998 8 965 22,2 7 533 28,5 1 755 21,1 2 662 25,8 863 27,1 0 0,0 1999-2003 5 247 13,0 8 537 32,3 1 264 15,2 1 950 18,9 524 16,4 140 41,2 2004-2007 498 1,2 3 942 14,9 453 5,5 867 8,4 41 1,3 8 2,4 Total 40 404 100 26 402 100 8 307 100 10 331 100 3 187 100 340 100

Table 5-20 : Distribution of service experience in seven intervals of GIS manufacturing years – data without countries 14 and 23 (absolute and relative values within individual voltage classes)

Manufacturing

year <100 kV 60≤U <200 kV 100≤U <300 kV 200≤U <500 kV 300≤U <700 kV 500≤U ≥700 kV

abs. % abs. % abs. % abs. % abs. % abs. %

before 1979 72 63,7 288 7,8 189 14,0 172 10,2 0 0,0 0 0,0 1979-1983 0 0,0 504 13,7 108 8,0 501 29,8 138 81,2 0 0,0 1984-1988 12 10,6 691 18,8 29 2,1 374 22,3 32 18,8 192 100,0 1989-1993 2 1,8 706 19,2 130 9,6 285 17,0 0 0,0 0 0,0 1994-1998 0 0,0 412 11,2 136 10,1 98 5,8 0 0,0 0 0,0 1999-2003 27 23,9 729 19,8 403 29,9 64 3,8 0 0,0 0 0,0 2004-2007 0 0,0 347 9,4 354 26,2 186 11,1 0 0,0 0 0,0 Total 113 100 3 677 100 1 349 100 1 680 100 170 100 192 100

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Table 5-21 shows the same data as tables 5-19 and 5-20 but the relative values are recalculated to total collected service experience value (100% is total number of GIS CB-bays service experience). Figures 5-9 provide graphical interpretations of the relative data from table 5-21.

Table 5-21: Distribution of service experience in seven intervals of GIS manufacturing years – all data and data without countries 14 and 23 (absolute and relative values within all collected data)

Manufacturing year All data data without countries 14

and 23 abs. % abs. % before 1979 4 391 4,9 721 10,0 1979-1983 7 314 8,2 1 251 17,4 1984-1988 14 407 16,2 1 330 18,5 1989-1993 17 610 19,8 1 123 15,6 1994-1998 21 778 24,5 646 9,0 1999-2003 17 662 19,9 1 223 17,0 2004-2007 5 809 6,5 887 12,4 Total 88 971 100,0 7 181 100,0

Figures 5-9: Distribution of service experience - absolute values in seven intervals of GIS manufacturing years for individual voltage classes

0 2000 4000 6000 8000 10000 12000 Service experience [CB ‐bay ‐years] Reported GIS service experience in dependence on manufacturing year interval (all data) 60≤U<100 kV 100≤U<200 kV 200≤U<300 kV 300≤U<500 kV 500≤U<700 kV ≥700 kV 0 100 200 300 400 500 600 700 800 Service experience [CB ‐bay ‐years] Reported GIS service experience in dependence on manufacturing year interval (data without countries 14 and 23) 60≤U<100 kV 100≤U<200 kV 200≤U<300 kV 300≤U<500 kV 500≤U<700 kV ≥700 kV

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Comparison with previous survey

In the population card of the 2nd_{GIS survey there was a column for inserting the year when}

each GIS substation was put into service. However, in the analysis brochure [13] the collected service experience used for failure frequency calculation is expressed only in two categories - for GIS commissioned before 1.1.1985 and after 1.1.1985, i.e. for GIS younger than 12 years (age of 1 to 11 years) and for older than 12 years. To compare the results with the 3rd_{survey it was therefore necessary to classify the data into the same two age intervals.}

The comparison is shown in table 5-22 and figure 5-10. The table shows data without one worst utility for the 2nd_{survey and only the complete data (data having its equivalent in failure}

cards) for the 3rd_{survey. This data is used for failure frequency comparison (see chapter}

5.6).

Table 5-22: Comparison of 2nd and 3rd GIS surveys collected GIS service experience of GIS

older than 11 years and 11 years old or younger in individual voltage classes (absolute values)

Voltage class

2nd survey [CB-bay-years] Collected GIS service experience – 3rd survey [CB-bay-years]

GIS age

>11 years ≤11 years GIS age >11 years GIS age ≤11 years GIS age

60≤U<100 kV 28 669 28 215 28 932 11 472 100≤U<200 kV 16 871 12 544 8 376 18 003 200≤U<300 kV 10 362 5 678 5 314 2 993 300≤U<500 kV 3 694 2 677 5 624 4 707 500≤U<700 kV 3 252 1 273 1 972 1215 ≥700 kV 0 200 192 148 Total 62 848 50 587 50 410 38 538

Figure 5-10: Comparison of 2nd and 3rd GIS surveys collected GIS service experience of GIS older than 11 years and 11 years old or younger

In the 2nd_{GIS survey the collected service experience for older GIS was greater than for}

younger in all voltage classes. In the 3rd_{survey, this is not valid for voltage class 2. As}

relative values are concerned very similar patterns are visible in voltage classes 3, 4 and 5. In spite of that the figure just reflects a difference between the 2nd_{and the 3}rd_{surveys utilities’}

participation. 0 5000 10000 15000 20000 25000 30000 35000 Service experience [CB ‐bay ‐years] Voltage class [kV] Comparison of collected GIS experince in two age groups >11 years old GIS 2nd survey (1995) ≤11 years old GIS 2nd survey (1995) >11 years old GIS 3rd survey (2007) ≤11 years old GIS 3rd survey (2007)

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Findings and commentary

The oldest reported GIS substation was manufactured and installed in 1960 and belongs to voltage class 1. The oldest voltage class 2 substations were installed in 1963 (1 substation) and in 1968 (2 substations). The oldest GIS of voltage classes 3 to 6 were installed in 1970, 1975, 1973 and in 1986 respectively.

In all seven manufacturing years intervals there was collected enough data in both data sets (i.e. total and total without two dominant countries) to be able to provide failure frequencies time trend analyses.

5.4.6 GIS maintenance practices service experience distribution

The respondents were asked to identify their maintenance philosophy in each reference year and in each line describing their population in the reference year. Therefore the response analysis is made in correlation to collected service experience.

The respondent had the following options to select that one which corresponds to their practice most appropriately:

• Time based maintenance philosophy (TBM) • Condition based maintenance philosophy (CBM) • Run to failure (RTF)

• Combination of TBM and CBM (e.g. RCM – reliability centered maintenance) • Other

Maintenance philosophies in relation to the collected service experiences in individual voltage classes are summarized in table 5-23 for all data and in table 5-24 for all data without countries 14 and 23. The values in both tables are expressed in absolute and in relative values. The bases for relative values calculations are numbers of collected service experiences in individual voltage classes. No respondent selected the “run to failure

philosophy” in any voltage class.

Figures 5-11 show graphically relative data in the tables.

Table 5-23: Distribution of service experience for types of GIS maintenance philosophies - all data (absolute and relative values within individual voltage classes)

Voltage class

Number of CB-bay-years referred to different maintenance practices (all data) Time based maintenance (TBM) Condition based maintenance (CBM) Combination of TBM and CBM Other

60≤U<100 kV 27 468 68,0 72 0,2 12 862 31,8 2 0,0 100≤U<200 kV 24 984 94,6 505 1,9 865 3,3 48 0,2 200≤U<300 kV 3 994 48,1 152 1,8 4 132 49,7 29 0,3 300≤U<500 kV 6 520 63,1 740 7,2 2 912 28,2 159 1,5 500≤U<700 kV 2 327 73,0 0 0,0 860 27,0 0 0,0 ≥700 kV 148 43,5 192 56,5 0 0,0 0 0,0 Total 65 441 73,6 1 661 1,9 21 631 24,3 238 0,3

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Table 5-24: Distribution of service experience for types of GIS maintenance philosophies – data without countries 14 and 23 (absolute and relative values within individual voltage classes)

Voltage class

Number of CB-bay-years referred to different maintenance practices (data without countries 14 and 23)

Time based maintenance (TBM) Condition based maintenance (CBM) Combination of TBM and CBM Other

60≤U<100 kV 39 34,5 72 63,7 0 0,0 2 1,8 100≤U<200 kV 2 259 61,4 505 13,7 865 23,5 48 1,3 200≤U<300 kV 133 9,9 152 11,3 1 035 76,7 29 2,1 300≤U<500 kV 209 12,4 740 44,0 572 34,0 159 9,5 500≤U<700 kV 126 74,1 0 0,0 44 25,9 0 0,0 ≥700 kV 0 0,0 192 100,0 0 0,0 0 0,0 Total 2 766 38,5 1 661 23,1 2 516 35,0 238 3,3

Figures 5-11: Relative distribution of service experience for different types of GIS maintenance strategies 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% GIS service experience maintenance strategies relative distribution (all data) Other Combination of time and condition based maint. Condition based maint. Time based maint. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% GIS service experience maintenance strategies relative distribution (data without countries 14 and 23) Other Combination of time and condition based maint. Condition based maint. Time based maint.

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Comparison with previous survey

In the 2nd_{survey, the GIS maintenance aspects were included in a specialized questionnaire}

card called “GIS life expectancy, maintenance, environmental:” This card is similar to 3rd

survey specialized questionnaire card called “GIS maintenance card”. The resulting analysis of responses as well as its comparison with results of the 2nd survey is included in technical brochure [6].

Findings and commentary

In either graphs (all data or in data without countries 14 and 23) no trend is visible that could be related to the voltage class distribution. The result is most probably influenced by the fact that different companies with different maintenance philosophies contributed to different voltage classes. There is however a visible difference between the philosophies interpreted from all data and data without countries 14 and 23. In all data analysis, the traditional policy of time based maintenance still prevails. Inputs from modern strategies as reliability centered and condition based maintenance in combination with the time based activities already appear. However in total they still represent only 26%. Countries other than 14 and 23 seem to be less conservative since condition based maintenance and combination of condition and time based maintenance appear more often. In total they represent already 23 and 35 % respectively.

Maintenance is an extremely important part of any asset management strategy and influences the GIS reliability and GIS availability very much. Therefore the survey contained a specialized GIS maintenance card for respondents to answer detailed questions about maintenance and other aspects of testing and service. The analysis of these cards is included in technical brochure [6].

5.5 GIS Failures

Respondents were asked to report about major (MaF) and minor (MiF) failures that happened in their GIS in the years 2004 to 2007. Details about GIS CB failures were reported in CB failure cards (see technical brochure [2]), GIS DE/ES failures in DE/ES failure cards (see technical brochure [3]), GIS IT failures in IT failure cards (see technical brochure [4]) and other GIS parts in GIS failure cards (see chapter 5.5.5). Chapter 5.5 and other chapters below provide a summary of all GIS failures using data from all four mentioned sources. For definitions of MaF and MiF see Appendix 1.

The reported number of MaF and MiF is analyzed in chapter 5.5 from the following points of views:

• Countries contribution to the survey and GIS voltage classes distribution (chapter 5.5.1)

• GIS extent distribution (chapter 5.5.2)

• GIS type of enclosure distribution (chapter 5.5.3) • GIS location distribution (chapter 5.5.4)

• GIS failed component distribution (chapter 5.5.5) • GIS age distribution (chapter 5.5.6)

The WG has doubts about completeness of minor failures reporting. Most of the utilities have got a very detailed database about major failures whereas minor failures are sometimes repaired without reporting into any information systems. The reader thus shall read the

information below only as information about reported events but shall not make a relative comparison between MaF and MiF events.

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Collected data about failures is reported as single phase in case of an internal failure of a single-phase encapsulated GIS or in case a failure occurs in auxiliary parts like in one of the single phase operating mechanisms. It is reported as three-phase in case of an internal failure of a three-phase encapsulated GIS or in a common auxiliary part like in three gang operating mechanism or in common control cubicle.

5.5.1 Countries contribution and GIS voltage classes failures distribution

Countries contribution to the survey is shown in table 5-25. Table 5-25 shows total absolute and relative data (100% for relative expression is total number of MaF, MiF respectively). The total number of MaF is too small to analyze the countries’ contribution to voltage classes.

Table 5-25: Contribution of countries to GIS major (MaF) and minor (MiF) failures survey (absolute and relative values within total)

Country code Number of MaF [%] Number of MiF [%]

1 7 1,96 3 0,20 2 0 0,00 4 0,27 3 1 0,28 9 0,60 4 2 0,56 4 0,27 7 2 0,56 6 0,40 8 2 0,56 56 3,72 9 5 1,40 69 4,58 10 0 0,00 1 0,07 11 0 0,00 3 0,20 12 1 0,28 33 2,19 13 5 1,40 105 6,98 14 203 56,70 532 35,35 17 20 5,59 417 27,71 18 0 0,00 7 0,47 19 9 2,51 43 2,86 20 9 2,51 65 4,32 21 15 4,19 133 8,84 23 50 13,97 3 0,20 24 16 4,47 1 0,07 27 0 0,00 1 0,07 28 10 2,79 4 0,27 29 1 0,28 6 0,40 Total 358 100,00 1 505 100,00

Collected GIS failures in individual voltage classes are summarized in table 5-26 for all data and in table 5-27 for all data without countries with dominant population, i.e. countries 14 and 23. The values in both tables are expressed in absolute and in relative values. The bases for the calculation of relative values are numbers of total collected major and total collected minor failures. Figures 5-12 show graphically absolute data of tables 5-26 and 5-27, i.e. portions of MaF and MiF in GIS that contribute to individual voltage classes.

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Table 5-26: Distribution of major (MaF) and minor (MiF) in GIS - all data (absolute and relative values within individual voltage classes)

Voltage class

Number of MaF Number of MiF

Absolute % Absolute % 60≤U<100 kV 154 43,0 292 19,4 100≤U<200 kV 64 17,9 291 19,3 200≤U<300 kV 28 7,8 212 14,1 300≤U<500 kV 92 25,7 604 40,1 500≤U<700 kV 16 4,5 106 7,0 ≥700 kV 4 1,1 0 0,0 Total 358 100,0 1 505 100,0

Table 5-27: Distribution of major (MaF) and minor (MiF) in GIS - data without countries 14 and 23 (absolute and relative values within individual voltage classes)

Voltage class

Number of MaF Number of MiF

Absolute % Absolute % 60≤U<100 kV 0 0,0 1 0,1 100≤U<200 kV 21 20,0 259 26,7 200≤U<300 kV 10 9,5 116 12,0 300≤U<500 kV 62 59,0 562 57,9 500≤U<700 kV 8 7,6 32 3,3 ≥700 kV 4 3,8 0 0,0 Total 105 100,0 970 100,0 0 100 200 300 400 500 600 700 Numebr of failures [ ‐] Voltage class [kV] Failures in GIS distribution (all data) MaF MiF

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Figures 5-12: Distribution of major (MaF) and minor (MiF) in GIS (absolute values)

Comparison with previous survey

As already written in chapter 5.4, the 2nd GIS experience survey collected only major failures that happened during the whole life time of reported GIS. Their number is thus supposed to be bigger than in the 3rd survey in which there were collected only failures that happened in four years period between 2004 and 2007.

Table 5-28 provides an overview of collected data. For the data from the 2nd_{survey it was}

necessary to exclude the big influence of one utility having had very old and very unreliable GIS in voltage class 2. The comparisons in all further subchapters of chapter 5.5 provide numbers of all failures without this worst utility data. This means that 275 failures which occurred in voltage class 2 substations all of them operated by one user and representing obsolete breaker technology, was excluded from 2nd_{survey analysis and is thus excluded}

from comparisons in the following subchapters as well.

Table 5-28: Comparison of collected GIS major failures in individual voltage classes in the 2nd and the 3rd GIS surveys (absolute values)

Voltage class

Collected number of GIS major failures –

2nd survey

Collected number of GIS major

failures – 3rd survey

All data

All data without

the worst utility country 14 and the Data without

worst utility All data countries 14 and 23Data without

60≤U<100 kV 28 28 13 154 0 100≤U<200 kV 465 190 174 64 21 200≤U<300 kV 138 138 115 28 10 300≤U<500 kV 179 179 179 92 62 500≤U<700 kV 49 49 44 16 8 ≥700 kV 12 12 12 4 4 Total 871 596 537 358 105

Regarding the 3rd survey the number of major failures without two dominant countries (14 and 23) represents only 19% of comparable collected data in the 2nd_{survey. The WG A3-06}

decided to provide most of the surveys comparisons below only for all data (for the 2nd_survey

that means all data without the worst utility). The reader can, if he wishes, find result details for the 2nd survey in [13]. Graphical interpretation of collected major failures in both surveys is shown in figure 5-13. 0 100 200 300 400 500 600 Number of failures [ ‐] Voltage class [kV] Failures in GIS distribution (all data without countries 14 nad 23) MaF MiF

Cigre TB 513

513

5

Final Report of the 2004 - 2007

International Enquiry on Reliability of

High Voltage Equipment

Part 5 - Gas Insulated Switchgear (GIS)

Working Group

A3.06

Working Group A3.06

Final Report of the 2004 - 2007 International Enquiry on

Reliability of High Voltage Equipment

Part 5 – Gas Insulated Switchgear (GIS)

Members

Corresponding Members

Copyright © 2012

Disclaimer notice

Table of Contents

5.1 Common Matters of the 2004-2007 Reliability Survey

5.2 Introduction

5.2.1 History of GIS experience surveys

5.2.2 The 3

GIS experience survey analysis

5.3 Participation in the Survey

Comparison with previous survey

Findings and commentary

5.4 GIS Service Experience Distribution

5.4.1 Country contribution and GIS voltage class service experience

distribution

Comparison with previous survey

Findings and commentary

5.4.2 GIS extent service experience distribution

Comparison with previous survey

Findings and commentary

5.4.3 GIS type of enclosure service experience distribution

Comparison with previous survey

Findings and commentary

5.4.4 GIS location service experience distribution

Comparison with previous survey

Findings and commentary

5.4.5 GIS age service experience distribution

Comparison with previous survey

Findings and commentary

5.4.6 GIS maintenance practices service experience distribution

Comparison with previous survey

Findings and commentary

5.5 GIS Failures

5.5.1 Countries contribution and GIS voltage classes failures distribution

Comparison with previous survey