Cigre TB 513

8/11/2019 Cigre TB 513

1/172

513

Final Report of the 2004 - 2007

International Enquiry on Reliability ofHigh Voltage Equipment

Part 5 - Gas Insulated Switchgear (GIS)

Working GroupA3.06

October 2012

8/11/2019 Cigre TB 513

2/172

Working Group A3.06

Final Report of the 2004 - 2007 International Enquiry onReliabil ity of High Voltage Equipment

Part 5 Gas Insulated Switchgear (GIS)

Members

M. Runde (NO) Convener, C. E. Slver (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. stlund (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 2012Ownership 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 noticeCIGRE gives no warranty or assurance about the contents of this publication, nor does it accept any responsibility, as to theaccuracy or exhaustiveness of the information. All implied warranties and conditions are excluded to the maximum extentpermitted by law.

ISBN: 978-2- 85873-206-7

8/11/2019 Cigre TB 513

3/172

ii

Table of Contents

5.1

Common

Matters

of

the

2004

2007

Reliability

Survey

.......................................................

1

5.2 Introduction...................................................................................................................... 2

5.2.1 History of GIS experience surveys ............................................................. 2

5.2.2 The 3rdGIS experience survey analysis .................................................... 2

5.3 ParticipationintheSurvey................................................................................................. 3

5.4 GISServiceExperienceDistribution................................................................................... 5

5.4.1 CountrycontributionandGISvoltageclassserviceexperiencedistribution.......................5

5.4.2 GIS extent service experience distribution ................................................. 9

5.4.3 GIS type of enclosure service experience distribution ............................. 12

5.4.4 GIS location service experience distribution ............................................ 14

5.4.5 GIS age service experience distribution................................................... 18

5.4.6 GIS maintenance practices service experience distribution ..................... 21

5.5 GISFailures....................................................................................................................... 23

5.5.1 Countries contribution and GIS voltage classes failures distribution ....... 24

5.5.2 GIS extent failures distribution ................................................................. 27

5.5.3 GIS type of enclosure failures distribution ............................................... 30

5.5.4 GIS location failures distribution .............................................................. 33

5.5.5 GIS failed component distribution ............................................................ 36

5.5.6 GIS age failures distribution ..................................................................... 46

5.6 GISMajorFailureFrequencies.......................................................................................... 50

5.6.1 Completeness of data .............................................................................. 50

5.6.2 GIS voltage class major failure frequency distribution ............................. 52

5.6.3 GIS extent major failure frequencies distribution ..................................... 56

5.6.4 GIS location major failure frequencies distribution ................................... 58

5.6.5 GIS type of enclosure major failure frequencies distribution .................... 61

5.6.6 SF6/air bushings, cable boxes and transformer bushing failure frequencies................................................................................................................. 63

5.6.7 GIS age major failure frequencies distribution ......................................... 64

5.6.8 GIS maintenance philosophies major failure frequencies distribution ...... 69

5.7 FailureCharacteristics....................................................................................................... 72

5.7.1 Major failure mode ................................................................................... 72

5.7.2 Number of major failures which caused fire or explosion......................... 76

5.7.3 Minor failure mode ................................................................................... 775.7.4 Failed subassembly ................................................................................. 78

8/11/2019 Cigre TB 513

4/172

iii

5.7.5 Failure origin ............................................................................................ 83

5.7.6 Failure primary cause .............................................................................. 85

5.7.7 Failure service conditions ........................................................................ 89

5.7.8 Contribution of environmental stresses to failures ................................... 93

5.7.9 Failure repair ............................................................................................ 95

5.7.10 Consequential measures ......................................................................... 98

5.7.11 GIS parts other than CB, DS/ES and IT failures characteristics ........... 100

5.8 CorrelationsBetweenPrevailingMajorFailuresCharacteristics...................................... 122

5.8.1 Correlations of major failure modes ....................................................... 122

5.8.2 Correlations of failed subassemblies ..................................................... 126

5.8.3 Correlations of major failure primary causes .......................................... 134

5.8.4 Correlations of major failure service conditions ..................................... 139

5.9 RecommendationforFutureSurveys.............................................................................. 143

5.10 SummaryandConclusions.............................................................................................. 144

5.10.1 Summary ofmain findings ..................................................................... 144

5.10.2 Recommendations for manufacturers and utilities ................................. 152

5.10.3 Conclusion ............................................................................................. 154

References ..................................................................................................................... 155

Appendix1 GISQuestionnaire............................................................................................... 156

Appendix2 Definitions.......................................................................................................... 164

8/11/2019 Cigre TB 513

5/172

1

5.1 Common Matters of the 2004-2007 Reliabi lity Survey

The results of the 2004 - 2007 reliability study of high voltage equipment are presented in sixTechnical 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].


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].


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


high voltage equipment, Part 5 - Gas Insulated Switchgear [5].


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 beingapplied, 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 thedifferent component types are included.

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

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

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

8/11/2019 Cigre TB 513

6/172

2

5.2 Introduction

5.2.1 History of GIS experience surveys

The 1stGIS 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 34countries and 18 manufacturers from 9 countries responded to the questionnaire. The usersexperience represented 1 817 GIS, 10 531 circuit breaker-bays (CB-bays) and 78 036 CB-bay-years, the manufacturers experience represented 4 867 GIS, 24 870 CB-bays and199 473 CB-bay-years. The questionnaire addressed: general data about GIS installations,factors which contributed to selection of GIS over AIS, adequacy of existingdesign/production/site test procedures, reliability, availability and maintainability, cause ofmajor failures, future trends/condition monitoring /diagnostics and general open-endedquestions. The survey and data analysis were published in [7], [8], [9] and [10] CIGREpapers during 1992 to 1994.

The 2

nd

GIS international survey questionnaire was circulated five years later, in 1996, withthe aim of collecting service experience data available up to 31.12.1995. 80 users from 30countries responded to the questionnaire. The collected data referred to 2115 GISinstallations, 13 696 CB-bays and 118 483 CB-bay-years. In comparison to the 1stquestionnaire, the 2ndquestionnaire was more focused on installation overview and majorfailure statistics (dataset 1) and GIS life cycle issues (dataset 2). Therefore only users wereaddressed. Besides the general data about GIS installations (similar to data sheet in the firstsurvey) the users were asked to report in dataset 1 the characteristics and serviceexperience (major failures) for each individual GIS from the beginning of their putting intoservice and in dataset 2 to answer more general questions concerning maintenance, lifetimeand 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 collectedpopulation and failure data in 2004 to 2007. The structure of the questionnaire was as muchas useful similar to the 2ndsurvey to enable a comparison. The survey structure is describedin details in technical brochure [1] and the GIS questionnaire cards and their relevantdefinitions can be found in Appendix 1 of this brochure.

5.2.2 The 3rdGIS experience survey analysis

The below shown analysis follows a structure of the GIS population cards, and GIS failurecards for circuit breakers, disconnectors/earthing switches, instrument transformers andother components in GIS. It uses data from all these five questionnaire cards. As questionsand answers in these cards were not identical it was necessary to make their re-coding toget 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

8/11/2019 Cigre TB 513

7/172

3

All chapters below include introduction (description of subchapters), collected data inabsolute and relative values, interpretation graphs, comparison with the 2nd GIS surveyresults (if applicable) and final summary of findings and their WGs commentary.

As the failure frequency is concerned there was taken the same unit as in the 2ndsurvey, 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, itsassociated isolating switches, instrument transformers, interconnecting bus up to andincluding 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 aredescribed here as follows:

Expression of a voltageclass in the

questionnaire1

Expression of a voltage class in chaptertables and graphs [kV]

Expression of a voltage classin a chapter text

60

8/11/2019 Cigre TB 513

8/172

4

Table 5-1: Number of countr ies (util ities) partic ipated in GIS survey (absolute)

Voltage class

Number of countries (utilities) contributing toreference year

Total numberof differentcountries

(utilities) in 4years2004 2005 2006 2007

60U

8/11/2019 Cigre TB 513

9/172

5

Comparison with previous surveyNumber of countries (24) as well as number of utilities (55) participating in the 3 rd GISexperience survey is lower than participation in the 2ndsurvey by 20% for countries (30) and31% 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 3rdsurvey, are not the same and there is only a certainoverlap (less than 50%) in both surveys. This makes the comparison of both surveys resultsproblematic. The brochure user is therefore kindly asked to keep this fact in mind whenreading the comparison with previous survey paragraphs below.

Findings and commentaryThe participation of countries and utilities in the four years (2004, 2005, 2006 and 2007) ofthe survey was quite even. The same is valid for their four years contributions in individualvoltage classes. Altogether 24 countries and 55 utilities took part in the survey with anaverage 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 andthe second one for all data without countries 14 and 23 data. The reason is to analyze thedata 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 avalue of reported GIS service experience, i.e. number of CB-bay-years. The reported serviceexperience population data [CB-bay-years] is analyzed here from the following point ofviews:

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 experiencedistribution

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

8/11/2019 Cigre TB 513

10/172

6

Table 5-5 : GIS service experience country contribu tion to the survey (absolute and relative values w ithin indiv

Countrycode

GIS Voltage class

60U

8/11/2019 Cigre TB 513

11/1727

Collected service experience in individual voltage classes is summarized in table 5-6 inabsolute numbers and in % (the base is total number of collected service experience). Figure5-1 shows a graph of absolute values for all data and it compares it with all data without twodominant countries 14 and 23.

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

Voltage class

All data Data without countries 14 and 23

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

60U

8/11/2019 Cigre TB 513

12/1728

Table 5-7: Comparison of collected GIS service experience in individual voltage classes in the2

ndand the 3

rdGIS surveys (absolute values)

Voltage class

Collected GIS service experience 2

ndsurvey [CB-bay-years]


rdsurvey [CB-bay-years]

All data

All data withoutthe worst utility

Data withoutcountry 14 andthe worst utility All data

Data withoutcountries 14 and 23

60U

8/11/2019 Cigre TB 513

13/1729

Findings and commentary

From the above shown tables it is evident that the reported service experience is dominatedby countries with codes 14 and 23. Both are countries that are traditionally known of usingmodern technologies and of applying effective maintenance strategies. Country with codenumber 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 thedomination by 46% (country 14) and by 37,8% (country 23). Only two countries reportedabout service experience in class 7. These two countries (country 1 and 23) share the totalservice experience in class 7 by approximately half and half.

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

The difference is already visible when evaluating the division of the service experience inindividual 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 isless than 10%. Evaluating data without countries 14 and 23 the majority of experience lies inclass 2 (51%), 3 (19%) and 4 (23%).

5.4.2 GIS extent service experience dis tribut ion

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

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

Hybrid GIS - substation the bays of which are made from a mix of GIS and AIStechnology components, i.e. in which the CB-bays contains combination of enclosedgas insulated and air insulated parts.

Collected service experiences in individual voltage classes are summarized in table 5-8 forall data and in table 5-9 for all data without countries 14 and 23. The values in both tablesare expressed in absolute and in relative values. The calculation bases for relative values arenumbers 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.

8/11/2019 Cigre TB 513

14/17210

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

Voltage class

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

Absolute % Absolute %

60U

8/11/2019 Cigre TB 513

15/17211

Figures 5-3: Distr ibution of service experience absolute values for the two types of GISinstallation extent

Comparison with previous surveyComparison with the 2ndGIS 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 individualvoltage classes in the 2

ndand the 3


Voltage class




rd survey [CB-bay-years]

Fully GIS Hybrid GIS Fully GIS Hybrid GIS

60U

8/11/2019 Cigre TB 513

16/17212

Findings and commentaryPortion of hybrid GIS installations is still relatively small. Hybrid GIS represents only about8% of all collected data. There is no difference between relative total data and relative datawithout two dominant countries. However there is a certain trend visible in increasing theirportion at higher voltage classes in which mixed technologies (MTS) installation can offeradvantages for new installations as well as for upgrading and extensions of existing AIS (fordetails about comparison of AIS-GIS-MTS features see CIGRE technical brochure [15].

5.4.3 GIS type of enclosure service experience distributionThe respondents were asked to divide their GIS installations population in dependence onnumber of HV conductors placed in one enclosure into the following two categories (fordetails 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 individualCB-bays.

Collected service experiences in individual voltage classes are summarized in table 5-11 forall 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 valuesare numbers of collected service experiences in individual voltage classes.

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

Voltage class

Number of CB-bay-years in CB-bay design of

Number of CB-bay-years connectedto busbar design of

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

Absolute % Absolute % Absolute % Absolute %

60U

8/11/2019 Cigre TB 513

17/17213

As the questionnaire asked about the design for two separate parts of GIS it was necessaryto synthesize the answers to get an overview about the collected service experience ofuniform design substations and of combined design substations. The results of this synthesisare 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 forcalculations of relative values are numbers of collected service experiences in individualvoltage 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 individualvoltage classes.

Table 5-13: Distribution of service experience for combinations of the two types of GISenclosure design - all data (absolute and relative values w ithin 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


60U

8/11/2019 Cigre TB 513

18/17214

Figures 5-5: Distribution of service experience (absolute values fo r combinations of the twotypes of GIS enclosure design]

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

Comparison with previous surveyThe 2ndGIS survey questionnaire did not ask a question about the referred GIS an enclosuredesign.

Findings and commentary

Combination of 1-phase busbars and 3-phase CB-bays appears very seldom in 13,8% of allcollected experience (thereof in 28% in voltage class 1) and almost does not exist in othercountries than in 14 and 23. Combination of 3-phase busbars and 1-phase CB-bays appearsmuch more frequently and represents 27% in total and 17% in other countries than 14 and23 collected experience. It can be found with a high portion (30%) even in voltage class 5GIS. Evaluating the total data this combination seems to be very popular in voltage classes 2and 4 in which it reaches 52% and 43% of service experience collected in these voltageclasses. In countries other than 14 and 23 this design combination is used in voltage classes1 (64%), 2 (15%), 3 (31%) and 4 (9%).

As unified designs are concerned the single phase GIS appears in all voltage classes- thehigher 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 classes5 and 6. Countries other than 14 and 23 use single phase GIS design even more frequentlyand this design prevails starting already voltage class 3. The three phase GIS design can befound up to voltage class 4 and it is used in countries 14 and 23 much more often than inother countries. It prevails in GIS up to voltage class 3, whereas in other counties only up tovoltage class 2.

5.4.4 GIS location service experience dist ribut ion

The respondents were asked to divide their GIS installations populations into the followingcategories (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 containerizedinstallations, installations under simple buildings as shelters without heating, altitudes>1000m, etc.)

GIS Outdoor Normal (Outdoor N) - for normal outdoor conditions

0

200

400600

800

1,000

1,200

1,400

1,600

1,800

Serviceexperie

nce[CB

Bay

years]

Voltageclass[kV]

GISdesigndistribution(datawithoutcountries14and23)

1phaseGIS

3phaseGIS

Busbar1phase+

CBbay3phase

Busbar3phase+

CBbay1phase

8/11/2019 Cigre TB 513

19/17215

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

Note: GIS whose only outdoor parts are bushings (SF6/air, SF6/transformer) and/ornecessary 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 tablesare expressed in absolute and in relative values. The bases for relative values calculationsare 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 indoornormal, indoor special, outdoor normal and outdoor special GIS locations CB-bays serviceexperiences in individual voltage classes.

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

Number of CB-bay-years

Indoor N Indoor S Outdoor N Outdoor S


60U

8/11/2019 Cigre TB 513

20/17216

Figures 5-6: Distribut ion of service experience (absolute values for types of GIS installationlocations)

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

Voltage class

Number of CB-bay-years (alldata)

Number of CB-bay-years (datawithout countries 14 and 23)

Indoor GIS Outdoor GIS Indoor GIS Outdoor GIS

Absolute % Absolute % Absolute % Absolute %60U

8/11/2019 Cigre TB 513

21/17217

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

Comparison with previous survey

The distinction between normal and special GIS locations was made only in the 3 rdsurvey. Comparison with the 2nd GIS experience survey in categories indoor-outdoor isprovided in table 5-18 and figure 5-8.

Table 5-18: Comparison of collected indoor and outdoor GIS service experience in individualvoltage classes in the 2

ndand the 3


Voltage class






60U

8/11/2019 Cigre TB 513

22/17218

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

As indoor/outdoor installations are concerned there is a visible difference when evaluating alldata and data without countries 14 and 23. Analyzing all data it seems that outdoorinstallations 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 ageneral installation policy. The utilities in countries other than 14 and 23 prefer indoorinstallations at all voltage classes (except class 5) in spite of the fact that size of GISbuilding or shelter can represent a certain design challenge.

5.4.5 GIS age service experience dis tribut ion

As the survey was running in the period of 4 years the reported GIS age overview would becomplicated (floating age). The age aspect is therefore expressed in another way in theway of analyzing manufacturing years. In the GIS population failure cards there wereidentified manufacturing years of individual GIS. In CB and other equipments population

cards there were identified only intervals of manufacturing years. The GIS data weretherefore also classified into the same intervals to provide the data analysis in the samestructure of classes.

Table 5-19 shows a distribution of collected GIS service experience in seven intervals of GISmanufacturing years for all data and in absolute and relative values (100% is number of GISCB-bays service experience collected within individual voltage classes). Table 5-20 showsthe 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 with in individual voltage classes)

Manufacturing

year

60U

8/11/2019 Cigre TB 513

23/17219

Table 5-21 shows the same data as tables 5-19 and 5-20 but the relative values arerecalculated 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 datafrom 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 collecteddata)

Manufacturing year All data data without countries 14and 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 GISmanufacturing years fo r indiv idual voltage classes

0

2000

4000

6000

8000

10000

12000

Serviceexperience[CB

bay

years]

ReportedGIS

service

experience

in

dependence

on

manufacturingyear interval(alldata)

60U

8/11/2019 Cigre TB 513

24/17220

Comparison with previous surveyIn the population card of the 2ndGIS survey there was a column for inserting the year wheneach GIS substation was put into service. However, in the analysis brochure [13] thecollected service experience used for failure frequency calculation is expressed only in twocategories - for GIS commissioned before 1.1.1985 and after 1.1.1985, i.e. for GIS youngerthan 12 years (age of 1 to 11 years) and for older than 12 years. To compare the results withthe 3rdsurvey 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 2ndsurvey and only the complete data (data having its equivalent in failurecards) for the 3rdsurvey. This data is used for failure frequency comparison (see chapter5.6).

Table 5-22: Comparison of 2nd

and 3rd

GIS surveys collected GIS service experience of GISolder than 11 years and 11 years old or younger in individual voltage classes (absolute values)

Voltage class





GIS age>11 years

GIS age11 years

GIS age>11 years

GIS age11 years

60U

8/11/2019 Cigre TB 513

25/17221

Findings and commentaryThe oldest reported GIS substation was manufactured and installed in 1960 and belongs tovoltage 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 yearand in each line describing their population in the reference year. Therefore the responseanalysis is made in correlation to collected service experience.The respondent had the following options to select that one which corresponds to theirpractice 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 individualvoltage classes are summarized in table 5-23 for all data and in table 5-24 for all data withoutcountries 14 and 23. The values in both tables are expressed in absolute and in relativevalues. The bases for relative values calculations are numbers of collected serviceexperiences in individual voltage classes. No respondent selected the run to failurephilosophy 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 - alldata (absolute and relative values w ithin individual voltage classes)

Voltage class

Number of CB-bay-years referred to different maintenance practices(all data)

Time basedmaintenance

(TBM)

Conditionbased

maintenance(CBM)

Combination ofTBM and CBM

Other


60U

8/11/2019 Cigre TB 513

26/17222

Table 5-24: Distribution of service experience for types of GIS maintenance philosophies datawithout 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 basedmaintenance

(TBM)

Conditionbased

maintenance(CBM)

Combination ofTBM and CBM

Other

Absolute % Absolute % Absolute % Absolute %60U

8/11/2019 Cigre TB 513

27/17223

Comparison with previous surveyIn the 2ndsurvey, the GIS maintenance aspects were included in a specialized questionnairecard called GIS life expectancy, maintenance, environmental: This card is similar to 3rdsurvey specialized questionnaire card called GIS maintenance card. The resulting analysisof responses as well as its comparison with results of the 2nd survey is included in technicalbrochure [6].

Findings and commentaryIn either graphs (all data or in data without countries 14 and 23) no trend is visible that couldbe related to the voltage class distribution. The result is most probably influenced by the factthat different companies with different maintenance philosophies contributed to differentvoltage classes. There is however a visible difference between the philosophies interpretedfrom all data and data without countries 14 and 23. In all data analysis, the traditional policyof time based maintenance still prevails. Inputs from modern strategies as reliability centeredand condition based maintenance in combination with the time based activities alreadyappear. However in total they still represent only 26%. Countries other than 14 and 23 seemto be less conservative since condition based maintenance and combination of condition andtime 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 andinfluences the GIS reliability and GIS availability very much. Therefore the survey containeda specialized GIS maintenance card for respondents to answer detailed questions aboutmaintenance and other aspects of testing and service. The analysis of these cards isincluded 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 werereported in CB failure cards (see technical brochure [2]), GIS DE/ES failures in DE/ES failurecards (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 otherchapters below provide a summary of all GIS failures using data from all four mentionedsources. 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 ofviews:

Countries contribution to the survey and GIS voltage classes distribution (chapter5.5.1)

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 havegot a very detailed database about major failures whereas minor failures are sometimesrepaired without reporting into any information systems. The reader thus shall read theinformation below only as information about reported events but shall not make arelative comparison between MaF and MiF events.

8/11/2019 Cigre TB 513

28/17224

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

5.5.1 Countries contribution and GIS voltage classes failures distributionCountries contribution to the survey is shown in table 5-25. Table 5-25 shows total absoluteand relative data (100% for relative expression is total number of MaF, MiF respectively). Thetotal 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 27,7118 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 dataand in table 5-27 for all data without countries with dominant population, i.e. countries 14 and23. The values in both tables are expressed in absolute and in relative values. The bases forthe calculation of relative values are numbers of total collected major and total collectedminor 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.

8/11/2019 Cigre TB 513

29/17225

Table 5-26: Distribution of major (MaF) and minor (MiF) in GIS - all data (absolute and relativevalues within individual vo ltage classes)

Voltage class

Number of MaF Number of MiF

Absolute % Absolute %

60U

8/11/2019 Cigre TB 513

30/17226

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

Comparison with previous surveyAs already written in chapter 5.4, the 2ndGIS experience survey collected only major failuresthat happened during the whole life time of reported GIS. Their number is thus supposed tobe bigger than in the 3rdsurvey in which there were collected only failures that happened infour years period between 2004 and 2007.

Table 5-28 provides an overview of collected data. For the data from the 2ndsurvey it wasnecessary to exclude the big influence of one utility having had very old and very unreliableGIS in voltage class 2. The comparisons in all further subchapters of chapter 5.5 providenumbers of all failures without this worst utility data. This means that 275 failures whichoccurred in voltage class 2 substations all of them operated by one user and representing

obsolete breaker technology, was excluded from 2ndsurvey analysis and is thus excludedfrom 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 3


Voltage class

Collected number of GIS major failures 2

ndsurvey

Collected number of GIS majorfailures 3

rd survey

All data

All data withoutthe worst utility

Data withoutcountry 14 and the

worst utility All dataData without

countries 14 and 23

60U

8/11/2019 Cigre TB 513

31/17227

Figure 5-13: Comparison of collected major failures in individual voltage classesin the 2

ndand the 3

rdGIS surveys (all data)

The 3rdGIS survey collected more major failures in voltage class 1 than in the 2ndGIS surveyin spite of the fact that the collected service experience was a bit smaller. The comparison ofthe other voltage classes show expected relations.

Findings and commentaryIt is necessary to repeat that because of incompleteness of minor failures reporting thereshall not be made any comparison of major and minor number of failures.

The absolute numbers of major failures provided in this chapter and chapters below serve asinput information for chapter 5.6 (failure frequencies calculation) and for 5.7 (failurecharacteristics). Their relative expression in individual voltage classes is provided here onlyfor information. The relative numbers, as well as absolute numbers, cannot be used for anymutual comparison since they are naturally influenced by scrutiny of minor failure collectionand by different amount of collected service experience as mentioned in chapter 5.4. For thisreason and for the above mentioned reason of incompleteness of minor failure data,commentaries are therefore provided only for total data of major failures in sub-chapters ofchapter 5.5.

5.5.2 GIS extent failures distribution

The respondents were asked to divide their GIS failures into the same categories of GISextent as in the GIS population, i.e. into the following two categories:

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

Hybrid GIS - substation the bays of which are made from a mix of GIS and AIStechnology components, i.e. in which the CB-bays contains combination of enclosedgas insulated and air insulated parts.

Collected number of failures in individual voltage classes is summarized in table 5-29 for alldata and in table 5-30 for all data without countries 14 and 23. The values in both tables areexpressed in absolute and in relative values. The bases for calculation of relative values arenumbers of failures in individual voltage classes. Figures 5-14 show graphically absolutedata of tables 5-29 and 5-30, i.e. portions of MaF and MiF collected in individual voltageclasses. Figure 5-15 shows an overview of all data failures in fully/hybrid GIS distribution.

0204060

80100120140160180200

Numberofmajorfailures[]

Voltageclass[kV]

ComparisonofcollectedGISmajorfailures

2ndsurvey

(1995)

3rd survey(2007)

8/11/2019 Cigre TB 513

32/17228

Table 5-29: Distr ibut ion of major (MaF) and minor (MiF) failures for the two types of GIS extent- all data (absolute and relative values within individual voltage classes)

Voltage class




60U

8/11/2019 Cigre TB 513

33/17229

Figures 5-14: Distribution of major (MaF) and minor (MiF) failures absolute values for the twotypes of GIS extent in individual voltage classes

Figure 5-15: Distribution of total number of major (MaF) and minor (MiF) failures absolutevalues for the two types of GIS extent

Comparison with previous surveyComparison of the 3rdGIS survey all data with the 2ndGIS experience survey is provided intable 5-31 and figures 5-16 (the 2ndsurvey data is all data without the worst utility data).

Table 5-31: Comparison of collected fully and hybrid GIS major failures in individual voltageclasses in the 2

ndand the 3


Voltage class


ndsurvey


rdsurvey


60U

8/11/2019 Cigre TB 513

34/17230

Figures 5-16: Comparison of collected fully and hybrid GIS major failures in i ndividual vo ltageclasses in the 2

ndand the 3

rdGIS surveys

The collected number of hybrid GIS major failures is one to two orders of magnitude lowerthan for fully GIS in both surveys. The fully GIS dominates the picture.

Findings and commentary94 % of all data major failures happened in fully GIS. That correspond quite well to thedistribution of collected service experience 92% of fully GIS. The same picture is obtainedwhen evaluating data without countries 14 and 23 (96% of MaF and 92% of serviceexperience in fully GIS). This difference can be explained by two facts :

The GIS part in hybrid is smaller than for fully GIS and thus there are less GIS partsto fail.

Hybrid GIS are in the average younger than fully GIS in spite of the fact that theoldest one is from 1968.

5.5.3 GIS type of enclosure failures distribution

The respondents were asked to divide their failures in GIS into the same categories of GISenclosure design as in GIS population, i.e. into the following two categories:

Single phase enclosure (1-phase)

Three phase enclosure (3-phase)They were supposed to do the selection based on the design of an enclosure the specificcomponent that suffered from a failure.

Collected number of failures in individual voltage classes is summarized in table 5-32 for alldata and in table 5-33 for all data without countries 14 and 23. The values in both tables areexpressed in absolute and in relative values. The bases for calculation of relative values arenumbers of failures in individual voltage classes. Figures 5-17 show graphically absolutedata of tables 5-32 and 5-33, i.e. portions of MaF and MiF collected in individual voltageclasses. Figure 5-18 shows the failure distribution of 1-phase/3-phase GIS componentdesign for all data.

0

20

40

60

80

100

120

140

160

180

200

Numbero

fmajorfailures[]

Voltageclass [kV]

Comparison

of

collected

fullyGIS

major

failures

2ndsurvey

(1995)

3rd

survey

(2007)

0

1

2

3

4

5

6

7

Numberofmajorfailures[]

Voltage

class

[kV]

Comparison

of

collected

hybrid

GIS

major

failures

2nd

survey

(1995)

3rd

survey

(2007)

8/11/2019 Cigre TB 513

35/17231

Table 5-32: Distribution of major (MaF) and minor (MiF) failures for the two types of GISenclosure design - all data (absolute and relative values w ithin individual voltage classes)

Voltage class


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


60U

8/11/2019 Cigre TB 513

36/17232

Figures 5-17: Distri bution of major (MaF) and minor (MiF) failures absolute values for the twotypes of GIS enclosure design in individual voltage classes

Figure 5-18: Distribution of major (MaF) and minor (MiF) failures absolute values for the twotypes of GIS enclosure design in total

Comparison with previous surveyThe 2ndGIS survey questionnaire did not ask a question about the referred GIS enclosure

design.

Findings and commentary48 % of all data major failures happened in single phase encapsulated GIS. That correspondquite well to the distribution of collected service experience of 44% of single phaseencapsulated GIS. A bit different picture is obtained when evaluating data without countries14 and 23 (92% of MaF and 75% of service experience in single phase encapsulated GIS),where the difference is higher. To explain this difference it is necessary to perform furtheranalysis as shown in chapter 5.6 and 5.7. However the simplest explanation can be thesame as for hybrid GIS three-phase enclosed GIS contain less material to fail.

0

100

200

300

400

500

600

Numbe

roffailures[]

Voltageclass[kV]

Failuresin1phaseor3phasecomponentdesigndistribution(all

datawithoutcountries14and23)

MaFin1phase

design

MaFin3phase

design

MiFin1phase

design

MiFin3phase

design

0

200

400

600

800

1000

1200

1400

1phase 3phase

Numberoffailures[]

FailedGIScomponentenclosuredesign

FailuresinGIS(alldata)

MaF

MiF

Total

8/11/2019 Cigre TB 513

37/17233

5.5.4 GIS location failures distr ibut ion

The respondents were asked to divide their failures in GIS into the same categories of GISlocation as in GIS population, i.e. into the following four categories:

GIS Indoor Normal (Indoor N)

GIS Indoor Special (Indoor S)

GIS Outdoor Normal (Outdoor N)

GIS Outdoor Special (Outdoor S)

As there was only 1 major failure reported in Outdoor Special GIS location and only 2 minorfailures reported in indoor special GIS location the further analysis is done only for indoor outdoor division.

Collected number of failures in individual voltage classes is summarized in table 5-34 for alldata and in table 5-35 for all data without countries 14 and 23. The values in both tables areexpressed in absolute and in relative values. The bases for relative values calculations arenumbers of failures in individual voltage classes. Figures 5-19 show graphically absolutedata in tables 5-34 and 5-35, i.e. portions of MaF and MiF collected in individual voltageclasses. Figure 5-20 shows an overview of all data failures in indoor/outdoor failed GIScomponent design distribution.

Table 5-34: Distribution of major (MaF) and minor (MiF) failures for the two types of GISlocation - all data (absolute and relative values within ind ividual vol tage classes)

Voltage class




60U

8/11/2019 Cigre TB 513

38/17234

Figures 5-19: Distribution of major (MaF) and minor (MiF) failures numbers for the two types ofGIS location in individual voltage classes

0

50

100

150

200

250

300

350

400

450

Numberoffailures[]

Voltageclass[kV]

Failuresinindoororoutdoorcomponentdesigndistribution(alldata)

MaFinindoorGIS

MaFinoutdoorGIS

MiFinindoorGIS

MiF

in

outdoor

GIS

0

50

100

150

200

250

300

350

400

450

Numberoffailures[

]

Voltageclass[kV]

Failuresinindoororoutdoorcomponentdesigndistribution(alldatawithout

countries14and23)

MaFinindoorGIS

MaFinoutdoorGIS

MiFinindoorGIS

MiFinoutdoorGIS

8/11/2019 Cigre TB 513

39/17235

Figure 5-20: Distribution of major (MaF) and minor (MiF) failures numbers for the two types ofGIS location in total

Comparison with previous surveyComparison of all data from the 3

rdGIS survey with the 2ndGIS experience survey data is

provided in table 5-36 and figures 5-21(the 2ndsurvey data is all data without the worstutility data).

Table 5-36: Comparison of collected indoor and outdoor GIS major failures in individualvoltage classes in the 2

ndand the 3


Voltage class


ndsurvey


rdsurvey


60U

8/11/2019 Cigre TB 513

40/17236

Outdoor GIS experience has relatively increased (in classes 2, 4 and 5 also absolutely) in allvoltage classes in 3rdGIS survey compared to 2ndGIS survey. That is also valid for numberof major failures namely in classes 1, 2 and 5.

Findings and commentary28,5 % of all data major failures happened in indoor GIS that represent 41 % of collectedservice experience. When evaluating data without countries 14 and 23, 63,8 % of all datamajor failures happened in indoor GIS that represent 88,6 % of collected service experience.

Ratio of these two numbers, i.e. percentage distribution of service experience to percentagedistribution to number of major failures, is almost the same in both cases (1,4 times). Thatshows that indoor GIS installations may behave a bit better than outdoor GIS (as later provenwith exception of voltage class 4 in chapter 5.6.4) and that can be explained by a simple factthat indoor GIS are not so much influenced by environmental effects.

5.5.5 GIS failed component distribution

Details about GIS circuit breakers (CB), disconnectors and earthing switches (DS/ES) andinstrument transformers (IT) failures are given in technical brochures [2], [3] and [4]. Chapter5.5.5 provides an overview to show different components contributions to failure statistics. In

addition it presents a more detailed analysis of failed components other than CB, DS/ES andIT. The label "GI" groups failures of busbars, busducts, surge arresters, different joints,bushings and cable boxes.

5.5.5.1 Basic GIS components in indiv idual voltage classes

Collected major and minor failures of GIS equipment in basic component division (CB,DS/ES, IT and GI) are summarized in table 5-37 for all data and for data without countries14 and 23. They are expressed in absolute and in relative values. The bases for relativevalues calculations are sums of collected major, minor resp., failures.

Figures 5-22 show graphically relative values of tables 5-37 for all data, i.e. different GIScomponents contribution to the total number of MaF and MiF for all collected data.

Table 5-37: Distribution of major (MaF) and minor (MiF) failures for the four basic GIS CB-baycomponents all data and data without countries 14 and 23 (absolute and relative values intotal col lected MaF and MiF)

Failed GIScomponent


Number of MaF Number of MiF Number of MaF Number of MiF


CB 124 34,6 791 52,6 56 53,3 545 56,2

DS/ES 164 45,8 233 15,5 25 23,8 95 9,8

GI 50 14,0 413 27,4 17 16,2 284 29,3IT 20 5,6 68 4,5 7 6,7 46 4,7

8/11/2019 Cigre TB 513

41/17237

Figures 5-22: Relative distribution of major (MaF) and minor (MiF) failures for the four basic GISCB-bay components

Collected failures in individual voltage classes are summarized in table 5-38 for all data andin table 5-39 for data without countries 14 and 23. The values in both tables are expressed inabsolute and in relative values. The bases for relative values calculations are numbers ofcollected failures in individual voltage classes.

Figures 5-23 show graphically relative values of table 5-38 for individual GIS componentscontributions to total number of MaF and MiF within individual voltage classes for allcollected data.

Table 5-38: Distribution of major (MaF) and minor (MiF) failures for the four basic GIS CB-baycomponents all data (absolute and relative values in individual voltage classes)

Voltage class

Number of MaF (all data)CB MaF DS/ES MaF GI MaF IT MaF


60U

8/11/2019 Cigre TB 513

42/17238

Table 5-39: Distribution of major (MaF) and minor (MiF) failures for the four basic GIS CB-baycomponents data without countries 14 and 23 (absolute and relative values in individualvoltage classes)

Voltage class

Number of MaF (data without countries 14 and 23)

CB MaF DS/ES MaF GI MaF IT MaF


60U

8/11/2019 Cigre TB 513

43/17239

Figures 5-23: Relative distribution of major (MaF) and minor (MiF) failures for the four basic GISCB-bay components all data in individual voltage classes

Comparison with previous surveyIn the 2ndsurvey there was an analysis provided only for major failures and only for all MaFdata without the worst utility failure data. This data, but without the others category, is usedfor comparison with the 3rdGIS survey results in table 5-40 (absolute and relative values,where 100% is total number of major failures) and in figure 5-24 (relative values).

Table 5-40: Comparison of collected GIS basic components major failures in the 2nd

and the 3rd

GIS surveys (absolute and relative values)

Failed GIScomponent

2nd

GIS survey 3rd

GIS survey

Absolute[number of MaF]

Relative [%] Absolute [numberof MaF]

Relative [%]

CB 176 34,5 124 34,6

DS/ES 116 22,7 164 45,8

GI 175 34,3 50 14,0

IT 43 8,4 20 5,6

Figure 5-24: Comparison of collected major failures of GIS CB-bay components in the 2

nd

andthe 3rd

GIS survey (relative values)

0%

10%

20%

30%40%

50%

60%

70%

80%

90%

100%

GIS equipmentminorfailures(MiF)voltageclasses

distribution(alldata)

IT

GI

DS/ES

CB

0

5

10

15

20

25

3035

40

45

50

CB DS/ES GI IT

Relativenumberofmajorfailures[%]

ComparisonofGIScomponentmajorfailuresbyfailed

equipment

2ndsurvey

(1995)

3rdsurvey

(2007)

8/11/2019 Cigre TB 513

44/17240

In the 2ndGIS survey, the portion of major failures of disconnectors and/or earthing switcheswas relatively smaller than in the 3rdsurvey and smaller than it would correspond to relativenumber of individual equipments in one GIS CB-bay. This fact was relatively compensatedby a higher portion of failed equipment other than circuit breakers, disconnectors/earthingswitches and instrument transformers the portion of which has decreased in the 3rdsurvey.

Findings and commentaryAs total data is concerned the relative distribution of major failure is dominated by

disconnector, earthing and/or combined disconnectors earthing switches MaF (46 %),followed by 35% MaF of circuit breakers, 5% of instrument transformers and 14% of otherparts of GIS. As total data without countries 14 and 23 is concerned the major failure relativedistribution is dominated by circuit breakers (53%), followed by disconnector, earthing and/orcombined disconnectors earthing switches MaF (24 %), 7% of instrument transformers and16% of other parts of GIS.

As minor failures distribution is concerned the WG hesitates very much to comment on it asthere is a big suspicious on incompleteness of the data. However if the distribution is at leastsimilar to reality there might be possible to point out on a small portion of MiF to a big portionof MaF for DS/ES.

The above shown numbers of major failures contribute to the resulting GIS CB-bay failurefrequency (see chapter 5.6) and cannot be used for failure frequency calculation of individualcomponents. It is necessary to keep in mind that one CB-bay always contains one circuitbreaker but several disconnectors and earthing switches (based on single line diagram,usually about 2-3 disconnectors and 3-4 earthing switches). The individual equipmentsfailure frequencies are provided in technical brochures [2], [3] and [4].

5.5.5.2 GIS components other than CB, DS/ES and IT

The GI failure cards provided the following options for selecting failed component other thanCB, DS/ES and IT :

Busduct and/or busduct interconnecting pieces Busbar and/or busbar interconnecting pieces

SF6-to-air bushing

Cable box / Cable sealing end

Power transformer or reactor interface chamber or bushing

Surge arrester

Other

Collected major and minor failures of GIS equipment other than CB, DS/ES and IT aresummarized in table 5-41 for all data and for data without countries 14 and 23. They areexpressed in absolute and in relative values. The bases for calculation of relative values are

sums of major and minor failures of these components.

Figures 5-25 show graphically relative data of tables 5-41 for all data, i.e. different GIScomponents other than CB, DS/ES and IT contribution to total number of these componentsMaF and MiF for all collected data.

8/11/2019 Cigre TB 513

45/17241

Table 5-41: Distribution of major (MaF) and minor (MiF) failures for GIS CB-bay componentsother than CB, DS/ES and IT all data (absolute and relative values in total collected MaF andMiF)

Failed GIScomponent


Number of MaF Number of MiF Number of MaF Number of MiF


Busduct10 20,0 102 24,7 4 23,5 93 32,7

Busbar 9 18,0 58 14,0 4 23,5 20 7,0

SF6-to-airbushing

5 10,0 77 18,6 1 5,9 77 27,1

Cable box 2 4,0 14 3,4 0 0,0 7 2,5

Transformerbushing

2 4,0 15 3,6 2 11,8 12 4,2

Surge arrester 0 0,0 2 0,5 0 0,0 1 0,4

Other 22 44,0 145 35,1 6 35,3 74 26,1

Figures 5-25: Relative dis tribution of major (MaF) and minor (MiF) failures for GIS CB-baycomponents other than CB, DS/ES and IT

20%

18%

10%4%4%

0%

44%

Distributionof

GIS

major

failures

(MaF)

of

equipmentotherthanCB,DS/ESandIT(alldata)

busduct

busbar

SF6toairbushing

Cablebox

Transformerbushing

Surgearrester

Other

25%

14%

19%3%4%

0%

35%

DistributionofGISminor failures(MiF)ofequipment

otherthanCB,DS/ESandIT(alldata)

busduct

busbar

SF6toairbushing

Cablebox

Transformerbushing

Surgearrester

Other

8/11/2019 Cigre TB 513

46/17242

Collected failures in individual voltage classes are summarized in table 5-42 (MaF and MiF)for all data. The values are expressed in absolute and in relative values. The bases forcalculation of relative values are numbers of collected failures in individual voltage classes.The number of this kind of failures for countries other than 14 and 23 is too small to provide aseparate analysis. Figures 5-26 show graphical interpretations of the relative values.

Table 5-42: Distribution of major (MaF) and minor (MiF) failures for GIS CB-bay componentsother than CB, DS/ES and IT all data (absolute and relative values in ind ividual vol tage

classes)

Voltage class

Number of MaF (all data)

Busbars andbusducts MaF

Any kind ofbushings MaF

Surge arresterMaF Other MaF


60U

8/11/2019 Cigre TB 513

47/17243

Figures 5-26: Relative distr ibut ion of major (MaF) and minor (MiF) failures for GIS CB-baycomponents other than CB, DS/ES and IT in individual voltage classes

Collected failures in seven manufacturing intervals are summarized in table 5-43 (MaF) andin table 5-44 (MiF) for all data. The values are expressed in absolute and in relative values.The bases for relative values calculations are numbers of collected failures in individual GIScomponents. The number of this kind of failures for countries other than 14 and 23 is toosmall to provide a separate analysis. Figures 5-27 show graphical interpretations of theabsolute values.

Table 5-43: Distr ibut ion of major failures (MaF) of GIS parts other than CB, DS/ES and IT inseven intervals of GIS manufacturing years- all data (Absolute and relative values withinindividual components)

Busduct Busbar SF6-to-airbushing

Cable box Transformer bushing

Surgearrester

Other

abs. [%] abs. [%] abs. [%] abs. [%] abs. [%] abs. [%] abs. [%]

before1979

0 0,0 2 22,2 1 0,0 0 0,0 0 0,0 0 - 3 13,6

1979-1983

2 20,0 1 11,1 0 0,0 0 0,0 0 0,0 0 - 0 0,0

1984-1988

2 20,0 0 0,0 0 0,0 2 100 2 100 0 - 1 4,5

1989-1993

0 0,0 1 11,1 0 0,0 0 0,0 0 0,0 0 - 9 40,9

1994-1998

3 30,0 2 22,2 2 40,0 0 0,0 0 0,0 0 - 3 13,6

1999-2003

1 10,0 1 11,2 2 40,0 0 0,0 0 0,0 0 - 3 13,6

2004-2007

2 20,0 2 22,2 0 0,0 0 0,0 0 0,0 0 - 3 13,6

Total 10 100 9 100 5 100 2 100 2 100 0 - 22 100

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

GIS equipment otherthanCB,DS/ESandITminorfailures

(MiF)voltageclassesdistribution(alldata)

other

surgearrester

Anykindof

bushing

busbar+busducts

8/11/2019 Cigre TB 513

48/17244

Table 5-44: Distribution of minor failu res (MiF) of GIS parts other than CB, DS/ES and IT inseven intervals of GIS manufacturing years-all data (absolute and relative values withinindividual components)

Busduct Busbar SF6-to-airbushing

Cable box Transformer bushing

Surgearrester

Other

abs. [%] abs. [%] abs. [%] abs. [%] abs. [%] abs. [%] abs. [%]

before1979

4 3,9 17 29,3 14 18,2 3 21,4 2 13,3 0 0,0 19 13,1

1979-1983

16 15,7 9 15,5 11 14,3 6 42,9 1 6,7 0 0,0 31 21,4

1984-1988

4 3,9 6 10,3 20 26,0 3 21,4 5 33,3 0 0,0 18 12,4

1989-1993

59 57,8 6 10,3 24 31,2 0 0,0 5 33,3 1 50,0 50 34,5

1994-1998

12 11,8 13 22,4 5 6,5 0 0,0 0 0,0 0 0,0 17 11,7

1999-2003

7 6,9 7 12,1 0 0,0 2 14,3 0 0,0 1 50,0 7 4,8

2004-2007

0 0,0 0 0,0 3 3,9 0 0,0 2 13,3 0 0,0 3 2,1

Total 102 100 58 100 77 100 14 100 15 100 2 100 145 100

Figures 5-27: Distribution of absolute values of major (MaF) and minor (MiF) failures of GISparts other than CB, DS/ES and IT in seven intervals of GIS manufacturing years

012

3456789

10

Nu

mberofMaF[]

ReportedGISmajorfailures(MaF)ofGISpartsotherthanCB,

DS/ESandITindependenceonGISmanufacturingyear

interval(Alldata)

Busduct

Busbar

SF6toairbushing

Cablebox

Transformerbushing

Surgearrester

Other

0

10

20

30

40

50

60

70

NumberofMiF[]

Reportedminorfailures(MiF)ofGISpartsotherthanCB,DS/ES

andITindependenceonGISmanufacturingyearinterval(all

data)

Busduct

Busbar

SF6toairbushing

Cablebox

Transformerbushing

Surgearrester

Other

8/11/2019 Cigre TB 513

49/17245

Comparison with previous surveyThe 2ndsurvey provided an analysis only for major failures and only for all MaF data withoutthe worst utility failure data. This data, with the others category included, is used forcomparison with the 3rdGIS survey results. Table 5-45 shows absolute and relative values(where 100% is total number of major failures of equipment other than circuit breakers,disconnectors/earthing switches and instrument transformers) and figure 5-28 expressesthese relative values graphically.

Table 5-45: Comparison of collected GIS components other than CB, DS/ES and IT majorfailures in the 2

ndand the 3

rdGIS surveys (absolute and relative values)

Failed GIScomponent

2nd

GIS survey 3rd

GIS survey

Absolute[number of MaF]

Relative [%] Absolute[number of MaF]

Relative [%]

Busbar+busducts 121 64,4 19 38,0

Any kind ofbushing 49 26,1 9 18,0

Surge arrester 5 2,7 0 0,0

Other 13 6,9 22 44,0

Figure 5-28: Comparison of collected GIS components other than CB, DS/ES and IT majorfailures in the 2nd

and the 3rd

GIS surveys (relative values)

In the 3rdsurvey nearly half of the major failures were not in the list of answers mentioned inthe questionnaire. That is very really puzzling and it causes that a comparison with the 2 ndsurvey is almost impossible.

Findings and commentaryAs total data is concerned the major failure relative distribution is dominated by busbars andbusducts MaF (38 %) followed by 18% MaF of different kinds of bushings. A similar picture isfound when evaluating data without countries 14 and 23 (41% and 7,5%). There was nomajor failure reported for GIS surge arresters but their installation is extremely rare at lowvoltage classes and they are not often used at high voltage classes, either. The portion of

busbar and busducts rises at higher voltages and that is natural as their lengths rise, too. Asthe evaluation of the age aspect is concerned the total number of MaF is too low to make anyserious conclusion even if the present data does not show any GIS age dependence. Minorfailure overview is provided only for very rough information as WG doubts aboutcompleteness of the MiF data.

0

10

20

30

40

50

60

70

Relativenumberofmajorfailures[%]

ComparisonofrelativenumberofmajorfailedGIS

component otherthanCB,DS/ESandIT

2ndsurvey

(1995)

3rdsurvey

(2007)

8/11/2019 Cigre TB 513

50/17246

There is a very high portion of other reported in the survey. The questionnaire,unfortunately, did not provide a space for any respondents commenting and the WG can justspeculate what this other can mean. That could include problems in earthing systems,supporting systems, cabling, and/or the high number just reflects a fact that the questionnairerespondent didnt have such an information available.

5.5.6 GIS age failures dis tribut ion

Since the survey was running in the period of 4 years the reported GIS age overview wouldbe complicated (floating age). The age aspect is therefore expressed in the way ofanalyzing manufacturing years. Even if the year of each failure is known the overview isclassified in the same way as for service experience to enable further failure frequencycomputing.

Tables 5-46 and 5-47 show distributions of collected GIS major (MaF) and minor (MiF)failures in seven intervals of GIS manufacturing years for all data and in absolute and relativevalues. 100% is number of GIS failures collected within individual voltage classes. Tables 5-48 and 5-49 show the same data but without two dominant countries. Figures 5-29 and 5-30provide graphical interpretations of the absolute values of all data.

Table 5-46: Distribution of major failures (MaF) in seven intervals of GIS manufacturing years -all data (absolute and relative values with in individual voltage classes)

Number of MaF

Manufacturingyear

60U

8/11/2019 Cigre TB 513

51/17247

Table 5-48: Distribution of major failures (MaF) in seven intervals of GIS manufacturing years -data without countries 14 and 23 (absolute and relative values within individual voltageclasses)

Number of MaF

Manufacturing year

60U

8/11/2019 Cigre TB 513

52/17248

Figure 5-30: Distribution of the number of minor (MiF) failures in seven intervals of GISmanufacturing years

Table 5-50 shows summaries (without classifying into voltage classes) of data from thetables above but the relative values are recalculated to total collected failure data (100% istotal number of MaF, MiF resp.).

Table 5-50: Distribution of major (MaF) and minor (MiF) failures in seven intervals of GISmanufacturing years all data and data without countries 14 and 23 (absolute and relativevalues of total collected MaF and MiF)

Manufacturingyear

All data Data without countries 14 and 23MaF abs. MaF % MiF abs. MiF % MaF abs. MaF % MiF abs. MiF %

before 1979 39 10,9 283 18,8 18 17,1 184 19,0

1979-1983 58 16,2 327 21,7 34 32,4 223 23,0

1984-1988 83 23,2 300 19,9 24 22,9 177 18,2

1989-1993 81 22,6 328 21,8 9 8,6 214 22,1

1994-1998 51 14,2 182 12,1 5 4,8 121 12,5

1999-2003 23 6,4 68 4,5 7 6,7 38 3,9

2004-2007 23 6,4 17 1,1 8 7,6 13 1,3

Total 358 100,0 1505 100,0 105 100,0 970 100,0

Comparison with previous surveyIn the population card of the 2ndGIS survey, there was a column for inserting the year theGIS substation was put into service. However, in the analysis brochure [13] the collectedservice 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 12years (age of 1 to 11 years) and for older than 12 years. To compare the results with the 3 rdsurvey it was therefore necessary to classify the data into the two same two age intervals.The comparison is shown in table 5-51 and figure 5-31. The table shows data without oneworst utility for the 2nd survey and only the complete data (data having its equivalent infailure cards) for the 3rd survey. This data will be used for failure frequency comparison (seechapter 5.6).

0

20

40

60

80

100

120

140

160

NumberofMiF[]

Minorfailures(MiF)independenceonGISmanufacturing

year interval(alldata)

60U

8/11/2019 Cigre TB 513

53/17249

Table 5-51: Comparison of 2nd

and 3rd

GIS surveys collected number of major failures of GISolder than 11 years and 11 years old or younger in individual voltage classes (absolute values)

Voltage class





GIS age>11 years

GIS age11 years

GIS age>11 years

GIS age11 years

60U

8/11/2019 Cigre TB 513

54/17250

5.6 GIS Major Failure Frequencies

5.6.1 Completeness of data

The above shown population (service experience) and failure data were analyzed from their"completeness" point of view. Data was considered complete, when a failure card was

always accompanied with its population card. If there was no failure card accompanied with apopulation card it was clearly stated by the respondent that the respective population did nothave any failure in a specific year. Portion of complete and incomplete population and failurecards is shown in table 5-52 for all data and in table 5-53 for data without countries 14 and23. Moreover the WG decided to exclude major failures caused by flood (28 MaF in class 1 -thereof 17 DE, 4 IT and 7 GI) from the final failure frequency calculation. Flood belongs toforce majeure causes that the equipment cannot be really designed for. In spite of that thecompleteness reached more than 99 % for collected service experience and more than 90%for collected major failure data. The resulting number of "complete" service experience and"complete" number of major failures without those caused by flood, i.e. data for failurefrequencies calculation, is shown in 3rdand 6thcolumns of is shown in tables 5-52 and 5-53.

Table 5-52: Overview of collected data and thereof data entering the failure frequencycalculations - all data

Voltage class[kV]

Total collectedexperience

[CB-bay-years]

Experiencemarked as

complete (C)for failurefrequencycalculation

% of Cmarked

experience

Total collectednumber of MaF

MaF markedas complete

(C)

% of Cmarked

MaF

60U

8/11/2019 Cigre TB 513

55/17251

Minor failure frequencies have not been calculated (there are big doubts about minor failurereporting completeness).

Some presented results include also statistics calculations described in technical brochure[1]. The confidence intervals and results of null and alternate hypotheses test between theresults of two independent groups or of a subgroup in relations to the whole population areprovided. The confidence level and significance level are 95% and 5% respectively.

Overview of further provided analyses GIS major failure frequencies in total and in individual voltage classes for all data and

data without countries 14 and 23 (including confidence intervals), comparison of alldata and data without countries 14 and 23 results, comparison of results of individualvoltage classes - chapter 5.6.2

Time trend of GIS major failure frequencies in individual voltage classes for all dataand data without countries 14 and 23 (including confidence intervals for all data) -chapter 5.6.7.

The results of major failure frequencies within individual voltage classes for all data anddata without countries 14 and 23 were tested for equality of the estimated failurefrequency. The hypotheses test showed equality of results (except for voltage class 4).From that point on more detailed calculations (GIS extent, location, encapsulation designand failure frequencies for different kinds of bushings) were made only for all data. Thefollowing analyses of MaF frequencies are provided for:

Fully GIS and Hybrid GIS in total and in individual voltage classes for all data(including confidence intervals), comparison of the results of individual voltageclasses - chapter 5.6.3

Indoor GIS and Outdoor GIS in total and in individual voltage classes for all data(including confidence intervals), comparison of the results of individual voltageclasses - chapter 5.6.4

Single phase GIS bays and three phase GIS bays in total and in individual voltageclasses for all data (including confidence intervals), comparison of the results of

individual voltage classes - chapter 5.6.5 SF6-to-air bushings, cable boxes and transformer bushing failure frequencies

chapter 5.6.6

As the GIS populat ion card asked for 3-phase data about Gas Insulated Switchgear(GIS) and those parts of hybr id substations made from GIS components population,the collected service experience is 3-phase. Collected data about failures is s inglephase or three-phase as mentioned in the introduct ion of chapter 5.5. Supposing thatany, even a single phase failure causes an outage of all three GIS phases the values ofsubsequently provided failure frequencies are related to 3-phase GIS circuit breakerbay arrangement.

Comparison with previous surveyTo get as much as possible a true comparison the WG decided to select only the followingtwo data sets from the 2ndsurvey :

all data without one the worst utility results set (275 failures which occurred in 18indoor class 2 substations representing 133 CB-bays, 2633 CB-bay-years)

all data without one utility having the worst results and without one dominant highlydeveloped country (representing 70074 CB-bay-years and only 59 major failures)

An overview of these two data sets is given in table 5-54. However, it shall be kept in mindthat the comparison is very approximate to make any real final conclusion as the participationof countries, utilities and reported GIS in the 3rdsurvey was different from the 2ndone.

8/11/2019 Cigre TB 513

56/17252

Table 5-54:. Overview of collected data in the 2nd

GIS survey entering the failure frequenciescomparison

Voltage class

[kV]

All data without the worst utility data All data without the worst utility and onedominant country data

Total collectedexperience

[CB-bay-years]

Total collected numberof MaF

Total collectedexperience [CB-

bay-years]

Total collectednumber of MaF

60U

8/11/2019 Cigre TB 513

57/17253

Table 5-56: Distribution of major failure frequency for GIS-CB-bay data without countries 14and 23 (absolute values within individual voltage classes and results of hypotheses tests onsignif icant dif ference from all data failure frequencies)

Voltage class

Major failure frequency [MaF/100 CB-bay-years]all data without countries 14 and 23

Result ofhypotheses tests:difference from all

data resultsPoint estimation Lower limit Upper limit

60U

8/11/2019 Cigre TB 513

58/17254

Comparison with previous surveyTable 5-57 and figure 5-33 provide a comparison of the 2ndand 3rdGIS surveys. They showabsolute values of major failure frequencies point estimations in individual voltage classesand results of hypotheses tests.

Table 5-57 : Comparison of 2nd

and 3rd

GIS surveys major failure frequencies (absolute values)

Voltage class

Major failurefrequency [MaF/100

CB-bay-years]

Results ofhypothesestests

Major failure frequency[MaF/100 CB-bay-years]

Results ofhypothesestests

2nd

GISsurvey -all datawithoutthe worstutility

3rd

GISsurvey all data

2nd

GISsurvey - alldata withoutthe worstutility and adominantcountry

3rd

GISsurvey all datawithoutcountries14 and 23

60U

8/11/2019 Cigre TB 513

59/17255

Findings and commentaryMajor failure frequency increases with voltage class in both analyses, i.e. for all data as wellas for data without countries 14 and 23. As mentioned in technical brochure [1] theconfidence interval is the wider the less service experience enters the calculation. The pointestimations as well as their confidence limits with confidence level of 95% are given in tables5-55 and 5-56.

The point estimations for all data for voltage classes 1, 2 and 3 are about 0.3

Documents

Cigre TB 513