२२० के वी एवं उ(cid:205)चतर (cid:874)वभव के सब(cid:232)टेशन(cid:585) के (cid:162)(cid:467)त(cid:274)(cid:232)त उपकरण(cid:585) पर (cid:874)वशषे (cid:163)(cid:585) क(cid:551) (cid:232)थायी स(cid:871)म(cid:467)त क(cid:551) (cid:464)रपोट(cid:91) ((cid:871)सत(cid:224)बर २०१५-(cid:465)दसंबर २०१६) REPORT OF STANDING COMMITTEE OF EXPERTS ON FAILURE OF 220 kV & ABOVE VOLTAGE CLASS SUBSTATION EQUIPMENT (SEPTEMBER 2015-DECEMBER 2016) भारत सरकार Government of India के (cid:198)(cid:254)ीय िव(cid:299)ुत (cid:255)ािधकरण Central Electricity Authority िव(cid:299)ुत मं(cid:253)ालय Ministry of Power नई िद(cid:208)ली New Delhi (िव(cid:299)तु अिधिनयम २००३ क(cid:236) धारा ७३(एल) के तहत के.िव.(cid:255)ा. के दािय(cid:194)व का िनव(cid:170)हन करते ह(cid:242)ए) (In fulfillment of CEA’s obligation under Section 73(1) of the Electricity Act, 2003) CENTRAL ELECTRICITY AUTHORITY TABLE OF CONTENTS SUBJECT PAGES INTRODUCTION 2 OBSERVATIONS 13 RECOMMENDATIONS 14 ANNEXURE-I 20 INVESTIGATION REPORTS OF FAILURE OF POWER TRANSFORMERS OF DTL ANNEXURE-II : 48 DETAILED INFORMATION IN RESPECT OF EACH FAILED EQUIPMENT REPORTED TO CEA BETWEEN 1ST SEPTEMBER 2015 AND 31ST DECEMBER 2016 AND BRIEF ANALYSIS OF FAILURE OF THESE EQUIPMENT ANNEXURE-III : 219 MINUTES OF MEETING OF THE STANDING COMMITTEE OF EXPERTS TO INVESTIGATE THE FAILURE OF 220 KV AND ABOVE VOLTAGE CLASS SUBSTATION EQUIPMENT HELD ON 1ST MARCH 2017 IN CEA ANNEXURE-IV : 226 OFFICE ORDER CONSTITUTING THE STANDING COMMITTEE Report on failure of 220 kV and above voltage class substation equipment 1 CENTRAL ELECTRICITY AUTHORITY EXECUTIVE SUMMARY 1.0 INTRODUCTION 1.1 A Standing Committee comprising experts in the field of design and operation of EHV Substations from CEA, various power utilities and research/academic institutes was constituted under Section 73, Clause(1) of the Electricity Act, 2003, to investigate the failure of 220 kV and above voltage class substation / switchyard equipment such as Power/Generator Transformer, Circuit Breaker (CB), Instrument Transformer [i.e. Current Transformer (CT), Potential Transformer PT & Capacitor Voltage Transformer(CVT)], Surge Arrester (SA), Isolator, Wave Trap, Coupling Capacitor, XLPE Cable etc. and recommend measures to avert recurrence of such failures in future. As a part of such activity, CEA has been receiving reports of failures of various substation / switchyard equipment from power utilities. Office order vide which Standing Committee was constituted is enclosed at Annexure- IV. 1.2 The prime objective of Standing Committee is to visit site of failure, investigate the cause of failure, discuss the cause of failure of various substation / switchyard equipment of Power utilities in the meeting, recommend remedial measures to prevent recurrence of such failures in future and prepare a compendium of all failures. In the process the participating utilities are mutually benefitted so as to adopt best practices. As per the requirement of the Standing Committee, all utilities are supposed to report the failure of substation/ switchyard equipment of 220 kV and above voltage class to CEA. In fact, number of failure cases remain unreported as many of power utilities [State Transmission Utilities, Private Utilities/Licensees, Central Transmission Utilities, Public Sector Power Utilities] in the country neither report the failure of substation / switchyard equipment nor participate in such National level meeting. Hence the basic purpose of formation of above standing committee gets defeated. 1.3 In most of the cases, the visit to site of failure do not materialize and analysis of cause of failure is done based on information provided by utilities in prescribed format. The information furnished by utilities is generally found to be inadequate for analysis of cause of failure. Either many vital information is found to be missing or not available with O&M section because the O&M history of equipment / transformer, records of all test results including tests carried out before & after failure incidences (factory tests, pre-commissioning tests, tests carried out during O&M etc.) are not properly maintained. 1.4 A meeting of the Standing Committee of experts was held in CEA on 1st March 2017 to discuss cause of failure of substation equipment for which information/failure report was received in CEA between 1st September 2015 and Report on failure of 220 kV and above voltage class substation equipment 2 CENTRAL ELECTRICITY AUTHORITY 31st December 2016 from various utilities. Minutes of the meeting are enclosed at Annexure - III. 1.5 In most of the cases of failure of CT / CVT / PT/ SA, the equipment had blasted. In such cases it becomes difficult to pin point the cause of failure. Some of the failures of equipment / transformers could be due to ageing. 1.6 Quantity of failed equipment and years of service put in by these equipment before failure, reported to CEA between 1st September 2015 and 31st December 2016, is given in Table-I. Details of these failures are provided at Annexure-II. TABLE-1 Nos. of equipment failed Years of Service Transformers/ Reactors Surge Coupling CB CT CVT/PT GT Arrester Capacitor 0-5 2 6 2 0 6 13 0 years 5-10 2 3 0 9 2 5 0 years 10-15 0 5 3 2 3 3 1 years 15-20 0 2 0 3 1 3 0 years More 0 than 20 5 1 2 10 4 1 years Total 21 4 6 * 16^ 22 # 28 $ 2 * Total reported CB failures are 7 Nos.; information on year of commissioning for 1 No. CB is not available, hence years of service could not be determined. ^ Total reported SA failures are 17 Nos.; information on year of commissioning for 1 No. SA is not available, hence years of service could not be determined. # Total reported CT failures are 26 Nos.; information on year of commissioning for 4 Nos. CTs is not available, hence years of service could not be determined. $ Total reported CVT/PT failures are 32 Nos.; information on year of commissioning for 4 Nos. CVTs/PTs is not available, hence years of service could not be determined. Report on failure of 220 kV and above voltage class substation equipment 3 CENTRAL ELECTRICITY AUTHORITY 1.7 Previous report was published in March 2016 which contained the information regarding failure of substation equipment reported to CEA between 1st October 2014 and 31st August 2015. 1.8 Failure of Transformers: (i) The transformer, the costliest equipment in a switchyard/substation, is expected to serve the entire life of a substation which is considered to be 35 years as per CERC norm. However, it has been observed that many Transformers have failed within first few years of service which is a matter of concern. (ii) Twenty-one (21) transformer failure cases have been reported to CEA during the period from September 2015 to December 2016 by nine (9) Utilities. Out of these twenty-one (21) transformers, one transformer is 765 kV class, seven (7) Nos. of transformers are of 400 kV class [5 Nos. ICTs and 2 Nos. GTs] and thirteen (13) Nos. of transformers are of 220kV class [one GT and 12 Nos. ICTs]. Seventeen (17) numbers of failures are due to internal insulation failure, two (2) number of failures are attributed to bushing failure, one failure on account of ageing and in case of one failure, sufficient information was not available to determine any cause of failure. It is a matter of concern that 9 Nos. of transformers have failed within 10 years of operation/service. It is highlighted that number of transformer failure cases remains unreported as many of power utilities [State Transmission Utilities, Private Utilities/Licensees, Central Transmission Utilities, Public Sector Power Utilities] in the Country do not report the failures. (iii) Summary of failure of Inter Connecting Transformers (ICTs) / Generator Transformers (GTs) reported to CEA between 1st September 2015 and 31st December 2016 is detailed below (Table 2): TABLE - 2 Year of Probable Utility/Name Date of Equipment Make Rating commis Cause of of substation failure sioning failure* Power DTL BHEL 220/33kV, 2005 02.02.2016 Internal transformer Geeta Colony 100MVA insulation (18 Nos.) failure DTL EMCO 315 MVA, 2010 08.03.2016 Internal Bawana 400/220/33 insulation kV failure DTL EMCO 100 MVA, 2006 04.09.16 Internal Papankalan 220/66-33/11 insulation kV failure Report on failure of 220 kV and above voltage class substation equipment 4 CENTRAL ELECTRICITY AUTHORITY DTL BHEL 100 MVA, 1994 11.09.16 Internal Park Street 220/66-33/11 insulation kV failure DTL BHEL 400/220/33 2000 11.12.2016 Internal Bawana kV, 315 MVA insulation failure DTL BHEL 100 MVA, 2005 01.12.2016 Internal Geeta Colony 220/33/11 insulation kV failure DTL EMCO 220/33/11k 2014 19.10.2016 Internal Wazirpur V, 100 insulation MVA failure PGCIL CGL 500 MVA, 2016 15.11.2016 Internal Bareilly 765/400 kV insulation failure HVPNL Areva 315 MVA, 2013 22.04.2015 Internal Nawada 400/220 kV insulation failure HVPNL BHEL 220/66 kV, 2003 13.03.2015 Internal Madanpur 100 MVA insulation failure APTRANSCO BHEL 100 MVA, 2010 11.10.2015 Internal Pulivendula 220 kV /132 insulation kV failure APTRANSCO EMCO 220/132kV, 1999 24.08.2016 Bushing Tadikonda 100 MVA failure APTRANSCO TOSHIBA 220/132 kV, 2015 24.09.2016 Internal Gudivada 160 MVA insulation failure TANTRANSCO EMCO 230/110/11 2008 01.12.2015 Sufficient Manali kV, 100 MVA information not available TANTRANSCO BHEL 100 MVA, 1994 31.03.2016 Internal Gummidipoon 230/110 kV insulation di failure KSEB BHEL 33.3 MVA, 1978 04.05.2016 Ageing Edamon 220/110 kV KPTCL CGL 1-Ph, 167 2004 02.06.2016 Bushing Hoody MVA, 400 failure /220/33 kV Report on failure of 220 kV and above voltage class substation equipment 5 CENTRAL ELECTRICITY AUTHORITY OPTCL BHEL 315 MVA, 2005 12.11.2016 Internal Meramundali 400/220/33 insulation kV failure Generator KPCL CGL 250MVA, 1991 23.05.15 Internal Transformers Raichur TPS 15.75/220kV insulation (3 Nos.) failure KPCL BHEL 207 MVA, 2015 28.08.2015 Internal Bellary TPS 21/400/√3 insulation kV failure KPCL CGL 250 MVA, 1994 28.02.2016 Internal Raichur TPS 15/420 kV insulation failure * Probable cause of failure is based on information, data & reports furnished by the utility. (iv) CEA Officers visited sites of Delhi Transco Ltd. (DTL) for joint investigation of following failure cases of transformers (Table-3). The Officers collected relevant data/information from site, interacted with substation staff, and carried out inspection of the transformer through inspection window, wherever feasible. Based on the information/data collected from the sites, preliminary reports were prepared. The reports of these visits are enclosed at Annexure-I. TABLE-3 Utility/Name Year of Date of Make Rating of substation commissioning failure DTL BHEL 220/33kV, 2005 02.02.2016 Geeta Colony 100MVA DTL EMCO 315 MVA, 2010 08.03.2016 Bawana 400/220/33 kV DTL EMCO 100 MVA, 2006 04.09.16 Papankalan 220/66-33/11 kV DTL BHEL 100 MVA, 1994 11.09.16 Park Street 220/66-33/11 kV DTL BHEL 400/220/33 kV, 2000 11.12.2016 Bawana 315 MVA DTL BHEL 100 MVA, 2005 01.12.2016 Geeta Colony 220/33/11 kV Report on failure of 220 kV and above voltage class substation equipment 6 CENTRAL ELECTRICITY AUTHORITY 1.9 Failure of Reactors: (i) Four (4) Nos. reactor failure cases have been reported to CEA during the period from September 2015 to December 2016 by PGCIL. Out of these, one reactor is of 765 kV class and remaining three are of 400 kV class. Three Nos. failures are attributed to internal insulation failure and one number failure is due to bushing failure. Cause of failure is based on information, data & reports furnished by the utility. It is a matter of concern that all four Nos. of reactors have failed within 10 years of operation/service. (ii) Summary of failure of Reactors reported to CEA between 1st September 2015 and 31st December 2016 is detailed below (Table-4): TABLE-4 Equipment Utility/Name Make Rating Year of Date of Probable of substation commissioning failure Cause of failure* Reactor PGCIL BHEL 420 kV, 2009 28.09.2016 Bushing (4 Nos.) Kota 80 MVAR failure PGCIL BHEL 420 kV, 2006 05.11.15 Internal Satna 50 MVAR insulation failure PGCIL CGL 765 kV, 2012 28.11.2015 Internal Bina 80 MVAR insulation failure PGCIL BHEL 420 kV, 2012 29.02.2016 Internal Binaguri 125 insulation MVAR failure * Probable cause of failure is based on information, data & reports furnished by the utility. 1.10 Failure of Circuit Breakers (CBs): Seven (7) Nos. of cases of CB failure have been reported to CEA during the period from September 2015 to December 2016 by four (4) Utilities. Out of these seven (7) Nos. of CBs, two CBs are of 400kV class and remaining five (5) Nos. of CBs are of 220kV class. In all these cases of CB failures, failed pole or component such as Pre-Insertion Resistor (PIR), Grading Capacitor etc. had to be replaced with the new one. Repair of failed CB was not possible in any of the cases. In most of the cases, cause of failure of CB was internal insulation failure. 1.11 Failure of Current Transformers(CTs): It is observed that twenty-six (26) Nos. of cases of CT failure have been reported to CEA during the period from September 2015 to December 2016 by six (6) Report on failure of 220 kV and above voltage class substation equipment 7 CENTRAL ELECTRICITY AUTHORITY Utilities. All twenty- six (26) CTs are of 220kV class. It is observed that in most of the cases, the CTs have blasted and have been replaced. It is a matter of concern that twelve (12) Nos. of CTs have failed within 10 years of operation. Information on year of commissioning is not available for four (4) Nos. of CT, hence service rendered by these CTs could not be ascertained. 1.12 Failure of Potential Transformers (PTs) / Capacitive Voltage Transformers (CVTs): It is observed that thirty-two (32) Nos. of cases of CVT / PT failure have been reported to CEA during the period from September 2015 to December 2016 by seven (7) Utilities. Out of these thirty-two (32) CVTs / PTs, five (5) Nos. of CVTs are of 400kV class and rest seventeen (17) Nos. of CVTs / PTs are of 220kV class. In most of the cases, the CVTs / PTs have blasted and have been replaced. It is a matter of concern that eighteen (18) Nos. of CVTs / PTs have failed within 10 years of operation. Information on year of commissioning is not available for four (4) Nos. of CVT/PT, hence service rendered by them could not be ascertained. 1.13 Failure of Surge Arresters (SAs): It is observed that seventeen (17) Nos. of cases of SA failure have been reported to CEA during the period from September 2015 to December 2016 by four (4) Utilities. Out of these seventeen (17) Nos. of SAs, three Nos. of SAs are of 400kV class and rest fourteen (14) Nos. of SAs are of 220kV class. In most of the cases, the SAs have blasted and have been replaced. It is a matter of concern that nine (9) Nos. of SAs have failed within 10 years of operation. Information on year of commissioning is not available for one No. SA, hence service rendered by it could not be ascertained. 1.14 Failure of Coupling Capacitor: Failure of two Nos. of Coupling Capacitors, both of 220 kV voltage class, have been reported to CEA between September 2015 to December 2016 by two Utilities. Both Coupling Capacitors have burst due to internal fault leading to operation of distance relay. 1.15 Summary of failure of CB/CT/CVT/PT/SA/Coupling Capacitor: TABLE-5 Equipment Year of Date of Utility Make Rating (Quantity) commissioning failure Circuit BBMB Siemens 220 kV 2015 31.05.15 Breaker (7) KPTCL ABB 220kV 2000 20.10.2015 Report on failure of 220 kV and above voltage class substation equipment 8 CENTRAL ELECTRICITY AUTHORITY KPCL CGL 2000 A 2002 12.11.2015 BBMB CGL 400kV, 3150A, 2001 22.01.2016 40KA for 3 Sec. KPCL BHEL 2000 A 1994 13.04.2016 APTRANSCO CGL 400kV, 2000 A 2012 06-09-2016 BBMB Siemens 220kV NA 08.12.2016 CT BBMB SCT 220 kV 2015 31.05.15 (26) TANTRANSCO TELK 230 kV 1985 24.08.2015 KSEB VITRANS 220 kV NA 19.05.2015 TANTRANSCO SCT 230 kV 2012 25.05.2015 TANTRANSCO TELK 230 kV 1986 26.09.2015 MPPTCL SCT 220 kV, 800- 2011 25.07.2015 400/1 A MPPTCL TELK 220 kV, 800- 1993 18.08.2015 400/1 A KPTCL W.S.Industries 220 kV NA 15.10.2015 KPTCL Mehru 220 kV 2012 24.10.2015 APTRANSCO TELK 220 kV 1981 22.12.2015 KPTCL SCT 220 kV Class 2007 22.02.2016 CT of Ratio 800/1-1-1-1- 1A KPTCL Sri 220 kV 2003 24.02.2016 Venkateshwar Electicals Ltd KPTCL HBB 220 kV, 800- 1984 26.02.2016 600-400- 200/1-1-1A TANTRANSCO Areva 220 kV, 600/1 2009 14.02.2016 A APTRANSCO TELK 220 kV 1993 21.02.2016 Report on failure of 220 kV and above voltage class substation equipment 9