swicon 2008 technical papers

8/12/2019 SWICON 2008 Technical Papers

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About IEEMA(Indian Electrical and ElectronicsManufacturers' Association)

THE ASSOCIATIONFounded in 1948, Indian Electrical and ElectronicsManufacturers' Association (IEEMA) is the representativenational organisation of manufacturers of electrical,professional electronics and allied equipment having over550 members whose combined annual turnover is over Rs1,00,000 crores i.e. US $ 22 billion.

Now in its 60th year of existence, IEEMA continues toprovide unique services to its members. IEEMA undertakesvarious activities, major ones being dissemination ofinformation of production statistics and governmentpolicy changes, representing the industry's views to thegovernment, price variation clauses covering a wide rangeof products and evolving industry standards. Training formembers and non-members on topical issues, library andbusiness center facilities are among the other initiativeson offer.

IEEMA as the representative organisation for the industryis also a part of many councils and committees constituted

by the Government.IEEMA has the distinction of being the first associationin India to achieve an ISO certification in January 1998and successfully re-certified for the second time for ISO9001:2000 in 2006.

IEEMA VISIONIn consultation with its stakeholders and to cater to theiremerging needs, IEEMA evolved a vision;

"Electricity for all and global excellenceleading to human enrichment"

To realise the vision, IEEMA has taken a bold step torestructure itself and has drawn an ambitious mediumterm programme to provide value added services to itsmembers and help facilitate their rapid expansion in bothdomestic and global business arena. IEEMA has realignedits structure and activities to successfully achieve the setvision objectives.

IEEMA's new vision is based on the five Building Blocks,which IEEMA members have short listed to be the mostcrucial for their success;

1. Credibility with all stakeholders

2. Excellence3. Global Presence

4. Enabling power to all

5. Eco-system focus

IEEMA ACTIVITIES & INITIATIVES

Voice of IndustryIEEMA as the voice of electrical industry maintains a

continuous dialogue with the Government and its variousdepartments, utilities, other users, standardization

bodies, educational institutions, research, development

and testing as a major part of this goal.

Initiatives with the Government

Co-ordination with the Ministry of Power for successful

implementation of Accelerated Power Development &

Reforms Programme (APDRP) and rural electrification

under the Rajiv Gandhi Grameen Vidyut Vitran Yojna

or RGVVY. Support to Bureau of Energy Efficiency forstandards and labeling, Programme on Energy Efficient

Products, interface with standards and testing Institutions,

organizing DRUM training programmes with Ministry ofPower etc.

International Co-operation

Networking with overseas counterpart associations from

many countries for exchange of information, assistanceto membership and other joint programmes aimed at

enhancing business co-operation opportunities. MOUs

with a number of countries like China, Korea, Spain,

Taiwan and Malaysia. IEEMA is also one of the foundermembers of FAEMA i.e. Federation of Asian Electrical

Manufacturers' Associations.

SME Focus

IEEMA has added this activity solely to facilitate the

betterment and up gradation of SMEs to globally excellentlevels and has initiated action.

Corporate Social Responsibility

IEEMA on its part in a small manner has launched a

media awareness campaign to Save Electricity and save

the environment, using print, voice and electronic media.10,000 secondary level school children too are being

exposed to this campaign through presentations, postersand brochures.The campaign is being carried forward

Cross Sectoral Networking

IEEMA is networking with other sectoral and apex

associations and chambers. Building up Industry academiarelations and assisting ministry of power to draw up

sustainable power solution models for rural India.

Commitment to Quality and Benchmarking

* Standardization : Formation of industrystandards, operation and maintenance guidelinesto serve specific need of members and the user

Industries.

About IEEMA


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* Quality : Promotion of product and systemquality through training, awareness programmes

and consultancy

* Benchmarking : CRISIL- LLYOD rating for Meters isnow in second stage while, for Cables andDistribution transformers is under planning,

Export division too is considering rating ofExporters.

Energy Conservation Initiatives

Promotion of energy conservation through promotion,

manufacture and usage of energy efficient products

through external media and IEEMA journal

Information Dissemination* Information Circulars : Circulation of information

about procedural and policy changes made bythe government in direct and indirect taxation,import-export policy, industrial regulations aswell as tender information, businessopportunities, standards and other matters ofinterest to the industry.

* Publications: Publication of IEEMA JOURNAL andIEEMAIL on monthly basis and IEEMA News& Views on every fortnight covering technicaland techno-commercial articles, industry

information, statistics, business opportunities,IEEMA activities and more. IEEMA Journal with asubscription of 10,000 celebrated its SilverJubilee in the year 2005-06.

* Directory of Members: Publication of directory ofmembers, i.e. IEEMA Directory containingexhaustive information about its members andthe industry.

* Special Services: Statistical Information -Circulation of monthly production and import-export statistics covering various segments of

the industry.

IEEMA JournalToday a synonym for the Indian electrical industry, IEEMAJournal was started with the intent of keeping its membersaware of technological and related developments in thelocal as well as international arena. And what startedas a small journal has today evolved into a full-fledgedmagazine that signifies a fine example of professionalismin the domain of trade publications. With an Audit Bureauof Circulation (ABC) certification for 10,000 copies, it isalso the only trade journal in India that enjoys a readership

of well over 50,000.

Price Variation ClausesEvolution and operation of equitable Price VariationClauses, covering a wide range of products, being used

both by purchasers and suppliers. Circulation of basic

prices and indices to operate these clauses on monthlybasis.

Commercial Terms

Formation of standard terms and conditions forcontracts.

IEEMA Websites

The IEEMA websites contain updated information aboutIEEMA, its members, the industry and various servicesoffered by the Association.

Separate web site is available only for members forinformation dissemination.ELECRAMA website caters tothe ELECRAMA participants.

Export Promotion

Organization of high-level delegation visits andparticipation in exhibitions abroad for export promotionMADE IN INDIA brand.

IEEMA Training Programmes

As a result of globalisation, the market conditions havebecome fiercely competitive. Under such circumstances,quality human resources emerge as the most vital factorfor effective operation of the industry. IEEMA, in itsconstant endeavour to find new and innovative ways

towards improvement of its services, plans to put focusedefforts on training activity catering to the needs of Indianindustry.

IEEMA Events

Under the aegis of IEEMA Events, the activities held willbe more of interactive series, promotions, seminarsand exchange-of-ideas forums. The focal point of allthese activities will revolve around bringing togetherprofessionals across borders for a common vision.

All in the interest of taking the industry to a new level.Giving India its much-deserved place in the world.

IEEMAGINE Seminars

Every year IEEMA organises IEEMAGINE, a discussionplatform to bring forth the issues pertaining to theindustry.

ELECRAMA Exhibitions

Started way back in 1990 with 283 exhibitors spreadover an area of 12,500 square metres, ELECRAMA hasbecome the largest international exhibition of electricaland industrial electronics industry in Asia, Middle Eastand Africa.

Since then there was no looking back. ELECRAMA saw atremendous growth of 1086 exhibitors spanning an areaof 40,000 square metres in the year 2006, breaking allpast records. And this is just the beginning.

About IEEMA


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Organising Committee

Mr. S.B. Gupte - Chairman : Siemens Ltd.

Mr. C.P. Vyas : ABB Limited

Mr. S. Khajanchi : Areva T&D India Ltd.

Mr. G.S. Kochar : Asiatic Electronic Industries

Mr. D.K. Dikshit : B.H.E.L

Mr. M Chakrabarti : Bhartia Industries Ltd.

Mr. A. Sarkar : Consultant, Schneider Electric India Pvt. Ltd.

Mr. J.G. Kulkarni : Crompton Greaves Ltd. Mr. D.K. Majumdar : Electroteknica Switchgears Pvt. Ltd.

Mr. Dilip Trivedi : Elmex Controls Pvt. Ltd.

Mr. Saibal Pal : Rockwell Automation India Pvt. Ltd.

Mr. Mahesh Desai : Siemens Ltd.

Mr. R. Subba Rao : Vijai Electricals Ltd.

Mr. Anil Nagrani : IEEMA

(Organizing Secretary)

SWICON 2008 Organising Committee


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Technical Committee

Mr. Hemant Tungare - Chairman : Siemens Ltd.

Dr. J.J. Patel : ABB Limited

Mr. Joji Sebastian : Areva T&D India Ltd.

Mr. M.P. Kulkarni : Ashida Electronics Pvt. Ltd.

Mr. Vishal Sikka : Asiatic Electronic Industries

Dr. H.S. Jain : B.H.E.L

Mr. C. Kundu : Bhartia Industries Ltd.

Mr. J. Santhosh : Central Power Research Institute

Mr. S.B. Potnis : Crompton Greaves Ltd.

Mr. G. Srinivas : Crompton Greaves Ltd.

Dr. M.K. Shah : E.R.D.A

Mr. Dilip Trivedi : Elmex Controls Pvt. Ltd.

Mr. Arvind Mathur : Jasper Engineers Pvt. Ltd. Mr. N.P. Jhaveri : Jyoti Ltd.

Mr. H.T. Mistry : Larsen & Toubro Limited

Mr. G. Babu : Schneider Electric India Pvt. Ltd.

Mr. B.C. Badiya : Siemens Ltd.

Mr. V.K. Kulkarni : Siemens Ltd.

Mr. Girish Muley : Siemens Ltd.

Mr. P. Ramamurthy : Siemens Ltd.

Mr. Gautam Shetye : Siemens Ltd.

Mr. R. Subba Rao : Vijai Electricals Ltd.

Mr. Anil Nagrani : IEEMA(Organizing Secretary)

Technical Committee SWICON 2008


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THE COUNCIL

Members of IEEMA EXECUTIVE COUNCILfor the year 2007-2008

President

Mr. S.C. Bhargava

Exe.Vice President Electrical Sector& Member of Divisional Board

Larsen & Toubro Limited

Vice President

Mr. P.P. Gupta

Managing DirectorTechno Electric & Engg. Co. Ltd.

Vice President

Mr. Murali Venkatraman

Vice Chairman & Managing DirectorW.S. Industries (India) Limited

Immediate Past President

Mr. D.J. Ramesh

Chairman & Managing DirectorVijai Electricals Limited

Elected Members

Mr. A.K. AgrawalGeneral Manager

Vam Electro Devices Pvt. Ltd.

Mr. Vishnu AgarwalManaging Director

Technical Associates Ltd.

Mr. A.K. BanerjeePresident (Swg)

Vijai Electricals Ltd.

Mr. Aaditya R. Dhoot

Jt. Managing DirectorIMP Powers Limited

Mr. Madhav M. Digraskar

PresidentABB Ltd.

Mr. Raj H. Eswaran

DirectorEasun Reyrolle Limited

Mr. P.V. Krishna

Head Power Plant Sales &Head Western Region

Wartsila India Ltd.

Mr. R. N. Khanna

Chairman & Managing DirectorControls & Switchgear Co. Ltd.

Mr. J. G. Kulkarni

Vice President CG Power (Asia)Crompton Greaves Limited

Mr. D.K. Majumdar

Chief Executive - OperationElectroteknica Switchgears Pvt. Ltd.

Mr. Vimal Mahendru

President Corporate AffairsIndo Asian Fusegear Ltd.

Mr. Jitendra U. Mamtora

Chairman & Managing DirectorTransformers & Rectifiers (India) Ltd.

Mr. D.R. Venkatesha Murthy

AdvisorKirloskar Electric Co. Ltd.

Mr. Vijay Paranjape

Director, Member Managing BoardSiemens Ltd.

Mr. Anil Saboo

Managing DirectorElektrolites (Power) Pvt. Ltd.

Mr. Sanjeev SardanaManaging Director

Yamuna Power & InfrastructureLimited

Dr. (Ms) Jaya SatheManaging Director

Gilbert & Maxwell Electricals

Pvt. Ltd.

IEEMA Executiv e Council


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Co-opted Members

Mr. R.D. ChandakManaging Director

KEC International Ltd.

Mr. A.N. ChaudhuriDirector

Modern Malleables Limited

Capt. V.W. KatreDirector

Aplab Limited

Ms. Indra Prem Menon

PresidentLakshmanan Isola Pvt. Limited

Standing Invitees

Mr. S. K. Datta

Chief (Electrical)Biecco Lawrie Ltd.

Mr. Rajesh S. Jain

Chairman & Managing DirectorEmco Limited

Mr. Premchand Goliya

Chairman & Managing DirectorMeco Instruments Pvt. Ltd.

Mr. A.K. Singh

DirectorElectrical Research & Development

Association (ERDA)

Mr. A.K. Tripathy

Director GeneralCentral Power Research Institute

Counsellors

Mr. A. K. Dhagat Mr. P. Krishnakumar

Director & CEOReliance Engineers Ltd.

Mr. V.P. Mahendru

Chairman and Managing DirectorIndo Asian Fusegear Ltd.

Mr. R.N. Mukhija

President (Operations)Electrical & Electronics Div. (EBG)


Mr. S. Ramaswamy

Chairmen of Divisions

Mr. Vijay P. Karia

Cables

Mr. Mustafa Wajid

Capacitors

Ms. Indra Prem Menon

Electrical Insulating Materials

Mr. Sanjeev Sardana

Exports

Mr. P. Sridharan

Insulators

Mr. S.C. Sarkar

Meters


Rotating Machines

Mr. S.B. Gupte

Switchgear & Controlgear

Mr. Akella S.S. Sarma

Surge Arresters

Mr. Mohan Gupta

Stamping & Laminations

Mr. Jitendra U. Mamtora

Transformer

Mr. A.S. Chouhan

Transmission & Distribution Projects

Mr. Nikhil Sanghvi

Winding Wire

Chairmen of Committees & Cells

Mr. Rajesh Jain &

Mr. S. Ramaswamy

Energy Conservation Cell

Mr. Cadavasal S. Kumar

Quality Cell

Chairmen - Regional Committees


Member & Chairman

Southern Region

Mr. Vimal Mahendru

Member & Chairman

Northern RegionMr. S.K. Datta

ChairmanEastern Region

Mr. Madhav M. Digraskar

Member & ChairmanWestern Region

Execu tive Council IEEMA


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INDEX OF SWICON-2008 SYNOPSES

1st Day, Monday, 21st January, 2008From 1100 - 1330 Hrs. (150 Min)

SESSION I - USERS FEEDBACK ( 9 Papers)

Common Session Chaired byMr. D. RainaGrand Ball Room (GBR) Hall 1 & 2

S.No. Title of Technical Paper Organization Page

1 Switchgear Maintenance with Infrared Thermography NDPL 3

2 Vacuum Switching Technology for Rectiformer Application: A Case Study BHEL 6

3 Life Cycle & Asset Management of HV Breakers & Power Transformers NDPL 124 Asset Management of EHV Class Circuit Breakers in Powergird

Network - A Case StudyPGCIL 19

5 Dynamic Contact Resistance Measurement on EHV Circuit Breakers- A Powerful Diagnostic Tool

PGCIL 23

6 EHV Disconnector Quality Issues in Indian Power Sector PGCIL 28

7 Gas Insulated Switchgear - a Decades Experience CESC LTD 33

8 Autocoordination of Protection Settings of Series Reclosers TAVRIDA (OS) 38

9 Condition based Ranking for Reliability Maintenance of Circuit Breaker OPTCL 43

LUNCH BREAK : 1330 - 1415 (45 Min)From 1415 - 1615 Hrs. (120 Min)

SESSION II - TESTING, STANDARDS & COMMON (8 Papers)

Common Session Chaired by Mr. B.N. KishoreGrand Ball Room (GBR) Hall 1 & 2

1 Full-pole Test Results for the Dead-tank Gas Circuit Breaker Rated on800kV, 50kA, 50Hz

KOREA ELECTROTECH (OS)

51

2 Laboratory Analysis on Short Circuit Performance of MV Switchgearsand New Trends in Encapsulated MV Vacuum Circuit Breakers

CPRI 57

3 Study of Behaviour of Medium Voltage Vacuum Circuit Breaker duringCapacitor Current Switching Tests - A CPRI Experience CPRI 63

4 A Simplified Method for Determining High Voltage Circuit BreakerContact Conditions - Dynamic Resistance Measurement

DOBLE ENGG.CO. (OS)

68

5 Realistic High-Power Testing Needs a Proper Choice of Test-Circuits KEMA (OS) 73

6 Inductive Load Switching: A New IEC Standard IEC 62271-110 andExperience from Testing

KEMA (OS) 79

7 Steps Towards RoHS Compliance - The Global Need WS TESTSYSTEMS

86

8 Surge Suppression in electromagnetic Coils L&T 91

COFFEE / TEA BREAK : 1615 - 1645 (30 Min)

Index Chronological


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1st Day, Monday, 21st January, 2008

From 1645 - 1830 Hrs. (105 Min)SESSION III - HIGH VOLTAGE (UHV) (6 Papers)

Common Session Chaired by Mr. S. RamaswamyGrand Ball Room (GBR) Hall 1 & 2

1 Testing of UHV Circuit Breakers KEMA (OS) 97

2 The Role of Surge Arrestor in Substation Insulation Co-ordination L&T, ECC 102

3 Circuit Breaker Platform for 550 Kv SIEMENS AG (OS) 108

4 Bypass Circuit Breaker for 800 kV DC SIEMENS AG (OS) 116

5 Transmission Solutions for 1100 kV Class Switchgear AREVA T&D (OS) 122

6 Dielectric Testing of 765 kV Circuit Breakers at UHVRL CPRI 128

FOLLOWED BY COCKTAILS & DINNERat LAWNS - Hotel Renaissance at 1900 onwardsHosted by ELECRAMA-2008

2nd Day, Tuesday, 22nd January, 2008

From 0900 - 1115 Hrs. (135 Min)

SESSION IV-A - HIGH VOLTAGE (8 Papers)

Parallel Session Chaired by Mr. S.P. HambardeGrand Ball Room (GBR) Hall 1

1 Evaluation of Gas Flow Parameters in Two-stage Blast InterrupterDuring Interruption

BHEL 135

2 Versatile Dead Tank circuit Breakers VIJAI ELECTRIC 141

3 Coupled Electromagnetic-thermal Analysis of 145 KV SF6 CircuitBreaker

CGL 145

4 Estimation of Break Down Voltages of Contact Gap in SF6 Gas CircuitBreakers CGL 150

5 Analysis of Breakdown Strength of SF6 Circuit Breaker During SmallCurrent Interruption

CGL 154

6 Reliability and Safety Requirement of the Circuit Breakers ABB LTD 158

7 Modeling of SF6 Circuit Breaker Arc Quenching Phenomena in PSCAD ABB LTD 163

8 Dead Tank based Compact Switchgear - Optimized High VoltageSubstation Equipment

SIEMENS AG (OS) 169

Chronological Index


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From 0900 - 1115 Hrs. (135 Min)SESSION IV-B - LOW VOLTAGE (8 Papers)

Parallel Session Chaired by Mr. Dilip TrivediGrand Ball Room (GBR) Hall 2

1 Trend from Mechanic to Electronic is Changing the Low VoltageSwitchgear Market Worldwide

SIEMENS AG (OS) 179

2 Energy Margin Approach to Improve Efficiency of Circuit BreakerMechanism

VJTI 184

3 Prediction of Arc Resistance Switchgear Testing VJTI 1904 Safety & Reliability Standards / Practices in International Market vis--

vis Indian IndustriesL&T 195

5 Energy Saving in Switchgear SIEMENS LTD 199

6 Ecodesign Principles : The Approach within a Switchgear Manufacturer SCHNEIDER (OS) 204

7 Recent Changes in IEC60947, LVSwitchgear Product Standards SIEMENS AG (OS) 213

8 A Novel Electroless Electrochemical Route for Fabricating SilverTinoxide Contact Materials

ERDA 218


From 1145 - 1330 Hrs. (105 Min)

SESSION V -A- HIGH VOLTAGE (7 Papers)

Parallel Session Chaired by Mr. N S SodhaGrand Ball Room (GBR) Hall 1

1 Lifetime Arcing Stresses of High-Voltage Circuit Breakers KEMA (OS) 225

2 Traveling Wave Reflections for Adaptive Auto Re-closing GOVT.COLL OFENGG

232

3 Effect of Oil Temperature on time-Current Characteristics of OilImmersed Expulsion Type Fuse used for CSP Transformers

ABB LTD 238

4 Evaluation of Gas Insulated Disconnector Switch for Bus charging andBus Transfer Currents

BHEL 242

5 New Network Concepts using Fault Current Limiter Circuit Breakers inSwitchgear

AREVA T&D (OS) 248

6 Improved Instrument Transformers for Switchgear Applications IIT 258

7 How to get reliable operation from Disconnectors ABB Ltd 263

Index Chronological


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From 1145 - 1330 Hrs. (105 Min)SESSION V-B - MEDIUM VOLTAGE (6 Papers)

Parallel Session Chaired by Dr. Fredinand A PlatterGrand Ball Room (GBR) Hall 2

1 Coupling of FEM Analysis with Short-Circuit Test Results for betterEvaluation of Vacuum Interrupters

CGL 271

2 Superconducting Fault Current Limiters - A Concept & its FutureProspects

CGL 278

3 Vacuum Interrupted and Embedded Pole technology for Reliable,Medium Voltage Indoor and Outdoor Breaker Application

ABB AG (OS) 283

4 Design Calculations for Structural Safety of Outdoor Breakers SIEMENS LTD 288

5 Active Protection against Internal Arcing Enhance Operators Safetyand Equipment Availability

ABB POWERTECHNOLOGY(OS)

293

6 Study of Fault Clearing by a Circuit Breaker in Presence of a shuntCapacitor Bank

ABB LTD 299

LUNCH BREAK : 1330 - 1415 (45 Min)

From 1415 - 1645 Hrs. (150 Min)

SESSION VI-CONTROL, PROTECTION & COMMUNICATION (9 Papers)

Common Session Chaired by Dr. K. Rajamani,Grand Ball Room (GBR) Hall 1 & 2

1 Non-Contact Type Shaft Current Monitoring and Protection System forGenerators

BHEL 309

2 Evaluation of Protective Relay Performance through using AdvancedSimulation Techniques

DOBLE ENGG. P.Ltd.

314

3 Emerging Future Trends in MV Switchgear for Integration / automationwith Special Reference to BHEL and NTPC

BHEL 322

4 Integration of Switchgear for Substation automation L&T 328

5 Integration of IEDs L&T 3336 Intelligent MCC: The concept and Advantages L&T 336

7 Advanced Thermal Protection of Asynchronous Motors usingSensorless Temperature Estimation

SCHNEIDER (OS) 341

8 Why we use Communication with Circuit Breakers SIEMENS AG (OS) 345

9 Intelligent Motor Management SIEMENS AG (OS) 348


From 1715 - 1800 Hrs. (45 Min)

SESSION VII - CONCLUDING SESSION

Common Session Chaired by Dr. M. RamamoortyGrand Ball Room (GBR) Hall 1 & 2

Chronological Index


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xiiSWICON 2008 Programme

PROGRAMME

SWICON-2008 (21st & 22nd January 2008)

DAY 1: MONDAY, 21ST JANUARY 2008 TIME: 0900 - 1830 HRS.

INAUGURATION & 3 COMMON SESSIONS ( Hall 1 & 2 ) ( 23 Papers )

0830 Hrs. 0900 Hrs. Delegate Registration (5 Counters)

0900 Hrs. 1030 Hrs. Inauguration Session Inaugural, Welcome, Keynote Addressand Life Time Achievement Awardetc.(90 Mits)

1030 Hrs. 1100 Hrs TEA/COFFEE 30 Minutes

1100 Hrs. 1330 Hrs. I Session - Users Feedback 9 Papers ( 150 Minutes)

1330 Hrs. 1415 Hrs. LUNCH 45 Minutes

1415 Hrs. 1615 Hrs. II Session - Testing & standards+Common

120 Minutes

1615 Hrs. 1645 Hrs. TEA / COFFEE 30 Minutes

1645 Hrs. 1830 Hrs. III Session - HIGH VOLTAGE (UHV) 6 Papers ( 105 Minutes)

1930 Hrs. onwards COCKTAILS & DINNER - AT VENUE

-RENAISSANCE

Along with ELROMA, ELECRAMA

Invitees

DAY 2: TUESDAY, 22ND JANUARY 2008 TIME : 0900 -1800 HRS.

TWO PARALLEL & TWO COMMON SESSIONS: ( 38 Papers )

0900 Hrs. 1115 Hrs. IV-A Session (Parallel) - High Voltage 1(HALL 1)

8 Papers (135 Minutes)

0900 Hrs. 1115 Hrs. IV-B Session (Parallel) - Low Voltage 1(HALL 2)


1115 Hrs. 1145 Hrs. TEA / COFFEE 30 Minutes

1145 Hrs. 1330Hrs. V-A Session (Parallel) - High Voltage(HALL 1)


1145 Hrs. 1330 Hrs. V-B Session (Parallel) - Medium Voltage(HALL 2)

45 Minutes

1330 Hrs. 1415 Hrs. LUNCH+ Change over to Joint Session 45 Minutes

1415 Hrs. 1645 Hrs. VI Session (Common) - Control,Protection and Communication


1645 Hrs. 1715Hrs. TEA / COFFEE 30 Minutes

1715 Hrs. 1800 Hrs. VII Session (Common) - Conclusion 45 Minutes


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1Day 1 - Session I Users Feedb ack

1st Day, Monday, 21st January, 2008

From 1100 - 1330 Hrs. (150 Min)

SESSION I - USERS FEEDBACK

( 9 Papers)

Organiser


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2SWICON 2008 Papers

THIS PAGE IS INTENTIONALLY LEFT BLANK


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Switchgear Maintenance with InfraredThermography

Sanjeev Atri

NDPL

Abstract:

The focus of this paper centers on the condition basedmonitoring which provide precise condition of criticalequipments like circuit breakers, power transformersetc of the power utility. To assess the condition of theequipment, Infrared thermography is one of the nondestructive techniques which are used as conditionmonitoring tools to predictive maintain the electrical

system. The main benefit of this technique is to finddeteriorating components prior to catastrophic failure.Thermography provides diagnostic aid and problemsolving.

By using this technique, Thermal distribution profileis captured of the equipment periodically on theload condition as a baseline. On larger more criticalcomponents such as transformers, circuit breakers etc,the baseline images and data stored is compared to thenew data collected from each inspection interval. Thedefect alters the thermal signature of the surface dueto change in the amount of heat generated.

Introduction:

The increasing demand for quality and reliable powernecessitates zero tolerance to any kind of defects.In order to achieve maximum reliability of the criticalequipments like power transformers, circuit

Breakers are to be monitored and maintained at regularintervals. In 2002 Distribution in Delhi was privatizedwhich led to formation of three distribution companies,NDPL (North Delhi Power Ltd.) is one of t hem.

At that time the failure rate of EHV clamps and accessories

of switchgears in grid substations were high due towhich it was challenging to maintain connectivity in thenetwork. To offset the failure rate in grids, conditionbased maintenance had been launched. Based on

which it was decided to run, repair and replace of theequipments. Infrared thermography technique was oneof the effective tools, used for CBM.

Measures adopted:

a) For hot spots:-

The infrared thermography technique was introduced inNDPL as a project in May2003 to locate t he abnormalities/

hot spots in the grid substations and follow up tillrectification. Inspection had been scheduled quarterlyin the 45 grids. As a result, rate of tripping in grid stat ionshas been reduced to 70%. Critical hot spots have beenreduced 10 to 3 per grid per quarter. The followingare the benchmarks adopted for Thermography forlocalization of Hot Spots:-

Temperatureobserved

Category Recommendations

Ambient + lessthan or equal to

20 C

Treated asNORMAL

Keep monitoring

Ambient +below 50 C

Treated asSERIOUS

To be Scheduledfor PM

Ambient +above 50 C

Treated asCRITICAL

Immediate action

Report Format:-

Thermovision Scanning Report

Name of Grid: 66/11KV DSIDC NRL 1

Date of Scanning: 7th Sept 2007

Time of Scanning: 17.30HRSAmbient Temperature: 34._ C

Detail of hot spots observed during Thermo scanning

Day 1 - Session I Users Feedb ack


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Loca tion: Power Tr.3 Load: 97Amps.B ph Rear Bus Isolatorclamp (Front bus Isolator s ide)

Temperature: 519.2 _ C,Category: Critical

Load: 150Amps.

Max. Temperature captured at Tr. tank 52.2._ C

Max. Temperature captured at Radiator 50.9._ C

Max. Temperature cap tured at Tap changer 62.7._ C

Abnormal Thermal pattern observed at tap

changer

b) For thermal distribution profile analysis:-

Ther mal signature of equipments like Power Transfor mers,circuit breakers, GIS substations, Capacitors etc have

been captured to study the thermal pattern variation

after every thermo scanning cycle. After detecting

thermal variation, the equipment is closely monitoredrepeatedly till abnormality confirmation. By adoptingsuch type technique, we have succeeded to save ourequipments.

Case study

Thermovision Scanning Report

Name of Grid: Jahangir puri

Date of Scanning: 17th Aug 2007

Time of Scanning: 12.30HRSAmbient Temperature: 37._ C

Loca tion: 50MVA Power Tr.2

After Rectification

Name of Grid: Jahangir puri

Date of Scanning: 21st Aug 2007

Time of Scanning: 18.00HRS

Ambient Temperature: 35._ C

Loca tion: 50MVA Power Tr.2 Load: 120Amps.

Max. Temperature captured at Tr. tank 46._ C

Max. Temperature captured at Radiator 44.9._ C

Max. Temperature captured at Tap changer 41.4._ C

After rectification the Thermal pattern at tap

changer observed normal

Nature of Fault: Abnormal heat generation in the Tapchanger at Tap no. 10 of Power Transfor mer.

Winding resistance test has been conducted by theprotection team, found abnormality in Y phase. Afterdismantling of tap changer, pitting marks were found attap contact no. 10 of Y phase

SWICON 2008 Papers


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Corrective Action taken: Tap no. 10 of Y ph has beenbypassed by the ring and tap position of transformer

has been shifted to tap 11. Infrared thermography hasbeen done for capturing thermal pattern on the tapchanger, which found normal.

For permanent corrective action, It has been planed inmonth of October2007

Conclusion:-

Properly implemented and maintained, infrared condition

monitoring as a part of a total predictive maintenance

program can increase reliability and improve op erating profit.

Infrared thermography assists in determining equipment

and facility maintenance priorities, enhance operationalsafet y and contr ibute to a stronger bottom line



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Vacuum Switching Technology for RectiformerApplication: A Case Study

Neelam Bhogal, Divya Joshi.

BHEL Bhopal

S.R. Chavan, K.N. Mathur

MPEB.

R.S. Malviya, U.P. Ekbote.

HEG Mandideep.

Introduction

Vacuum switching technology has dominated mediumvol tage switchgear due to its superior performance. Highnumber of normal and fault current operations, minimalmaintenance requirement, high reliability and low energyrequirement place this technology much above others.Vacuum technology is considered ideal for frequentswitching application due to var ious reasons like sealed

for life vacuum interrupter, maintenance free, low arcenerg y, less arcing time, rapid dielectric recover y andno switching By- Products. Very low & constant contactresistance, no oxidation in vacuum ensures that contactsremain metallically clean even after years of operation.Due to extremely long electr ical and mechanical life andno fire risk feature it is preferred to use vacuum circuitbreaker as a switching device in special applications likeArc furnace, Rectiformer switching etc.

Rectiformer Application:

Rectiformer switching duty imposes frequent switching

at variable loads & several make-break operations oneafter the another during changeover. This special dutycalls for reliable breakers and proper design of powersupply system.

Rectiformers are generally used in Graphite industries,Aluminum industries, Caustic soda industries and Alkaliindustries.

Hindustan Electro Graphite Ltd (HEG) Mandideep Bhopalis one of the leading manufacturer of graphite in Asiawhere in rectiformers are used for graphitization. Inthis, rectiformer converts 36 KV AC system voltage to200VDC, 120000 Amps to heat the calcined Petroleumcoke/PITCH (Charcoal) cylindrical bars to 300 0deg Centfor graphitization.

In the system considered in the case study, vacuum

switchgears are connected to 28 MVA rectifiertransformers. Output of each rectiformer is terminatedto a common Bus which feeds Graphitization furnaceof rating 200 Volts D.C. and 240KA. CPC in the formof granules obtained from petroleum industries arecrushed in different sizes and mixed with PITCH to formpaste. This mixture is then extruded in the form of barscalled green electrode. Green electrodes are thenbaked at 750C to 800C to form baked electrode. The

Graphitization furnace consist s of 2 columns of numberof baked electrodes which are shorted at one end. Thepositive terminal of supply bus is connected to oneend of the furnace column and the negative terminal ofsupply bus is connected to the end of the other furnacecolumn. The DC current is p asse d from positive Bus. Thecharge in the furnace is comparatively low resistancecharge. As this charge gets graphitized, the resistancefurther decreases and so the current increases. Theultimate current is as high as 240 KA. The temperatureof the charge is increased to level of 300 0C by passingthe current through itself, thereby heating it.

The furnace requirement is of the order of 240 KA. Asit is not economically possible to provide such a largecurrent by one unit, two units are paralleled. Each unitsupplies 120 K.A. The single line diagram of system isshown in Fig-1. The process requirement is such thatconstant power is fed to charge for a fixed duration.The power is to be kept constant. This is achieved by 70position On Load Tap Changer ( OLTC ) and a saturablecore reactor provided in each rectiformer.

Combination of OLTC and the controlled current insaturable core reactor, controls the A.C. output of each

rectifier transformer and thus keeps the D.C outputconstant. Each unit has an independent controller andthe power reference to each controller is half of thetotal power to be fed to the furnace.

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Switching operation in rectiformer

application:

1. Any one of the rectiformer is switched ON first withthe controller in MANUAL Mode.

2. After a delay of about 5 minutes, the other rectiformeris switched ON with its controller also in MANUALMode.

3. The controllers are then put in AUTO Mode one after

the other. Each rectiformer then gets loaded to therequired level automatically through the controller.

4. After completion of the required power input tothe furnace, the controllers for each unit are put inMANUAL Mode. The rectifier transformer OLTCis brought to tap 1 (minimum tap) and then unit isswitched OFF. Similarly the operation on the otherunit is carried out before it is switched OFF.

5. The switching ON and switching OFF operation foreach unit takes place two times, (i.e. switching ONtwo times and switching OFF two times) in a period

of 28 hours. In case of tripping on any fault, the breakeris opened on load. With auto circuit, the OLTC comesto tap 1 i.e. minimum tap. The restarting of the furnacefollows the same sequence as described above.

System interconnection :

At M/s HEG Mandideep, for rectiformer switchingapplication 36KV 25KA indoor vacuum switchgear typeVM36 of M/s BHEL make are installed. This switchboardis feeding rectiformers No. 6 & 7 and is interconnectedto 36KV indoor Captive Power Plant (CPP) switchboardthrough Tie Feeder.

Fig-3 36kV, kA v acuum circuit breaker trolly

Fig-1

The single line diagram of switchgear s is show n in Fig-2

Generally Grid supply of 132KV is taken from one 40

MVA transformer and also the Generator of CPP feedsthe load of rectiformer through Tie feeder Breaker No.6and Breaker No.11. Graphite s/s is paralleled with CPPswitchboard . Graphite switchboard feeding the load ofretiformers and CPP switchboard are at locations morethan half a Km apart.

History of fault

Fig-3 & Fig-4 shows 33KV, 25KA indoor vacuumswitchgear type V M36 of M/s BHEL make installed at M/

Fig-2



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s HEG Mandideep.

The 33KV switchgears for rectiformer No. 6 & 7 werecommissioned and operated for supply to rectiformerNo.6 in March 05 and CPP switchboards werecommissioned in May 05.

First flashover:

The first flashover was reported on 19/06/05 in breakerfeeding rectiformer in Graphite substation .

(36kV, 25 kA vacuum circuit breaker trolley )

The observations made during investigation were asbelow:

- Flash over marks were observed on vacuum circuitbreaker trolley.

- R- phase and Y-phase vacuum interrupters were foundpunctured.

- Insulating support rod between pole head were foundburnt.

- Insulating shrouds of R-phase and Y- phase were foundblackened from inside.

- Black mark was observed around the R-phase & Y-phase vacuum interrupter ceramic body.

- Breakers operation checked and found O.K.- Inst. Earth fault relay operated in Bus coupler breaker

No. 3 and 132KV Grid Incomer breaker No. 4 and Tiebreaker No. 5.

The observation made during investigation were asbelow:

- Flashover marks were found in cable chamber only. Noflashover marks were observed in Breakerchamber and Bus bar chamber.

- R- phase and Y-phase epoxy insulators supportingcable lugs were found cracked and burnt.

- All insulating phase barriers in cable chamber werefound blackened.

- 3 Nos. Current transformers found OK.

- Control cables in Cable Chamber found burnt.

- Spots of flashover marks were observed on LHS sheetof CT chamber and rear cover.

- Pitting mark was found in mounting channel of bottominsulators.

- Flashover marks were observed on support insulatorsof adjacent feeder PT panel.

Sequence of tripping operation:

Refer Fig-2.

Initially Breaker sl. No 1, 3 to 11 were ON.

Tie-Breaker No.1 between Graphite switchboardand CPP switchboard tripped on instantaneous overcurrent.

Grid Incomer breaker No.4 tripped on instantaneousover current.

Generator incomer breaker No.10 tripped on IDMTearth fault.

Incomer breaker No.6 and No.11 of CPP Switchboardtripped on IDMT under voltage.

Full blackout occurred in Graphite substation & CPPSwitchboard.

Grid incomer breaker No.4 & Tie-Breaker No.1 wereSwitched ON.

Tie to CPP switchboard (Breaker No.5) and GridIncomer breaker No.-4 tripped on earth fault creatingfull black-out condition.

Incomer breaker No.6 of CPP switchboard rackedout.

Grid Incomer breaker No. 4 closed and supply restoredto Graphite substation & to CPP switch board throughincomer breaker No.11.

Third flashover :

Third flashover was reported on 22/07/05. Flashov eroccurred in two switchgear panels feeding to

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lFig-4 (36kV, 25 kA switc hgear panel )

Second flashover:

Second Flash over was reported on 30/06/05 in Incomer

Breaker ( Breaker No-9) of 36KV CPP switchboard.

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Rectiformers of 33KV switchboard of GraphiteSubstation.

Observations made during investigation were asbelow:

Breaker - A

- Flash over and Pitting marks were observed on R-Phasevacuum interrupter to pole head.

- Vacuum in all 3 interrupters was found intact.

- Black marks were observed on all 3 bottle frombottom.

- Pole head mounting plate found black near R-Phase

vacuum interrupter.

- Insulating shrouds found intact from outside. No blackmarks were observed from inside.

Breaker B

- Vacuum loss observed in B-Phase vacuum interrupter

- R- Phase vacuum interrupter found healthy.

- Black marks observed at the bottom of R-Phase & B-Phase vacuum interrupter.

- Shrouds were found intact from outside. No blackmarks observed in B-Phase shroud from inside.

- Pitting marks observed on top R-Phase to polemounting plate and on link connecting operating rod.

- Megger value of support insulators and operating rodfound infinity.

Sequence of operations during flashover:

- Breakers were running on load.

- Breakers feeding to Rectiformer Unit 6 & 7 wereclosed.

- At 5 A.M. load was 26 MW, 6.3 MVA Aux. Transformerbreaker tripped on earth fault.

- Flashover marks found on insulator in Aux. Transformerbreaker No.7.

- Aux. Transformer breaker racked out and isolated .Capacitor bank breakers were not in service.

- Incomer#2 breaker No.6 of CPP switchboard trippedwhich was feeding to Graphite switchboard.

- Generator breaker No.10 tripped.

- Power restored from MPEB and started power plant.- Incomer#2 breaker No.6 of CPP switchboard closed.

- Furnace was started.

- Generator came into running at 10.00 AM

- 2 Rectiformers tripped because of failure in Trolleysystem (High Temp)

- Breakers were switched ON.

- Both Breakers Tripped again after one hour.

- Trolley system high temp. signal

- Rectiformer breakers switched on.

- After half an hour Bus coupler breaker No.3 betweenSiemens breaker and BHEL switch board tripped onover current on B- Phase.

- Furnace stopped at 6 PM.

FAILURE ANALYSIS:

The 33KV switchgears for rectiformer No. 6 & 7 werecommissioned and operated for supply to rectiformerNo.6 in March 05. It continued to behave without anytrouble until the CPP was commissioned & connectedto this Graphite switchboard in which rectifor mer No.7was taken on load in May 05.

For the various faults the analysis was carried out andthe reasons are enumerate below:

In all the failures tr ipping had occurred from 132/33 KV

transformer as well as the CPP.1. Overvoltages:

Observations made during different failures aresuggestive of voltage surges in excessive of with standstrength of respective insulation having developedduring the perio d of the supply to the 36 KV switch gearfrom the 132KV s/s & CPP operating in parallel.

The flashover and resulting failure of other equipmentstarted after the commissioning of HEGs 1x30 MVA CPPand commencement of its supply to the rectiformers No.6&7 through the 36 KV indoor switch gear connectedin parallel with the supply from the MPSEB Grid throughthe 132/33 KV step down 2x40 MVA Transformershaving earthed neutral on primary as well as thesecondary side in the vacuum circuit breaker, the build upof dielectric s trength across the parting moving & fixedcontact is very fast . In this particular case where therated fault current of the order of 25000 Amps has tobe successfully interrupted, currents of small magnitudeassociated with magnetizing, current of transformercould get extinguished before current zero, in other wordsit would get chopped. As the current flowing throughthe inductance cannot change abruptly it continues

to flow by circulating in its winding capacitance. Thiscauses voltage across them to increase. Thus besidesincreasing the voltage across the transformer winding,it would cause increase in the restr ike voltage across the



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two contacts which could assume very high value andcause rupture of the insulation. The observation listed

above are suggestive of high voltage having appearedacross the vacuum interrupter resulting in flash over.

2. System earthing:

As the CPP installation , although standing on a welldesigned earth mat of its own , is about half a kilo meteraway from the 33KV Graphite switchboard installation,also standing on a separate earth mat, the interveninghalf a KM of path of the earth fault current through therocky stretch would offer a very high resistance . Assuch under the p ost 132/33 KV -S/s-isolator-regime theCPP-33 KV switch gear system operates as an insulatedor un-grounded neutral system. On such insulatedneutral system or ungrounded system, the voltage onthe un-faulted phases goes up and could assume a valueof phase to phase voltage above the ground. The riseof their normal voltage from 33/RT3 above the groundto 33 KV steady level is accompanied by oscillatorytransients which under unfavorable position of point onwave when fault occur and could reach a peak value of2.65 times i.e. 50.5 KV. In such cases t he insulating partsof the equipment connected in the system are stressedcontinuously and damaged to the extent mentionedabove under obs ervations made after faults.

3. Relay co-ordination:

As the 33 KV switchgear installation stands on an earthmat connected to on which the 2x40 MVA 132/33 KVTransformer with their earthed neutral are in operation, substantially high magnitude earth fault current willflow from the 132KV S/s and in view of the lack of co-ordinated relay setting cause the operation of theserelay first and trip the 33 KV incoming. As a result of this33 KV switchgear will lose the benefit of good earth forthe flow of earth fault current. The 33 KV switch gear

will remain energized from the CPP until its feed tr ippedout. Obser vations of second and third fault indicatesthis problem.

4. Environment:

In the relatively more humid conditions prevailing inJune/July and the unavoidable carbonaceous micronlevel dust pollution that would have prevailed, leakagecurrents followed by tracking would have commencedon the insulating surface. Varying condition of pollutedarea and consequential difference in resistivity alongthe tracking path could eventually cause electrical

breakdow n of air around and finally flashover across t heinsulation resulting in earth fault.

5. Harmonics

Switching of rectiformer nonlinear load currents varywidely from a sinusoidal wave shape and they are

extremely high in harmonic content. The harmoniccreate numerous problems in electrical systems andequipments like transformer and generator. Theseharmonics causes overheating at far below the ratings.These results from eddy current and hysteresis lossesof iron core, skin effect in conductors of windings. Inaddition the harmonics current acting on impedanceof the source cause harmonics in the source voltage,which is then applied to connected equipment causingoverheating.

The harmonics also complicate the application ofcapacitors for power factor correction. At the point of

application of the capacitor the harmonic voltage andcurrent can reach dangerous magnitudes as well as theylower the actual power factor. The sign of overheatingwere obs erv ed in second and third failure.

6. Parallel switching of rectiformers:

On parallel switching of one rectiformer when anotherone is on load, a unique phenomenon of high saturationof transformer cores which could persist for severalseconds. This could cause current of the order of fullload current to flow for a long time & since furnace loadwould be already on , very heavy current could flow for

several seconds. When the two rectiformers have tobe switched OFF after the load cycle gets completed, the two may remain paralleled on the secondary sideby DC bus, the order of magnetizing current which thetwo rectiformers carry and which have to be interruptedby VCB , the instant of opening of controlling VCBs coulddiffer which may have unique values war ranting onerousinterrupting duties on the two VCBs with over vol tage.

Besides non-simultaneous instant of actual change ofcontact (tap changing contacts in rectiformers) couldmomentarily require handling of more than its share offull load. This may impose unique duties on the VCBs.And result into failures as obs erve d.

Recommendations :

1) Proper System design incorporating various RCcircuits, Reactors & Capacitors to reduce over voltages(harmonic as well as switching) generated in thesystem . An appropriate surge diverting set-up needsto be provided.

2) System Earthing : A suitably designed interconnectionbetween the two earth mat of Graphite substationand CPP switchboard appears necessary to curb

occurrence of high voltage surges discussed in theanalysis above . The design should take into accountthe magnitude of the prospective earth fault currentand based on earth resistivity, corrosive nature of soil,

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lay earth bus bars of suitable cross section of area at asuitable depth below ground level, keeping calculated

spacing between several earth buses interconnectedat suitable intervals so as to keep the earth potentialwithin limits.

3) Proper Relay co-ordination shall be ensured. The co-ordination of relay operating time be reviewed toensure selective tripping of faulty feeders only.

4) The capacity of anti condensation heaters in the switchgear cubicle shall be enhanced and shall suitably andthese be kept ON for longer duration during humidconditions.

5) Use of _- _ and _-Y transformers in pairs as supply

to conversion equipment greatly reduce the adverseeffects of non linear loads. The effect is the same as thatof multi- pulse equipment Installing reactors betweenthe power supply and the conversion equipment reducethe harmonic components of the current drawn by nonlinear load . Also filter capacitors are protected fromswitching surges produced by switched utility. Lastlyover sizing the system can be done.

6) Frequent maintenance of equipment shall be doneinvariably to (i) clean the insulating parts and (ii) Checkthe healthiness of vacuum interrupter mechanically.

Corrective Actions:1) M/s Areva make Metal Oxide Lightening arrestors were

provided in the system on rectifier transformer havingrating 30KV rms, 10KA discharge current with 3 secdischarge duration. Nominal discharge current 30kA, pressure release current 40 kA class A, minimumcreepage distance 900 mm Insulation level withstandcapacity pf dry & wet 70 kV rms for one minute .Impulse withstand voltage 170 kVp. as per IS 3070-1993 / IEC 60099-part 4 1988.

2) System earthing between Graphite substation and

CPP switchboard was inter connected by using 2 Nos.flats of GI of size 8 x 50 sq mm.

3) Relay co-ordination was revisited so that trippingof feeder breakers were ensured before tripping ofupstream breakers.

4) Maintenance of equipment is being carried outregularly.

5) For anti condensation, 3 nos. of heaters were providedin each breaker chamber , bus bar chamber and cablechamber.

Conclusion:

The analysis of various faults carried out suggest thatthe system design is very important and care should be

taken for providing stable system by interconnectingthe different earth locations of the system, providing

suitable surge arrestors and sequencing of relayoperation. In addition frequent maintenance playmajor role in keeping the var ious equipments in runningcondition even in harsh environmental condition.

After implementation of corrective measures sugges tedabove, no failure has occurred since then.



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Life Cycle and Asset ManagementCondition Monitoring and Residual Life Analysis of the Circuit breakers

and Power Transformers:

G.S.Srinivasaragavan, D.R.Dharmadhikari

NDPL Delhi

Abstract

The focus of this paper centers on the Condition

Monitoring and Residual Life Assessment. These are

the modern scientific tools which provide accurate

measurement on the condition of t he critical equipments

like power transformers and Circuit breakers. The

need of the RLA is based on the idea of operating the

equipments till the end of their us eful life, rather than its

design life. This paves way for the performance basedmanagement of the assets. To assess the condition

of the equipment, it requires the deployment of Non

destructive techniques and procedures. The results of

the tes ts per forme d on the equipments were compared

against the manufacturer standards and plotted

against the tripping data available with the company

database. The results were interpreted to match the

fault data and fault levels of grid stations recorded in

the recent past. Using the available knowledge and in

conjunction with a structured process of data collation

and interpretation, the thresholds associated with the

features representing the condition of the CB and PowerTransformers were determined. The knowledge and

understanding of the satisfactory and unsatisfactory

condition of the equipments was gained and made

explicit from the analysis of the Thermography, trending

of DGA test results for past 3 years, DCRM signatures

and trip coil signatures.

I. Introduction:

The increasing demand for quality and reliable powernecessitates zero tolerance to any kind of defects.In order to achieve maximum reliability the critical

equipments like Circuit Breakers & Power Transformersare to be monitored and maintained a t regular intervals.In 2002 Distribution in Delhi was privatized which ledto formation of three Distribution companies, NDPL

(NORTH DELHI POWER LIMITED - A joint venture of TATAPOWER & DELHI Govt.) was one of them. After for mationof NDPL, health check on var ious equipments across thenetwork had been carried out, based on which it wasdecided to run, repair & replacement of the equipments.The preliminary phase of repairing & replacing of thecritical equipments was completed. These equipmentshad also completed 2-3 years of service, during whichcertain equipments had been s tressed by feeding faults

of considerable magnitude.As part of life assessment of the equipments, a studywas carried out on grid station equipments especiallyon Circuit breakers and Power Transformers which hadoperated and fed fault currents during their service. Thispaper deals with the analysis made on the Tripping dataand fault current seen by the breaker under

fault conditions and various tests performed on theequipment. The tests performed on these equipmentswere mos tly OFF-Line and ther mal scanning an effectiveON-Line tool was used to monitor the performance ofthe equipments.

Ii. Holistic Approach To Condition Monitoring

And Rla:

Significant amount of money and time are sp ent in managing

critical assets each year and a variety of approach has

been employed, yet there are high profile failures that hit

the headlines. Any occurrence in the sys tem and operati on

costs lots of money, in the forms of:

Operational disruption

Loss of lives

InjuriesAssets damaged

Damage to corporate reputation

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Environmental damage and pollution

What are the sources of problem?Lack of maintenance

Ageing equipment

Inadequate design

Poor specification

Time constraints

Poor safety / operational management

O&M Manual not up to date

Poor / inadequate training

Inadequate consideration of environment and human

Performance interactionThings are no longer running as we planned

Poor construction quality

Performance management:

The need to adopt more effective performance andasset management regimes is one of the importanttopic for the utility industries. The universal question is:how can we strike the right balance between reliabilityand quality of supply, and capital and operationalexpenditure?

Commonly used processes adopt a reliability basedapproach to managing systems. These are based onunderstanding the failure rates of equipments andimplementing interventions based on that knowledge.Key elements missing from this approach are theunderstanding of the consequences of the failures andrisk that such failures present to the operations.

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Methodology:

Identify Problems

Analyze the Problems

Evaluate

Treat

Track and Monitor

Review

Communicate and Document

Procedure:

The following procedure was adopted for breakers,

the tripping record of each and every breaker for past2 years was collected (almost all the breakers werereplaced starting from first half of 2005) and the faultcurrent recorded by the Numerical relays on t he breakerin the recent past were noted down, the average valuewas taken as reference and multiplied to the trippingand cumulative fault current seen by the breaker wasobtained. The various tests performed on the breakerincluded PI, Contact resistance, Breaker operating timeand Dynamic contact resistance. Thermal scanningon breaker poles with very high contact resistancewas used for monitoring the same. The condition ofoperating mechanism and auxiliary contacts was also

assessed by t he timing and coil signatures.

In case of transformers the DGA analysis of oil werecarried out once in 6 months. As part of ON-Linemonitoring thermal scanning of the transformers weredone. The various test performed on transformerincluded IR, PI, Magnetic balance, LV Tan delta, TTR,Winding resistance and Device checks. The results wereanalyzed to assess the condition of the Equipment andremedial act ions w ere taken.

III. Application Of Condition Monitoring:

Circuit Breakers:

CBs are expected to protect circuits and plant byinterrupting Short-Circuit current within a time in therange of 80-150ms.Condition monitoring involves OFFline test like Insulation resistance, contact resistance,Timing, Dynamic contact resistance and trip coil currentsignatures.

The significance of Dynamic contact resistance is that itdetermines the condition of the arcing tip which nevergets reflected in the conventional tests. In principleDCRM injects100A DC through the power contacts ofCircuit breakers while breaker is undergoing close-open

operation. During this short time span it measures thevol tage drop across the contacts dynamically and relaysit to the CB operational analyzer. The classical four wiremeasurement method is employed to measure contact



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resistance. Change in Micro Ohm values as moving andfixed contacts engage and disengage is plotted against

time and a graphical record is obtained through theanalyzer. This dynamic record of micro ohm signaturehelps to analyze the condition of the arcing contacts.

The significance of trip coil signatures is aimed onthe concept that the deterioration in CB conditionalso results from its inertia, where the effects ofStiction arising due to non operation or rusting ofmechanical parts can also result in CB failure or slowoperation of the breaker when it is most needed.The deterioration of mechanical parts resulting fromfrictional forces, coagulation of lubricants, etc. remainsdisguised and subsequently neglected. Measurement

of CBs trip signature provides a useful insight into theoperation of the CB and its condition. In addition toits primary function of controlling of the breaker tripoperation, the trip coil performs a secondary role asa noninvasive condition monitoring sensor. Capturingthe trip coil current signature from the breaker atfirst trip will serve as record for subsequent breakercondition assessment. The control or trip unit of the CBtransforms the trip signal into the physical operationof the breaker mechanism. The trip coil consisting of aconducting coil wrapped around a movable iron plungereventually dislodges the trip latch via a nonmagnetictappet and a trip bar and ultimately, activates the main

latch, unlocking the op erating shaft and discharging theopening spr ing causing the main contacts of the breakerto open. On initiating the trip command the trip coil isenergized by the station DC supply. The current flowingthrough the CB trip coil generates magnetic filedaffecting a force upon the plunger moving it towards thebreaker latch mechanism. At the same time the motionof the iron plunger induces EMF in the coil. When trip coilis energized the current rises causing a magnetic fieldto apply force on the iron plunger. When the force onplunger exceeds that of stiction, the plunger begins tomove. The motion of plunger induces an EMF in the coil

by effectively reducing the current flowing through it.As the plunger continues to accelerate through the coil,the current flowing through the trip coil continues to falluntil the plunger eventually strikes the la tch mechanismwhere a sudden reduction in velocity of the plungeroccurs resulting in a corner in the current signature. Thecombined mass of the plunger and the latch reduces theplungers momentum, causing further reduction in thecoil current until it hits a buffer bringing it to rest. Withplunger at rest, the current increases to maximum ratingof the coil. Meanwhile the latch unlocks the springoperating mechanism, releasing the stored energyrequired to open the main contacts. As the coil is de-

energized by the breaker auxiliary contacts, the trip coilcurrent decays quickly to zero in accordance with thecoil inductance causing the plunger to return to its initialposition. The trip signature captured is characterized by

five salient features

1. Latch (ms) : Time taken for the trip coil solenoid torelease the latch and initiate the mechanism.

2. Buffer (ms) : Time taken for the breaker to come offlatch and operating mechanism to start moving.

3. Mcon (ms) : Time of main contact separation.

4. Acon (ms) : Time taken for the auxiliary contact to openand coil current to begin reducing to zero.

5. End (ms) : Time at which coil current reaches zero.

Power Transformers:

Dissolved gas analysis of Transfor mer oil is based on thebreakdow n of the molecules of oil locally, in certain typesof electrical faults such as ionisation, heating, arcingand pyrolysis of cellulose. It is a powerful diagnostictechnique for on line monitoring the internal conditionsof Transformers due to its capability to detect defect s inthe early stages before they develop into major faults.

In this method it is possible to check whether aTransformer is subjected to a normal amount of ageing

and heating or whether there are incipient defects.In order to make the interpretations applicable tothose cases of condition monitoring, where rise inconcentration of one or more individual gases is beingobserved. The simplified approach, which forms thenew method of interpretation, is given in the table.

Sr. No. Rise in gas concentration Interpretation1 Nil Normal Ageing2 H2 Corona Partial Discharge3 CH4 and C2H6 Thermal fault of low

temperature range up to300C

4 C2H4 With or without CH4,C2H6, & H2

Thermal fault of 300C or700C or abo ve

5 C2H2 with without H2,C2H4, C2H6

Arc or flash over orpersistent sparking may bealong with overheating.

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The two commonly used interpretation techniques ofDGA were used:

Rogers Ratio Method

IEC 599 Method

NDT & Trend Analysis:

Initially Three grid stations (Gulabi Bagh, Rewari Line,Rohtak Road) were selected for carrying out RLA onequipments. Critical equipments like Transformers and33/66KV Circuit Breakers were considered for the study.Dynamic Contact Resistance measurement was carriedout on Circuit Breakers as part of RLA study. Softwaretool developed by our Business Associate was us ed for

condition monitor ing and trend analysis of the electricalequipments.

Testson Breakers

IR Contactresistance

Timing DCRM No. oftrippingcapturedsince July2005

Transformer -1 1

SB Mill-1 2

Ramapura-2 2

Delhi I/C-4 Notdone

4

Delhi O/G-1 4

Delhi O/G-2 Notdone

Notdone

9

Delhi I/C -1 6

Delhi I/C-2 4

Vishal - 1 5

Rampura-1 5

Rama Road 19

DMS/PrasadNagar

3

Shaza da bagh 2

Vishal-2/Sudar.park

11

Examples of Major discrepancies observed

were as follows:

1. Incomer Delhi - 4, Breaker R & B phase poles were notclosing properly. Contact resistance was not gettingrecorded, While meggering across the pole, the gapgot bridged at 5KV. Manufacturer had visited the siteand decided to replace the poles. Poles were replacedon 13-04-2007.

2. S.B. Mill -2, Breaker Closing operation was successful

only after issuing repeated commands. The problemwas attended by Manufacturer representative byadjusting the mechanism assembly at site.

3. S.B.mill -1, Breaker BHEL make, spring charging motor

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was getting stuck half way after closing operationof breaker. The problem was sorted by checking the

linkages of the mechanism.4. Power transformer-1 WTI, Buchholz trip were

functioning intermittently because of loose connectionat marshalling box, the same was rectified.

5. Faizroad / Anandparvath breaker closing operation wasnot successful from timing kit (which gives commandsimilar to scada 10 cycles) but was closing manuallyby switch where command time is for few secondsrange. The mechanism was adjusted by manufacturer.However tripping time recorded is 65 ms (limit is 45 +- 10 ms). Needs to be attended.

Thermography:

This technique is an effective tool in identifying thediscrepancies by virtue of the thermal distributionalong the surface of the scanned objects.

Thermography image of grid equipments

Name of Grid: Gulabi Bagh

Date of Scanning: 28th March 2007

Time of Scanning: 11.30HRS

Ambien t Temperature: 33_ C

Heat distr ibution on Trf-1

Radiator fins no 4 Radiator is Blocked



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Analysis of the Captured data:

Average values of Breaker Contact resistance andbreaker close and open timing of different makes wereplotted and compared against the limits provided by themanufacturer.

LIMITS

Make Contactresistance

Closetiming

Opentiming

Closingdiscrepancy

openingdiscrepancy

Mfg. 1 50 _ 80 ms 40 ms 4 ms * 3 ms *

Mfg. 2 45 _ 85 ms 50 ms 4 ms * 3 ms *

Mfg. 3type-1

50 _ 85 ms 55 ms 4 ms 3 ms

Mfg. 3type-2

50 _ 60 ms 35 ms 4 ms 3 ms

Contact resistance measured were plotted

against No. of t ripping of the breakers

The breaker trip coil analysis also revealed

the condition of the mechanism.

Auxilary contact

did not open

Good Signature-

Mfg - 3 Type -2

The graph clearly indicates that there is direct correlation

between the No. of tripping (No. of times Fault currents

seen by the breaker) and the conta ct resistance.

Calculation of the Remnant Life of the

equipment against the design value:

Based on the design values, the breaker should be

capable of interrupting the faults current until the

cumulative value reaches 15000KA2. The fault current

recorded by the Numerical relays on the breaker in the

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recent past were noted down, the average value was

taken as reference and multiplied by No. of tripping

and cumulative fault current seen by the breaker wasobtained.

Make LINE If Avg. If (A) If 2 800 kV), standards are not yetavailable. Simple extrapolation of the exist ing standards

does only sometimes cover service conditions asconfirmed by network studies of 1100 kV systems. IECand CIGRE are working on expansion of the existingequipment standards.

5. REFERENCES

[1] Nayak R.N., Sehgal Y.K., Subir Sen, Integrati on of 1200 kV AC Sys-

tems for Future Indian Grid, IEC/CIGRE UHV Symposium, 2007[2] IEC/CIGRE UHV Sympo sium, July 2007, Bejing

[3] IEC Standard 62271-100, Ed. 1.1, High-voltage switc hgea r andcontrolgear - Part 100: High-voltage alternating-current circuit-breakers, IEC, 2003

[4] IEC Technical Report 61633, High-voltage al ternating current circuit-breakers - Guide for short-circuit and switching test procedures formetal-enclosed and dead tank circuit-breakers, IEC, 1995

[5] Janssen A.L.J., te Paske L.H., Knol P., Smeets R.P.P, Shin A., Limi-tations of High-Power Testing Methods for EHV and UHV CircuitBreakers, CIGRE Conference 2002

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The Role of Surge Arrestor in SubstationInsulation Coordination

D. Maheswaran S.Angelson Rajeshkumar C. Saiprakash


Abstract

In the electrical power industry, the sy stem voltage havegrown above 765kV worldwide. As the system nominalvoltage increases, the expected lightning as well as theswitching over vol tages also increase. Any EHV stationshould be designed for a low probability of insulationfailure. The protection of substa tion equipments againstover voltages is not only a question of which arrestor

to be chosen, but also important is to determine thenumber and particularly the location of arrestorsrequired in order to obtain adequate protection. Thispaper is intended to analyze the role of surge arrestorsin EHV/UHV in mitigating the expected over voltages. Acase s tudy is presented by w hich the behavior of surgearrestor for lightning & switching over voltages, thenumber of surge arrestors and suitable locations in thatsubstation is analyzed.

1. Introduction

In recent years, the power system in India is growingat a very rapid pace. As the generation of powersystem grows, the voltage level needs to be increasedto transmit the large power generated. Hence, theintroduction of 765kV in India. In this context, the studyof insulation co-ordination of switchgears & equipmentsof substation at EHV (400 & 765kV), are very important,since the selection of insulation dominates the cost andsafety of equipments and switchgear. It has become amandatory practice by utilities to perform the insulationco-ordination study for EHV, especially for 765kVoutdo or substation as well as Gas Insulated substationprojects.

One way of tackling these ov er voltage is to design the

insulation strength of the equipments and switchgearsto withstand the expected over voltage with sufficientsafety margin. This directly relates to higher cost of theequipments.

The other way is to reduce the expected over voltagesat the equipments of substations to a permissible level.There are few ways of doing the same viz. 1) use of surgearrestors 2) use of closing resistor 3) provision of shieldwire etc.

2. Description Of The System - Case Study

The system taken for case study is the 400kV GISsubstation of Powergrid at Tehri which is being executed

by Lar sen& Toubro Limited. The overall SLD of the Tehri isshown in Fig-1

The length of the associated 400 kV transmission linesfrom Tehri GIS: Koteshwar line- 8 km (2 Nos.), Tehri line- 6 km (2 Nos.) and Meerut line - 180 km (2 Nos.)

3. Study Method

The studies have been carried out using an Electro-Magnetic Transient Program -PSCAD/EMTDC software.For the purpose of measurement over voltagesgenerated in the system, one long line (Meerut) and

one short line (Koteshwar) have been modeled otherlines have been omitted. This will fairly ensure themeasurement of severe over voltage condition that mayappear in the sys tem. The above is done bas ed on thefact that the presence of other circuit elements reducesthe level of over voltages in the system.. The systemmodeled in the PS-CAD software is as shown in Fig-2.

3.1 Switching Over Voltage Study

Switching over voltages or slow-front over voltagesappear in the system due to Line energization, Line re-energization, Fault and fault clearing, Load rejection,Switching of capacitive or inductive currents, Distantlightning strokes on the conductor of overhead lines.

In the present system study, the over voltages dueto line energization and re-energization have been

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considered. The over voltages due to other cases arenot cr itical/ applicable for the present system.

The re-energization may generate high slow-front overvoltages due to trapped charges on the energized line.For studying the switching over voltages due to re-energization, a case of three phase fast re-closing hasbeen simulated for 180 km long transmission line (TehriGIS station - Meerut).

3.2 Lightning Overvoltage Study

A lightning surge generates over voltage waves, whichmay enter into a sub-station either by direct st roke or asa traveling wave from the incoming transmission lines.As p er IEC-60071-2, back-flashover does not occur at

the tower close to the substation owing to the goodsubstation earthing. The shielding failures also do notoccur in the first span of the overhead line. Hence, thelightning surge has been applied at a distance of oneoverhead line span length, which results in maximumpossible steepness [1]. The amplitude and shape of t helightning current surge injected in the overhead line is100kA, 8/20 _ sec wave. The Basic Insulation Level for400 kV substations is 1425 kVp [2]. Any lightning whichproduces over voltages beyond this magnitude will

result in a flashover or a permanent damage to any ofthe components of the switchyard. In the present studyover v oltage due to direct stroke (shielding penetration)has been considered

Fig-1. Overall System SLD

Fig-2. System modeled in PS-CAD software



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3.3 Study Criteria

The switchyard equipment at a considerable distancefrom the surge arrester, experience the reducedprotective margins. IEC 60071-2 stipulates a minimummargin of 5% for External Insulation and 15%. forInternal Insulation. An Atmospheric Correction Factor(Ka) for 400kV substation, located at an alti tude of 932mtr above sea level is calculated and found to be 1.077.The maximum allowable voltages based on the abovemargins have been indicated in the Table-1.

The study verifies that the over-voltage developedat the equipment terminals due to lightning strike aswell as switching are less than the maximum allowable

voltages.Table-1: Voltages as per the mar gins stipulated in IEC-60071-2 for 40 0kV

WithstandVoltage

Type ofinsulation

Margin Maximum allowablevoltage

BIL= 1425 External 1.13 1261.06 (2.23 p.u.)

Inter nal 1.15 1239.13 (2.19 p.u.)

BIL = 1050 External 1.075 976.74(1.72 p.u.)

Inter nal 1.15 913.04 (1.61 p.u)

4. SYSTEM MODELING

The modeling of the equipment for switching andlightning surge studies is based on the guidelinesformulated by IEEE working group [4]. The parameters ofthe various equipments are used as inputs in the PSCADprogram.

4.1 Modeling Of The Transmission Line

Transmission lines can be modeled in two differenttechniques viz, Begeron Model and Frequency dep endantmodel in PSCAD. The frequency dep endent line modelrepresents the frequency dependency of all parameters.

This model is necessary for studies requiring a verydetailed representa tion of the line over a wide frequencyrange. Hence, the frequency dependant phase modelhas been chosen.

4.2 Modeling Of The Circuit Breaker

The circuit breaker has been modeled a s a switch, i.e, anideal conductor (zero impedance) when closed and anopen circuit (infinite impedance) when open.

4.3 Modeling Of The Lightning Arrestor

Surge Arrestors have been modeled as a non-linearresistor having Volt-Ampere characteristic furnishedby the manufacturer (in our case M/s Elpro-Drg.No:3K2401).

4.4 Modeling Of The Bus Duct

For both switching and lightning over voltage studies, thebus duct has been modeled as a coupled PI section.

4.5 Modeling Of The Lightning Surge Generator

In the lightning over voltages studies, the lighting surgeimpinging on the system was applied on the systemusing the lightning surge generator model of thePSCAD/EMTDC. The 100kAp, 8/20-_sec current impulsewave shape has been used.

4.6 Modeling Of The Multi Run Control Component

For varying the point on wave of switching of the circuitbreaker, the multi run component in PSCAD/EMTDC wasutilized. The CB was close d at various instants of thewave in order to f ind out the maximum over vol tage.

5. Over Voltage Study & Results

5.1 Switching Overvoltage Study

Switching overvoltage studies of two cases namelyLine energization with no charges on the line and Linere-energization with the charges present on the linecorresponding to the earlier status of the line.

5.1.1 Line Energization Study

Configurations of different cases considered are shownin Table-2. The same has been simulated and switching

surges due to line energization are being plotted infigures from Fig-3 to Fig-6.

5.1.2 Line Re-Energization Study

Configurations of different cases considered are shownin Table-3. The same has been simulated and switchingsurges due to line re-energization are being plotted infigures from Fig-7 to Fig-10.

5.2 Lightning Over Voltage Study

This deals with the study of lightning over voltagesoccurring in the system due to back flashover orshielding failure.

The magnitude of over voltage due to back flash overvoltage [3] was calculated and found that the flash overvoltage across the insulators is less than the breakdown voltage.

Lightning surge due to shielding failure was studiedby injecting the 100kA amplitude current surge at theentry point of the substation [2]. Simulation results arepresented in figures Fig-12 to Fig-13.

The rated lightning withs tand voltage of the equipment sis 1425kVp. Considering a safety factor of 1.2, thelightning overvoltages have to be maintained at 1188kVpor below at all location within the substation.

The lightning surge considered for the study is shownin Fig-11.

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Table-2: Configurations and Results for Line Energization cases

Configuration Line Energization case Over voltage measured in p.u

Meerut CB open, withoutLA in Meerut end.

180km line between Meerut and Tehri GIS isenergized by closing the CB at GIS end at theinstant corresponding to the probability of highestover voltage in the system

Voltage measured at Meerutend is 2.05 p.u. (668.3kV)Refer: Fig-3

Meerut CB open, with LA inMeerut end.

180km line between Meerut and Tehri Tehri GISis energized by closing the CB at GIS end at theinstant corresponding to the probability of highestover vol tage in the system.

Voltage measured at Meerutend is 1.095 p.u. (356.97kV)Refer: Fig-4

GIS CB open, without LA inGIS end.

180km line between Meerut and Tehri GIS isenergized by closing the CB at Meerut end at theinstant corresponding to the probability of highestover voltage in the system

Voltage measured at GIS endis 1.975 p.u. (643.85kV)Refer: Fig-5

GIS CB open, with LA in GISend.

180km line between Meerut and Tehri GIS isenergized by closing the CB at Meerut end at theinstant corresponding to the probability of highestover voltage in the system

Voltage measured at GIS endis 1.10 p.u. (358.6kV)Refer: Fig-6

Fig-3 Voltage at Meerut end without LA in Meerut end (energizing

from GIS end)

Fig-4 Voltage at Meerut end with LA in Meerut end (energizing from

GIS end)

Fig-4 Voltage at GIS end without LA in GIS end (energizing from

Meerut end)

Fig-5 Voltage at GIS end with LA in GIS end (energizing from Meerut

end)



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Table-3: Configurations and Results for Line Re-energization cases

Circuit configuration Line Re-energization case Over voltage measured in p.u

Withou t LA in Meerut end 180km line b et ween Meerut andTehri GIS opened at maximumpositive peak and closed again atmaximum negative peak from GISend.

Voltage measured at Meerut endis 2.78 p.u. (906.28kV) .Trappedchargers are clamped to 1 p.u. at timeof op ening the breaker. Refer: Fig-7

With LA in Meerut end. 180km line between Meerut andTehri GIS opened at maximumpositive peak and closed again atmaximum negative peak from GIS

end

Voltage measured at Meerut end is1.10 p.u (358.6kV) Refer: Fig-8

Without LA in GIS end. 180km line between Meerut and TehriGIS opened at maximum positivepeak and closed again at maximumnegative peak from Meerut end

Voltage measured at Meerut end is2.68 p.u (873.68kV) Trapped chargersare clamped to 1 p.u. at time ofopening the breaker Refer: Fig-9

With LA in GIS end. 180km line between Meerut and TehriGIS opened at maximum positivepeak and closed again at maximumnegative peak from Meerut end

Voltage measured at GIS end is 1.11p.u. (361.86kV) Refer: fig-10

Fig-7: Voltage at Meerut end without LA in Meerut end (re-energizing

from GIS end)

Fig-9: Voltage at GIS end without LA in GIS end (re-energizing from

Meerut end)

Fig-8: Voltage at Meerut end with LA in Meerut end (re-energizing

from GIS end)

Fig-10: Voltage at GIS end with LA in GIS end (re-energizing from

Meerut end)

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6. Conclusion

From the line energization and re-energization study(5.1) it is observed that the maximum over voltage with

Table-4: Configurations for Lightning cases

Circuit configuration Lightning Case Over Voltage in p.uWit h LA in GIS Light ning sur ge injected in Tehr i GIS

substation at the entr y of the lineVoltage measured at GIS end is 1.79 p.u.(585.24kV) Refer: Fig-12

Without LA in GIS end Lightning surge injected in Tehri GISsubstation at the entr y of the line

Voltage measured at GIS end is 6.11p.u.(1995kV) Refer: Fig-13

Fig-11: Light ning surge injected

Fig-12: Volta ge at GIS end with LA during the lightning condition

Fig-13: Voltage at GIS end without LA during the lightning condition

LAs in the circuit (Ref Table-2&3) is within the acceptablevalues (Ref Table-1).

From the lightning over voltage study (5.2), it is observedthat the maximum over voltage due to shieldingfailure with LAs in the Circuit (Ref Table-4) is within the

acceptable values (Ref Table-1).

Hence it can be concluded that number and the respectivelocations of LAs are adequate to limit the overvoltagesdue to switching and lightning to accep table values.

7. REFERENCES

[1] IEC-60 071-1, Insula tio n co-o rdination Part 1: definitions, pr inciplesand rules seventh edition, 1993-12

[2] IEC-60071-2, Insula tio n co-ordinat ion Part 2: Applica tion guide,Third edit ion, 1996-12

[3] Andrew R Hileman, Insulation Coordination for Power Systems,Marcel Dekker

[4] IEEE working group 15.08.09- Modeling and Analys is of sys temTransients using digital Programs- 1998.

[5] IEC-60099-5, Surge ar rester selecti on and applicat ion recom-mendations.



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Circuit Breaker Platform for 550 kV

D. Fredrich, K. Schuler, N. Trapp

Siemens AG, Berlin, Ger many

1 Introduction

Circuit-breakers have a protective function in ahigh-voltage transmission and distribution system.High reliability and continuous availability are basicrequirements for the service. Based on long-termservice experience with high-voltage circuit-breakersthe exis ting product port folio has been completed witha circuit-breaker platform for 550 kV [1-7]. This platform

supersedes the previous products for this voltagerating, which were representatives of the successfultype family of double nozzle circuit-breakers withelectro-hydraulic operating mechanisms [8-14]. Now allcircuit-breakers in the product portfolio from 72 kV up to800 kV use the same principle of arc assist interrupterunits and a stored-energy spring-spring operatingmechanism. The operating experiences for this productfamily are adding up to more than 450 000 circuit-breakerbay-years. The platform includes live tank and dead tankcircuit-breakers for air-insulated ou tdoor switchgear andcircuit-breakers for gas-insulated switchgear and highly

integrated switchgear as well.2 Circuit-breaker Platform, a Modular Design

Concept

Very of ten modern circuit-beakers for one and the sameset of ratings are offered in various configurationscorresponding to the respective application: e. g. livetank (LT) and dead tank (DT) circuit-breakers, circuit-breakers for gas-insulated (GIS) or highly integratedswitchgear (HIS) or circuit-breakers for of so-calledhybrid or compact switchgear. If the developmentresponsibility for the different types of constructions

lies in a single hand, then advantages for both, theuser and the manufacturer, can be gained by creating amodular design concept (platform) with standardisedmodules and assembly groups from a common kit.

Where a product platform is developed instead ofthree or four different products, the manufacturercan concentrate his entire development force on onesubject. The development process can be optimisedand shortened without impact on the product quality;on the contrary, the quality of the final products will beimproved as the development efforts have not to besplit.

The parts used for the individual modules of the

products are manufactured in higher numbers.Therefore, more efficient manufacturing processes canbe utilised, resulting in reduced effort for the productionand harmonised assembly procedures. This leads tooptimised and stable processes and at the end to anincreased product quality.

As the manufacturer can focus his development workon a single subject, the product platform, he is ableto acq

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