Problems connected with Commissioning of Power Transformers

Size: px
Start display at page:

Download "Problems connected with Commissioning of Power Transformers"

Transcription

1 Problems connected with Commissioning of Power Transformers ABSTRACT P Ramachandran ABB India Ltd, Vadodara, India While commissioning large Power Transformers, certain abnormal phenomena were noticed. Some of these are arcing across the tank flanges with burning of paint, mal operation of differential relay protection and excessive current from star connected winding neutral to earth. Case histories are given describing the problems, causes for the same and the mitigation measures taken to avoid repetition of the problems. INTRODUCTION Large Power Transformers are commissioned (energized first time) at site after installation and electrical testing. Energisation is normally done from high voltage (HV) side in case of step down transformers and from low voltage (LV) side for generator step up transformers (GSU). In rare cases, commissioning will be done from opposite side(from LV side in case of step down transformers and from HV side in case of GSUs) This may be necessary when the station is not ready but the transformer healthiness is to be ensured in advance. While commissioning power transformers, certain problems were noticed. The phenomenon or failure mode, cause of failure, rectification and preventive measures for such occurrences are explained. Some of the peculiar phenomena noticed are arcing across the transformer tank flange, mal-operation of differential relay and excessive neutral current in star connected windings. The case studies reported below are from sites and the mitigation measures suggested may be useful to engineers involved in the installation and commissioning of power transformers. CASE HISTORIES Arcing across the tank flange (curb) Joints MVA 3 phase generator transformer with dual LV, 570/ MVA, 132/ kv, with HV side OLTC, flux density in core = 1.649T Leakage flux density =0.409T at 370 MVA,Tank Length= 11.7 meters, Inrush current Peak =6.9 ka, Impedance= 25/46/16.7% on 570 MVA base(hv-lv1,hv-lv2,lv1-lv2) 2. Transformer is energized from HV side, and synchronized to generator voltage on LV using Generator circuit breaker. Tank cover and lower tank are connected together by flexible copper wires (70 mm 2 ) at two positions, diagonally opposite corners. In addition, six numbers LV flexible copper links are provided on LV side of tank connecting top cover to lower tank, to take care of induced currents from LV leads to turret. Tank is grounded to earth using 240 mm 2 copper cables at two positions on opposite sides. 3. During energisation, flash over is noticed occasionally between cover and lower tank causing burning of paint at some bolt positions. Arc flash over is momentary and occurs only at the time of energisation of transformer.

2 Paint Burning at Tank Curb Bolt Figure1 4 Cause of the Phenomenon: During energisation, magnetizing inrush currents cause leakage flux to flow out of winding to tank and cover causing difference in induced voltages between cover and tank, resulting in arc flash over. This will happen only when inrush current is high or maximum. Maximum inrush current will occur when transformer is energized exactly when the voltage sine wave is crossing the zero value. This is the reason why flash over is not noticed during all energisation events as inrush current may not be that high on all occasions. Carbonization on painting due to such flashover is rarely noticed during energisation. In this particular case, it may be due to the high rating of transformer or tank with longer length. When transformers are short circuit tested at High Power laboratories by pre-set method, arc flash over at tank curb is noticed during voltage application. This is due to controlled switching adopted to create maximum asymmetrical over current from inrush current. 5 Mitigation measures: Three additional 95 mm 2 insulated copper cables are connected between cover to ground directly. 6 Preventive measures: In case of large transformers with longer tank, two numbers shorting copper links may not be adequate.it is better to provide more number of connecting links distributed along the tank curbs or remove painting at some bolt positions to get tank to cover galvanic connection through bolts and then repaint over it to avoid corrosion. Adopt controlled switching for the HV breaker to minimize inrush current, thereby leakage flux. Controlled switching (also referred as point on wave switching or point on cycle switching) of a circuit breaker involves operation of the switching device at a specific pre-determined point in relation to the power frequency current or voltage. For reducing the inrush current in power transformers, it involves switching on at peak of voltage of sine wave (to reduce inrush current) and switching off at current zero (to reduce residual flux in core) 2-6

3 Back Charging of Generator Transformers 1. Back charging (energizing from HV side with LV open) of generator transformers(gt) is necessary in power stations to ensure that GT is healthy, well before the generator / turbine installation is completed. This energisation is onerous than charging from LV side due to the high transferred surges to LV from HV side and the sudden application of full rated HV voltage, rather than building up voltage slowly from generator. 2. Since the transferred voltages to LV may exceed the Basic Insulation Level (BIL) of LV, back charging shall be done only with Lightning Arrester (LA) and surge absorber of the generator in circuit. When generator circuit breaker (GCB) is used, make sure that on the transformer side of the breaker, surge absorber and LA are connected. On some models of GCB, LA and capacitor on transformer side are optional items and hence shall be checked at the time of ordering of GCB. 3. Back charging shall be done at maximum tap with the entire tap winding in circuit. This will slightly reduce inrush current as the flux density will be less than at rated tap. It will also result in increased 2 nd harmonic content in inrush current reducing chances of mal operation of differential relay. This will avoid part winding resonance in the floating tap winding and consequent insulation failure in tap winding. This type of resonant over voltages can occur when natural frequency of regulating winding is near to the frequency components in the switching surge. Similar failure of dielectric breakdown in regulating winding was reported in generator transformers when back charged at rated tap, with 10 % regulating winding floating. 3-6

4 Mal-operation of Differential Relay 1. Recently in new transformers it is seen that differential relay trips during back charging of large generator transformers. This is due to the mal-operation of the harmonic restraining feature of the relay. Harmonic restraining feature (i.e. blocking the operation of relay when there is 2 nd harmonics in the overcurrent) was incorporated in differential relays around 1930 s. This was to prevent the relay from operation during magnetizing inrush current (which can be 5~15 times of full load current) and for relay operation only during over currents from internal faults. Normally inrush current used to have second harmonic content of 20~30% of the peak value of inrush current and the fault current will be with less 2 nd harmonics content. So the relay sleeps when 2 nd harmonic content is more than 10~15% and will operate when 2 nd harmonic current in unbalanced current is less. Due to the improvements in core material (Hi-B & Domain refined cold rolled grain oriented silicon steel-crgo) and core construction (step lap construction), 2 nd harmonic content in inrush current of modern large capacity transformers is less than 10%. In such cases, the differential relay will operate during back charging as the 2 nd harmonic content in inrush current is less than the setting time of relay. 2. If we reset relay for a lower 2 nd harmonic percentage, then the fault clearing time for a real internal fault will increase. Hence engineers are developing new differential relays based on new principle of operation such as wave form blocking criterion (a pattern recognition algorithm that searches for intervals within each fundamental power system cycle). 3. Sometimes it is necessary to reduce the inrush current, especially in large units, to avoid adverse effects on transformer windings from over currents. Inrush current will be minimum when the switching is done at the peak of the applied voltage sine wave. Special devices (preinsertion resistors, point on wave switching relay) are available to go with circuit breakers to achieve this end. In India, controlled switching is provided in all 765kV circuit breakers and in some of the 400kV circuit breakers used for transformer switching. This reduces the magnetizing inrush current. High neutral current When the neutral of star connected HV winding is earthed, a small current flow to earth is normal. But sometimes this may be quite high, more than 10 % of full load current, resulting in mal operation of restricted earth fault (REF) protection. In such cases, the cause is to be investigated and countermeasures are to be taken. 1. In a substation feeding to arc furnace transformer, continuous neutral current was noticed. Transformer was 80 MVA 220/33 kv of YNynd11 connection with a stabilizing delta tertiary winding. HV transformer neutral continuously showed 6-7 A current flow and to avoid tripping REF relay had to be set at 20 %. Table 1 Phase Currents and Neutral Current Circuit R Phase Y Phase Current B Phase current Star neutral current(a) (A) (A) current(a) HV under 10% Load LV Under 10% load

5 The above condition can occur in case of an unbalance in primary HV phase voltages which can be verified by measuring phase to neutral voltages. Phase angle errors can be checked by measuring phase to phase voltages. Reason for the unbalanced voltages can be lack of transpositions on the transmission line feeding the substation. 2. In a 100 MVA 11/138 KV YNd11 generator transformer with 19 tap on-load tap-changer (OLTC) neutral current was nearly 10 % of the load current when operated at certain taps and the same increased proportional to the load current. The transformer was provided with three single pole OLTC (MR type 3xMI 802) on HV side. When tested, the voltage ratio was tallying at all taps when measured under sequence of 19 to 1 taps. But when measured under 1 to 19 tap sequences, ratio and winding resistance in U phase was coming identical at certain taps viz 3&4, 7&8, 11&12 and 15 &16.High neutral current was also noticed when operated at these taps. Tap No At MW load, neutral current displayed in REX 521 relay was 21.3 A at tap no.12, 2.3 A at tap no.11 and nil at tap no.9 Actual Ratio U Phase 1 >19 tap Table 2 Measured Turns Ratio U Phase 19 > 1 tap V phase 1 >19 tap V phase 19 > 1 tap W phase 1 >19 tap W phase 19 > 1 tap On investigation, it was found that there was a rotational lag adjustment required in U phase between the tap changer and motor drive. When this was corrected by decoupling the drive and tap selector shaft, the ratio error came correct on both directions and neutral current disappeared. 3 Sometimes large transient neutral current can occur due to DC content in the magnetizing inrush current. This can cause spurious operation of earth fault protection. The above phenomena can occur due to the non-simultaneous closing of three phases of the circuit breaker.(ref 1) CONCLUSION When commissioning large power transformers certain abnormal phenomena can occur which may delay or prolong the commissioning process.some of the problems noted at site are reported with the reasons for such occurrence and mitigation measures to be adopted. REFERENCES [1] Pender, J.T and Kirkland, I. Large Transient neutral currents during energisation of 3 phase transformers Proceedings IEEE Vol 122 No.4 April 1975 Pages

6 BIOGRAPHY P Ramachandran has been employed at ABB India since 1999, and currently works as Technical Advisor, Power Products. He is involved in Transformer Engineering since He represented India in CIGRE study committee A2 during He received his Bachelor of Science in Electrical Engineering from the University of Kerala and Master of Business Administration from Cochin University, Kerala. 6-6

Numbering System for Protective Devices, Control and Indication Devices for Power Systems

Numbering System for Protective Devices, Control and Indication Devices for Power Systems Appendix C Numbering System for Protective Devices, Control and Indication Devices for Power Systems C.1 APPLICATION OF PROTECTIVE RELAYS, CONTROL AND ALARM DEVICES FOR POWER SYSTEM CIRCUITS The requirements

More information

Transformer Protection

Transformer Protection Transformer Protection Nature of transformer faults TXs, being static, totally enclosed and oil immersed develop faults only rarely but consequences large. Three main classes of faults. 1) Faults in Auxiliary

More information

CHAPTER 3 REVIEW OF POWER TRANSFORMER PROTECTION SCHEMES

CHAPTER 3 REVIEW OF POWER TRANSFORMER PROTECTION SCHEMES CHAPTER 3 REVIEW OF POWER TRANSFORMER PROTECTION SCHEMES 3.1. Introduction Power Transformer is the nerve centre of any power distribution system. The capacity of power transformers is generally decided

More information

Substation Preventive Maintenance

Substation Preventive Maintenance Substation Preventive Maintenance PROVINCIAL ELECTRICITY AUTHORITY 1 Presentation Contents 1) A kind of substation 2) Electrical equipment details of AIS substation 3) Electrical equipment details of GIS

More information

Protection of Electrical Networks. Christophe Prévé

Protection of Electrical Networks. Christophe Prévé Protection of Electrical Networks Christophe Prévé This Page Intentionally Left Blank Protection of Electrical Networks This Page Intentionally Left Blank Protection of Electrical Networks Christophe Prévé

More information

TECHNICAL BULLETIN 004a Ferroresonance

TECHNICAL BULLETIN 004a Ferroresonance May 29, 2002 TECHNICAL BULLETIN 004a Ferroresonance Abstract - This paper describes the phenomenon of ferroresonance, the conditions under which it may appear in electric power systems, and some techniques

More information

Impact Assessment Generator Form

Impact Assessment Generator Form Impact Assessment Generator Form This connection impact assessment form provides information for the Connection Assessment and Connection Cost Estimate. Date: (dd/mm/yyyy) Consultant/Developer Name: Project

More information

Earth Fault Protection

Earth Fault Protection Earth Fault Protection Course No: E03-038 Credit: 3 PDH Velimir Lackovic, Char. Eng. Continuing Education and Development, Inc. 9 Greyridge Farm Court Stony Point, NY 10980 P: (877) 322-5800 F: (877) 322-4774

More information

KNOW MORE ABOUT THE TRANSFORMERS. Glossary Transformers

KNOW MORE ABOUT THE TRANSFORMERS. Glossary Transformers KNOW MORE ABOUT THE TRANSFORMERS Glossary Transformers Ambient temperature The existing temperature of the atmosphere surrounding a transformer installation. Ampere The practical unit of electric current.

More information

Modern transformer relays include a comprehensive set of protective elements to protect transformers from faults and abnormal operating conditions

Modern transformer relays include a comprehensive set of protective elements to protect transformers from faults and abnormal operating conditions 1 Transmission transformers are important links in the bulk power system. They allow transfer of power from generation centers, up to the high-voltage grid, and to bulk electric substations for distribution

More information

thepower to protect the power to protect i-gard LITERATURE Low and medium voltage

thepower to protect  the power to protect i-gard LITERATURE Low and medium voltage thepower to protect i-gard LITERATURE Low and medium voltage distribution systems Arc Flash Hazards and High Resistance Grounding Grounding of Standby and Emergency Power Systems Neutral Grounding Resistors

More information

Shortcomings of the Low impedance Restricted Earth Fault function as applied to an Auto Transformer. Anura Perera, Paul Keller

Shortcomings of the Low impedance Restricted Earth Fault function as applied to an Auto Transformer. Anura Perera, Paul Keller Shortcomings of the Low impedance Restricted Earth Fault function as applied to an Auto Transformer Anura Perera, Paul Keller System Operator - Eskom Transmission Introduction During the design phase of

More information

Embedded Generation Connection Application Form

Embedded Generation Connection Application Form Embedded Generation Connection Application Form This Application Form provides information required for an initial assessment of the Embedded Generation project. All applicable sections must be completed

More information

A Study on Ferroresonance Mitigation Techniques for Power Transformer

A Study on Ferroresonance Mitigation Techniques for Power Transformer A Study on Ferroresonance Mitigation Techniques for Power Transformer S. I. Kim, B. C. Sung, S. N. Kim, Y. C. Choi, H. J. Kim Abstract--This paper presents a comprehensive study on the ferroresonance mitigation

More information

Simulations of open phase conditions on the high voltage side of YNd05-power plant transformers

Simulations of open phase conditions on the high voltage side of YNd05-power plant transformers Simulations of open phase conditions on the high voltage side of YNd05-power plant transformers Disclaimer: All information presented in the report, the results and the related computer program, data,

More information

Generator Protection GENERATOR CONTROL AND PROTECTION

Generator Protection GENERATOR CONTROL AND PROTECTION Generator Protection Generator Protection Introduction Device Numbers Symmetrical Components Fault Current Behavior Generator Grounding Stator Phase Fault (87G) Field Ground Fault (64F) Stator Ground Fault

More information

STRAY FLUX AND ITS INFLUENCE ON PROTECTION RELAYS

STRAY FLUX AND ITS INFLUENCE ON PROTECTION RELAYS 1 STRAY FLUX AND ITS INFLUENCE ON PROTECTION RELAYS Z. GAJIĆ S. HOLST D. BONMANN D. BAARS ABB AB, SA Products ABB AB, SA Products ABB AG, Transformers ELEQ bv Sweden Sweden Germany Netherlands zoran.gajic@se.abb.com

More information

Embedded Generation Connection Application Form

Embedded Generation Connection Application Form Embedded Generation Connection Application Form This Application Form provides information required for an initial assessment of the Embedded Generation project. All applicable sections must be completed

More information

Phase Shifting Transformers. Presented by

Phase Shifting Transformers. Presented by Phase Shifting Transformers Presented by Phase Shifting Transformers (PST s) (a.k.a. Phase Angle Regulators) VS φ S P V V S = X L L X L sin( φ φ ) L S VL φ L PST s are power flow control devices between

More information

Tertiary Winding Design in wye-wye Connected Transformers Restricted Siemens Energy 2013 All rights reserved.

Tertiary Winding Design in wye-wye Connected Transformers Restricted Siemens Energy 2013 All rights reserved. Pomona, CA, May 24 & 25, 2016 Tertiary Winding Design in wye-wye Connected Transformers Scope of Presentation > Tertiary vs. Stabilizing Winding? Tertiary vs. Stabilizing Winding? Need for Stabilizing

More information

POWER FACTOR CORRECTION. HARMONIC FILTERING. MEDIUM AND HIGH VOLTAGE SOLUTIONS.

POWER FACTOR CORRECTION. HARMONIC FILTERING. MEDIUM AND HIGH VOLTAGE SOLUTIONS. POWER FACTOR CORRECTION. HARMONIC FILTERING. MEDIUM AND HIGH VOLTAGE SOLUTIONS. This document may be subject to changes. Contact ARTECHE to confirm the characteristics and availability of the products

More information

Report on investigation of failure of 315 MVA Auto transformer at 400 kv Bawana Substation of Delhi Transco Ltd.(DTL)

Report on investigation of failure of 315 MVA Auto transformer at 400 kv Bawana Substation of Delhi Transco Ltd.(DTL) Report on investigation of failure of 315 MVA Auto transformer at 400 kv Bawana Substation of Delhi Transco Ltd.(DTL) 1.0 Introduction: 1.1 DTL vide letter No. F.DTL/206/F.06/2015-16/Mgr(Bawana)/353 dated

More information

System Protection and Control Subcommittee

System Protection and Control Subcommittee Power Plant and Transmission System Protection Coordination Reverse Power (32), Negative Sequence Current (46), Inadvertent Energizing (50/27), Stator Ground Fault (59GN/27TH), Generator Differential (87G),

More information

Tab 2 Voltage Stresses Switching Transients

Tab 2 Voltage Stresses Switching Transients Tab 2 Voltage Stresses Switching Transients Distribution System Engineering Course Unit 10 2017 Industry, Inc. All rights reserved. Transient Overvoltages Decay with time, usually within one or two cycles

More information

A1-101 INFLUENCE OF SPECIAL SHORT CIRCUIT ON ELECTRICAL GENERATOR DESIGN. Ding Zhong MENG (HONG KONG, CHINA)

A1-101 INFLUENCE OF SPECIAL SHORT CIRCUIT ON ELECTRICAL GENERATOR DESIGN. Ding Zhong MENG (HONG KONG, CHINA) 1, rue d'artois, F-758 Paris http://www.cigre.org A1-11 Session 4 CIGRÉ INFLUENCE OF SPECIAL SHORT CIRCUIT ON ELECTRICAL GENERATOR DESIGN Ding Zhong MENG (HONG KONG, CHINA) SUMMARY Refer to the IEC Standard

More information

Generator Advanced Concepts

Generator Advanced Concepts Generator Advanced Concepts Common Topics, The Practical Side Machine Output Voltage Equation Pitch Harmonics Circulating Currents when Paralleling Reactances and Time Constants Three Generator Curves

More information

DIFFERENCE BETWEEN SWITCHING OF MOTORS & GENERATORS WITH VACUUM TECHNOLOGY

DIFFERENCE BETWEEN SWITCHING OF MOTORS & GENERATORS WITH VACUUM TECHNOLOGY DIFFERENCE BETWEEN SWITCHING OF MOTORS & GENERATORS WITH VACUUM TECHNOLOGY Dr. Karthik Reddy VENNA Hong URBANEK Nils ANGER Siemens AG Germany Siemens AG Germany Siemens AG Germany karthikreddy.venna@siemens.com

More information

BE Semester- VI (Electrical Engineering) Question Bank (E 605 ELECTRICAL POWER SYSTEM - II) Y - Y transformer : 300 MVA, 33Y / 220Y kv, X = 15 %

BE Semester- VI (Electrical Engineering) Question Bank (E 605 ELECTRICAL POWER SYSTEM - II) Y - Y transformer : 300 MVA, 33Y / 220Y kv, X = 15 % BE Semester- V (Electrical Engineering) Question Bank (E 605 ELECTRCAL POWER SYSTEM - ) All questions carry equal marks (10 marks) Q.1 Explain per unit system in context with three-phase power system and

More information

ISO Rules Part 500 Facilities Division 502 Technical Requirements Section Aggregated Generating Facilities Technical Requirements

ISO Rules Part 500 Facilities Division 502 Technical Requirements Section Aggregated Generating Facilities Technical Requirements Division 502 Technical Applicability 1(1) Section 502.1 applies to: Expedited Filing Draft August 22, 2017 the legal owner of an aggregated generating facility directly connected to the transmission system

More information

save energy, it is precious SYNERGY transformers Mfg. of all types of Distribution / Power & Furnace Transformers

save energy, it is precious SYNERGY transformers Mfg. of all types of Distribution / Power & Furnace Transformers save energy, it is precious Mfg. of all types of Distribution / Power & Furnace Transformers SYNERGY transformers SAFETY AND EFFICIENCY, COMBINED WITH LONG-TERM RELIABILITY, ARE THE HALLMARKS OF WORLD-RENOWNED

More information

Commissioning Manual Distribution Transformers - Three-phase Oil Filled

Commissioning Manual Distribution Transformers - Three-phase Oil Filled 1LPL000006A2110 rev. 1 Commissioning Manual Distribution Transformers - Three-phase Oil Filled 1LPL000006A2110 rev. 1 2 / 7 Table of contents 1 Commissioning and start-up... 3 1.1 Transformer survey...

More information

Effects of Harmonic Distortion I

Effects of Harmonic Distortion I Effects of Harmonic Distortion I Harmonic currents produced by nonlinear loads are injected back into the supply systems. These currents can interact adversely with a wide range of power system equipment,

More information

Power Transformers Basics

Power Transformers Basics Power Transformers Basics Transformer Basic Objective Introduce Basic Transformer Theory as it Relates to Diagnostics Provide a Better Understanding of the Diagnostic Test Environment Identify Important

More information

IV/IV B.Tech (Regular) DEGREE EXAMINATION. Electrical &Electronics Engineering

IV/IV B.Tech (Regular) DEGREE EXAMINATION. Electrical &Electronics Engineering Hall Ticket Number: 14EE704 November, 2017 Seventh Semester Time: Three Hours Answer Question No.1 compulsorily. Answer ONE question from each unit. IV/IV B.Tech (Regular) DEGREE EXAMINATION Electrical

More information

A Review Comprehension: Guideline for Testing of HV, EHV and UHV Substation Equipment

A Review Comprehension: Guideline for Testing of HV, EHV and UHV Substation Equipment International Research Journal of Engineering and Technology (IRJET) eissn: 23 0056 Volume: 04 Issue: 02 Feb 2017 www.irjet.net pissn: 072 A Review Comprehension: Guideline for Testing of HV, EHV and UHV

More information

This webinar brought to you by the Relion product family Advanced protection and control IEDs from ABB

This webinar brought to you by the Relion product family Advanced protection and control IEDs from ABB This webinar brought to you by the Relion product family Advanced protection and control IEDs from ABB Relion. Thinking beyond the box. Designed to seamlessly consolidate functions, Relion relays are smarter,

More information

PJM Manual 07:: PJM Protection Standards Revision: 2 Effective Date: July 1, 2016

PJM Manual 07:: PJM Protection Standards Revision: 2 Effective Date: July 1, 2016 PJM Manual 07:: PJM Protection Standards Revision: 2 Effective Date: July 1, 2016 Prepared by System Planning Division Transmission Planning Department PJM 2016 Table of Contents Table of Contents Approval...6

More information

Solution for Effect of Zero Sequence Currents on Y-Y Transformer Differential Protection

Solution for Effect of Zero Sequence Currents on Y-Y Transformer Differential Protection ABSTRACT National conference on Engineering Innovations and Solutions (NCEIS 2018) International Journal of Scientific Research in Computer Science, Engineering and Information Technology 2018 IJSRCSEIT

More information

Basic Principles and Operation of Transformer

Basic Principles and Operation of Transformer Basic Principles and Operation of Transformer CONSTRUCTIONAL ASPECTS Cores In order to enhance core s magnetic properties, it is constructed from an iron and silicon mixture (alloy). The magnetic core

More information

Wind Power Facility Technical Requirements CHANGE HISTORY

Wind Power Facility Technical Requirements CHANGE HISTORY CHANGE HISTORY DATE VERSION DETAIL CHANGED BY November 15, 2004 Page 2 of 24 TABLE OF CONTENTS LIST OF TABLES...5 LIST OF FIGURES...5 1.0 INTRODUCTION...6 1.1 Purpose of the Wind Power Facility Technical

More information

(2) New Standard IEEE P (3) Core : (4) Windings :

(2) New Standard IEEE P (3) Core : (4) Windings : (d) Electrical characteristics (such as short-circuit withstand, commutating reactance, more number of windings, etc); (e) Longer life expectancy; (f) Energy efficiency; (g) more demanding environment.

More information

OPEN-PHASE DETECTION TECHNIQUES FOR CRITICAL STANDBY SUPPLIES

OPEN-PHASE DETECTION TECHNIQUES FOR CRITICAL STANDBY SUPPLIES OPEN-PHASE DETECTION TECHNIQUES FOR CRITICAL STANDBY SUPPLIES U AJMAL, GE Grid Solutions UK Ltd, usman.ajmal@ge.com S SUBRAMANIAN, GE Grid Solutions UK Ltd, sankara.subramanian@ge.com H Ha GE Grid Solutions

More information

Southern Company Interconnection Requirements for Inverter-Based Generation

Southern Company Interconnection Requirements for Inverter-Based Generation Southern Company Interconnection Requirements for Inverter-Based Generation September 19, 2016 Page 1 of 16 All inverter-based generation connected to Southern Companies transmission system (Point of Interconnection

More information

PRE COMMISSIONING TESTS ON EQUIPMENT AT 33/11 KV SUB STATIONS. IR Values are to be read on the megger by meggering the Power transformer

PRE COMMISSIONING TESTS ON EQUIPMENT AT 33/11 KV SUB STATIONS. IR Values are to be read on the megger by meggering the Power transformer PRE COMMISSIONING TESTS ON EQUIPMENT AT 33/11 KV SUB STATIONS TESTS ON TRANSFORMERS 1. IR Values This is measured to measure the Insulation Resistance of the whole transformer. a) For 33/11 KV Power Transformer

More information

CONTENTS. 1. Introduction Generating Stations 9 40

CONTENTS. 1. Introduction Generating Stations 9 40 CONTENTS 1. Introduction 1 8 Importance of Electrical Energy Generation of Electrical Energy Sources of Energy Comparison of Energy Sources Units of Energy Relationship among Energy Units Efficiency Calorific

More information

DIFFERENTIAL PROTECTION METHODOLOGY FOR ARBITRARY THREE-PHASE POWER TRANSFORMERS

DIFFERENTIAL PROTECTION METHODOLOGY FOR ARBITRARY THREE-PHASE POWER TRANSFORMERS DFFERENTAL PROTECTON METHODOLOGY FOR ARBTRARY THREE-PHASE POWER TRANSFORMERS Z. Gaji ABB AB-SA Products, Sweden; zoran.gajic@se.abb.com Keywords: power transformer, phase shifting transformer, converter

More information

A Special Ferro-resonance Phenomena on 3-phase 66kV VT-generation of 20Hz zero sequence continuous voltage

A Special Ferro-resonance Phenomena on 3-phase 66kV VT-generation of 20Hz zero sequence continuous voltage A Special Ferro-resonance Phenomena on 3-phase 66kV VT-generation of Hz zero sequence continuous voltage S. Nishiwaki, T. Nakamura, Y.Miyazaki Abstract When an one line grounding fault in a transmission

More information

Embedded Generation Connection Application Form

Embedded Generation Connection Application Form Embedded Generation Connection Application Form This Application Form provides information required for an initial assessment of the Embedded Generation project. All applicable sections must be completed

More information

REPORT ON INVESTIGATION OF FAILURE OF 100 MVA, 220/66-33/11 KV POWER TRANSFORMER AT 220KV GEETA COLONY SUBSTATION OF DELHI TRANSCO LTD.

REPORT ON INVESTIGATION OF FAILURE OF 100 MVA, 220/66-33/11 KV POWER TRANSFORMER AT 220KV GEETA COLONY SUBSTATION OF DELHI TRANSCO LTD. REPORT ON INVESTIGATION OF FAILURE OF 100 MVA, 220/66-33/11 KV POWER TRANSFORMER AT 220KV GEETA COLONY SUBSTATION OF DELHI TRANSCO LTD. (DTL) 1.0 Introduction: 1.1 DTL vide letter No. F.DTL/206/2015-16/Mgr(T)O&M-E-2/22

More information

Catastrophic Relay Misoperations and Successful Relay Operation

Catastrophic Relay Misoperations and Successful Relay Operation Catastrophic Relay Misoperations and Successful Relay Operation Steve Turner (Beckwith Electric Co., Inc.) Introduction This paper provides detailed technical analysis of several catastrophic relay misoperations

More information

ON-SITE TESTING OF SPECIAL TRANSFORMERS

ON-SITE TESTING OF SPECIAL TRANSFORMERS ON-SITE TESTING OF SPECIAL TRANSFORMERS Simanand GANDHI JEYARAJ, Megger Ltd, UK, Simanand.gandhi@megger.com, Robert MILNE, UK Power Networks, UK, robert.milne83@googlemail.com Grant MITCHELL, Transmag

More information

Company Directive STANDARD TECHNIQUE: SD7F/2. Determination of Short Circuit Duty for Switchgear on the WPD Distribution System

Company Directive STANDARD TECHNIQUE: SD7F/2. Determination of Short Circuit Duty for Switchgear on the WPD Distribution System Company Directive STANDARD TECHNIQUE: SD7F/2 Determination of Short Circuit Duty for Switchgear on the WPD Distribution System Policy Summary This document provides guidance on calculation of fault levels

More information

Effects of GIC on Power Transformers and Power Systems

Effects of GIC on Power Transformers and Power Systems Effects of GIC on Power Transformers and Power Systems Prepared by Dr. Ramsis Girgis and Kiran Vedante (USA) in the name of CIGRE SC A2 Background There has been some misconception in the electric power

More information

RAIDK, RAIDG, RAPDK and RACIK Phase overcurrent and earth-fault protection assemblies based on single phase measuring elements

RAIDK, RAIDG, RAPDK and RACIK Phase overcurrent and earth-fault protection assemblies based on single phase measuring elements RAIDK, RAIDG, RAPDK and RACIK Phase overcurrent and earth-fault protection assemblies based on single phase measuring elements User s Guide General Most faults in power systems can be detected by applying

More information

EASUN REYROLLE LIMITED

EASUN REYROLLE LIMITED OCTOBER 2003 APPLICATION AND COMMISSIONING MANUAL FOR NUMERICAL BIASED DIFFERENTIAL PROTECTION RELAY TYPE - MIB202 EASUN REYROLLE LIMITED 1 ISSUE NO : 1 st Issue DATE OF ISSUE : 01-10 - 2003 DEPARTMENT

More information

Transformer Protection

Transformer Protection Transformer Protection Transformer Protection Outline Fuses Protection Example Overcurrent Protection Differential Relaying Current Matching Phase Shift Compensation Tap Changing Under Load Magnetizing

More information

Liquid-Filled Transformers

Liquid-Filled Transformers Liquid-Filled Transformers Custom Transformers at Standard Prices NIAGARA TRANSFORMER CORP. Induction Furnace Transformer Cycloconverter Rectifier Duty Transformer Arc Furnace Transformer Full Range of

More information

Power System Protection Manual

Power System Protection Manual Power System Protection Manual Note: This manual is in the formative stage. Not all the experiments have been covered here though they are operational in the laboratory. When the full manual is ready,

More information

148 Electric Machines

148 Electric Machines 148 Electric Machines 3.1 The emf per turn for a single-phase 2200/220- V, 50-Hz transformer is approximately 12 V. Calculate (a) the number of primary and secondary turns, and (b) the net cross-sectional

More information

Benefits of SFRA - Case Studies

Benefits of SFRA - Case Studies 6 th International Conference on Large Power Transformers- Modern Trends Benefits of SFRA - Case Studies B B Ahir Gujarat Energy Transmission Corporation Limited 1 Outline Condition Monitoring in GETCO

More information

Tertiary Winding in Power Transformers P Ramachandran,India

Tertiary Winding in Power Transformers P Ramachandran,India Tertiary Winding in Power Transformers P Ramachandran,India 1. What is the function of tertiary and stabilizing tertiary windings in a Transformer? Tertiary Winding: An additional winding (third winding

More information

ANALYSIS OF A FLASHOVER OPERATION ON TWO 138KV TRANSMISSION LINES

ANALYSIS OF A FLASHOVER OPERATION ON TWO 138KV TRANSMISSION LINES ANALYSIS OF A FLASHOVER OPERATION ON TWO 138KV TRANSMISSION LINES Authors: Joe Perez, P.E.: SynchroGrid, College Station, Texas Hung Ming Chou, SynchroGrid, College Station, Texas Mike McMillan, Bryan

More information

REDUCTION OF TRANSFORMER INRUSH CURRENT BY CONTROLLED SWITCHING METHOD. Trivandrum

REDUCTION OF TRANSFORMER INRUSH CURRENT BY CONTROLLED SWITCHING METHOD. Trivandrum International Journal of Scientific & Engineering Research, Volume 7, Issue 4, April-216 628 REDUCTION OF TRANSFORMER INRUSH CURRENT BY CONTROLLED SWITCHING METHOD Abhilash.G.R Smitha K.S Vocational Teacher

More information

2 Grounding of power supply system neutral

2 Grounding of power supply system neutral 2 Grounding of power supply system neutral 2.1 Introduction As we had seen in the previous chapter, grounding of supply system neutral fulfills two important functions. 1. It provides a reference for the

More information

Single Earthed Neutral and Multi Earthed Neutral. Single Earthed Neutral and Multi Earthed Neutral: Multi Grounded Neutral System (MEN):

Single Earthed Neutral and Multi Earthed Neutral. Single Earthed Neutral and Multi Earthed Neutral: Multi Grounded Neutral System (MEN): Single Earthed Neutral and Multi Earthed Neutral. SEPTEMBER 6, 2011 5 COMMENTS Single Earthed Neutral and Multi Earthed Neutral: In Distribution System Three Phase load is unbalance and non linear so The

More information

Advanced Applications of Multifunction Digital Generator Protection

Advanced Applications of Multifunction Digital Generator Protection Advanced Applications of Multifunction Digital Generator Protection Charles J. Mozina Beckwith Electric Company 6190-118th Avenue North Largo, FL 33773-3724 U.S.A. Abstract: The protection of generators

More information

NERC Protection Coordination Webinar Series July 15, Jon Gardell

NERC Protection Coordination Webinar Series July 15, Jon Gardell Power Plant and Transmission System Protection Coordination Reverse Power (32), Negative Sequence Current (46), Inadvertent Energizing (50/27), Stator Ground Fault (59GN/27TH), Generator Differential (87G),

More information

MV ELECTRICAL TRANSMISSION DESIGN AND CONSTRUCTION STANDARD. PART 1: GENERAL 1.01 Transformer

MV ELECTRICAL TRANSMISSION DESIGN AND CONSTRUCTION STANDARD. PART 1: GENERAL 1.01 Transformer PART 1: GENERAL 1.01 Transformer A. This section includes liquid filled, pad mounted distribution transformers with primary voltage of 12kV or 4.16kV (The University will determine primary voltage), with

More information

TABLE OF CONTENT

TABLE OF CONTENT Page : 1 of 34 Project Engineering Standard www.klmtechgroup.com KLM Technology #03-12 Block Aronia, Jalan Sri Perkasa 2 Taman Tampoi Utama 81200 Johor Bahru Malaysia TABLE OF CONTENT SCOPE 3 REFERENCES

More information

Proceedings of the 5th WSEAS Int. Conf. on SIMULATION, MODELING AND OPTIMIZATION, Corfu, Greece, August 17-19, 2005 (pp )

Proceedings of the 5th WSEAS Int. Conf. on SIMULATION, MODELING AND OPTIMIZATION, Corfu, Greece, August 17-19, 2005 (pp ) Proceedings of the 5th WSEAS Int. Conf. on SIMULATION, MODELING AND OPTIMIZATION, Corfu, Greece, August 7-9, 5 (pp567-57) Power differential relay for three phase transformer B.BAHMANI Marvdasht Islamic

More information

Power Plant and Transmission System Protection Coordination Fundamentals

Power Plant and Transmission System Protection Coordination Fundamentals Power Plant and Transmission System Protection Coordination Fundamentals NERC Protection Coordination Webinar Series June 2, 2010 Jon Gardell Agenda 2 Objective Introduction to Protection Generator and

More information

POWER TRANSFORMER SPECIFICATION, DESIGN, QUALITY CONTROL AND TESTING 18 MARCH 2009

POWER TRANSFORMER SPECIFICATION, DESIGN, QUALITY CONTROL AND TESTING 18 MARCH 2009 POWER TRANSFORMER SPECIFICATION, DESIGN, QUALITY CONTROL AND TESTING 18 MARCH 2009 Nkosinathi Buthelezi Senior Consultant: Power Transformers and Reactors Presentation Content Standardization of Power

More information

Pinhook 500kV Transformer Neutral CT Saturation

Pinhook 500kV Transformer Neutral CT Saturation Russell W. Patterson Tennessee Valley Authority Presented to the 9th Annual Fault and Disturbance Analysis Conference May 1-2, 26 Abstract This paper discusses the saturation of a 5kV neutral CT upon energization

More information

MV network design & devices selection EXERCISE BOOK

MV network design & devices selection EXERCISE BOOK MV network design & devices selection EXERCISE BOOK EXERCISES 01 - MV substation architectures 02 - MV substation architectures 03 - Industrial C13-200 MV substation 04 - Max. distance between surge arrester

More information

Insulation Co-ordination For HVDC Station

Insulation Co-ordination For HVDC Station Insulation Co-ordination For HVDC Station Insulation Co-ordination Definitions As per IEC 60071 Insulation Coordination is defined as selection of dielectric strength of equipment in relation to the operating

More information

Unit Protection Differential Relays

Unit Protection Differential Relays Unit Protection PROF. SHAHRAM MONTASER KOUHSARI Current, pu Current, pu Protection Relays - BASICS Note on CT polarity dots Through-current: must not operate Internal fault: must operate The CT currents

More information

Transformer protection IED RET 670

Transformer protection IED RET 670 Gunnar Stranne Transformer protection IED RET 670 Santiago Septiembre 5, 2006 1 Transformer protection IED RET670 2 Introduction features and applications Differential protection functions Restricted Earth

More information

Variation in SFRA plot due to design and external parameter

Variation in SFRA plot due to design and external parameter Chapter 6 Variation in SFRA plot due to design and external parameter 6.1 Introduction As the experience grows with Sweep Frequency Response Analysis in world, it is useful to discuss the measurements

More information

Transformer Protection Principles

Transformer Protection Principles Transformer Protection Principles 1. Introduction Transformers are a critical and expensive component of the power system. Due to the long lead time for repair of and replacement of transformers, a major

More information

TN, TT & IT Earthing Arrangements

TN, TT & IT Earthing Arrangements TN, TT & IT Earthing Arrangements In IT and TN-C networks, residual current devices are far less likely to detect an insulation fault. In a TN-C system, they would also be very vulnerable to unwanted triggering

More information

Pomona, CA May 24 & 25, LTC Applications - Location, Series & Preventative Auto Transformers

Pomona, CA May 24 & 25, LTC Applications - Location, Series & Preventative Auto Transformers Pomona, CA May 24 & 25, 2016 LTC Applications - Location, Series & Preventative Auto s siemens.com/answers Introduction Tap changer at active part Example of 3-phase tapchanger Page 2 Winding Configurations

More information

Reducing the magnetizing inrush current by means of controlled energization and de-energization of large power transformers

Reducing the magnetizing inrush current by means of controlled energization and de-energization of large power transformers International Conference on Power System Transients IPST 23 in New Orleans, USA Reducing the magnetizing inrush current by means of controlled energization and de-energization of large power transformers

More information

SPAD 346 C Stabilized differential relay

SPAD 346 C Stabilized differential relay SPAD 346 C Stabilized differential relay Stabilized Differential Relay Type SPAD 346 C Features Integrated three-phase differential relay, three-phase overcurrent relay and multiconfigurable earth-fault

More information

Upgrading Your Electrical Distribution System To Resistance Grounding

Upgrading Your Electrical Distribution System To Resistance Grounding Upgrading Your Electrical Distribution System To Resistance Grounding The term grounding is commonly used in the electrical industry to mean both equipment grounding and system grounding. Equipment grounding

More information

Extensive LV cable network. Figure 1: Simplified SLD of the transformer and associated LV network

Extensive LV cable network. Figure 1: Simplified SLD of the transformer and associated LV network Copyright 2017 ABB. All rights reserved. 1. Introduction Many distribution networks around the world have limited earth-fault current by a resistor located in the LV winding neutral point of for example

More information

ARC FLASH HAZARD ANALYSIS AND MITIGATION

ARC FLASH HAZARD ANALYSIS AND MITIGATION ARC FLASH HAZARD ANALYSIS AND MITIGATION J.C. Das IEEE PRESS SERIES 0N POWER ENGINEERING Mohamed E. El-Hawary, Series Editor IEEE IEEE PRESS WILEY A JOHN WILEY & SONS, INC., PUBLICATION CONTENTS Foreword

More information

Switching Induced Transients:

Switching Induced Transients: Switching Induced Transients: Transformer switching is the most commonly performed operation in any power delivery system and most of the times this operation can be performed without any undesirable consequences.

More information

UProtection Requirements. Ufor a Large scale Wind Park. Shyam Musunuri Siemens Energy

UProtection Requirements. Ufor a Large scale Wind Park. Shyam Musunuri Siemens Energy UProtection Requirements Ufor a Large scale Wind Park Shyam Musunuri Siemens Energy Abstract: In the past wind power plants typically had a small power rating when compared to the strength of the connected

More information

Current Transformer Requirements for VA TECH Reyrolle ACP Relays. PREPARED BY:- A Allen... APPROVED :- B Watson...

Current Transformer Requirements for VA TECH Reyrolle ACP Relays. PREPARED BY:- A Allen... APPROVED :- B Watson... TECHNICAL REPORT APPLICATION GUIDE TITLE: Current Transformer Requirements for VA TECH Reyrolle ACP Relays PREPARED BY:- A Allen... APPROVED :- B Watson... REPORT NO:- 990/TIR/005/02 DATE :- 24 Jan 2000

More information

RESIDUAL LIFE ASSESSMENT OF GENERATOR TRANSFORMERS IN OLD HYDRO POWER PLANTS

RESIDUAL LIFE ASSESSMENT OF GENERATOR TRANSFORMERS IN OLD HYDRO POWER PLANTS RESIDUAL LIFE ASSESSMENT OF GENERATOR TRANSFORMERS IN OLD HYDRO POWER PLANTS Authored by: Sanjay Srivastava, Chief Engineer (HE&RM), Rakesh Kumar, Director (HE&RM), R.K. Jayaswal, Dy. Director (HE&RM)

More information

شركة كهرباء محافظة القدس المساهمة المحدودة JERUSALEM DISTRICT ELECTRICITY CO. LTD.

شركة كهرباء محافظة القدس المساهمة المحدودة JERUSALEM DISTRICT ELECTRICITY CO. LTD. Our Ref : 2/2018- Date : Messrs: Dear Sir, Tender 2/2018 Main Transformers You are kindly requested to quote for the supply and delivery DDP to our stores the transformers detailed in the attached schedules

More information

Transformer Factory Testing

Transformer Factory Testing Transformer Factory Testing John J. Foschia Test Engineer John.Foschia@spx.com September 2018 Reasons for Testing Compliance with user specifications Assessment of quality and reliability Verification

More information

Differential Protection with REF 542plus Feeder Terminal

Differential Protection with REF 542plus Feeder Terminal Differential Protection with REF 542plus Application and Setting Guide kansikuva_bw 1MRS 756281 Issued: 09.01.2007 Version: A Differential Protection with REF 542plus Application and Setting Guide Contents:

More information

Connection of Embedded Generating Plant up to 5MW

Connection of Embedded Generating Plant up to 5MW Engineering Recommendation No.3 of the Electricity Distribution Code Connection of Embedded Generating Plant up to 5MW Version 1.0 30th November 2005 Prepared by: Al Ain Distribution Company, Abu Dhabi

More information

Prevention of transformers damage in HPP with double generating units connected to GIS via HV cables

Prevention of transformers damage in HPP with double generating units connected to GIS via HV cables nd This paper is part of the Proceedings of the 2 International Conference on Energy Production and Management (EQ 2016) www.witconferences.com Prevention of transformers damage in HPP with double generating

More information

DATA SHEET FOR LIGHTING TRANSFORMER APPD. BY VDV PROJECT NO

DATA SHEET FOR LIGHTING TRANSFORMER APPD. BY VDV PROJECT NO PART - A : SPECIFIC REQUIREMENTS THIS DATA SHEET IS APPLICABLE FOR IN BOILER A CLIMATIC CONDITIONS PACKAGE 1 DESIGN AMBIENT TEMPERATURE 45 C 2 ALTITUDE ( ABOVE MSL ) 6.71 MTRS. 3 RELATIVE HUMIDITY 74 %

More information

Specialists in HV and MV test and diagnostics. Testing in Substations

Specialists in HV and MV test and diagnostics. Testing in Substations Specialists in HV and MV test and diagnostics Testing in Substations Testing in Substations Testing in Substations At 4fores we specialize in the diagnosis and measurement of all types of existing technologies

More information

Back to the Basics Current Transformer (CT) Testing

Back to the Basics Current Transformer (CT) Testing Back to the Basics Current Transformer (CT) Testing As test equipment becomes more sophisticated with better features and accuracy, we risk turning our field personnel into test set operators instead of

More information

ELECTRICAL POWER TRANSMISSION TRAINER

ELECTRICAL POWER TRANSMISSION TRAINER ELECTRICAL POWER TRANSMISSION TRAINER ELECTRICAL POWER TRANSMISSION TRAINER This training system has been designed to provide the students with a fully comprehensive knowledge in Electrical Power Engineering

More information

7SG14 Duobias-M Transformer Protection

7SG14 Duobias-M Transformer Protection 7SG14 Duobias-M Transformer Protection Document Release History This document is issue 2010/02. The list of revisions up to and including this issue is: Pre release Revision Date Change 2010/02 Document

More information