online_TS_3.02.04_i5

March 26, 2018 | Author: akmezim | Category: Transformer, Power Engineering, Power (Physics), Physical Quantities, Electric Power
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This document is for internal and contract specific use only.Disclaimer NGG and NGET or their agents, servants or contractors do not accept any liability for any losses arising under or in connection with this information. This limit on liability applies to all and any claims in contract, tort (including negligence), misrepresentation (excluding fraudulent misrepresentation), breach of statutory duty or otherwise. This limit on liability does not exclude or restrict liability where prohibited by the law nor does it supersede the express terms of any related agreements." Copyright © National Grid plc 2011, all rights reserved All copyright and other intellectual property rights arising in any information contained within this document are, unless otherwise stated, owned by National Grid plc or other companies in the National Grid group of companies. No part of this publication may by reproduced in any material form (including photocopying and restoring in any medium or electronic means and whether or not transiently or incidentally) without the written permission of National Grid plc This information should not be forwarded to third parties. National Grid Technical Specification TS 3.02.04 Technical Specification Addendum Addendum No 3 Uncontrolled When Printed Page 1 of 2 ADDENDUM Date Effective From 24 November 201115 J uly 2011 Originated by Approved by Name Tony Westmorland David Wright Job Title Generator & Asset Compliance Engineer ENI Manager Department Policy ENI Date 24 November 2011 16 March 2012 ORIGINAL DOCUMENT DETAILS DOCUMENT TITLE Current Transformers for Protection and General Use DOCUMENT NUMBER TS 3.2.4 ISSUE NUMBER 5 Rev. 2 ISSUE DATE December 2003 ADDENDUM DETAILS The above document shall be read in conjunction with the following amendments: Check appropriate boxes below Addition Replacement X Deletion AMENDMENTS Delete Amendment 1 Replace Schedule of Particulars - Schedule 10 with new schedule as detailed below: - National Grid Technical Specification TS 3.02.04 Technical Specification Addendum Addendum No 3 Uncontrolled When Printed Page 2 of 2 SCHEDULE 10 TABLE OF PARTICULARS FOR 420 kV, 300 kV AND 145 kV CURRENT TRANSFORMERS Note: For tapped current transformers the knee-point voltage, magnetising current and secondary resistance are specified for the full winding, shown underlined. Reference Clauses CT Designation Ratio Minimum Knee-Point Voltage (Vk) or Class Maximum Magnetising Current (mA) at Vk/2 Maximum Sec Res (ohms) at 75C 4.2 to 4.4 420 kV, 4000 A (i) PX A (ii) PX B (iv) Measurement/ Protection 1/1000/2000 1/1200/2000 1/1000/2000 3570 780 30 VA Class 1 5P20 60 24 Not Specified 4.4 2.7 3.0 4.2 to 4.4 300 kV, 3150A (i) PX A (ii) PX B (iii) Measurement/ Protection 1/600/1200/2000 1/600/1200/2000 1/600/1200/2000 2750 2000 30 VA Class 1 5P20 60 30 4.7 3.1 4.2 to 4.4 145 kV, 2000A (i) PX A (ii) PX B (iii) Measurement/ Protection + PXB + Class 1 1/500/600/1000/1200 1/500/600/1000/1200 1/500/600/1000/1200 1000 1000 30VA Class 1 5P20 800 60 30 30 2 2 2 National Grid - Internal and Contract Specific Document Number TS 3.02.04 Addendum Addendum No 2 Uncontrolled When Printed Page 1 of 2 ADDENDUM Date Effective From 17 August 2010 Originated by Approved by Name Tony Westmorland David Wright Job Title Applied Policy Engineer Electricity Network Investment Manager Department Asset Policy ENI, Asset Management Date 17/08/2010 18/10/2010 ORIGINAL DOCUMENT DETAILS DOCUMENT TITLE Current Transformers for Protection and General Use DOCUMENT NUMBER TS 3.2.4 ISSUE NUMBER 5 ISSUE DATE December 2003 National Grid - Internal and Contract Specific Document Number TS 3.02.04 Addendum Addendum No 2 Uncontrolled When Printed Page 2 of 2 ADDENDUM DETAILS The above document shall be read in conjunction with the following amendments: Check appropriate boxes below Addition x Replacement Deletion Schedule 10 – Add new Schedule of Particulars for 400kV, 5000A Current Transformers as detailed below: - SCHEDULE 10 TABLE OF PARTICULARS FOR 420 KV CURRENT TRANSFORMERS TS Reference Clauses CT Designation Turns Ratio Knee-Point Voltage (Vk) or IEC Rating and Class Magnetising Current (mA) Max Sec Res (ohms) 4.2 to 4.4 420 KV, 5000 A PXA 1/1000/2000/3000 3000/1 450(R ct + 7.5) - - PXB 1/1000/2000/3000 3000/1 90(R ct + 5) 40 at Vk/2 5.0 at 75°C MEASUREMENT AND PROTECTION 1/1000/2000/3000 3000/1 2000/1 1000/1 30 VA Class 1 5P20 30 VA Class 1 5P20 30 VA Class 1 5P10 Notes: 1. This specification has been issued for current transformers with a 5000A continuous current rating with 2xPXA, 1xDual Purpose and 2PXB cores. For current transformers with a maximum continuous current rating of 4000A, refer to separate schedule of particulars. 2. The accuracy class and knee points are to be maintained for the ratios which are underlined in the table above. 3. The Current Transformer shall be assigned a short time overload rating of 2 times rated current for 3 minutes. (refer to Table 1 of TS 2.1) 4. The Current Transformer shall be assigned a post fault continuous current rating of 1.206 times rated current. (refer to Table 1 of TS 2.1) 5. The Current Transformer characteristics (knee point, mag current etc.) are as defined in the table above. Requirements for Dual Purpose Measurement/Protection Current Transformers 1. Current transformers intended for the dual purpose of measurement and protection shall meet the performance requirements of IEC 60044-1, Clause 4.2.1 and the above table. 2. All measurement/protection CTs shall have an extended measuring range of 200% In except CTs for Transformers and Quad Boosters which shall have an extended measuring range of 300% In. 3. All measurement/protection CTs shall meet the short time overload ratings given in Table 1 of TS 2.1. National Grid - - Internal and Contract Specific Technical Specification TS 3.2.4 Technical Specification Addendum Addendum No 1 Uncontrolled When Printed Page 1 of 1 TECHNICAL SPECIFICATION ADDENDUM DOCUMENT TITLE Current Transformers for Protection and General Use DOCUMENT NUMBER TS 3.2.4 ISSUE NUMBER 5 ISSUE DATE December 2003 This Technical Specification shall be read in conjunction with the following amendments: Check appropriate boxes below Addition Replacement X Deletion AMENDMENTS Schedule 10 – Replace Schedule of Particulars for 300kV Current Transformers with new schedule as detailed below: - SCHEDULE 10 TABLE OF PARTICULARS FOR 300 kV CURRENT TRANSFORMERS TS Reference Clauses CT Designation Turns Ratio Knee Point Voltage (Vk) or IEC Rating Class Magnetising Current (mA) Max Sec Res (ohms) 4.2 to 4.4 300 kV, 3150A PXA 1/600/1200/2000 2000/1 1200/1 267(R ct + 7.5) 160(R ct + 7.5) - - - - PXB 1/600/1200/2000 2000/1 1200/1 137(R ct + 3.0) 82(R ct + 3.0) 60 at Vk/2 60 at Vk/2 2.4 at 75°C 2.4 at 75°C MEASUREMENT AND PROTECTION 1/600/1200/2000 2000/1 30 VA Class 1 5P20 1200/1 600/1 30 VA Class 1 5P20 30VA Class 1 5P10 Date Effective From 01 J anuary 2010 Originated by Authorised by Approved by Name Tony Westmorland Ursula Bryan David Wright Job Title Applied Policy Engineer Asset Policy Manager Electricity Network Investment Manager Department Asset Policy Asset Policy ENI, Asset Management Date 05/01/2010 05/02/2010 08/02/2010 National Grid Technical Specification Current Transformers for Protection and General Use NGTS 3.2.4 Issue 5 December 2003 CONTENTS Page Foreword...................................................1 1 Scope ..............................................1 2 References ......................................1 3 General Requirements ....................2 4 Performance Requirements.............3 5 Testing Requirements .....................4 6 List Of Schedules ............................7 Appendix A..............................................18 Appendix B..............................................19 Authorised for Issue by: Mike Dean Asset Strategy Manager Uncontrolled when printed. This document will be valid on the day of printing only REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed © National Grid 2003 “No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise, without the written permission of the National Grid obtained from the issuing location. The contents of National Grid engineering documents are based on the needs of National Grid and the conditions under which it operates. It should not therefore be assumed that the specifications and requirements stated therein necessarily meet the particular circumstances and requirements of other organisations. The principles set out in this document are for information only and therefore National Grid is not liable to customers / suppliers for any loss or damage resulting from reliance on the contents. It is the responsibility of such external organisations to check that the document is the latest version and is appropriate for their purposes.” (National Grid Legal Services. November 1999) Registered Office Registered in 1-3 Strand England and Wales London No. 2366977 WC2N 5EH Published by: National Grid NGT House Warwick Technology Park Gallows Hill Warwick CV34 6DA Uncontrolled when printed. This document will be valid on the day of printing only. Administrative enquiries regarding this document should be directed to: Asset Support at Warwick, Telephone: 01926 655063 Technical enquiries regarding this document should be directed to: Contact name: Tony Westmorland Asset Policy Telephone: 01926 655966 REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 1 CURRENT TRANSFORMERS FOR PROTECTION AND GENERAL USE FOREWORD This Specification defines the functional and performance requirements for current transformers (CTs) for protection and general use on The National Grid Transco (NGT) UK Transmission System (Electricity). It supports the more general requirements defined in the companion documents NGTS 1, NGTS 2.1 and NGTS 2.2. 1 SCOPE This is a functional and performance specification for CTs used for protection and measurement application. For CTs used in Settlements Metering applications reference should be made to NGTS 3.2.6. 2 REFERENCES 2.1 International, European and British National Documentation This document makes reference to, or should be read in conjunction with, the documents listed below. Where a standard has been harmonised into a Euronorm, only this latter reference is given. The issue and date of the documents detailed below shall be applicable at the time of issue of this specification unless a specific issue date is given IEC 60044-1 Instrument transformers- Part 1: Current Transformers IEC 567 Guide for the sampling of gases and of oil from oil filled electrical equipment and for the analysis of free and dissolved gases. IEC 60044-6 Requirements for protective Current Transformers for transient performance BS EN 60694 Common specifications for high voltage switchgear and controlgear standards BS 7626 Current Transformers 2.2 National Grid Technical Specifications The following NGTS documentation is relevant to current transformers and should be read in conjunction with this document. NGTS 1 Ratings and General Requirements for Plant, Equipment, Apparatus and Services for use on and Direct Connections to the National Grid Transmission System NGTS 2.1 Substations NGTS 2.2 Switchgear for use on, and at Connection Points to, the National Grid System NGTS 2.3 Transformers and Reactors for use on 132, 275 and 400 kV Systems NGTS 2.6 Protection REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 2 2.3 Definitions and Abbreviations The definitions used in NGTS1 and NGTS2.2 apply to this document. 3 GENERAL REQUIREMENTS All CTs shall comply with NGTS 1, NGTS 2.1, NGTS 2.2 and IEC 60044-1. In addition, the following clauses apply: 3.1 General Requirements for all Current Transformers 3.1.1 Additional specification and testing requirements for protection Class PX cores are given in Appendix E. For information, these requirements are identical to those given in the now obsolete BS 3938 Class X sections. 3.1.2 Secondary ratings and transformation ratios shall be selected from the attached Schedules and shall be specified in the contract Enquiry Document or Supplementary Agreement as appropriate 3.1.3 A single secondary terminal box shall be mounted on the transformer to accommodate the necessary secondary terminal connections. 3.1.4 Secondary terminals and connections shall be suitable for their required purpose regarding rating, reliability and the effects of environmental conditions and corrosion. 3.1.5 Secondary terminal boxes shall comply to at least IP54 environment of BSEN60529 as required by NGTS 1 3.1.6 Primary and secondary terminal markings, and rating plate markings shall be in accordance with IEC 60044 1 3.1.7 The rated continuous primary current of the current transformer shall be chosen to exceed the maximum continuous rating of the associated circuit and shall be selected from the standard values detailed in IEC 60044-1 3.1.8 A thermal short-time current rating (Ith) shall be assigned to all current transformers in accordance with IEC 60044-1. The value of Ith shall not be less than the corresponding value for the associated switchgear or transformer primary plant. 3.1.9 Current transformer secondary terminals should allow the application of shorting/earthing links or wiring for maintenance purposes. Separately, a terminal for earthing purposes shall be provided within the terminal box and shall be clearly marked. 3.1.10 For all oil filled CTs the supplier shall declare the type of insulating oil being used. 3.1.11 For oil-filled equipment fitted with an external oil expansion system, means shall be provided to give a permanent visual indication of the volume of the oil. The status of the indicator should be visible from ground level. 3.1.12 For oil filled CTs where the oil expansion system is wholly internal ie gas cushion or flexible diaphragm, the CT shall be fitted with a permanent internal pressure indicator. The status of the indicator shall be visible from ground level. 3.1.13 All oil filled CTs shall be fitted with an oil sample valve, situated at the base of the CT, suitable for taking oil samples for Dissolved Gas Analysis (DGA) in accordance with IEC 567. The sample valve shall be situated on the earthed base tank of the CT. Valves where the oil is extracted by using a hypodermic needle are not suitable. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 3 3.1.14 Both ends of the CT secondary windings shall be earth free. 3.2 Additional Requirements for Post-Type Current Transformers 3.2.1 An insulation test terminal (test tap) shall be provided for the purpose of performing capacitance and dielectric loss (tan ) measurements of the primary insulation during routine maintenance. The test terminals shall be suitably identified. 3.3 Additional Requirements for Current Transformers for GIS Application 3.3.1 Current transformers may be mounted internally or externally to the GIS enclosure. 3.3.2 Adequate protection against adverse environmental conditions shall be provided for externally mounted CTs as required in NGTS 2.2. 3.4 Additional Requirements for Ring-Type Current Transformers 3.4.1 Current transformers mounted internally to power transformers shall be capable of operating in an environment as detailed in NGTS 2.3. 3.4.2 Current transformers supplied as loose equipment for power transformer application shall be equipped with secondary terminals or shall be supplied with leads of suitable length for this application. Such leads shall be capable of satisfying the test requirement of Clause 5.4.3. 3.4.3 Current transformers supplied with throughwall bushings can be mounted internally or externally to the bushing. Current transformers mounted internally shall be capable of operating within that environment. Current transformers mounted externally shall be suitably protected against the effects of adverse environmental conditions as required by NGTS 2.2. 3.4.4 Current transformers supplied as loose equipment for other switchgear applications shall be capable of operating within that environment. Current transformers for other switchgear applications, mounted externally, shall be suitably protected against the effects of adverse environmental conditions as required by NGTS 2.2. 3.5 Additional Requirements for Measurement/Protection and Class PX Protective Current Transformers 3.5.1 Measurement/Protection and class PX protective current transformers with a rated primary current of 2500 A or below and with untapped secondary windings shall have a rated secondary current of 1A (as selected from IEC 60044-1). The rated secondary current for current transformers of this primary rating with tapped secondary windings shall be 1 A corresponding to the highest transformation ratio. 3.5.2 Measurement/Protection and class PX protective current transformers with a rated primary current in excess of 2500 A shall have a rated secondary current selected from the values stated in IEC 60044-1 4 PERFORMANCE REQUIREMENTS 4.1 General All current transformers shall comply with the performance requirements of IEC 60044-1 for the primary ratings detailed in NGTS 1, NGTS 2.1 and NGTS 2.2. The following requirements shall also apply as appropriate: REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 4 4.2 Protection Type PX-A Current Transformers 4.2.1 Protection type PX-A current transformers shall meet the additional requirements given in Appendix E providing accurate transformation up to the maximum fault current rating of the associated main plant. This performance shall be maintained under both fault and steady-state conditions without saturation 4.2.2 Type PX-A current transformers shall also meet the performance requirements of Schedule 10 of this Specification. 4.3 Protection Type PX-B Current Transformers 4.3.1 Protection type PX-B current transformers shall meet the additional requirements given in Appendix E providing accurate steady-state transformation up to the maximum fault current rating of the associated main plant. 4.3.2 Type PX-B current transformers shall also meet the performance requirements of Schedule 9 of this Specification. 4.4 Dual Purpose Measurement/Protection Current Transformers 4.4.1 Current transformers intended for the dual purpose of measurement and protection shall meet the performance requirements of IEC 60044-1, Clause 4.2.1 and Schedule 10 of this Specification. 4.5 Interposing Current Transformers 4.5.1 Short duration overload capabilities are assigned to the main current transformers and the associated interposing current transformers shall be capable of carrying the corresponding current. 4.6 Line Drop Compensation Current Transformers (as used in tap change voltage control schemes) 4.6.1 Line drop compensation current transformers shall comply with accuracy class 5 of BS 7626. 5 TESTING REQUIREMENTS 5.1 Type Tests 5.1.1 All current transformers shall be type tested in accordance with IEC 60044-1 (type tests) and IEC 60044-1 (special tests). The additional requirements for protection class PX cores given in Appendix B. Current transformers using a gas insulation system, a leakage test on the gas system shall be performed by the supplier to demonstrate compliance with NGTS 2.2. 5.1.2 Radio interference voltage tests to IEC 60694 are to be performed on open-terminal current transformers. 5.1.3 A multi chopped impulse test shall be performed on all oil filled current transformers rated 72.5 kV and above. The test method is given in Appendix D. 5.1.4 Temperature Rise - The thermal time constant of all equipment shall be determined on both rising and falling temperature. 5.1.5 For oil filled equipment oil samples for DGA shall be taken before and after the dielectric type tests and shall comply with 5.5.3. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 5 5.1.6 Accuracy at Short-Term Continuous Current Levels - Current transformers which have a measurement specification shall have their errors determined at a current of 12000 A for 420 kV rating and 7500 A for 300 kV rating respectively. These currents shall be withstood for a period of 3 minutes. 5.1.7 Routine tests shall be performed before and after all type tests. 5.2 Routine tests 5.2.1 All current transformers shall be routine tested in accordance with: IEC 60044-1 (routine tests) IEC 60044-1 (special tests) The additional requirements for protection class PX transformers are given in Appendix B. 5.3 Additional Routine Tests 5.3.1 Accuracy Tests a) These shall be performed in a laboratory having traceability to National/International standards. b) The overall accuracy and uncertainty of the measurement shall be demonstrated prior to testing and shall be commensurate with the accuracy class of the transformer under test. c) Full accuracy routine tests to IEC 60044-1. 5.3.2 Capacitance and dielectric loss angle (tan δ) measurements of the primary insulation over the voltage range 10 kV to rated voltage shall be performed. 5.3.3 Leads for loose current transformers as detailed in Clause 3.4.2 of this Specification shall withstand a power frequency test voltage of 5 kV (peak). For PXA application, the test levels shall be determined by tests in Appendix B 14.2.2. 5.3.4 An oil sample for DGA shall be taken as described in 5.5 from all oil filled CTs. The sample shall be taken at least 24 hours after the final routine electrical testing has been performed. The results shall be included in the routine test report as detailed in Clause 5.5. 5.4 Routine Test Reports 5.4.1 Routine test reports shall include details of all routine measurements made in accordance with this specification. The information regarding the overall accuracy and uncertainty of the accuracy measurements shall also be recorded. 5.4.2 During the partial discharge (PD) test, the value of measured PD at the specified test voltage shall be recorded together with the value of the PD extinction voltage. Extinction voltage is defined as the voltage level at which measurable PD is completely extinguished upon decreasing test voltage. The background PD level at the time of the test should also be recorded in the report. 5.4.3 Where oil samples are taken for Dissolved Gas Analysis (DGA) the report shall contain the following information: a) Name and Address of the laboratory where the analysis was performed b) The Accuracy, Precision and Detection Limits for the individual gas measurement expressed in either parts per million (ppm) or percentage by volume. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 6 c) The Sampling Procedure (stating the Standard Method IEC 567 if applicable). d) The Gas Extraction Method used (stating the Standard Method IEC 567 if applicable). e) Calibration Procedure adopted by the laboratory, including details of the number of points used over the range (f)and the gases used. f) Accreditation Status of the laboratory for the purposes of DGA testing. g) Date Sampled and Analysed. h) Report the following: Measurement Units No. Decimal Places Oil Volume Tested mls 0 Total Gas Content % 2 Hydrogen ppm 0 Methane ppm 0 Ethane ppm 0 Ethylene ppm 0 Acetylene ppm 0* Carbon monoxide ppm 0 Carbon dioxide ppm 0 Oxygen ppm 0 Nitrogen ppm 0 Moisture mg/l 0 *Note: For DGA samples associated with Type Tests, the acetylene value shall be quoted to one decimal place REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 7 6 LIST OF SCHEDULES Schedule 1 Overhead Line Feeder Circuits Schedule 2 Synchronous Compensators Associated with Auto-Transformers Schedule 3 Static Compensators (Reactors and Capacitors) Associated with Auto- Transformers Schedule 4 Series Reactors Schedule 5 Shunt Reactors Schedule 6 Bus Sections and Couplers and other users Directly Connected via NGC bus bar protection Schedule 7 Auto-Transformer Circuits Schedule 8 Transformer Neutral and Neutral End Current Transformer Units for use with Supergrid Auto-Transformers and Shunt Reactors Schedule 9 Secondary ratings and rated transformation ratios for double wound transformer current transformer circuit. Schedule 10 Table of Particulars for 420 kV, 300 kV and 145 kV Current Transformers REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 8 SCHEDULE 1 OVERHEAD LINE FEEDER CIRCUITS Class X Protection Current Transformers Measurement/Protection Current Transformers System Voltage Rated Current of Switchgear Rated Continuous Thermal Current Turns Ratio Extended Primary Current Rating % kV A A Main Busbar Thermal Accuracy Rated Transformation Ratio 275 275 400 2000 2500 4000 2000 2500 4000 1/600/1200 1/600/1200 1/1000/2000 1/600/1200 1/600/1200 1/2000 170 210 200 420 420 500 1200/600/1 1200/600/1 2000/1000/1 REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 9 SCHEDULE 2 SYNCHRONOUS COMPENSATORS ASSOCIATED WITH AUTO-TRANSFORMERS Class X Protection Current Transformers Measurement/Protection Current Transformers Compensator Rating Voltage Current Rated Current of Switchgear Rated Continuous Thermal Current Turns Ratio Extended Primary Current Rating % Rated Transformer Ratio MVA kV A A A Main REF* UEF** Connections Thermal Accuracy Back Up Reverse Power 60 13 2665 3000 3000 1/600 1/600 1/300 1/600 - - 3000/5 3000/5 * REF - restricted earth fault ** UEF - unrestricted earth fault REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 10 SCHEDULE 3 STATIC COMPENSATORS (REACTORS AND CAPACITORS) ASSOCIATED WITH AUTO-TRANSFORMERS Class X Protection Current Transformers Measurement/Protection Current Transformers Compensator Rating Voltage Current Rated Current of Switchgear Rated Continuous Thermal Current Turns Ratio Extended Primary Current Rating % MVA kV A A A HV Connections Compensator Protection REF* UEF** and Instantaneous Earth Fault Thermal Accuracy Rated Transfor- mation Ratio 60 30+30 13 13 2665 1335+ 1335 3000 2000 3000 2000 1/600 1/600 1/600 1/1500 1/600 1/1500 1/1500 # 1/300+ 1/1500# - - - - 3000/5 3000/5 * REF - restricted earth fault ** UEF - unrestricted earth fault # A relay may be required + 300/1 ratio to be specified when earth fault current is restricted to 300 A by NER. 1500/1 ratio to be specified when earth fault current is restricted by impedance of earthing transformer only. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 11 SCHEDULE 4 SERIES REACTORS Class X Protection Current Transformers Measurement/Protection Current Transformers Rating System Voltage Current Rated Current of Switchgear Rated Continuous Thermal Current Turns Ratio Extended Primary Current Rating % MVA kV A A A Main Busbar Thermal Accuracy Rated Transformation Ratio 90 750 750 1320 2000 132 275 275 400 400 395 1575 1575 1905 2890 800 2000 2500 4000 4000 800 2000 2500 4000 4000 1/500/1000 1/600/1200 1/600/1200 1/1000/2000 1/1000/2000 1/500/1000 1/600/1200 1/600/1200 1/2000 1/2000 - 170 210 200 200 - 170 210 200 290 1200/600/1 1200/600/1 1200/600/1 2000/1000/1 2000/1000/1 REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 12 SCHEDULE 5 SHUNT REACTORS Class X Protection Current Transformers Measurement/Protection Current Transformers Rated Continuous Thermal Current A Turns Ratio Extended Primary Current Rating Thermal and Accuracy % Rating System Voltage Current Rated Current of Switchgear MVA kV A A Located near Switchgear Located in Bushing Main Protection Feeder Protection or if Applicable Connections Protection if Applicable Located near Switchgear Located in Bushing Rated Transformation Ratio 100 275 210 2000 2000 500 1/600/1200 1/600/1200 1/600/1200 170 - 1200/600/1 * 100 275 210 2500 2500 500 1/600/1200 1/600/1200 1/600/1200 210 - 1200/600/1 * 200 400 290 4000 4000 500 1/1000 1/1000/2000 1/2000 200 - 2000/1000/1 * * 0.5 A relay to be specified. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 13 SCHEDULE 6 BUS SECTIONS AND BUS COUPLERS ALSO OTHER USER CT’s AT CONNECTION POINTS AND ASSOCIATED WITH NGC BUSBAR PROTECTION Class X Protection Current Transformers Measurement/Protection Current Transformers Turns Ratio System Voltage Rated Current of Switchgear Rated Continuous Thermal Current Extended Primary Current Rating % kV A A Busbar Thermal Accuracy Rated Transformation Ratio 275 275 400 2000 2500 4000 2000 2500 4000 1/600/1200 1/600/1200 1/1000/2000 170 210 200 420 420 500 1200/600/1 1200/600/1 2000/1000/1 REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 14 SCHEDULE 7 AUTO TRANSFORMER CIRCUITS Class X Protection Current Transformers Measurement/Protection Current Transformer Turns Ratio Extended Primary Current Rating % Nominal Rating System Voltage Current Rated Current of Sw/gear Rated Continuous Thermal Current A* Thermal * Accuracy ** MVA kV A A Located near Sw/gear Located in Bushing Main HV and LV Connections Busbar Back Up LV Located near Sw/gear Located in Bushing Located near Sw/gear Located in Bushing Rated Transform- ation Ratio 120 180 240 240 500 750 1000 275 132 275 132 275 132 400 132 400 275 400 275 400 275 250 530 380 790 500 1050 350 1050 720 1050 1080 1580 1440 2100 2500 800 2500 1250 2500 2000 4000 2000 4000 2500 4000 2500 4000 2500 2500 800 2500 1250 2500 2000 4000 2000 4000 2500 4000 2500 4000 2500 450 800 660 1200 870 1600 610 1600 1100 1600 1700 2500 2200 3200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/600/1200 1/500/1000 1/600/1200 1/500/1000 1/600/1200 1/500/1000 1/1000/2000 1/500/1000 1/1000/2000 1/600/1200 1/1000/2000 1/600/1200 1/1000/2000 1/600/1200 1/600/1200 1/500/1000 1/600/1200 1/500/1000 1/600/1200 1/500/1000 1/2000 1/500/1000 1/2000 1/600/1200 1/2000 1/600/1200 1/2000 1/600/1200 1/500/1000# 1/500/1000# 1/500/1000# 1/500/1000# 1/600/1200 1/600/1200 1/600/1200 210 - 210 110 210 170 200 170 200 210 200 210 200 210 - - - - - 135 - 135 - 135 - 210 110 270 210 - 210 130 210 180 200 180 200 210 200 270 200 350 - - - 130 - 180 - 180 - 180 110 270 150 350 1200/600/1 1200/600/1 1200/600/1 1200/600/1 1200/600/1 1200/600/1 2000/1000/1 1200/600/1 2000/1000/1 1200/600/1 2000/1000/1 1200/600/1 2000/1000/1 1200/600/1 * Designed to cater for 150% overload ** Designed to cater for 200% overload # At busbar stations where post-type CT housings are installed and LV connection protection is specified, the back-up protection is to be supplied from the Type A 1/600/1200 CT. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 15 SCHEDULE 8 TRANSFORMER NEUTRAL AND NEUTRAL END CURRENT TRANSFORMER UNITS FOR USE WITH SUPERGRID AUTO TRANSFORMERS AND SHUNT REACTORS 275/132 kV, 400/275 kV and 400/132 kV auto-transformers and 400 kV and 275 kV Shunt Reactors (11 kV primary insulation) Type Primary Conductor Rating (A) (sec) Turns Ratio Function Transformer 275/132 kV (Up to 360 MVA) 8200 3 sec 1/600/1200 At Least 2 Secondaries, Neutral Earth Fault Check, Fault recorder etc Transformer 400/275 kV (Up to 1000 MVA) 6600 1 sec 1/1000/2000 " Transformer 400/132 kV (Up to 360 MVA) 10 600 3 sec 1/1000/2000 " Shunt Reactor 275 kV (Up to 100 MVA) 2100 1 sec 1/600/1200 Neutral Earth Fault Check Shunt Reactor 400 kV (Up to 200 MVA) 2900 1 sec 1/1000/2000 " Table A- Neutral Current Transformers 275/132 kV, 400/275 kV and 400/132 kV auto-transformers and 400 kV and 275 kV Shunt Reactors (11 kV Primary Insulation) Type Primary Conductor CMR (I hv - I lv ) amp Turns ratio Function Transformer 275/132 kV (Up to 360 MVA) 820 1/600/1200 Auto Transformer Overall Protection Transformer 400/275 kV (Up to 1000 MVA) 660 1/600/1200 " Transformer 400/132 kV (Up to 360 MVA) 1060 1/600/1200 " Shunt Reactor 275 kV (Up to 100 MVA) 210 1/600/1200 Shunt Reactor Overall Protection Shunt Reactor 400 kV (Up to 200 MVA) 290 1/1000 " Table B - Neutral End Current Transformers (3 Single Phase Windings Starred) REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 16 SCHEDULE 9 SECONDARY RATINGS AND RATED TRANSFORMATION RATIOS FOR DOUBLE WOUND TRANSFORMER CURRENT TRANSFORMER CIRCUITS Current Class X Protection Current Transformers Measurement/Protection Current Transformers Turns Ratio Type Nominal Rating System Voltage VT Ratio At Nominal Ratio Tap Position At Mean Tap Positi on Rated Current of Sw/gear Rated Continuous Thermal Current A Main Protection Extended Primary Current Rating* Thermal and Accuracy % MVA kV A A A L o c a t e d N e a r S w / g e a r L o c a t e d N e a r B u s h i n g M a i n C T I n t e r p o s i n g C T B a c k u p L V H V a n d L V C o n n e c t i o n s B u s b a r L V u n r e s t r i c t e d e a r t h f a u l t L o c a t e d n e a r S w / g e a r L o c a t e d i n B u s h i n g R a t e d T r a n s f o r m a t i o n R a t i o E G B a c k u p H V Star/ Delta 75 275 33 - 33000/110 157 1312 166 1312 2500 2000 2500 2000 300 2000 1/200 1/800/1600 0.577/1.0 1.0/1.0/1.0 - 1/1000/2000 1/600/1200 1/800 1/600/1200 1/800 - 1/600/1200 210 - - - 1200/600/1 2000/1 Star/ Delta 100 275 33 - 33000/110 210 1750 221 1750 2500 2500 2500 2700 400 2700 1/200 1/800/1600 0.577/1.0 1.0/1.0/1.0 - 1/1000/2000 1/600/1200 1/800 1/600/1200 1/800 - 1/800/1600 210 135 - 135 1200/600/1 2000/1 Star/ Delta 120 275 33 - 33000/110 250 2100 265 2100 2500 2500 2500 3200 450 3200 1/400 1/800/1600 0.577/0.7 0.7/1.0/1.0 - 1/800/1600 1/600/1200 1/800 1/600/1200 1/800 - 1/800/1600 210 160 - 160 1200/600/1 2000/1 Star/ Star 120 275 66 - 66000/100 250 1050 250 1050 2500 2000 2500 2000 450 1600 1/400 1/800/1600 0.577/0.7 1.0/1.0/0.7 - 1/800/1600 1/600/1200 1/800 1/600/1200 1/800 - 1/600/1200 210 170 - 140 1200/600/1 1200/1 Star/ Delta 120 275 66 - 66000/110 250 1050 250 1050 2500 2000 2500 2000 450 1600 1/400 1/800/1600 0.577/0.7 0.577/0.7 - 1/800/1600 1/600/1200 1/800 1/600/1200 1/800 - 1/600/1200 210 170 - 140 1200/600/1 1200/1 Star/ Star 180 275 66 - 66000/110 380 1580 380 1580 2500 2000 2500 2400 700 2400 1/400 1/800/1600 0.577/1 1/1/1 - 1/800/1600 1/600/1200 1/800 1/600/1200 1/800 - 1/800/1600 210 120 - 120 1200/600/1 2000/1 Star/ Delta 180 275 66 - 66000/110 380 1580 380 1580 2500 2000 2500 2400 700 2400 1/400 1/800/1600 0.577/1.0 0.577/1.0 - 1/800/1600 1/600/1200 1/800 1/600/1200 1/800 - 1/800/1600 210 120 - 120 1200/600/1 2000/1 Star/ Delta 180 400 66 - 66000/110 260 1580 260 1580 4000 2000 4000 2400 500 2400 1/400 1/800/1600 0.577/0.7 1/1/1 - 1/800/1600 1/1000/2000 1/800 1/2000 1/800 - 1/800/1600 200 120 - 120 2000/1000/1 2000/1 Notes 1 275/33 transformers’ mean tap position is -5%. 275/66 and 400/66 transformers mean tap position corresponds with the nominal ratio tap position. 2 Double wound transformers, not covered by the schedule, should be referred to the General Manager, Engineering and Technology. 3 For Settlement Metering CTs see NGTS 3.2.6. * Designed to cater for 150% overload. jxa/cw/may.01 REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 17 SCHEDULE 10 TABLE OF PARTICULARS FOR 420 kV, 300 kV AND 145 kV CURRENT TRANSFORMERS Ratio Reference Clauses CT Designation Turns Current Knee-Point Voltage (Vk) or IEC Rating and Class Magneti sing Current (mA) Max Sec Res (ohms) 4.2 to 4.4 420 kV, 4000 A (i) Prot A 1/1000/2000 300 (R ct + 7.5) (ii) Prot B 1/2000 60 (R ct + 5) 40 at Vk 2 5.0 at 75°C (iii) Prot B Special Ratio 1/600/1200 82 (R ct +3) 60 at Vk 2 2.4 at 75°C (iv) Measure- ment/Protection 1/1000/2000 2000/1 30 VA Class 1 5P20 1000/1 30 VA Class 1 5P10 4.2 to 4.4 300 kV, 2000 or 2500 A (i) Prot A 1/600/1200 160 (R ct + 7.5) (ii) Prot B 1/600/1200 82 (R ct + 3) 60 at Vk 2 2.4 at 75°C (iii) Prot B Special Ratio 1/600/1200 1200/1 30 VA Class 1 5P20 600/1 30 VA Class 1 5P10 4.2 to 4.4 145 kV, 2000A (i) Prot A 1/600/1200 1/500/1000 50 (R ct + 17) 60 (R ct + 12) (ii) Prot B 1/500/1000 95 (R ct + 2.5) 60 at Vk 2 2.4 at 75°C (iii) Prot B Special Ratio 1/600/1200 1200/1 30VA Class 1 5P20 600/1 30VA Class 1 5P10 Note - For tapped current transformers the knee-point voltage, magnetising current and secondary resistance are specified for the full winding, shown underlined. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 18 APPENDIX A MULTICHOPPED IMPULSE TYPE TEST SPECIFICATION All oil filled CTs rated at 72.5 kV and above, shall be subjected to a 600 chopped negative polarity impulse test at 60% of the rated BIL level for that equipment. The time to chop shall be between 2-5 s. A full set of routine electrical tests shall be performed, and oil samples for dissolved gas analysis shall be taken, both before and after this test. The supplier shall submit to NGC details of how the test will be conducted. The three criteria which must all be satisfied for the CT to pass the test are: A1 The results of the routine electrical tests, performed before and after the chopped impulse test, are the same within the error specification for the test field. A2 No evidence of degradation is found when the CT is dismantled and examined after the test. A3 Any increases in the DGA levels are within the limits listed below. Dissolved Gas Allowable increase after 3 days (ppm) Hydrogen (H 2 ) 5 Methane (CH 4 ) 3 Ethane (C 2 H 6 ) 3 Ethylene (C 2 H 4 ) 2 Acetylene (C 2 H 2 ) no detectable increase The application of this test to CTs which have an ERIP or SRBP condenser core shall be subject to agreement between NGC and the supplier. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 19 APPENDIX B ADDITIONAL REQUIREMENTS FOR PROTECTION CLASS PX TRANSFORMERS Within the scope of IEC 60044-1 paragraph 5 additional requirements may be specified for certain protective systems. The specification and tests for Class PX transformers was addressed in BS 3938. This document was withdrawn in June 1998. The following amendment has been tabled by the United Kingdom BSI PEL 38 Instrument Transformer Technical Committee for inclusion IEC 60044-1 addressing these requirements. The numbering of this section is identical to the submission made to IEC. When the amendment has been incorporated into IEC 60044-1 this document will be revised. B1.1 Scope Modify 5th paragraph For certain protective systems, ........resonant earthed networks), additional requirements are given in Clause 14 for class PX transformers. After 5th paragraph add Clause 14 covers the requirements and tests in addition to those in clauses 3 to 10 that are necessary for current transformers for use with electrical protective relays, and in particular for forms of protection for which knowledge of the transformer secondary excitation characteristic, secondary winding resistance, secondary burden resistance and turns ratio is sufficient to assess its performance in relation to the protective relay system with which it is to be used. B1.2 Normative references Add 44-6 (1992) :instrument transformers, Part 6 : Requirements for protective current transformers for transient performance B2 Definitions B2.1 General definitions Add B2.1.32 rated resistive burden (R b ) : For definition see IEC Publication 60044-6 Clause 3.11. B2.1.33 secondary winding resistance (R ct ) : For definition see IEC Publication 60044-6 Clause 3.12. B2.3 Additional definitions for protective current transformers. B2.3.10 Excitation characteristic : A graphical or tabular presentation of the relationship between the r.m.s value of the exciting current and a sinusoidal r.m.s e.m.f applied to the secondary terminals of a current transformer, the primary and other windings being open circuited, over a range of values sufficient to define the characteristics from low levels of excitation up to the rated knee point e.m.f. B2.3.12 Rated knee point e.m.f (E k ) : That minimum sinusoidal e.m.f. (r.m.s) at rated power frequency when applied to the secondary terminals of the transformer, all other terminals being open- circuited, which when increased by 10% causes the r.m.s exciting current to increase by no more than 50%. Note: - The actual knee point e.m.f will be the rated knee point e.m.f. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 20 B2.3.13 Rated turns ratio : The required ratio of the number of primary turns to the number of secondary turns eg Example 1: 1/ 600 (one primary turn with six hundred secondary turns) Example 2: 2/1200 (a current transformer of similar ratio to example 1 but employing two primary turns). B2.3.14 Turns ratio error: The difference between the rated and actual turns ratios. expressed as a percentage. Turns ratio error (%) = (actual turns ratio - rated turns ratio) × 100 rated turns ratio B6 Classification of tests B6.1 Type tests Modify as follows : (f) determination of errors (see 11.4 and/or 12.4, 11.6, 12.5, 14.3) B6.2 Routine tests Modify as follows : (d) power-frequency withstand test on secondary winding ( see 8.3 or 14.4.4); (e) power-frequency withstand tests, between sections ( see 8.3 or 14.4.4 ); (f) inter-turn over voltage test (see 8.4 or 14.4.5); (g) determination of errors (see 11.5 and/or 12.4, 11.6, 12.6, 14.4) B10.2 Rating plate markings Modify as follows : (e) The rated output and the corresponding accuracy class, together with additional information specified in the later parts of these recommendations (see 11.7 and/or 12.7, 13.8, 14.5). B14 Additional requirements for Class PX protective current transformers B14.1 Specification of performance for Class PX protective current transformers: The performance of class PX current transformers shall be specified in terms of the following: (a) rated primary current (I pn ) (b) rated secondary current (I sn ) (c) rated turns ratio. The turns ratio error shall not exceed ± 0.25% (d) rated knee point e.m.f. (E k ) (e) maximum exciting current (I e ) at the rated knee point e.m.f. and / or at a stated percentage thereof (f) maximum resistance of the secondary winding at a temperature of 75°C (Rct) REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 21 (g) rated resistive burden (Rb) (h) dimensioning factor (K x ) Note - The rated knee point e.m.f. is generally determined as follows: ( ) sn b ct x k I R R K E ´ + ´ = B14.2 Insulation requirements for class PX protective current transformers. B14.2.1 Insulation requirements for secondary winding The secondary winding insulation of class PX current transformers having a rated knee point voltage E k ≥ 2 kV shall be capable of withstanding a rated power frequency withstand voltage of 5 kV r.m.s for 60 s. For E k < 2 kV the withstand voltage shall be 3 kV r.m.s for 60 s. B14.2.2 Inter-turn insulation requirements For Class PX transformers having a rated knee point e.m.f of 450 V or less the rated withstand voltage for inter-turn insulation shall be 4.5 kV peak. For those with a rated knee point e.m.f of greater than 450V, the rated withstand voltage for the inter-turn insulation shall be a peak voltage of 10 times the r.m.s value of the specified knee point e.m.f, or 10 kV peak, whichever is the lower. Note: For some EHV transmission systems a higher limiting value of peak voltage may be agreed between the manufacturer and the purchaser. B14.3 Type tests for class PX protective current transformers Class PX current transformers shall in addition to the requirements of clause 7 be tested as below. B14.3.1 Proof of low reactance type An inspection of drawings shall be made in accordance with the requirements of IEC Publication 60044-6 Clause 7.3.1 a) in order to establish proof of low leakage reactance design. If compliance with the requirements of low leakage reactance design cannot be established to the mutual satisfaction of the manufacturer and purchaser by reference to drawings then the composite error shall be determined for the complete secondary winding using either of the direct methods of test given in Appendix A Clause A.5 or A.6 of this document, at a secondary current of K x . I sn and with a secondary burden R b . Proof of low leakage reactance design shall be considered to have been established if the value of composite error from the direct method of test is less than 1.1times that deduced from the secondary excitation characteristic. Note - The value of primary current required to perform direct composite error tests on certain transformer types may be beyond the capability of facilities normally provided by manufacturers. Tests at lower levels of primary current may be agreed between the manufacturer and purchaser. B14.4 Routine tests for class PX protective current transformers Class PX current transformers shall in addition to the requirements of clause 8 be tested as below: B14.4.1 Rated knee point e.m.f. (E k ) and maximum exciting current (I e ) A sinusoidal e.m.f. of rated frequency equal to the rated knee-point e.m.f. shall be applied to the complete secondary winding, all other windings being open-circuited and the exciting current measured. REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed NGTS 3.2.4 Issue 5 December 2003 Page 22 The e.m.f. shall then be increased by 10% and the exciting current shall not increase by more than 50%. All measurement shall be performed using r.m.s. measuring instruments. Due to the non sinusoidal nature of the measured quantities the measurements should be performed using r.m.s measuring instruments having a crest factor ≥3. The excitation characteristic shall be plotted at least up to the rated knee point e.m.f. The exciting current (I' e ) at the rated knee-point e.m.f. and at any stated percentage, shall not exceed the rated value. The number of measurement points shall be agreed between the manufacturer and the purchaser. B14.4.2 Secondary winding resistance (Rct) The resistance of the complete secondary winding shall be measured. The value obtained when corrected to 75°C shall not exceed the specified value. B14.4.3 Turns ratio error ( t ) The turns ratio shall be determined in accordance with IEC publication 60044-6 Annex E. The turns ratio error shall not exceed the value given in Clause 14.1 (c). Note - A simplified test involving measurement of the ratio error with zero connected burden may be substituted by agreement between the manufacturer and purchaser. B14.4.4 Insulation tests Tests shall be performed to demonstrate compliance with Clause 14.2.1 . For test method refer to Clause 8.3. B14.4.5 Inter-turn insulation tests Tests shall be performed to demonstrate compliance with Clause 14.2.2. For test method refer to Clause 8.4 B14.5 Marking of rating plate of Class PX current transformers B14.5.1 Principal marking : See Clauses 10.2. B14.5.2 Special marking (a) rated turns ratio (b) rated knee point e.m.f. (E k ) (c) maximum exciting current (I e ) at the rated knee point e.m.f. and/or at the stated percentage thereof. (d) maximum resistance of the complete secondary winding at a temperature of 75°C (R ct ) The following may also be required by the purchaser: (e) dimensioning factor (K x ) (f) rated resistive burden (Rb) REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed RECORD OF REVISION DOCUMENT NO: NGTS 3.2.4 ISSUE NO: 5 This issue has been revised and amended as follows: DATE DETAILS OF REVISION AUTHORISATION December 2003 Editorial changes REFER EXTERNAL COMPANIES TO ASSET SUPPORT 474 - 5063 Uncontrolled when Printed
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