lled when Printed
National Grid
Technical
Specification
Protection
NGTS 2.6
Issue 3
November 1998
CONTENTS
Page
Foreword................................................1
Scope .....................................................1
References............................................1
General Requirements .......................3
Performance Requirements ........... 10
Test Requirements........................... 13
Equipment Life and Lifetime
Support................................................ 14
NGC Type Registration.................... 15
Appendix............................................. 15
Figures ................................................ 18
Authorised for Issue by:
John Scott
General Manager
Engineering & Technology
Uncontrolled
when Printed ©
The National Grid Company plc 2000
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 NGC obtained from the issuing location.
The contents of The National Grid Company plc engineering
documents are based on the needs of NGC 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 NGC 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.
(NGC Legal Services. November 1999)
Registered Office
Registered in
National Grid House
England and Wales
Kirby Corner Road
No. 2366977
Coventry
CV4 8JY
Published by:
The National Grid Company plc
Kelvin Avenue
Leatherhead
Surrey KT22 7ST
Administrative enquiries regarding this document should be directed to:
ET Business Resources at Leatherhead, Telephone: 01372 383818
Contact name:
Ip Wing Chu (author)
Network Control and Telecommunications
Telephone:
01372 383656
Uncontrolled
when Printed
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. NGTS 2.6
Issue 3
November 1998
Page 1
PROTECTION
1
FOREWORD
This Specification defines the requirements for protection systems and associated connections at the National Grid
Company plc (NGC) owned substations. This Specification is part of a hierarchical structure of documentation
comprising three levels of functional specifications. This document is a Level 2 Specification.
1
SCOPE
This Specification describes the overall functional and performance requirements for protection systems, outlines
the common systems required, and the extent to which they should be applied to transmission plant and apparatus
for typical substation configurations.
It applies to all the 400 kV, 275 kV and 132 kV transmission networks owned by NGC, which includes transformer
low voltage (LV) connections, transformer tertiary connections and associated plant and apparatus.
Detailed requirements relating to the individual protection and associated systems are specified in the NGTS Level 3
documents.
2
REFERENCES
This Specification makes reference to, or should be read in conjunction with, the following documents.
2.1
IEC, CENELEC or BS Standards
IEC 56
High Voltage Alternating-current Circuit-breakers
IEC 68-2-1
Basic Environmental Test Procedures - Tests - Cold
IEC 68-2-2
Basic Environmental Test Procedures - Tests - Heat
IEC 68-2-3
Basic Environmental Test Procedures - Tests - Damp Heat, Steady State
IEC 68-2-30
Basic Environmental Test Procedures - Tests - Damp Heat, Cyclic
IEC 255-0-20
Contact Performance of Electrical Relays
IEC 255-1-00
All-or-nothing Electrical Relays
IEC 255-5
Insulation Tests for Electrical Relays
IEC 255-6
Measuring Relays and Protection Equipment
IEC 255-11
Interruptions to and Alternating Components (Ripple) in D.C. Auxiliary Energising
Quantity of Measuring Relays
IEC 255-21-1
Vibration Tests (Sinusoidal)
IEC 255-21-2
Shock and Bump Tests
IEC 391
Marking of Insulated Conductors
IEC 529
Classification of Degrees of Protection Provided by Enclosures
Uncontrolled
when Printed NGTS 2.6
Issue 3
November 1998
Page 2
2.2
NGC Technical Specifications
NGTS 1
Overview - National Grid System
NGTS 2.1
Substations
NGTS 2.2
Switchgear for the National Grid System
NGTS 2.3
Transformers and Reactors for use on 132 kV, 275 kV and 400 kV Systems
NGTS 2.7
Specification for Substation Control Systems
NGTS 2.12
Substation Auxiliary Supplies
NGTS 2.13
Electronic Equipment
NGTS 2.15
Automatic Switching Requirements
NGTS 2.19
Ancillary Light Current Equipment
NGTS 2.23
Substation Information Bus
NGTS 3.2.1
Circuit Breakers and Switches
NGTS 3.2.4
Current Transformers for Protection and General Use on the 132 kV, 275 kV and 400 kV
Systems
NGTS 3.2.5
Voltage Transformers for use on the 132 kV, 275 kV and 400 kV Systems
NGTS 3.2.6
Current and Voltage Measurement Transformers for Settlement Metering of the 33 kV, 66 kV,
132 kV, 275 kV and 400 kV Systems
NGTS 3.2.8
Line Traps for use on 275 kV and 400 kV Systems
NGTS 3.6.1
Unit Feeder Main Protection
NGTS 3.6.2
Protection for Auto-transformers
NGTS 3.6.3
Busbar Protection for 400 kV and 275 kV Double Busbar Switching Stations
NGTS 3.6.4
Non-unit Protection for Feeders
NGTS 3.6.5
Intertripping and Protection Signalling Systems
NGTS 3.6.6
Protection for Static VAR Compensators
NGTS 3.6.7
Back-up Protection
NGTS 3.6.8
Circuit-breaker Fail Protection
NGTS 3.6.9
Cross site Communication Links for Teleprotection
NGTS 3.6.10
Power Line Carrier Coupling Equipment
NGTS 3.6.11
Communications for Teleprotection
NGTS 3.6.12
Fault Recorders
NGTS 3.6.13
Circuit-breaker Trip Circuit Supervision Systems
NGTS 3.6.14
Copperwork Protection
NGTS 3.6.15
Trip Relays and Trip Relay Resetting
NGTS 3.6.16
Protection for Double-wound Transformers
NGTS 3.6.17
Protection for Quadrature Boosters
NGTS 3.6.18
Protection for Shunt Reactors
NGTS 3.6.19
Protection for Series Reactors
NGTS 3.6.20
Protection for Bus Sections and Bus Couplers
NGTS 3.6.21
Protection for 132 kV Mechanically Switched Capacitors
NGTS 3.6.22
Protection for Transformer Tertiary or LV Connections to Static Compensation Equipment
NGTS 3.6.23
Protection for 400 kV and 275 kV Mechanically Switched Capacitors
NGTS 3.12.1
48 V D.C. Supplies
NGTS 3.12.2
110 V D.C. Supplies
NGTS 3.12.3
Substation LVAC Supplies
NGTS 3.15.1
DAR and Plant Isolation
Uncontrolled
when Printed NGTS 2.6
Issue 3
November 1998
Page 3
3
GENERAL REQUIREMENTS
3.1
General
3.1.1
Protection Philosophy
In order to achieve the necessary performance requirements at 400 kV and 275 kV, protection of the network shall
follow the philosophy whereby no single failure of protection and its associated systems shall permit a fault to remain
connected to the primary system. In this context failure shall mean failure to operate, or failure to operate within a
specified maximum operating time, or in a time whereby other protection, which should not normally have operated,
has sufficient time to perform a correct back-up function.
To implement this philosophy, it is necessary to ensure that all faults are detected by at least two independent high
speed protection systems (referred to as main protections), the outputs of which are selectively allocated to
independent tripping systems with separate D.C. supplies. In addition, these protection systems shall preferably
operate on different principles and be of different hardware platforms.
To cater for failure of both main protections, back-up protection independent of main protection shall be provided. In
addition circuit-breaker fail protection shall be provided to cater for failure of circuit-breakers and associated tripping
circuits.
At 132 kV, a single high speed protection system (referred to as main protection) is required unless otherwise
specified by NGC. In addition, back-up protection independent of main protection shall be provided.
3.1.2
Protection Discrimination
When a system fault occurs, main protection equipment is required to detect the fault rapidly and initiate the opening
of only those circuit-breakers which are necessary to disconnect the faulted apparatus from the network. Protection
equipment associated with adjacent apparatus may detect the fault, but must be able to discriminate between an
external fault and a fault occurring on the specific apparatus which it is designed to protect.
3.1.3
Protection Sensitivity
Unless otherwise specified in the contract, settings to be applied to protection systems shall be specified by the
Contractor and the calculations shall be submitted to NGC for assessment and agreement. The settings for feeder
main protection shall be such as to permit correct operation of the protection for earth faults with a fault resistance
up to 100 ? . Any limitation imposed by the protection eq