Practical Power System Protection

Author(s): Leslie Hewitson, Mark Brown, Ramesh Balakrishnan
Publisher: Newnes
Date : 2005

Plant operators, electricians, field technicians and engineers will gain a practical understanding of the role and workings of power system protection systems from this work. An understanding of power systems and their optimized management will increase plant efficiency and performance as well as increasing safety levels. This book provides both the underpinning knowledge and basic calculations needed to understand, specify, use and maintain power protection systems, and the practical techniques required on a daily basis.

After studying this book you will have an excellent knowledge of the principles of protection. You will also have a better understanding of the possible problems likely to arise in day-to-day work with power protection systems.

Key areas of knowledge and expertise developed will include:

* Fundamentals of electrical power protection and applications
* Different fault types
* Perform simple fault and design calculations
* Practical knowledge of protection system components
* Apply relay settings
* Improve the safety of your site with the knowledge gained

* Increase plant efficiency, performance and safety levels by developing your understanding of power system protection
* Gain a practical knowledge of the engineering challenges of power system protection: fault types, component types, relay settings, etc.
* Coverage includes both the fundamentals and the basic fault and design calculations needed to specify, use and maintain power protection systems

Review
"...gives the reader a working knowledge to understand how many of today's protection systems operate." - IEEE Electrical Insulation Magazine, 2006

Contents

Preface

1 Need for protection
1.1 Need for protective apparatus
1.2 Basic requirements of protection
1.3 Basic components of protection
1.4 Summary

2 Faults, types and effects
2.1 The development of simple distribution systems
2.2 Fault types and their effects

3 Simple calculation of short-circuit currents
3.1 Introduction
3.2 Revision of basic formulae
3.3 Calculation of short-circuit MVA
3.4 Useful formulae
3.5 Cable information
3.6 Copper conductors

4 System earthing
4.1 Introduction
4.2 Earthing devices
4.3 Evaluation of earthing methods
4.4 Effect of electric shock on human beings

5 Fuses
5.1 Historical
5.2 Rewireable type
5.3 Cartridge type
5.4 Operating characteristics
5.5 British standard 88:1952
5.6 Energy 'let through'
5.7 Application of selection of fuses
5.8 General 'rules of thumb'
5.9 Special types
5.10 General
5.11 IS-limiter

6 Instrument transformers
6.1 Purpose
6.2 Basic theory of operation
6.3 Voltage transformers
6.4 Current transformers
6.5 Application of current transformers
6.6 Introducing relays
6.7 Inverse definite minimum time lag (IDMTL) relay

7 Circuit breakers
7.1 Introduction
7.2 Protective relay-circuit breaker combination
7.3 Purpose of circuit breakers (switchgear)
7.4 Behavior under fault conditions
7.5 Arc
7.6 Types of circuit breakers
7.7 Comparison of breaker types

8 Tripping batteries
8.1 Tripping batteries
8.2 Construction of battery chargers
8.3 Maintenance guide
8.4 Trip circuit supervision
8.5 Reasons why breakers and contactors fail to trip
8.6 Capacity storage trip units

9 Relays
9.1 Introduction
9.2 Principle of the construction and operation of the electromechanical IDMTL relay
9.3 Factors influencing choice of plug setting
9.4 The new era in protection - microprocessor vs electronic vs traditional
9.5 Universal microprocessor overcurrent relay
9.6 Technical features of a modern microprocessor relay
9.7 Type testing of static relays
9.8 The future of protection for distribution systems
9.9 The era of the IED
9.10 Substation automation
9.11 Communication capability

10 Coordination by time grading
10.1 Protection design parameters on medium- and low-voltage networks
10.2 Sensitive earth fault protection

11 Low-voltage networks
11.1 Introduction
11.2 Air circuit breakers
11.3 Moulded case circuit breakers
11.4 Application and selective coordination
11.5 Earth leakage protection

12 Mine underground distribution protection
12.1 General
12.2 Earth-leakage protection
12.3 Pilot wire monitor
12.4 Earth fault lockout
12.5 Neutral earthing resistor monitor (NERM)

13 Principles of unit protection
13.1 Protective relay systems
13.2 Main or unit protection
13.3 Back-up protection
13.4 Methods of obtaining selectivity
13.5 Differential protection
13.6 Transformer differential protection
13.7 Switchgear differential protection
13.8 Feeder pilot-wire protection
13.9 Time taken to clear faults
13.10 Recommended unit protection systems
13.11 Advantages of unit protection

14 Feeder protection cable feeders and overhead lines
14.1 Introduction
14.2 Translay
14.3 Solkor protection
14.4 Distance protection

15 Transformer protection
15.1 Winding polarity
15.2 Transformer connections
15.3 Transformer magnetizing characteristics
15.4 In-rush current
15.5 Neutral earthing
15.6 On-load tap changers
15.7 Mismatch of current transformers
15.8 Types of faults
15.9 Differential protection
15.10 Restricted earth fault
15.11 HV overcurrent
15.12 Buchholz protection
15.13 Overloading

16 Switchgear (busbar) protection
16.1 Importance of busbars
16.2 Busbar protection
16.3 The requirements for good protection
16.4 Busbar protection types

17 Motor protection relays
17.1 Introduction
17.2 Early motor protection relays
17.3 Steady-state temperature rise
17.4 Thermal time constant
17.5 Motor current during start and stall conditions
17.6 Stalling of motors
17.7 Unbalanced supply voltages
17.8 Determination of sequence currents
17.9 Derating due to unbalanced currents
17.10 Electrical faults in stator windings earth faults phase-phase faults
17.11 General
17.12 Typical protective settings for motors

18 Generator protection
18.1 Introduction
18.2 Stator earthing and earth faults
18.3 Overload protection
18.4 Overcurrent protection
18.5 Overvoltage protection
18.6 Unbalanced loading
18.7 Rotor faults
18.8 Reverse power
18.9 Loss of excitation
18.10 Loss of synchronization
18.11 Field suppression
18.12 Industrial generator protection
18.13 Numerical relays
18.14 Parallel operation with grid

19 Management of protection
19.1 Management of protection
19.2 Schedule A
19.3 Schedule B
19.4 Test sheets
Index

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