## Contents

The book then provides detailed analysis on the application of protection relays and automation solutions within electrical applications.
In this edition we have introduced new concepts to encompass distributed generation, arc protection, design for safety and the impacts of IEC 61850 standards in electrical solutions.

## A1

#### Fundamentals of Protection Practice

Introduction, Protection equipment, Zones of protection, Reliability, Selectivity, Stability, Speed, Sensitivity, Primary and back-up protection, Output devices, Tripping circuits, Trip circuit supervision, Deterioration in service, Protection performance, Testing, Time grading, Unit systems, Contact systems, Operation indicators, Series sealing, Shunt reinforcing, Shunt reinforcement with sealing

## A2

#### Fundamental Theory

Vector algebra, Vector OP, Manipulation of complex quantities, Circuit quantities and conventions, Impedance notation, Basic circuit laws, theorems and network reduction, Complex variables, Complex numbers, Mathematical operators, Circuit variables, Sign conventions, Power, Single-phase and polyphase systems, Circuit laws, Circuit theorems, Junction law, Branch law, Mesh law, Superposition theorem, Thévenin’s theorem, Kennelly’s star/delta theorem, Network reduction

## A3

#### Fault Calculations

Fault Calculations, Three phase fault calculations, Symmetrical component analysis of a three-phase network, Equations and network connections for various types of faults, Current and voltage distribution in a system due to a fault, Effect of system earthing on zero sequence quantities, Reduction of typical power system network, Positive sequence network, Negative sequence network, Zero sequence network, Single-phase-earth fault (A-E), Three-phase fault (A-B-C or A-B-C-E), Single-phase open circuit fault, Cross-country faults, Current distribution, Voltage distribution, Residual current and voltage, Solid fault-isolated neutral, Variation of residual quantities, Solid fault-resistance neutral

## A4

#### Equivalent Circuits and Parameters of Power System Plant

Equivalent Circuits and Parameters of Power System Plant, Synchronous machines, Armature reaction, Steady state theory, Salient pole rotor, Transient analysis, Asymmetry, Machine reactances, Negative sequence reactance, Zero sequence reactance, Direct and quadrature axis values, Effect of saturation on machine reactances, Transformers, Transformer positive sequence equivalent circuits, Transformer zero sequence equivalent circuits, Auto-transformers, Transformer impedances, Overhead lines and cables, Calculation of series impedance, Calculation of shunt impedance, Overhead line circuits with or without earth wires, OHL equivalent circuits, Cable circuits, Overhead line and cable data, Three-winding transformers, Positive sequence equivalent circuit, Zero sequence equivalent circuit

## B1

#### Relay Technology

relay Technology, Electromechanical relays, Static relays, Digital relays, Numerical relays, Additional features of numerical relays, Numerical relay issues, Numerical distance relay features, Hardware architecture, Application software, Relay software, VT/CT supervision, Measured values display, CB control/state indication/condition monitoring, Disturbance recorder, Time synchronisation, Programmable logic, Provision of setting groups, Relay data management, Relay testing and commissioning, Software version control

## B2

#### Current and Voltage Transformers

Current and Voltage Transformers, Electromagnetic voltage transformers, Capacitor voltage transformers, Current transformers, Novel instrument transformers, Measuring transformers, Errors, Secondary leads, Protection of voltage transformers, Residually connected voltage transformers, Construction, Cascade voltage transformers, Transient performance, Voltage protection of auxiliary capacitor, Transient behaviour of capacitor voltage transformers, Ferro-resonance, Accuracy limit current of protection current transformers, Composite error, Class PX current transformers, Wound primary type, Bushing or bar primary type, Core-balance current transformers, CT winding arrangements, Summation current transformers, Air-gapped current transformers, Line current CTs, Overdimensioned CTs, Anti-remanence CTs, Linear current transformers, Secondary winding impedance, Secondary current rating, Rated short-time current, Transient response of a current transformer, Practical conditions, Harmonics during the transient period, Test windings, Optical instrument transducers, Optical sensor concepts, Hybrid transducers, Zero-flux (Hall Effect) current transformer, Other sensing systems, Rogowski coils, Hybrid magnetic-optical sensor

## B3

#### Industrial and Commercial Power System Protection

Industrial and Commercial Power System Protection, Busbar arrangement, Discrimination, HRC fuses, Industrial circuit breakers, Protection relays, Co-ordination problems, Fault current contribution from induction motors, Automatic changeover systems, Voltage and phase reversal protection, Power factor correction and protection of capacitors, Examples, Fuse characteristics, Discrimination between fuses, Effect of ambient temperature, Protection of motors, Miniature Circuit Breakers (MCBs), Moulded Case Circuit Breakers (MCCBs), Air Circuit Breakers (ACBs), Vacuum Circuit Breakers (VCBs), Oil Circuit Breakers (OCBs), SF6 circuit breakers, Improved safety, Earth fault protection with residually-connected CTs, Use of 3-pole CBs, Four-wire dual-fed substations, Use of single earth electrode, Capacitor control, Capacitor protection, Motor power factor correction, Fuse co-ordination, Grading of fuses/MCCBs/overcurrent relays, Relay characteristic and time multiplier selection, Protection of a dual-fed substation, General considerations, Relay B settings, Motor protection relay settings, Comments on grading, Relays C settings

## C1

#### Overcurrent Protection for Phase and Earthfaults

Overcurrent Protection for Phase and Earthfaults, Co-ordination procedure, Principles of time/current grading, Standard I.D.M.T. overcurrent relays, Combined I.D.M.T. and high set instantaneous overcurrent relays, Very inverse (VI) overcurrent relays, Extremely inverse (EI) overcurrent relays, Other relay characteristics, Independent (definite) time overcurrent relays, Relay current setting, Relay time grading margin, Recommended grading margins, Calculation of phase fault overcurrent relay settings, Directional phase fault overcurrent relays, Ring mains, Earthfault protection, Directional earthfault overcurrent protection, Earthfault protection on insulated networks, Earthfault protection on Petersen Coil earthed networks, Examples of time and current grading, Discrimination by time, Discrimination by current, Discrimination by both time and current, Transient overreach, Relay timing error, Overshoot, CT errors, Circuit breaker interrupting time, Final margin, Overall accuracy, Grading: Fuse to fuse, Grading: Fuse to relay, Inverse time relays, Independent (definite) time relays, Relay connections, 90° Relay quadrature connection, 90°-30° characteristic (30° RCA), 90°-45° characteristic (45° RCA), Application of directional relays, Grading of ring mains, Effective setting of earthfault relays, Static, digital and numerical relays, Electromechanical relays, Sensitive earthfault protection, Relay connections, Residual voltage, Negative sequence current, Sensitive earthfault, Residual voltage, Sensitive earthfault protection, Sensitive wattmetric protection, Relay phase fault setting example, CT ratio selection, Relay overcurrent settings – Relays 1/2, Relay earthfault settings, Grading of a ring main

## C2

#### Line Differential Protection

Line Differential Protection, Convention of direction, Conditions for direction comparison, Circulating current system, Balanced voltage system, Summation arrangements, Examples of electromechanical and static unit protection systems, Digital / numerical current differential protection systems, Carrier unit protection schemes, Current differential scheme – analogue techniques, Phase comparison protection scheme considerations, Examples, Transient instability, Bias, Stability Limit of the Voltage Balance System, Balanced voltage electromechanical system, Static circulating current unit protection system, Time synchronisation of relays, Application to mesh corner and 1 1/2 breaker switched substations, Lines with shunt capacitance, System tripping angles, Effect of load current, Modulating quantity, Fault detection and starting, Normally quiescent power line carrier, Scheme without capacitive current compensation, Fault detector operating quantities, Scheme with capacitive current compensation (blocking mode), Unit protection of a plain feeder, Unit protection of a transformer feeder

## C3

#### Distance Protection

Distance Protection, Principles of distance relays, Relay performance, Relationship between relay voltage and ZS / ZL ratio, Voltage limit for accurate reach point measurement, Zones of protection, Distance relay characteristics, Distance relay implementation, Effect of source impedance and earthing methods, Distance relay application problems, Other distance relay features, Distance relay application example, Electromechanical/static distance relays, Digital/numerical distance relays, Zone setting, Amplitude and phase comparison, Plain impedance characteristic, Offset mho/lenticular characteristics, Third zone and busbar back-up zone, Carrier starting unit in distance schemes with carrier blocking, Application of lenticular characteristic, Fully cross-polarised mho characteristic, Partially cross-polarised mho characteristic, Quadrilateral characteristic, Protection against power swings, Other characteristics, Starters for switched distance protection, Phase fault impedance measurement, Earth fault impedance measurement, Minimum voltage at relay terminals, Minimum length of line, Under-reach - Effect of remote infeed, Forward reach limitations, Voltage transformer supervision, Power swing blocking, Line impedance, Zone reach, Zone time delay settings, Earth fault impedance reach settings, Earth fault resistive reach settings, Phase fault resistive reach settings

## C4

#### Distance Protection Schemes

Distance Protection Schemes, Zone 1 extension scheme, Transfer trip schemes, Blocking over-reaching schemes, Directional comparison unblocking scheme, Comparison of transfer trip and blocking relaying schemes, Direct under-reach transfer tripping scheme, Permissive under-reach transfer tripping (PUP) scheme, Permissive under-reaching acceleration scheme, Permissive over-reach transfer tripping (POP) scheme, Weak infeed conditions, Blocking over-reaching protection scheme using zone 2 element, Practical blocking schemes, Blocking over-reaching protection scheme using zone 1 element, Weak infeed conditions

## C5

#### Protection of Complex Transmission Circuits

Protection of Complex Transmission Circuits, Parallel feeders, Multi-ended feeders – unit protection, Multi-ended feeders – distance protection, Multi-ended feeders - application of distance protection schemes, Protection of series compensated lines, Examples, Unit protection systems, Current reversal on double circuit lines, Distance protection, Under-reach on parallel lines, Behaviour of distance relays with earth faults on the protected feeder, Distance relay behaviour with earth faults on the parallel feeder, Distance relay behaviour with single-circuit operation, A.C. pilot wire protection, Dual pilot schemes, ‘Translay’ balanced voltage protection, Power line carrier phase comparison schemes, Differential relay using optical fibre signalling, Current differential protection for tee’d feeders using optical fibre signalling, Apparent impedance seen by distance relays, Effect of pre-fault load, Effect of the fault current flowing outwards at one terminal, Maloperation with reverse faults, Blocking schemes, Signalling channel considerations, Transfer trip under-reach schemes, Directional comparison blocking schemes, Transfer trip over-reach schemes, Distance relay applied to parallel circuits, Residual compensation, Phase fault resistive reach settings, Zone 3 reach, Zone time delay settings, Earth fault reach settings, Zone 1 earth fault reach, Zone 2 earth fault reach, Ground fault resistive reach settings

## C6

#### Busbar Protection

Busbar Protection, Busbar faults, Protection requirements, Types of protection system, System protection schemes, Frame-earth protection (Howard protection), Differential protection principles, High impedance differential protection, Low impedance biased differential protection, Numerical busbar protection, Speed, Stability, Single-busbar frame-earth protection, Frame-earth protection - sectioned busbars, Frame-earth protection - check system, Frame-earth scheme - double bus substation, Differential protection for sectionalised and duplicate busbars, Location of current transformers, CT location for mesh-connected substations, Supervision of CT secondary circuits, Check feature, Arrangement of CT connections, Summary of practical details, Designed stability level, Current transformers, Setting voltage, Knee-point voltage of current transformers, Effective setting (secondary), Current transformer secondary rating, Peak voltage developed by current transformers, High impedance relay, Effective setting or primary operating current, Check feature, Supervision of CT secondary circuits, Arrangement of CT connections, Static low impedance biased differential protection, Bias, Stability with saturated current transformers, Operation for internal faults, Discrepancy alarm feature, Transfer tripping for breaker failure, Master/follower measuring units, Reliability considerations

## C7

#### Transformer and Transformer-Feeder Protection

Transformer and Transformer-Feeder Protection, Winding faults, Magnetising inrush, Transformer overheating, Transformer protection – overview, Transformer overcurrent protection, Restricted earth fault protection, Differential protection, Differential protection stabilisation during magnetising inrush conditions, Combined differential and restricted earth fault schemes, Earthing transformer protection, Auto-transformer protection, Overfluxing protection, Tank-earth protection, Oil and gas devices, Transformer-feeder protection, Intertripping, Condition monitoring of transformers, Examples of transformer protection, Star-connected winding with neutral point earthed through an impedance, Star-connected winding with neutral point solidly earthed, Delta-connected winding, Phase to phase faults, Interturn faults, Overload, System faults, Core faults, Overvoltages, Tank faults, Externally applied conditions, Harmonic content of inrush waveform, Fuses, Overcurrent relays, Line current transformer primary ratings, Filtering of zero sequence currents, Ratio correction, Phase correction, Bias setting, Transformers with multiple windings, Time delay, Inrush detection blocking – Gap detection technique, Harmonic restraint, Application when an earthing transformer is connected within the protected zone, Oil Pressure relief devices, Rapid pressure rise relay, Buchholz protection, Non-unit schemes, Feeder phase and earth faults, Feeder phase faults, Earth faults, Unit schemes, In-zone capacitance, Neutral displacement, Provision of zero-sequence filtering, Unit protection of a delta-star transformer, Ratio compensation, Restricted earth fault protection, Determine differential current at tap extremities

## C8

#### Generator and Generator-Transformer Protection

Generator and Generator-Transformer Protection, Generator earthing, Generator differential protection, Differential protection of generator-transformers, Inter-turn protection, Overcurrent protection, Stator earthfault protection, Stator earthfault protection for entire stator winding, Overvoltage protection, Undervoltage protection, Low forward power/reverse power protection, Unbalanced loading, Protection against inadvertent energisation, Under/overfrequency/overfluxing protection, Rotor faults, Loss of excitation protection, Pole slipping protection, Stator overheating faults, Complete generator protection schemes, Distributed generation, Examples of generator protection settings, Ungrounded:, Resonant ground with a ground fault neutraliser:, High resistance ground with a distribution transformer, Biased differential protection, High impedance differential protection, CT requirements, Generator/step-up transformer differential protection, Unit transformer differential protection, Inter-turn protection, Incomplete longitudinal current differential protection, Transverse zero sequence current differential protection, Longitudinal zero sequence overvoltage protection, Plain overcurrent protection, Voltage-dependent overcurrent protection, Voltage controlled overcurrent protection, Voltage restrained overcurrent protection, Direct-connected generators, Neutral overcurrent protection, Sensitive earthfault protection, Neutral voltage displacement protection, High resistance earthing – neutral overcurrent protection, Distribution transformer earthing using a voltage element, Neutral voltage displacement protection, Restricted earthfault protection, Low-impedance biased REF protection, High impedance REF protection, Protection based on third harmonic voltage, Protection based on low frequency injection, Low forward power protection, Effect of negative sequence current, Negative phase sequence protection, Overfluxing, Under/overfrequency, Rotor earthfault protection, Potentiometer method, Injection methods, Rotor shorted turn protection, Rotor earthfault protection for brushless generators, Protection against loss of excitation, Small generators, Large generators (>5 MVA), Impedance-based protection characteristics, Protection settings, Protection using reverse power element, Protection using an under impedance element, Dedicated pole-slipping protection, Pole slipping protection by impedance measurement, Use of lenticular characteristic, Direct-connected generator, Generator-transformer units, Generator types, Protection aspects, Low fault currents, Tapped lines, Active power dependent underfrequency load shedding, Reactive power dependent undervoltage Q-V protection, Islanding detection, Rate of change of frequency relay, Setting guidelines, Voltage vector shift relay, Protection settings of a small industrial generator, Differential protection, Voltage controlled overcurrent protection, Stator earthfault protection, Neutral voltage displacement protection, Negative phase sequence current protection, Overvoltage protection, Loss of excitation protection, Underfrequency protection, Reverse power protection, Large generator transformer unit protection, Biased differential protection, Inadvertent energisation protection, Negative phase sequence protection, Voltage restrained overcurrent protection, Overfluxing protection, Reverse power protection, 100% Stator earthfault protection, Reverse power protection, Over/underfrequency protection, Overvoltage protection, Loss of excitation protection, Pole slipping protection

## C9

#### A.C. Motor Protection

A.C. Motor Protection, Modern relay design, Thermal (overload) protection, Start/Stall protection, Short circuit protection, Earth fault protection, Negative phase sequence protection, Wound rotor induction motor protection, RTD temperature detection, Bearing failures, Undervoltage protection, Loss-of-load protection, Anti-backspin function, Additional protection for synchronous motors, Motor protection examples, Start time safe stall time, Re-acceleration, Stall protection, Number of starts limitation, Motor differential protection, Self balance differential protection, Solidly-earthed system, Resistance-earthed systems, Low resistance earthing, High resistance earthing, Insulated earth system, Petersen coil earthed system, Out-of-step protection, Protection against sudden restoration of supply, Underfrequency protection, Low-forward-power protection, Protection of a HV motor, Thermal protection, Short circuit protection, Earth fault protection, Locked rotor/excessive start time protection, Stall protection, Negative phase sequence protection, Other protection considerations, Protection of an LV motor, CT ratio, Overcurrent (short-circuit) protection, Thermal (overload) protection, Negative sequence (phase unbalance) protection, Loss of phase protection

## C10

#### A.C. Railway Protection

A.C. Railway Protection, Protection philosophy, Classical single-phase feeding, Catenary thermal protection, Catenary backup protection, Auto-transformer feeding, Feeder substation protection, Delta function, Example of classical system protection, Feeding diagram, Protection philosophy, Reverse reaching zones, Distance zone time delay settings, Load avoidance, Impact of trains with regenerative braking, Enhanced modern relay characteristics, Other relay characteristics, Definite-time overcurrent protection (DTOC), Back-up overcurrent protection (BUOC), Description of auto-transformer feeding, Auto-transformer system protection philosophy, Distance protection zone reaches, Backup protection, Section impedance data, Calculation of fault current, Zone time delays, Overcurrent protection, Back-up overcurrent (BUOC) at feeder stations, Overcurrent setting for BUOC instantaneous stage, Overcurrent setting for BUOC definite-time delayed stage, Mechanical damage protection, Definite time overcurrent (DTOC), Dewirement protection, Maximum ambient temperature, Default ambient temperature, Thermal protection, Thermal reference current/ temperature, Thermal time constants, Summary of catenary protection settings

## C11

#### Arc Protection

Arc Protection, Arc flash phenomenon, Causes of arc faults in switchgear, Impacts and consequences of arc faults, Arc protection related standards, Arc protection and mitigation methods, The principle of arc protection based on simultaneous detection of light and overcurrent, How to avoid nuisance tripping caused by switching arcs, Arc protection systems, Elimination of the arc fault, Typical application examples, Fast optical detection of light, Stand-alone arc protection systems, Arc protection integrated in numerical protection relays, Dedicated arc protection systems, The importance of the arc elimination time, Circuit breakers, Current-limiting fuses, Short-circuit devices (arc eliminators)

## D1

#### Auto-Reclosing

Auto-Reclosing, Application of auto-reclosing, Auto-reclosing on HV distribution networks, Factors influencing HV auto-reclose schemes, Auto-reclosing on EHV transmission lines, High speed auto-reclosing on EHV systems, Single-phase auto-reclosing, High speed auto-reclosing on lines employing distance schemes, Delayed auto-reclosing on EHV systems, Operating features of auto-reclose schemes, Auto-close circuits, Examples of auto-reclose applications, Dead Time, System stability and synchronism, Type of load, Circuit breaker characteristics, Protection reset time, Reclaim time, Type of protection, De-ionisation of fault path, Number of Shots, Circuit breaker limitations, System conditions, Energy recovery time, Protection characteristics, De-Ionisation of fault arc, Air blast circuit breakers, Circuit breaker characteristics, SF6 circuit breakers, Choice of dead time, Choice of reclaim time, Number of shots, Transfer-trip or blocking schemes, Scheme operation, Synchronism check relays, Initiation, Type of protection, Anti-pumping devices, Reclaim timer, CB lockout, Manual closing, Reclosing impulse, Multi-shot schemes, Standby transformers, Bus coupler or bus section breaker, Double busbar substation, Basic scheme – banked transformers omitted, Scheme with banked transformers, Four-switch mesh substation, Single switch substation, Transient fault, Persistent fault, Transient mesh corner fault, Transformer fault, Persistent mesh corner fault

## D2

#### Signalling and Intertripping in Protection Schemes

Signalling and Intertripping in Protection Schemes, Unit protection schemes, Teleprotection commands, Intertripping, Performance requirements, Transmission media, interference and noise, Signalling methods, Direct tripping, Blocking scheme, Permissive tripping, Performance requirements - Intertripping, Performance requirements - Permissive tripping, Performance requirements - Blocking schemes, Private pilot wires and channels, Rented pilot wires and channels, Power line carrier communications techniques, Radio channels, Optical fibre channels, D.C. voltage signalling, Plain tone signals, Frequency shift keyed signals

## D3

#### IEC 61850 and Applications

IEC 61850 and Applications, What is IEC 61850?, Why choose IEC 61850?, History of IEC 61850, Evolution of IEC 61850, General philosophy, Global approach, Parts of the standard, Abstract service interface, Data modelling, Engineering process, Documentation, Interoperability vs. interchangeability, Advantages vs. conventional hard-wiring, Communication services, General communication architecture, Client-server communication, GOOSE communication, Sampled values, Time synchronisation, Typical applications, Applications with client-server communication, Applications with GOOSE communication

## D4

Frequency and Load Shedding, Frequency protection, Load shedding, Load restoration, Turbine abnormal, Underfrequency 81U, ROCOF 81R, Overfrequency 81O, Supervised ROCOF 81RF, Average ROCOF 81RAV, Frequency-based theory, Frequency-based, Fast load shedding, Active power dependent, Undervoltage-based, Tripping, Computation, Automatic restoration

## E1

#### Type Testing, Offer Safety and Reliability

Type Testing, Offer Safety and Reliability, Functional tests, Electrical type tests, Electromagnetic compatibility tests, Product safety type tests, Environmental type tests, Software type tests, Dynamic validation tests, Production tests, Reference standards, Routine factory production tests, Commissioning tests, Periodic maintenance checks, Type tests, Type test reports, Accredited laboratories, Accreditation, Accredited type test reports, IEC 61850 communication testing, IEC 61850 accreditation and recognition, IEC 61850 certificate and report accredited, Rating tests, Relay burden, Relay inputs, Relay output contacts, Auxiliary supplies, d.c. and a.c. voltage dip and short interruption, Gradual shut-down/start-up for a.c. & d.c. power supply, Slow & fast damped oscillatory wave, a.c. ripple on d.c. supply, Fast transient, Power frequency interference, Electrostatic discharge (ESD), Surge immunity, Conducted emissions test plot, Radiated, radio-frequency, electromagnetic field immunity, Conducted disturbance induced by RF - immunity tests, Power frequency magnetic field, Thermal withstand, Dielectric voltage withstand, Insulation resistance, Single fault condition assessment, Earth bonding impedance, Insulation withstand for over-voltages, CE marking, Humidity test, Cyclic temperature/humidity test, Temperature test, Fast cyclic temperature, Enclosure protection test, Mechanical tests, Unit testing environment, Software/software integration testing, Software/hardware integration testing, Verification testing, Static unit testing, Dynamic unit testing, Validation testing, Traceability of verification and validation tests, Software modifications - Regression testing, Use of microprocessor based simulation equipment, Use of power system analogue models, Simulation hardware, Simulation software, Simulator applications

## E2

#### Relay Commissioning

Commissioning tests, Insulation tests, Relay self-test procedure, Current transformer tests, Polarity check, Magnetisation curve, Voltage transformer tests, Polarity check, Ratio check, Phasing check, Protection relay setting checks, Test blocks/plugs for secondary injection equipment, Secondary injection test, Schemes using digital or numerical relay technology, Schemes using electromechanical / static relay technology, Primary injection testing, Test facilities, CT polarity check, CT ratio check, Primary injection testing of relay elements, Testing of protection scheme logic, Tripping and alarm annunciation tests, Periodic maintenance tests, Frequency of inspection and testing

## AX1

#### Terminology

Terminology, glossary, Protection Engineer phrases, Protection and Control terms

## AX2

#### ANSI & IEC Function References

ANSI & IEC Function References, IEC 61850, ANSI Standard C37-2, IEC 60617, IEC LN, IEC equivalents

Index