Protective Relay Principles

335 Pages·2009·6.41 MB·English

by  Anthony F. Sleva

P r o t e c t i v e
R e l a y
P r i n c i p l e s
© 2009 by Taylor & Francis Group, LLC
P r o t e c t i v e
R e l a y
P r i n c i p l e s
Anthony F. Sleva
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
© 2009 by Taylor & Francis Group, LLC
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© 2009 by Taylor & Francis Group, LLC
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Library of Congress Cataloging-in-Publication Data
Sleva, Anthony F.
Protective relay principles / Anthony F. Sleva.
p. cm.
Includes bibliographical references and index.
ISBN 978-0-8247-5372-6 (alk. paper)
1. Protective relays. I. Title.
TK2861.S49 2009
621.31’7--dc22 2008040966
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© 2009 by Taylor & Francis Group, LLC
Contents
Preface ..............................................................................................................xiii
Author ................................................................................................................xv
Acknowledgments ........................................................................................xvii
1. Power System Components .....................................................................1
1.1 Transmission Lines ..........................................................................1
1.2 Distribution Lines ............................................................................5
1.3 Transformers ...................................................................................10
1.4 Circuit Breakers ..............................................................................15
1.5 Buses ................................................................................................16
1.6 Switchyards .....................................................................................18
1.7 Fuses.................................................................................................19
1.8 Substations ......................................................................................22
1.9 Reclosers ..........................................................................................23
1.10 Generators .......................................................................................24
2. Power System Subcomponents .............................................................27
2.1 Current Transformers ....................................................................27
2.2 Voltage Transformers .....................................................................31
2.3 Capacitive Coupled Voltage Transformers .................................32
2.4 Protective Relays ............................................................................34
2.5 Control Relays.................................................................................34
2.6 Master Trip Relays .........................................................................35
2.7 Programmable Logic Controllers ................................................35
2.8 Insulators .........................................................................................35
2.9 Bushings ..........................................................................................36
2.10 Cable Terminators ..........................................................................36
2.11 Disconnect Switches ......................................................................36
2.12 Air Break Switches .........................................................................38
2.13 Motor-Operated Air Break Switches ...........................................38
2.14 Ground Switches ............................................................................39
2.15 Surge Arrestors ...............................................................................39
2.16 Sectionalizers ..................................................................................40
2.17 Batteries ...........................................................................................40
3. Abnormal Power System Conditions ..................................................41
3.1 Short Circuits ..................................................................................41
3.1.1 Three-Phase Faults............................................................42
3.1.2 Phase-to-Phase Faults .......................................................44
3.1.3 Double Phase-to-Ground Faults .....................................44
3.1.4 Single Phase-to-Ground Faults .......................................45
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vi Contents
3.1.5 Turn-to-Turn Faults ...........................................................47
3.1.6 Winding-to-Winding Faults ............................................47
3.1.7 Winding-to-Ground Faults ..............................................47
3.1.8 Plate-to-Plate Faults ..........................................................47
3.2 Overloads ........................................................................................48
3.3 Overvoltage .....................................................................................48
3.4 Undervoltage...................................................................................49
3.5 Overfrequency ................................................................................49
3.6 Underfrequency .............................................................................50
3.7 Open Phase .....................................................................................51
3.8 Single Phasing ................................................................................51
3.9 Phase Unbalance ............................................................................52
3.10 Volts per Hertz ................................................................................54
4. Short-Circuit Calculations .....................................................................57
4.1 Symmetrical Components ............................................................57
4.2 Positive Sequence Networks .........................................................59
4.3 Negative Sequence Networks.......................................................60
4.4 Zero Sequence Networks ..............................................................60
4.5 Operators .........................................................................................61
4.6 Sequence Diagram Connections—Three-Phase Faults ............63
4.7 Sequence Diagram Connections—Phase-to-Phase Faults .......64
4.8 Sequence Diagram Connections—Single Phase-to-
Ground Faults .................................................................................65
4.9 Per-Unit Quantities ........................................................................65
4.10 Sample Calculations ......................................................................67
4.11 Sample Calculations—Three-Phase Faults .................................68
4.12 Sample Calculations—Phase-to-Phase Faults ............................69
4.13 Sample Calculations—Single Phase-to-Ground Faults ............71
4.14 Sample Calculations—Mutual Coupling ....................................74
5. Protective Relay Functions ....................................................................79
5.1 Time Overcurrent Relay (51) .........................................................80
5.2 Instantaneous Overcurrent Relay (50) ........................................82
5.3 Overvoltage Relay (59) ...................................................................83
5.4 Undervoltage Relay (27) ................................................................85
5.5 Distance Relay (21) .........................................................................86
5.6 Differential Relay (87) ....................................................................88
5.7 Directional Relay (67) ....................................................................89
5.8 Underfrequency Relay (81) ............................................................90
5.9 Overfrequency Relay (81) ..............................................................91
6. Protective Relay Functional Combinations .......................................93
6.1 Voltage-Controlled Time Overcurrent Relay .............................93
6.2 Torque-Controlled Time Overcurrent Relay ..............................94
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Contents vii
6.3 Logic-Controlled Instantaneous Overcurrent Relay ................94
6.4 Torque-Controlled Instantaneous Overcurrent Relay ..............95
6.5 Logic-Controlled Overvoltage Relay ...........................................95
6.6 Logic-Controlled Undervoltage Relay ........................................95
6.7 Logic-Controlled Distance Relay .................................................96
6.8 Current-Supervised Distance Relay ............................................96
6.9 Logic-Supervised Differential Relay ...........................................96
6.10 Current-Supervised Differential Relay .......................................97
6.11 Current-Supervised Underfrequency Relay ..............................97
6.12 Dual Underfrequency Relays .......................................................97
7. Zones and Regions of Protection .........................................................99
7.1 Zones of Protection ........................................................................99
7.1.1 Relay Characteristics and Applied Setpoint ...............101
7.1.1.1 Overcurrent Relays .........................................101
7.1.1.2 Distance Relays ................................................102
7.1.1.3 Differential Relays ...........................................103
7.1.2 Instrument Transformer Location, Connection,
Polarity, and Ratio ...........................................................103
7.1.2.1 Overcurrent Relays .........................................103
7.1.2.2 Distance Relays ................................................104
7.1.2.3 Differential Relays ...........................................104
7.1.3 Control Scheme Logic ....................................................105
7.1.4 Power System Configuration .........................................105
7.2 Regions of Protection ....................................................................111
7.2.1 Relay Characteristics and Applied Setpoint ................113
7.2.1.1 Overvoltage Relays...........................................113
7.2.1.2 Undervoltage Relays ........................................115
7.2.1.3 Underfrequency Relays ...................................115
7.2.1.4 Overfrequency Relays .....................................116
7.2.1.5 Unbalanced Voltage Relays .............................117
7.2.2 Instrument Transformer Location, Connection,
Polarity, and Ratio ............................................................117
7.2.2.1 Overvoltage Relays...........................................117
7.2.2.2 Undervoltage Relays ........................................117
7.2.2.3 Underfrequency Relays ...................................117
7.2.2.4 Overfrequency Relays .....................................117
7.2.2.5 Unbalanced Voltage Relays .............................118
7.2.3 Control Scheme Logic .....................................................118
7.2.4 Power System Configuration ..........................................118
8. Physical Characteristics of Protective Relays ..................................123
8.1 Electromechanical Relays ...........................................................123
8.2 Solid-State Relays .........................................................................125
8.3 Microprocessor-Based Relays .....................................................126
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viii Contents
8.4 Relay Operation ............................................................................126
8.5 Relay Packaging ...........................................................................127
9. Setting Considerations .........................................................................131
9.1 Power System Configuration and Operation ...........................131
9.1.1 Mutual Coupling .............................................................133
9.1.2 Ground Bank Action ......................................................135
9.2 Power System Requirements ......................................................140
9.3 Maximum Short-Circuit Current—Fault in Protected
Zone ................................................................................................141
9.4 Maximum Relay Short-Circuit Current—Fault in
Adjacent Zone ...............................................................................142
9.5 Minimum Relay Short-Circuit Current—Fault in
Protected Zone..............................................................................142
9.6 Fault Current Ratio ......................................................................143
9.7 Relay Sensitivity ...........................................................................145
9.8 Circuit Loading ............................................................................146
9.9 Relay Coordination ......................................................................151
9.10 Directionality ................................................................................152
9.11 Accuracy of Calculations ............................................................153
9.12 Device Accuracy ...........................................................................154
9.13 Circuit-Breaker Operating Times ..............................................155
9.14 Transient Overreach ....................................................................155
9.15 Cold Load Inrush .........................................................................157
9.16 Redundancy ..................................................................................159
9.17 Relay Drift .....................................................................................159
9.18 Security ..........................................................................................160
9.19 Arc Flash Hazard .........................................................................160
9.20 Circuit Breaker-Failure Detection and Isolation.......................161
9.21 Free-Standing CT Flashover Detection ......................................162
9.22 Switchable Settings .......................................................................162
9.23 Recovery Voltage Inrush ..............................................................162
10. Protection and Control Schemes ........................................................163
10.1 Alternative Protective Relay Trip Logic ....................................171
10.2 Supervised Protective Relay Logic ............................................173
11. Protective Relay Coordination ............................................................175
11.1 Instantaneous Current Relays ....................................................175
11.2 Time Overcurrent Relays .............................................................176
11.2.1 Maximum Current Flow with Normal Fault
Clearing .............................................................................176
11.2.2 Maximum Current Flow When a Remote Circuit
Breaker Fails to Open .....................................................177
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Contents ix
11.2.3 Maximum Ratio of Through Current for
Restricted Faults on Each Remote Line .......................177
11.2.4 Maximum Ratio of Through Current for
Restricted Faults on Each Remote Line and
Remote Circuit Breaker Fails to Open .........................178
11.3 Instantaneous Voltage Relays .....................................................178
11.4 Time-Delayed Voltage Relays .....................................................179
11.5 Instantaneous (Zone 1) Impedance Relays ...............................179
11.6 Time-Delayed (Zone 2 or Zone 3) Impedance Relays .............180
11.7 Instantaneous Frequency Relays ...............................................180
11.8 Time-Delayed Frequency Relays ...............................................181
12. Distribution-Line Protection: Radial Lines .....................................183
12.1 Distribution-Line Protection Philosophy .................................184
12.1.1 Time Overcurrent Phase Relays ...................................185
12.1.2 Instantaneous Overcurrent Phase Relays ...................185
12.1.3 Time Overcurrent Ground Relays ................................185
12.1.4 Instantaneous Overcurrent Ground Relays ................186
12.2 Setpoint Margin Considerations ................................................186
12.3 Distribution-Line Protection ......................................................188
12.4 Time Overcurrent Phase Relay Pickup Setting—Load
Capability ......................................................................................191
12.5 Time Overcurrent Ground Relay Pickup Setting—Load
Capability ......................................................................................191
12.6 Low Set Instantaneous Overcurrent Phase Relay Pickup
Setting ............................................................................................192
12.7 Low-Set Instantaneous Overcurrent Ground Relay
Pickup Setting ..............................................................................192
12.8 High-Set Instantaneous Overcurrent Phase Relay Pickup
Setting ............................................................................................193
12.9 High-Set Instantaneous Overcurrent Ground Relay
Pickup Setting ..............................................................................196
12.10 Time Overcurrent Phase Relay Pickup Setting—
Sensitivity Check ..........................................................................197
12.11 Time Overcurrent Phase Relay Pickup Setting—Time
Delay ..............................................................................................197
12.12 Time Overcurrent Phase Relay Pickup Setting—
Upstream Coordination ..............................................................204
12.13 Time Overcurrent Ground Relay Pickup Setting—
Sensitivity Check ..........................................................................205
12.14 Time Overcurrent Ground Relay Pickup Setting—Time
Delay ..............................................................................................206
12.15 Time Overcurrent Relay Ground Pickup Setting—
Upstream Coordination ..............................................................207
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x Contents
13. Distribution-Line Protection: Network Lines .................................213
13.1 Networked Distribution-Line Protection Philosophy .............214
13.1.1 Time Overcurrent Phase Relays ....................................214
13.1.2 Definite Time Overcurrent Phase Relays ....................215
13.1.3 Instantaneous Overcurrent Phase Relays ...................215
13.1.4 Time Overcurrent Ground Relays ................................215
13.1.5 Definite Time Overcurrent Ground Relays .................215
13.1.6 Instantaneous Overcurrent Ground Relays ................215
13.2 Setpoint Margin Considerations .................................................216
13.3 Distribution-Line Protection ......................................................218
13.4 Time Overcurrent Phase Relay Pickup Setting—Load
Capability ......................................................................................218
13.5 Time Overcurrent Ground Relay Pickup Setting—Load
Capability ......................................................................................221
13.6 Instantaneous Overcurrent Phase Relay Pickup Setting .......221
13.7 Instantaneous Overcurrent Ground Relay Pickup Setting ....224
13.8 Definite Time Overcurrent Phase Relay Pickup Setting ........225
13.9 Definite Time Overcurrent Ground Relay Pickup Setting ....225
13.10 Time Overcurrent Phase Relay Pickup Setting—
Sensitivity Check ..........................................................................226
13.11 Time Overcurrent Phase Relay Pickup Setting—Time
Delay ..............................................................................................226
13.12 Time Overcurrent Phase Relay Pickup Setting—
Upstream Coordination ..............................................................227
13.13 Time Overcurrent Ground Relay Pickup Setting—
Sensitivity Check ..........................................................................229
13.14 Time Overcurrent Ground Relay Pickup Setting—Time
Delay ..............................................................................................231
13.15 Time Overcurrent Relay Ground Pickup Setting—
Upstream Coordination ..............................................................231
14. Transmission-Line Protection .............................................................235
14.1 Phase Distance Relays .................................................................236
14.2 Ground Distance Relays ..............................................................246
14.3 Overcurrent Ground Relays .......................................................247
14.4 Instantaneous Overcurrent Ground Relays .............................250
14.5 Time Overcurrent Ground Relays .............................................251
14.6 Directional Unit Sensitivity for Ground Faults .......................254
14.7 Current-Polarized Ground Relays .............................................254
14.8 Voltage-Polarized Ground Relays ..............................................255
14.9 High-Speed Relaying Schemes ..................................................255
14.9.1 Permissive Overreaching Scheme ................................256
14.9.2 Directional Comparison Blocking Scheme .................257
14.9.3 Direct Underreaching Transfer Trip Schemes ............258
14.9.4 Direct Transfer Trip Schemes ........................................259
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