Motores

INDEX
Abnormal conditions other than short circuits,,
8
A-c tripping, 335
Angle-impedance relay, 79
for tripping on 1088 of synchronism,
362
Angle of maximum torque, adjustment,,
57
of power relays, 52, 55
of shortcircuit relays, 55
Arcs, effect on distance relays, 345 resistance,
302
Arc - furnace - transformer protection,
270
ASA accuracy classification,, of currenttransformers,, 121
of potential transformers, 133
Attenuation, carrier-current, 378
Automatic reclosing, see Reclosing,
automatic
Auxiliaries,, station, protection of, 229
see also Motor protection
Back-up relaying, defined, 6
effect of intermediate current sources,
347
for bus protection, 275, 291
generator external fault,227
reversed third zone, 175, 349
transformer external fault, 264, 268with pilot relaying, 378, 386
Blind spot in pilot relaying, 94
Blinder with directional-comparison relaying,
386, 390
Blocking pilot, 88, 91
Blocking terminal, with a-c wire-pilot relaying,
375
INDEX

with directionalcomparison pilot
relaying, 392
with phase-comparison pilot relaying,
383
Broken-delta connection, burden calculation,
140
for detecting grounds in ungroundedsystems,, 320
for polarizing directionalground relays,
151
of capacitance potential devices,
135, 140
Buchholz relay, 281
Burden, current-transformer, 114 potential
transformer, 133
Bus protection, automatic reclosing, 292 by
back-up relays, 275, 291
circuitbreaker by-psasing, 292
combined power transformer and bus, 287
current differential with overcurrent relays,
278 current differentialwith overvoltage
relays, 288 current differential with
percentage relays, 284 directional
comparison, 277 fault bus,, 275 grounding
secondaries of differentially connected CT’s,
291 partial-differential, 282 ring-bus,, 290
testing, 292 voltage differential with linear
cou, 284
Bushing potential device, see Capacitance
potential device
Capacitance potential device, broken burden,
140comparison with instrument PT’s, 144
couplingcapacitor insulation coordination,
142 effect of overloading, 138

1

Capacitance potential device, equivalent
circuit, 135 non-linear burdens, 139 standard
accuracy, 137 standard rated burdens, 136
Capacitor, series, effect on distance relaying,
367
Capacitor tripping, 335

Current-balance relay, directional type, 62 for
line protection,330 overcurrent type, 58
Current biasing, for mho relay, 82 for offset
impedance relay, 77 to avoid distance-relay
misoperation on arcs, 346
Current compensation for ground distance
relays,, 360

Carrier-current attenuation, 378
Current switching for distance relays, 368
Carrier-current-pilot relaying, see Pilot relaying,
carrier-current
Circuit breaker, by-passing, 292 standardcapacities, 3
Circulating-current pilot relaying, 92, 94
Cold-load pickup, 334
Cold-load restoration, 334
Compensated voltage, see Transformer
compensation

Current transformers,, accuracy calcula , 113
ASA accuracy classification, 121 burden, 114
for generator differential relaying, 198
ratiocorrection-factor curves,, 116 secondaryexcitation curves,, 117 grounding the
secondaries ofdifferentially connected CT’s,
291 overvoltage in secondary, 124 polarity
and connections, 126 proximity effect, 126
Current transformers, requirements for pilot
relaying, 377 secondary leakage reactance,
117, 119, 120 transient errors, 124, 278, 318
types, 113 zero-phase-sequencecurrent shunt,
- 130, 249

Constant-product characteristic, 38

Contact races in pilot relaying, 91

D-coffset, effect on induction relays, 32, 39
overreach of distance relays, 82, 350
overreach of overcurrent relays, 308 time
constant, 279

Continuous pilot, 109

D-c relays, single-quantity, 22 directional, 24, 49

Control spring, 17

Differential relays, 63 see also
Percentagedifferential relays

Contact definitions, 17

Conventions, vector, 53
Corrosion, effect of polarity on, 19...