Evaluation of protective relaying, 12 loss of excitation Expulsion protective gaps, effect of, on distance relays 1088 of synchronism,, 218 miscellaneous,, 228 External-fault back-up relaying, see Back-up motoring open circuits,, 215 over excitation,, 225 over Fail ures. electrical. see Faults False residual current. 318 Line protection with distance relays, current and voltage switching, 368 expulsion Fault bus. 275 protective gaps, effect of, 367 fuse blo effect of, 361 electronic relays, 369 Faults, mitigation of effects of, 2 prevention of intermediate current sources. effect of 347 2 probability of, effect on practice, ll see also low-tension current, use of, 356 low-tension Short circuits voltage, use of, 352 magnetizing inrush, effec of, 359 overreach, 951, 360 purposeful Fire, protection against, 230 ipping on loss of synchronism, 361 reclosing, automatic, 366 series capacitor, Fire-pump-motor protection, 230 effect of, 367 see also Distance relays Footing resistance, tower, 303 Line protection with overcurrent relays, a-c and capacitor tripping, 335 uency, compensation of relays for changes adjustment of ground vs phase re lays. 316 adjustment of inverse-time-overcur effect on induction relays,, 32, arc and ground resistance, 302 directional feature. 310 Frequency-converter protection, see Generator fuses. coordination with. 335 protection ground faults in ungrounded systems, Fundamental principles of protective relaying, 4 ground-fault neutralizers, effect of, Fuse, coordinating with a, 335 instantaneous overcurrent relays,, use of.306 Fuse blowing, potential-tranaformer, effect on inverseness,, choice of, in relay char distance relays, 361 acteristics. 305 limiting ground-fault-current magn eltect on generator relays, tude. effect of. 317 loop circuits,, effect on relay adjust 303 misoperation prevention of aingle Generator protection, bearing overheating, 228 directionak-overcurrent re during ground faults. 314 external-fault back-up, m field ground, 218 negative-phase sequence ground di INDEX4 I N D E X Evaluation of protective relaying, 12 Expulsion protective gaps, effect of, on distance relays, 367 External-fault back-up relaying, see Back-up relaying Fail ures,, electrical, see Faults False residual current, 318 Fault bus, 275 Faults, mitigation of effects of, 2 prevention of, 2 probability of, effect on practice, 11 see also Short circuits Fire, protection against, 230 Fire-pump-motor protection, 230 Footing resistance, tower-, 303 Frequency, compensation of relays for changes in, 49 effect on induction relays,, 32, 39 Frequency-converter protection, see Generator protection Fundamental principles of protective relaying, 4 Fuse, coordinating with a, 335 Fuse blowing, potential-tranaformer, effect on distance relays,, 361 effect on generator relays,, 228 Generator protection, bearing overheating, 228 external-fault back-up, m field ground, 218 loss of excitation, 223 1088 of synchronism,, 218 miscellaneous,, 228 motoring, 225 open circuits,, 215 over excitation,, 225 over speed,, 226 Line protection with distance relays, current and voltage switching, 368 expulsion protective gaps, effect of, 367 fuse blowing, effect of, 361 electronic relays, 369 intermediate current sources, effect of, 347 low-tension current, use of, 356 low-tension voltage, use of, 352 magnetizing inrush, effect of, 359 overreach, 351, 360 purposeful tripping on loss of synchronism, 361 reclosing, automatic, 366 series capacitor, effect of, 367 see also Distance relays Line protection with overcurrent relays, a-c and capacitor tripping, 335 adjustment of ground vs. phase re lays, 316 adjustment of inverse-time-overcur rent relays, 297 arc and ground resistance, 302 directional feature, 310 fuses, coordination with, 335 ground faults in ungrounded systems, detection of, 319 ground-fault neutralizers, effect of, 321 instantaneous overcurrent relays,, use of, 306 inverseness,, choice of, in relay char acteristics, 305 limiting ground-fault-current magni tude, effect of, 317 loop circuits,, effect on relay adjust , 303 misoperation prevention of aingle directional-overcurrent re during ground faults, 314 negative-phase sequence ground di