42 holding coil, seal-in coil, and target, 43 Polarizing quantity, of a-c directional relays'37 of d-c directional relays, 6l of directional Ratio correction factor. see Current units of ground relays, 151, 326 transformers: voltage trans formers Polyphase directional relays, advantages and Reactance relay, characteristic on R-x diagram disadvantages, 313 response to positive-and 79 operating characteristic, 78 partial- negative volt-amps, 183 differential bus protection, 282 see also Line protection with distance relays Potential device, see Capacitance potential device Reclosing, automatic, affected by remote tripping, 367 effect on blocking-terminal Potential transformers, accuracy, 133 ilot equipment, 376 mitigation of fault connections. 146 effect of fuse blowing on ffects, 2 of bus breakers,, 292 single-phase distance relaying, 36l on generator relaying, switching, 399 synchronism check, 333, 366 228 low-tension voltage for distance relays, with distance relaying, 366 with overcurrent 148 laying, 333 with pilot relaying, Power-balance relaying for line protection, 330 Rectifier-transformer protection, 271 Power-rectifier-transformer protection, 271 Regulating-transformer protection, ex fault back-up, 208 in-phase type, 265 phase-shiftin Power swings, see Loss of synchronism type, 267 Power transformer and autotransformer Reliability, a functional relay characteristic, 9 protection, external-fault backup, 264 gasaccumulator and pressure relays, 261 Remote tripping by carrier current, 384 by grounding protective relay, 268 overcurrent microwave, 398 by pilot wire, 97 for power relaying, 261 percentagedifferential relaying transformer protection, 268 frequency-shift 241 CT accuracy requirements, 251 CT connections. 242 CT ratios. 250 magnetizing inrush, effect of, 254 parallel banks, 258 Replica-type relays, for generator protection, percent slope, choice of, 252 two-winding 216 for motor protection, 232, 235 relay for threewinding transformer, 252 zer phasesequence-current shunt, 249 remote Reset, adjustment of, 19 defined, 17 ratio to tripping, 263 pickup, electromagnetic relays, 22 induction relays, 32 time of induction relays, 33, 49 Primary relaying defined, 4 eversed third zone for back-up with carrier Product restraint for generator differential pilot, 349 where a line includes a relays. 204 transformer. 175 Protective relaying, evaluation of, 12 function R-X diagram, los-of-synchronism char 176 of. 3 functional characteristics of 9 appearance to distance relays, 181 principle fundamental principles of, 4 of. 72. 156 short-circuit characteristics. 1 60 appearance to distance relays,, 167 wyedelta Ratings, relay, contact, 43 current and voltage, transformer between relay and fault, 172 NDEXI N D E X 7 Polarizing quantity, of a-c directional relays’ 37 of d-c directional relays, 61 of directional units of ground relays, 151, 326 Polyphase directional relays, advantages and disadvantages, 313 response to positive- and negative volt-amps, 183 Potential device, see Capacitance potential device Potential transformers, accuracy, 133 connections, 146 effect of fuse blowing, on distance relaying, 361 on generator relaying, 228 low-tension voltage for distance relays, 148 Power-balance relaying for line protection, 330 Power-rectifier-transformer protection, 271 Power swings, see Loss of synchronism Power transformer and autotransformer protection, external-fault backup, 264 gasaccumulator and pressure relays, 261 grounding protective relay, 263 overcurrent relaying, 261 percentagedifferential relaying, 241 CT accuracy requirements, 251 CT connections, 242 CT ratios, 250 magnetizing inrush, effect of, 254 parallel banks, 258 percent slope, choice of, 252 two-winding relay for threewinding transformer, 252 zero￾phasesequence-current shunt, 249 remote tripping, 263 Primary relaying defined, 4 Product restraint for generator differential relays, 204 Protective relaying, evaluation of, 12 function of, 3 functional characteristics of, 9 fundamental principles of, 4 Ratings, relay, contact, 43 current and voltage, 42 holding coil, seal-in coil, and target, 43 Ratio correction factor, see Current transformers; Voltage trans formers Reactance relay, characteristic on R-X diagram, 79 operating characteristic, 78 partial￾differential bus protection, 282 see also Line protection with distance relays Reclosing, automatic, affected by remote tripping, 367 effect on blocking-terminal pilot equipment, 376 mitigation of fault effects, 2 of bus breakers,, 292 single-phase switching, 399 synchronism check, 333, 366 with distance relaying, 366 with overcurrent relaying, 333 with pilot relaying, 399 Rectifier-transformer protection, 271 Regulating-transformer protection, ex fault back-up, 208 in-phase type, 265 phase-shifting type, 267 Reliability, a functional relay characteristic, 9 Remote tripping, by carrier current, 384 by microwave, 398 by pilot wire, 97 for power￾transformer protection, 263 frequency-shift system, 264 Replica-type relays, for generator protection, 216 for motor protection, 232, 235 Reset, adjustment of, 19 defined, 17 ratio to pickup, electromagnetic relays, 22 induction relays, 32 time of induction relays, 33, 49 Reversed third zone, for back-up with carrier pilot, 349 where a line includes a transformer, 175 R-X diagram, los-of-synchronism char , 176 appearance to distance relays,, 181 principle of, 72, 156 short-circuit characteristics, 160 appearance to distance relays,, 167 wyedelta transformer between relay and fault, 172