Section 8 Current protection8.1 Instantaneous phase overcurrent protection PHPIOCIP14506-1 v68.1.1 IdentificationM14880-1 v4Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberInstantaneous phase overcurrentprotection 3-phase outputPHPIOC3I>>SYMBOL-Z V1 EN-US508.1.2 Application M12911-3 v5Long transmission lines often transfer great quantities of electric power from production toconsumption areas. The unbalance of the produced and consumed electric power at each endof the transmission line is very large. This means that a fault on the line can easily endangerthe stability of a complete system.The transient stability of a power system depends mostly on three parameters (at constantamount of transmitted electric power):• The type of the fault. Three-phase faults are the most dangerous, because no power canbe transmitted through the fault point during fault conditions.• The magnitude of the fault current. A high fault current indicates that the decrease oftransmitted power is high.• The total fault clearing time. The phase angles between the EMFs of the generators onboth sides of the transmission line increase over the permitted stability limits if the totalfault clearing time, which consists of the protection operating time and the breakeropening time, is too long.The fault current on long transmission lines depends mostly on the fault position anddecreases with the distance from the generation point. For this reason the protection mustoperate very quickly for faults very close to the generation (and relay) point, for which veryhigh fault currents are characteristic.The instantaneous phase overcurrent protection 3-phase output PHPIOC can operate in 10 msfor faults characterized by very high currents.8.1.3 Setting guidelines IP14979-1 v1M12915-4 v8The parameters for instantaneous phase overcurrent protection 3-phase output PHPIOC areset via the local HMI or PCM600.This protection function must operate only in a selective way. So check all system andtransient conditions that could cause its unwanted operation.1MRK 505 363-UEN A Section 8Current protection127Application manual
