Section 11 Secondary system supervision11.1 Current circuit supervision CCSSPVC IP14555-1 v511.1.1 IdentificationM14870-1 v5Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberCurrent circuit supervision CCSSPVC - 8711.1.2 Application M12395-13 v8Open or short circuited current transformer cores can cause unwanted operation of manyprotection functions such as differential, earth-fault current and negative-sequence currentfunctions. When currents from two independent three-phase sets of CTs, or CT cores,measuring the same primary currents are available, reliable current circuit supervision can bearranged by comparing the currents from the two sets. If an error in any CT circuit is detected,the protection functions concerned can be blocked and an alarm given.In case of large currents, unequal transient saturation of CT cores with different remanence ordifferent saturation factor may result in differences in the secondary currents from the two CTsets. Unwanted blocking of protection functions during the transient stage must then beavoided.Current circuit supervision CCSSPVC must be sensitive and have short operate time in order toprevent unwanted tripping from fast-acting, sensitive numerical protections in case of faultyCT secondary circuits.Open CT circuits creates extremely high voltages in the circuits which isextremely dangerous for the personnel. It can also damage the insulation andcause new problems.The application shall, thus, be done with this in consideration, especially if theprotection functions are blocked.11.1.3 Setting guidelines M12397-17 v7GlobalBaseSel: Selects the global base value group used by the function to define (IBase),(UBase) and (SBase).Current circuit supervision CCSSPVC compares the residual current from a three-phase set ofcurrent transformer cores with the neutral point current on a separate input taken fromanother set of cores on the same current transformer.The minimum operate current,IMinOp, must be set as a minimum to twice the residual currentin the supervised CT circuits under normal service conditions and rated primary current.1MRK 505 363-UEN A Section 11Secondary system supervision199Application manual
