Sepam - HV/MV Protection and control units (ENG) - Trinet

Directional earth fault for compensated neutral systemsANSI code67NCfunction n° F48X 1 i X i 2*OperationMeasurement of Io phase shift with respect to VoIn order to facilitate commissioning, the phase shift ϕo between the earth faultcurrent Io and the residual voltage Vo may be measured:c using the pocket terminal,c via the communication link (Jbus/Modbus)*.ϕoPrincipleThis protection is single-pole.It picks up when the active component of the earthfault current is greater than a set point in the chosendirection (normal or inverse).It is time delayed. The time delay is definite(definite time).It is characterized by its capacity to detect very short,repetitive faults during the time delay(recurring faults).The function determines the projection Ipo of currentIo on the residual voltage Vo axis.The Ipo value is compared with the Iso set point:the protection picks up in the following direction:c normal if Ipo i -Iso,c inverse if Ipo u +Iso and if the earth fault vectoris in a sector that can be adjusted with respect to theresidual voltage.This sector makes it possible to obtain a highlysensitive and stable function.This protection is operational whenever the residual–> –> –>voltage value (V1+V2+V3) is greater than the setpoint Vso.This protection is appropriate for compensatedneutral systems (earthed by a Petersen coil).IoBlock diagramcore bal. CT+ ACE 990V1V2V3VoI1I2I3CT+ CSH302 A core bal.CSH30 A core bal.CSHV0 > Vs0VoIo Io cos (ϕo-θo)Iso&&0 t0 tt memtt00F481/5F481/1normal zoneF481/2F481/3inverse zoneF481/4normal zone inverse zoneIpo-IsoIsoVoIoProtection operation zonesProtection detection directionThe normal and inverse directions correspondto the diagram below.inversenormal* available as of version 9940 SFT2800.2/16 Protection functions