Sepam 2000 - Schneider Electric

Neutral voltage displacement (59N)Detection of insulation faults in ungrounded systemsby measurement of neutral voltage displacement.This protection is generally used for transformerincomers or busbars.Underfrequency (81)Detection of variances with respect to ratedfrequency, in order to maintain high quality powersupply. This protection can be used for overall trippingor forload shedding.Undervoltage (27)Protection used by automated functions (changeover,load shedding).The function checks for undervoltage in each of thesystem voltages measured.Remanent undervoltage (27R)Monitoring of the clearing of voltage sustained by selfpoweredprotections after the opening of the circuit.This protection is used to prevent reclosing on livelines. It monitors system voltage U21.Thermal overload (49)Protection of equipment against thermal damage caused by overloads.Thermal capacity usedis calculated according to a mathematical model,with 2 time constants, taking into account the effect of negative sequence currentby means of an adjustable weighting factor. The function comprises:v an adjustable alarm setting,v an adjustable trip setting.Recommendations:v use the same setting for T1 and T2,v set the negative sequence/unbalance coefficient to 0.Breaker failure (50BF-62)Back up protection in the event that the incoming breaker fails to operatewhen a retripping order is given by the same breaker or a tripping order is givenby adjacent breakers. The function is ensured for single-phase and three-phaseoperations.Percentage-based overcurrent (50/51)Detection of an unbalance current between the two neutral points of capacitor bankmounted in a double-star arrangement. This current indicates that the componentsof one of the batteries are damaged.Synchro-check (25)Allows closing of the breaking device if the two circuits have voltage,frequency or phase variances within the planned limits.HV/MV substation Installation - Use - Commissioning2/13