Patent ID: 9618586
Date: 2017-04-11
CPC Classifications: G01R,H02H

Claim:
1. A method for use in fault detection in a protected unit included in a power system, the protected unit being adapted to convey power via at least one current path therein, wherein the protected unit is selectively disconnected from at least a portion of the rest of the power system and the protected unit is selectively connected to the at least a portion of the rest of the power system, the method being for facilitating detection of any fault in the protected unit after the protected unit has been connected to the at least a portion of the rest of the power system, the method comprising: sensing, with a sensor, a current in the at least one current path in the protected unit at one end thereof during a plurality of different time periods, thereby obtaining a plurality of sensed currents; determining, with a processing unit, compliance of at least one of the sensed currents with a respective first current criteria based on a first current threshold value, which first current criteria is a smaller than threshold criteria for a negative current and otherwise a larger than threshold criteria; on a condition that there is determined that at least one of the sensed currents comply with the respective first current criteria, generating a signal with the processing unit indicating that there is a fault in the protected unit; and on a condition that there is determined that none of the sensed currents comply with the respective first current criteria, generating a signal with the processing unit indicating that there is not a fault in the protected unit, wherein on a condition that at least one of the generated signal or signals indicate that there is a fault, the protected unit is selectively disconnected from the at least a portion of the rest of the power system, the sensed current in the at least one current path in the protected unit is sensed during at least three different respective time instants t t