Saturday, July 16, 2016

Testing of RESTRICTED EARTH FAULT RELAY (87N)

Restricted Earth Fault Relay is tested with secondary injection test set with electronic meter. . Isolate the Relay current Measuring Element & Trip Alarm contact by inserting the Test Block MMB01. . Set the seal in coil rating to 0.2 A dc. . Set the trip level value to 0.2 A. . Connect the Relay trip output contacts (terminal # 1 & 2) to both trip the test set, and stop a timer. . Inject single phase current into current element (terminal # 5 & 6) & slowly increase the current until the 0.2A is reached. . Checked that the output contacts closed and right side flag (on the relay front operated). . Inject 5 times the current setting i.e. 1A, in the relay and note that the timing is < 50ms. . Connect the Relay Trip output contacts (terminals # 1 & 2) to REF- Lockout Relay circuit (86-coil with series cut-off contact) and the output of Lockout contact to both trip the test set, and stop a timer, (refer schematic diagram) . Apply 125VDC to lockout relay circuit. . Inject single phase current into current element (terminal # 5 & 6) & slowly increase the current until the 02.A is reached. . Checked that the ouput contacts (terminal # 1 & 2) closed and both Flags (left “Trip” flag and right” Seal in flag”) operated plus the operation of lockout relay.

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