Testing of DC Under-Voltage Relay (27)

. Before testing technical data of devices to be checked. . Testing to be performed by voltage injection on coil. . Connect DC variable voltage to the coil and increase voltage until relay close and decrease voltage until relay open. Note this voltage. . Check operational of relay indicator or aux. contact for Closed and Open. . Repeat to apply DC voltage at the supply terminals. Check for pick-up and drop-out values