Relay Testing

PIC-Monitor

The PIC-Monitor provides a simple means of automatically determining the pick-up and drop-off values and the drop-off ratio of protection relays. This could also be the excitation of the second instantaneous tripping set (high set) of an overcurrent relay, for example. The test quantities are issued as stair-step pulsed ramps for this purpose. The pulse duration selected should of course be shorter than the tripping time of the first high set to prevent the latter from responding. The amplitudes are increased until the pickup value has been reached (e.g. rising flank of excitation). To ascertain the drop-off value, a stair-step descending ramp is then output, the output values being decreased until the drop-off value has been reached (e.g. falling flank of excitation). The programme automatically calculates the test quantities with reference to the start and end values set for the ramps and the fault loop(s) which have been selected. The reaction of the test object is recorded in real time during the test and the drop-off ratio is calculated automatically afterwards. The test is evaluated using the pick-up and drop-off values set for the test object.