Differential protection assembly monitoring method for protection of e.g. car washing station, involves controlling closing of main and secondary interruption devices to carry out test of secondary current lines

摘要

The method involves controlling closing of main and secondary interruption devices (1, 10). Measurement of differential current is performed, and the measured current is compared with an alarm threshold. A closure of tested secondary device is maintained when the measured current is less than the threshold. The main device is opened, the tested secondary device is opened, and other non-tested secondary devices are closed, and the main device is closed successively to carry out a test of secondary current lines (200) when the measured current is higher than the threshold. An independent claim is also included for a differential protection assembly.