| 摘要 |
PURPOSE:To improve the protective performance of the title device upon normal time by a method wherein an intercepting command is outputted when the output of a high-sensitivity type current differential element is removed and the output of a low-sensitivity type current differential element as well as the output of a failure detecting element are established for a given period of time under a condition that the condition of generation of an excitation rush current for a transformer for a branch load substation is established. CONSTITUTION:A high-sensitivity type current differential element 4 is locked and the locking is continued until a time limit reset timer 3 is reset when either one of a breaker throwing command detecting element 1 or a system voltage increase detecting element 2 is outputted. The intercepting output for a breaker is outputted by the OR of the output and a low-sensitivity type current differential relay element 5 as well as the AND of the output and a failure detecting element 6. In this case, protection during the generating period of transformer exciting rush current is effected by the low-sensitivity type current differential element 5. According to this method, high-sensitivity protection can be effected without spoiling any protecting performance upon a normal time even in a system wherein branch load terminals which are not equipped with the relaying devices are existing in a protecting division. |
