| 摘要 |
<p>This invention provides a protection relay (1) that protects the power transmission lines of a three-phase AC power system (20). In response to detection of a fault, the protection relay (1) opens a CB (4a) of the fault phase for which the fault has occurred. After opening the CB (4a), the protection relay (1) determines, on the basis of a voltage measurement value (VL) of the fault phase detected by a VT (3), whether the fault has been eliminated. If having determined that the fault has been eliminated, the protection relay (1) closes the CB (4a) again.</p> |
