| 摘要 |
PROBLEM TO BE SOLVED: To provide a protection relay which applies to an AC feeding system, suppresses an unnecessary operation due to an accident outside a protection section without need for time cooperation, and detects a hetero-phase accident by a fault contact. SOLUTION: A hetero-phase fault contact protection relay 1 is applied to the AC feeding system using a feeding transformer 3 converting three phase AC received from an electric power supply 2 into two sets of single-phase, orthogonal A seat power supply and B seat power supply. A phase difference and a scalar difference between phase voltage of the A seat power supply, which is divided by a middle point, and phase voltage of the B seat power supply, which is divided by the middle point, are calculated. When the phase difference is within a prescribed phase differenceθk and the scalar difference is not more than a prescribed voltage value Vk1, it is determined to be a hetero-phase accident due to a fault contact in the A seat power supply and the B seat power supply, and a protection operation is performed. COPYRIGHT: (C)2008,JPO&INPIT
|
