| 摘要 |
PROBLEM TO BE SOLVED: To completely perform protection against the phase interruption of a neutral line by providing a first system released immediately when an earthquake is detected and a second system which is not cut off, and using the neutral line in common to connect a trunk breaker to the neutral line. SOLUTION: On the load side of a trunk breaker 1, the branch breaker group 2 of a first system and the branch breaker 5 of a second system are provided, the branch breaker 2 of the first system is connected to an opening and closing part 7 on the secondary side, and when the contacts 4 of an earthquake sensing relay 3 output a cut-off signal to the opening and closing part 7 immediately after sensing an earthquake, the contacts 4 are cut off all at once. The second system is not cut off in sensing an earthquake, and the contacts 6 of the earthquake sensing relay 3 output a cut-off signal to the trunk breaker 1 at the recovery of service interruption to cut off the trunk breaker 1 and however, the neutral line 8 of the first system is used in common without passing through the neutral line and the contacts of the second system to be connected to the neutral pole of the trunk breaker 1. As a result, since the protection against the phase interruption of the neutral line of both systems is completely performed by a single trunk breaker, the protection from an overvoltage can be achieved. |
