| 摘要 |
Two switches (5,6) are provided, one in each conduit, and are controllable for breaking/maintaining a connection between the poles and the apparatus sides. The arrangement is such that the apparatus is only controlled when both breakers are controlled at the same time. - A device (10-19) is incorporated in permanent connection with the conduits which makes possible control, with the switches open, as to whether some break has occurred on the conduits between the voltage source and the apparatus. It can also control the function of both switches to close and open without causing control of the apparatus and detect an earth fault occurring on the conduits between the switches and the apparatus. Also incorporated is a by-pass conduit (10,11) parallel-coupled with the switches. It includes devices (18,19) which react to a current through it and a voltage bridge (14) connecting both conduits between the switches and the voltage source. This bridge has three series-coupled resistances (15-17) and two level comparators (18,19). |
