| 摘要 |
PURPOSE:To surely detect a ground fault, in a new urban transit system, by preventing a recirculating flow of zero phase current, induced in a current unbalance line different from the power feeding line to a vehicle, to up and down feeder clables. CONSTITUTION:Another transformer 3C, having capacity half the total capacity of a substation, is prepared, and a selector switch 24 is provided. In this way, even for a fault of either transformer 3A or 3B, electric power can be fed to both feeder buses 60A, 60B, further the buses 60A, 60B are separated from each other by a three phase transformer, and a zero phase current, caused by external induction, can be prevented from recirculation. In this case, though an equipment of the conventional method is utilized as left in that state, in case of setting a new substation, 1.5 times the total transformer capacity is only required by three sets of transformers 3C, 3D, 3E and the total capacity of the transformer can be reduced. |
