Abstract: The power supply installation for a direct current railroad comprises two diode bridge-connected circuits, only two thyristor breakers each connected in parallel to each of the two diode bridge-connected circuits, four dc disconnecting switches each connected between a diode bridge-connected circuit and one of four electric car power supply lines constituting a double track, separately. Further, the two diode bridge-connected circuits are connected by a dc disconnecting switch closed only in case of an accident. In case a ground fault occurs at a power supply line, a powering current to the defective line is interrupted by one of the breakers, together with an extension power supply current supplied from an adjacent substation, without exerting an influence of accident upon the other power supply lines. Further, even if one of the breakers is broken, powering currents are kept supplied to all the power supply lines through a mutual spare bus bar.

Abstract: Four sets of a first pair of diodes, a second pair of diodes and a GTO breaker are connected between the power rectifier, the power inverter and four electric car power supply lines arranged in parallel with each other and separated by two dead sections. Therefore, it is possible to cut off powering current and regenerative current simultaneously by simply turning off the GTO breaker. Further, even if a regenerative electric car is running on the electric car power supply lines, it is posible to prevent the occurrence of an arc at the other dead sections due to a potential difference between two power supply lines. Further, in case of powering/regenerative bus bar accident, it is possible to effectively cut off both a regenerative current and an extension power supply current flowing from the power supply lines by the four GTO breakers of a relatively small interrupt capability without exerting the influence of power suspension upon other adjacent substations supplying the extension power supply current.

Abstract: A disconnecting switch arrangement for a high voltage disconnecting switch equipped with an earthing device for use particularly in a metal clad insulated substation. The arrangement comprising a disconnecting unit, an earthing unit and an actuating unit for actuating the disconnecting unit and the earthing unit. The disconnecting unit comprises a stationary contact member, a common stationary contact member at a standard spacing from the stationary contact member and a common movable contact member for disconnecting from and connecting with the stationary contact member and the common stationary contact member and is moved in a circular motion by the actuating unit. The earthing unit is comprised by an earthing contact member, the common stationary contact member and the common movable contact member each of which is commonly used with the disconnecting unit.