Vacuum switch assembly

Claim 2

A polyphase vacuum switch assembly, comprising vacuum switching valves which are in series with the load and the same in number with the phases of a loadcircuit, a star-connected unbalance-detecting unit connected to the load circuit in parallel therewith, a rectifier connected to neutral point of the unbalance-detecting circuit, a DC capacitor connected between the rectifier and the ground so as to be charged by the neutral voltage through the rectifier, and a DC voltage monitor detecting a voltage across the DC impedance element.

Claim 3

A polyphase vacuum switch assembly according to claim 1, wherein said polyphase is three-phase.

Claim 4

A polyphase vacuum switch assembly according to claim 1, wherein said high impedance of each arm of said star-connected unbalance-detecting unit is a capacitor.

Claim 5

A polyphase vacuum switch assembly, comprising vacuum switching valves which are in series with the load and the same in number with the phases of a load circuit; a star-connected surge-absorbing unit connected to the load circuit in parallel therewith, each arm of the star-connected surge-absorbing unit consisting of a series circuit including a discharge gap, a resistor, and a fuse; and a star-connected unbalance-detecting unit connected to the surge-absorbing unit in parallel therewith, a rectifier connected to neutral point of the unbalance-detecting circuit, a DC capacitor connected between the rectifier and the ground so as to be charged by the neutral voltage through the rectifier, and a DC voltage monitor detecting a voltage across the DC capacitor in excess of a certain level, each arm of said star-connected unbalance-detecting unit comprises a high capacitive impedance element whose free end is connected to a point on a corresponding arm of the surge-absorbing unit, the high capacitive impedance elements of the unbalance-detecting unit simultaneously functioning as absorbing elements in the surge-absorbing unit.

Claim 6

A polyphase vacuum switch assembly, comprising vacuum switching valves which are in series with the load and the same in number with the phases of a load circuit; a star-connected surge-absorbing unit connected to the load circuit in parallel therewith, each arm of the star-connected surge-absorbing unit consisting of a series circuit including a discharge gap, a resistor, and a fuse; and a star-connected unbalance-detecting unit connected to the surge-absorbing unit in parallel therewith, a rectifier connected to neutral point of the unbalance-detecting circuit, a DC capacitor connected between the rectifier and the ground so as to be charged by the neutral voltage through the rectifier, and a DC voltage monitor detecting a voltage across the DC capacitor in excess of a certain level, each arm of said star-connected unbalance-detecting unit comprises a high capacitive impedance element whose free end is connected to a point on a corresponding arm of the surge-absorbing unit, the high capacitive impedance elements of the unbalance-detecting unit simultaneously functioning as absorbing elements in the surge-absorbing unit.

Claim 7

In a polyphase vacuum switch assembly, which includes vacuum switching valves which are in series with the load and the same in number as the phases of a load circuit; a star-connected surge-absorbing unit connected to the load circuit in parallel therewith, each arm of the star-connected surge-absorbing unit consisting of a series circuit including a discharge gap, a resistor, and a fuse successively connected from the neutral point of the star connection; and a star-connected unbalance-detecting unit each arm of which is connected respectively to a corresponding arm of the surge-absorbing unit at a point between the resistor and air gap on each arm, a rectifier connected to the neutral point of the unbalance-detecting circuit, a DC capacitor connected between the rectifier and the ground so as to be charged by the neutral voltage through the rectifier, and a DC voltage monitor for detecting a voltage across the DC capacitor in excess of a predetermined level in a recoverable manner, each arm of said star-connected unbalance-detecting unit comprises a high-impedance capacitor element wHose free end is connected respectively to a point between the resistor and the air gap of the corresponding arm of the surge-absorbing unit, whereby the high impedance capacitor element in the unbalance-detecting unit functions as an absorbing element in the surge-absorbing unit.

Claim 8

In a polyphase vacuum switch assembly, which includes vacuum switching valves which are in series with the load and the same in number as the phases of a load circuit; a star-connected surge-absorbing unit connected to the load circuit in parallel therewith, each arm of the star-connected surge-absorbing unit consisting of a series circuit including a discharge gap, a resistor, and a fuse successively connected from the neutral point of the star connection; and a star-connected unbalance-detecting unit each arm of which is connected respectively to a corresponding arm of the surge-absorbing unit at a point between the resistor and air gap on each arm, a rectifier connected to the neutral point of the unbalance-detecting circuit, a DC capacitor connected between the rectifier and the ground so as to be charged by the neutral voltage through the rectifier, and a DC voltage monitor for detecting a voltage across the DC capacitor in excess of a predetermined level in a recoverable manner, each arm of said star-connected unbalance-detecting unit comprises a high-impedance capacitor element wHose free end is connected respectively to a point between the resistor and the air gap of the corresponding arm of the surge-absorbing unit, whereby the high impedance capacitor element in the unbalance-detecting unit functions as an absorbing element in the surge-absorbing unit.