Abstract: The gas circuit breaker comprises a metal container filled with an insulating gas; first and second contacts disposed opposite each other in the metal container so that they can be brought into and out of engagement with each other; and a metal shield arranged in the metal container to enclose the two contacts. A part or a whole of the surface of the shield is oxidized and covered with a fluororesin layer. The gas circuit breaker with this construction can protect the shield surface against flaking and scores when subjected to mechanical impacts and can maintain high dielectric strength without increasing the size of the circuit breaker.

Abstract: A puffer type gas-blast circuit breaker includes a guide section arranged at a coupler section between a shaft section of a puffer cylinder and a dielectric operating rod, for guiding both in the axis direction of a current interruption section and in the radial direction thereof, thereby to suppress or eliminate the occurrence of misalignment of center axis between movable components and fixed ones thus causing a gap to remain constant between a dielectric nozzle and a fixed arc contact. With such an arrangement, the gap between the nozzle and the contact can be kept uniform even when the pole-to-pole distance is increased with an increase in the high withstanding voltage of the breaker. This ensures that the surface-creeping electric field on the inner surface of the dielectric nozzle can be at a desired design value, thus enabling to provide a stable pole-to-pole insulation characteristic during current interruption operations.

Abstract: For the purpose of providing a gas circuit breaker with a structure of hydraulic pressure operation system capable of detecting the occurrence of an incomplete closed state of the valves therein to prevent their erroneous motion during the subsequent motion, and a liquid-pressure driving system to be used therefor, a check valve is arranged so as to suppress the flow into the space on the side of the downstream of a closed-circuit operation spool valve, wherein the space on the side of the downstream of the closed-circuit operation spool valve is connected through a second diaphragm to a low-pressure oil tank and the operation time or operation number of a liquid-pressure pump is measured.

Abstract: A puffer type gas breaker is provided, in which high-temperature gas, heated by an electric arc produced immediately after a large current is broken, is quickly discharged to enhance inter-pole dielectric performance. A fixing portion for fixing an arc contact is provided in a cylindrical exhaust pipe for exhausting the high-temperature gas heated by an electric arc produced between poles immediately after a large current is broken. A rectifying member or members is provided in the fixing portion of the cylindrical exhaust pipe. An exhaust port or ports is formed in the fixing portion of the cylindrical exhaust pipe, and a shield is disposed around the outer periphery of the exhaust port or ports.

Abstract: Occurrence of erroneous operation in which circuit closing operation unexpectedly happens after circuit opening operation even though an abnormality such that a circuit closing system is left in a circuit closing condition even after completion of the circuit closing operation. Accordingly, a circuit closing control valve has such an arrangement that its pilot chamber becomes a low pressure so that the circuit closing control valve is opened, and a lock valve having two pilot chambers connected to a circuit closing pilot valve and a circuit opening pilot valve, which are both become a low pressure, is located in a passage connecting between the pilot chamber of the circuit opening control valve and a return port.

Abstract: An insulation gas filled circuit breaker in which a circuit breaking portion including two separably opposing contacts and a capacitor connected in parallel between the two contacts in the circuit breaking portion are disposed in a closed metal container filled with gas having an insulating property. A shield is provided at both the side of the capacitor facing the circuit breaking portion and the side of the capacitor facing the closed metal container for relaxing the electric field concentration near the capacitor. The top end of the shield is positioned so as to extend from the contacting face between the capacitor and an electrode pressing the capacitor toward the capacitor by a predetermined distance, whereby the dielectric strength of the capacitor connected in parallel with the circuit breaking portion is increased and a highly reliable and compact insulation gas filled circuit breaker of a high voltage and a large capacity use is provided.

Abstract: Breaking poles (1) and (2) are respectively secured to respective conductor bodies (4) and (5) and electrically connected thereto, and the conductor bodies (4) and (5) are fixedly secured and connected to each other by an interpole insulating support body (3). Interpole capacitors (7) are accommodated in the respective side walls of the interpole insulating support body (3). These parts for the breaking portion are accommodated within a grounded metal container (19) together with insulating gas and are secured to an operating box (18) via an insulating support body (17). The breaking poles (1) and (2) are designed to be transmitted an actuating force from the operating box (18) via an actuating insulation rod (not shown) and perform a breaking/making operation.

Abstract: A compression gas puffer type circuit breaker has a magnetic body surrounding a conductor between a stationary arc contact and a main bus conductor. The magnetic body is protected from being exposed to heated puffer gas generated when a movable arc contact is separated from the stationary arc contact by disposing an insulator partition plate supporting the conductor at the downstream end of a cylindrical contact base carrying a main stationary contact and upstream of the magnetic body. Conductors are disposed around the magnetic body so as to increase flux linkage with the magnetic body when an arcing current flows through the conductor during a circuit breaking operation.