Abstract: Two trigger electrodes are insulatingly extended through one of two main opposite electrodes and connected to both ends of a secondary winding of a current transformer. The secondary winding has a central tap connected to that main electrode through which the trigger electrodes extend. A voltage is applied across the main electrodes and a trigger pulse is supplied to the trigger electrodes through the current transformer to initiate an electric discharge across the main electrodes.

Abstract: Two main toroidal electrodes are supported to individual support plates to oppose to each other. A rod-shaped consumable electrode disposed on one of the support plates loosely extends through the central opening of the toroidal electrode supported to the same support plate as the consumable electrode and terminates within the central opening of the other toroidal electrode. The consumable electrode opposes to a similar consumable electrode disposed on the other support plate. All the electrodes are higher in electric resistivity than the support plates and may be formed of carbon.

Abstract: An overvoltage across each of N series capacitors is sensed by an individual overvoltage sensor through an associated current transformer and applied to a central control apparatus. Each capacitor is connected across an electric valve with a trigger electrode and also across a normally open circuit breaker. Another current transformer includes a secondary winding connected to the trigger valve electrode and a primary winding connected across a discharge circuit controlled by the central control apparatus. With an overvoltage developed across any capacitor, the discharge circuit discharges the electric valve and then closes the circuit breaker.

Abstract: A protecting apparatus for a series capacitor in an AC power circuit includes an enclosure filled with a low pressure insulating gas. A discharge gap device, a bypass switch for the series capacitor and an electromagnetic repulsion device for closing the bypass switch in response to the discharge of the series capacitor are assembled in the enclosure in alignment with each other. A metallic cylinder is provided around the assembly forming a return path for the capacitor discharge current to cooperate with the gap device and its support. In this way, the impedance of the capacitor discharge passage can be effectively reduced to permit rapid removal of excess terminal voltage from the series capacitor.