Abstract: An apparatus for the deletion of extraneous signals to a radio frequency monitor is described having a first radio frequency sensor disposed at the neutral common ground of a dynamoelectric machine and delivering radio frequency signals from all sources to a switch at the input of a radio frequency monitor and further having auxiliary radio frequency sensors disposed at sources of normal radio frequency activity and providing signals of such normal activity to a deletion pulse generator which issues a blocking pulse to said switch thereby deleting RF noise from normal sources which otherwise may produce false warnings and restrict the diagnostic utility of radio frequency monitoring of an electric power generator or an electric motor.

Abstract: In a shielded power cable of the type comprising inner and outer conductors separated by cable insulation defining a displacement current path between the conductors for high frequency currents, the cable insulation incorporates one or more coaxial layers of semiconductive material consisting of cable insulation material loaded with a conductive filler, such as carbon fibres or spheres. The semiconductive layer is designed to maximize high frequency losses thereby to facilitate attenuation of high voltage surges caused by lightning or by switching.

Abstract: In a system for continuously monitoring partial discharge in high voltage electrical equipment thereby to give advance warning of impending breakdown of solid-insulated components, means are provided to distinguish electrical signals indicative of partial discharge from those resulting from noise or external transients. Current pulses in the various partial discharge paths are detected, and by solid-state circuitry their relative polarities are compared and an appropriate signal is made according to the comparison.