Abstract: An improved, integrally cast, synthetic resin insulator (22) especially adapted for use in an electrical cutout device (20) is provided which can be readily fabricated and gives greatly enhanced beam strength and arc track resistance characteristics. The preferred insulator (22) is cast using an epoxy resin such as bisphenol A filled with a relatively large quantity of glass beads and hydrated alumina. The filler fraction contributes to lowered viscosity, deaerability and improved settling properties while the resin is in an uncured state, and moreover enhances the arc track resistance and mechanical strength of the resin system after curing. The preferred insulator (22) is cast to present a longitudinal bow giving the insulator (22) an arcuate central axis. Further, the periphery of the insulator (22) is formed with a series of superposed, generally oval-shaped in cross-section, outwardly flaring skirts (30) interconnected by smooth transition regions (32) free of stress-inducing sharp corners.

Abstract: A portable tool for making and breaking high magnitude load currents is provided which is reliable in operation, can be used in applications lacking mechanical switching or cutout apparatus, and provides a secondary, visual assurance to the user when a load is broken. The device preferably includes a pair of vacuum bottle-enclosed, load-making and -breaking contacts, along with a series-connected pair of visually observable contacts exteriorly of the vacuum bottle. Spring-biased operating mechanism assures that the bottle-enclosed contacts actually make and break the load current during use of the tool, while the secondary contacts are operated in sequenced relationship to the make and break contacts. When the device is used to break a current load, transparent portions of the tubular walls of the device permit the user to visually perceive a large open air gap between the secondary contacts.

Abstract: Pad-mounted double-fused switchgear especially adapted for use in underground distribution systems is provided which includes an oil tank having manually operable vacuum switch apparatus therein in conjunction with closely adjacent, series-connected, combination current limiting fuse-expulsion link protective fuse structure for maintaining the required momentary electrical rating of the overall switch apparatus notwithstanding of a relatively low-rated switch element, and for providing thermal protection for the switchgear. Double-fusing within the oil tank also serves to reduce electrical duty on upstream and downstream equipment, increases the interruption rating of the switchgear, and enhances overall system coordination.