Abstract: An elongate high voltage insulator is formed of a rod or tube of insulating material, with a pair of electrodes spaced apart longitudinally thereof. At least part, and preferably the whole of the outer surface of the insulating material is covered by a layer of material including a particulate filler of varistor powder in a matrix having a switching electrical stress-controlling characteristic that is in electrical contact with each of the electrodes. The insulator core may be made of porcelain, and the stress-controlling material may be zinc oxide.

Abstract: An elongate high voltage insulator (2) is formed of a rod or tube (4) of insulating material, with a pair of electrodes (6) spaced apart longitudinally thereof. At least part, and preferably the whole of the outer surface of the insulating material (4) is covered by a layer of material (8) comprising a particulate filler of varistor powder in a matrix having a switching electrical stress-controlling characteristic that is in electrical contact with each of the electrodes (6). The insulator core (4) may be made of porcelain, and the stress-controlling material (8) may comprise zinc oxide.

Abstract: An arrangement for and method of limiting the electrical stress in a region of high electric field strength associated with high voltage equipment, especially power cables, employs two overlapping layers of semiconductive material that have different a.c. electrical impedance characteristics to surround the region. The inner layer may be a heat-shrinkable tube having a linear characteristic, and the outer layer may have a non-linear characteristic and be provided as an internal coating on a further heat-shrinkable tube of insulating material. Such an arrangement provides good electrical protection in terms of both a.c. and impulse performance.

Abstract: The invention provides an L-shaped connector for connecting a high voltage electric cable to a bushing of a transformer, switchgear, or other electrical apparatus. A first arm of the connector is tapered to be a push-fit on to the bushing, and the other arm has a heat-shrinkable tubing integral therewith for receiving, and sealing on to, a stripped cable. Electrical connection to the cable is made completely within the insulating body of the connector, by a screw-threaded pin that is accessed through the first arm of the connector.

Abstract: A heat-recoverable article such as a heat-shrinkable wrap-around sleeve is provided with at least one auxiliary conduit so as to facilitate its application to the installation and repair of break-out joints from main-line cables, especially power and telephone cables. The auxiliary conduit is formed by bonding together appropriate regions of the internal principal surface of the article, coupled if necessary with a cutting step. Bonding is preferably achieved by use of a cross-linking material such as a peroxide.

Abstract: A heat-recoverable article such as a heat-shrinkable wrap-around sleeve is provided with at least one auxiliary conduit so as to facilitate its application to the installation and repair of break-out joints from main-line cables, especially power and telephone cables. The auxiliary conduit is formed by bonding together appropriate regions of the internal principal surface of the article, coupled if necessary with a cutting step. Bonding is preferably achieved by use of a cross-linking material such as a peroxide.