GB527357A - Improvements relating to high voltage insulators - Google Patents

Abstract

527,357. Insulators. MARSHALL, C. W., and FORREST, J. S. March 27, 1939, No. 9579. [Class 36] An insulator assemblage in which a predetermined potential drop takes place across each unit of the assemblage has the insulator parts so formed that the ohmic resistance across them, when dry, is sufficiently comparable with the resistance across their surfaces when wet that a destructive potential difference across any one part is avoided. The resistance of each part should be approximately the same whether wet or dry and may be of the order of 1 megohm per kilovolt. The required resistance may be obtained by selecting suitable materials for the manufacture of the insulator, for example a ceramic material of the carborundum type, or by coating the surface with a semi-conducting material. Alternatively a resistance of the required value may be arranged externally of the assemblage and connected between the metal parts, or it may extend through a bore formed in the insulator between two metal parts with which it makes contact. As shown each insulator part comprises a tubular body 28 which is encircled by a shed 29 and has an internal partition 30. The upper and lower ends of the tubular parts are engaged by metal caps 31 which are attached to caps of neighbouring insulators. In the partition 30 is an aperture in which the resistance element 32 is secured by cement, or the casing of the resistor may be formed of ceramic material and fired in situ. Conductors 33, 34 extend from each end of the resistor and may be soldered to the metal caps 31 before assembly.