Publication: Electrical World
New York, NY, United States
NEWS OF MANUFACTURERS
EHV Nesting-Cone' Insulators Announced.
A new high-strength switch and bus insulator, said to combine the advantages of cap-and-pin and station post insulators without the short-comings of either, has been introduced by I-T-E Circuit Breaker Co. The new Multicone insulator is being offered in the US for 345 and 500-kv applications by the Victor Insulator Div of I-T-E, at Victor, NY. In Canada a similar insulator is available for 230 through 735-kv, from Canadian Porcelain Co Ltd, an I-T-E subsidiary.
The new insulator features nesting cone-shaped porcelain shells, cemented together to form a laminated construction described as having unusual strength. The conical shape of porcelain shells, as well as malleable iron caps and bases are said to reduce unit stresses in the cemented joints to a minimum. The solid core construction is said to completely eliminate the possibility of puncture.
As now being offered for the US market, the new I-T-E multicone insulator utilizes high-strength porcelain and the snug fit of the nesting cones reportedly provides higher cantilever strength and greater resistance to breakage in handling than any other EHV insulator presently available. Moreover, shape of skirts is such that there is said to be no breakage due to negative switching surge flashovers.
The skirts arc described as being spaced relatively far apart and shaped with better rain deflection characteristics than other existing post construction—reportedly excellent wet switching surge withstand values are obtained without the necessity of using rain shields. Several deep corrugations, running in concentric rings underneath the insulator skirts, offer increased line-to-ground leakage distance as compared to other insulator types of the same nominal voltage and BIL rating.
The multiple cone insulator was originally developed in France, the first going into service at 420-kv in 1958. Manufacturers in England and Italy have been licensed to produce the new insulator, and to date there are approximately 18,000 stacks in service on the European Continent and in England. Canada and Australia, at voltages from 72.5 through 420-kv. These insulators, unlike those now being offered by Victor do not utilize the high strength alumina porcelain.