The present invention relates to a surge arrester for shunting electrical surges to ground.
Overvoltage surges, which travel along an electric power distribution system and which are not properly averted or diverted, often damage transformers and other electrical equipment of the electric power distribution system, as well as the electrical equipment of residential, commercial and industrial customers supplied by the electric power distribution system. Consequently, surge arresters are commonly used in an electric power distribution system for shunting overvoltage surges to system ground before the overvoltage surges can damage the electrical equipment connected in, or to, the electric power distribution system.
A typical surge arrester used in electric power distribution systems comprises an insulating housing, a stack of surge arresting blocks, end connectors which are in electrical contact with each end of the surge arresting blocks and which are arranged to electrically connect the surge arrester between first and second electrical lines, and a fault disconnector for disconnecting the surge arrester from the first and/or second electrical lines in the event of a fault in the surge arresting block. The number of surge arresting blocks in the stack of surge arresting blocks depends on the geometry of the surge arresting blocks and the voltage rating of the surge arrester. For example, a surge arrester rated at 9 KV usually has two or three surge arresting blocks.
The insulating housing of the typical non-porcelain surge arrester is not strong enough to support and contain the stack of surge arresting blocks. Therefore, a support member, such as a fiberglass wrap or a fiberglass sleeve, is provided around the stack of surge arresting blocks and the end connectors in order to contain and support the surge arresting blocks within the insulating housing. Additional elements, such as springs, wave washers, and/or the like, are provided in order to compress the surge arresting blocks.
Because of the use of a support member and multiple surge arresting blocks, a surge arrester as described above is expensive to produce. The present invention is directed to a surge arrester which eliminates the need for a support member and/or which uses a reduced number of surge arresting blocks.
In accordance with one aspect of the invention, a method of forming a surge arresting block comprises the following steps: a) providing a threaded element in an isostatic press; b) placing surge responsive material in the isostatic press; and, c) controlling the isostatic press with a pressure/time profile arranged to bond the material together in order to form the surge arresting block, wherein the isostatic press causes threads to be formed in the surge arresting block by the threaded element.