Application of Special Arresters on 138 kV Lines of Application Power Company
Special zinc oxide series gapped line arresters were installed on Appalachian Power Company 138 kV lines having high tower footing resistance and severe lightning exposure. This effort was part of an experiment to explore means of reducing lightning flashovers in exposed locations where low ground resistances are not feasible. Because of possible future voltage uprating of these lines, the arresters were built in the form of high strength nonporcelain mechanical struts, designed to limit phase conductor swing. This paper describes the field installation of these experimental arresters and their instrumentation and reports operating experience in 1983.
Development and Application of Lightning Arresters for Transmission Lines
A lightning arrester with a series gap for transmission lines has been developed to prevent faults due to lightning. It has shown excellent performance since 1986 on 77 kV service lines in heavy lightning regions. A 275 kV lightning arrester has also been developed, and a field test was started on a service line in 1988. The authors describe the requirements for lightning arresters for transmission lines, design concepts, specifications, and operational records on the 77 kV lines for three years. The gapped-type lightning arrester is considered the most practical given the existing technology. To obtain light and small lightning arresters, an ethylene-propylene rubber shed was adopted for external insulation and a special pressure relief mechanism was introduced in place of the pressure relief guide of the station arresters. The follow current can be cut off within a period of 0.25 to 0.5 cycles even under contaminated and wet conditions. >
The Expulsion Protective Gap
THE EXPULSION protective gap consists of a fiber tube of proper bore and dimensions so arranged with an internal gap that lightning discharges are conducted within the tube and the power follow current is stopped through the expulsion action of the tube. Its action during interruption of follow current is similar to that of the expulsion fuse. In practice the expulsion gap is provided with a series gap, the whole assembly being electrically in parallel with the insulation to be protected.