The electrical characteristics of 132-kV line insulators under various weather conditions

The insulation of high-tension lines in industrial areas is one of the major problems in the operation of high-tension systems. This paper gives the results of an investigation into the electrical characteristics of 132-kV insulators under various weather conditions in a district subject to atmospheric pollution. It was found that the steady value of the leakage current of an insulator chain varies between 0.2 and 1.0 mA, depending on the weather conditions. In fog or with dirty insulators under humid conditions the leakage current is very unsteady and continuous surging usually takes place, the magnitude of the current-surges often reaching 100 mA. These current-surges are due to surface discharges on the insulators and are usually self-extinguishing owing to the resistance of their path being increased by the heating effect of the current, but a severe surge may develop into a complete flashover. The frequency and magnitude of these current-surges provide a criterion by which to judge the performance of insulators. Information is also given on the surface resistivity of porcelain, the characteristics of some special types of insulators, and the cleaning of insulators.