Pole-top fires risk assessment: A South African perspective

Pole-top fires on 22 kV overhead woodpole electricity distribution lines are addressed. The mechanism covered is where, under certain conditions, the surface of one or more phase insulators collects pollution, which conducts leakage current when lightly wetted. This leakage current can flow into and onto the wood of the structure and can, in certain cases, cause the wood to track, char and ignite. Experiences from tests and the field are used to perform a risk assessment of different mitigation options using criteria such as pollution (leakage current) performance, lightning performance and bird safety. A proposal for different structure configurations for use in different areas is made. The rationale behind the proposal is described, practical considerations and limitations are discussed and further research is recommended.