Investigation of pole fire on a 22kV wooden power pole structure

Wooden pole fires caused by leakage current flow are a major problem faced by various power distribution utilities in Australia and many other parts of the world. The excessive leakage current activity in wooden structures caused by contamination of insulators over a period of time starts to deteriorate the insulation characteristics leading to pole fires and subsequently power cut-off. This paper reports an investigation of a fire at the bolt mounting a transformer to a 22kV wooden structure experienced by one of the electricity distribution utilities in Australia. A comparative analysis is undertaken between a undamaged and damaged poles of similar ages and species. The effect of surface conductivity and varying moisture content on leakage current flowing through the wooden structure is also studied. An Infrared camera study is also undertaken to study the heat mechanism caused by leakage current flow. A relatively low leakage current magnitude is observed to be enough current flow to create sufficient heat, causing smoldering. A combination of environmental factors and pole configuration created the right circumstances for the resulting pole fire.