Study of Leakage Current Distribution in a Wooden Pole using a Three Dimensional Resistance Model

The distribution and transmission networks are two vital components of a reliable power system. When considering these networks, many countries use wood for fabricating service poles for the overhead power lines. A main disadvantage of using wooden poles is the formation of pole top fires, which initiates catastrophic events such as bushfires. This paper studies the leakage current distribution of a wooden pole which contains an inserted king bolt used to support the cross arm. A three dimensional resistance model is built up based on the electrical ladder network, and the leakage current is simulated for different scenarios that could occur in practice. The analysis show that a large part of the leakage current passes through the heartwood to the ground, except in the area of the metal bolt. This current increases at high moisture contents making the pole vulnerable to fire. The location of the bolt affects the leakage current as well, and the current reduces when the location of the bolt is varied along the length of the pole from top to bottom. The results also show that this model is superior to a two dimensional model, with a clear deviation in the actual current flow patterns.