Study of electrical field and micro arcing in a wooden supporting structure using Finite Element Method

The power distribution and transmission networks in many countries use wood for fabricating service poles for the overhead power lines. In this paper, we model a wooden pole used in an 11kV three phase distribution system. We use this model to study the electric fields induced in the wooden supporting structures, in order to determine the possibility of micro arcing inside them, using Finite Element Analysis. The three dimensional model takes into consideration both the resistive and capacitive properties, and closely resembles the actual pole. We show that the electric field distribution of the utility pole changes significantly with the change of weather conditions, and the size of the air gap at the wood-metal interface where the electric field is at its maximum. Also, we show that the electric field in this gap can be reduced significantly by modifying the king bolt using an epoxy coating. This reduction will minimize the chance of micro arcing inside the air gap near the bolt, which will reduce the long term degradation of the wooden structure.