Microwave reflection sensor for determination of decay in wooden cross-arms

Abstract

In Malaysia more than 90% of the cross-arms of the 275 kV and 132 kV transmission lines use Chengal wood. As a result of natural weathering the wood is degraded, normally dark-colored woods tend to fade and other changes include warping, loss of some surface fibers and surface roughening and in some woods, after more than decade of exposure, the state of decay is very extensive. For this reason there is a need for a portable, easy, light, small and accurate sensor for decay detection in the wooden cross-arms especially to be used by maintenance staff. In this project a microwave reflection sensor working at 10.7 GHz has been developed for detection of the stages of decay in the wooden cross-arms. The classification of decay is based on the amount of moisture than can be absorbed by the weathered wood and secondly based on the density of wood at different stages of decay at particular moisture content especially at EMC. This method is able to categorized the wood into three stages of decays i.e. Severe decay, incipient decay and sound wood and has managed to detect inner decay or a defective area up to 2 cm from the surface of the wood.