High accuracy DOA estimation of electromagnetic pulses using analogue signal processing

Partial discharges (PDs), which occur at coupling points of tension insulators or binding spots of insulated wire of distribution lines, might cause television interference or ground fault. A technique for location of the sources of PDs using time differences in arrival of electromagnetic pulses radiated from PDs has been investigated recently, because it is difficult to find the sources by visual inspection from the ground. However, the technique requires a large and expensive apparatus such as digital storage oscilloscope able to record waveforms of the electromagnetic pulses very fast. We investigate a new technique to estimate the direction of arrival (DOA) of the electromagnetic pulses using analogue signal processing. The experimental analogue circuits for measurement of the time (phase) differences are composed of general purpose modules, i.e., amplifiers, filters, local oscillator, dividers, mixers, etc, and the DOA of the electromagnetic pulse is indicated using a circular symbol superimposed onto the photo image taken with a CCD camera. From the results of the experiments on the DOA estimation, it was proved that the new technique is available for high accuracy DOA estimation of the electromagnetic pulses radiated from PDs in air. ©2010 The Institute of Electrical Engineers of Japan.