DIRECTIVITY OF ACOUSTIC-SIGNALS FROM PARTIAL DISCHARGES IN OIL

For partial discharges in oil, the relationship between, the apparent discharge magnitude, electrically measured in picocoulombs, and the ac oustic signal amplitude from the same discharge, shows large variation s. If the acoustic signal is detected with several detectors simultane ously, it is found that the acoustic amplitudes are correlated in a re latively narrow angular range. For larger angular separation, the acou stic amplitudes are uncorrelated and not anticorrelated. Some physical aspects of streamers in oil are illuminated by this observation and s ome theoretical considerations. The streamer velocity may, for example , be estimated.