Partial discharge detection in cable termination using acoustic emission techniques and adaptive signal processing

A practical system, based on acoustic emission techniques, for detection of partial discharge activity in cable terminations is presented. Analysis of the received signal is carried out in both the time domain and in the frequency domain using a neural network approach. Laboratory synthesized samples were used with controlled discharges. Signals received by the sensor were recorded by a digital oscilloscope and then analyzed by computer. Time domain analysis provided an indication of the size of the discharge. The relationship between the acoustic signal and the discharge size is demonstrated. The frequency content of the signal is used to differentiate between the signals generated by different discharge sources. Variation of the acoustic signal with applied voltage has shown that the discharge may be detected at its inception. Practical samples of cable terminations containing known discharges were also tested. The system could detect these discharges and give an upper bound on their energy dissipation. The system is acoustic in nature and thus virtually free from electrical interference. An optical fibre coupling between the acoustic transducer and the test equipment protects the system from flashover and allows for on-line testing of cable terminations