Acoustic emission signatures of arcs and sparks

Partial discharge(microsparks) and flashover faults (arcs) associated with electrical power apparatus emit acoustic pressure waves which are useful for detection and location purposes. Although these emissions are modified by different forms of electrical insulation and by the structures involved, it is helpful to know their approximate spectrum signatures and levels so that acoustic sensing systems can be optimized. Based on both observations and some theory, it is demonstrated that generally, high energy (kj) flashover faults radiate maximum acoustic levels in the low frequency region from ∼ 120Hz to ∼10 kHz, whereas, low energy (μJ) partial discharges (P.D.) have maximum acoustic emission at higher frequencies in the ∼10 to ∼400 kHz range. As the acoustic emission levels are approximately inversely related to frequency, then useful measurements can be made over a wide range of frequencies, and it is hoped that the results reported here will help in the selection of acoustic sensors for incipient fault detection. In addition, it is demonstrated that the acoustic emission signatures of positive streamer P. D. from sharp-edged electrodes and metallic slivers in transformer oil; of insulation cavity P.D.; and of bouncing metallic particles in metal enclosures; have unique features which are useful for identification.