Electromagnetic spectrum radiated from gas discharges and its relation to partial‐discharge characteristics

Electromagnetic spectrum radiated from partial discharges (PD) andflashover occurring in air have been measured for needle‐plane electrodes. The experimental results showed that the gain of the electromagnetic wave for both PD andflashover decrease with an increase of the distance from the discharge source in the frequency range from 30 MHz to 300 MHz. The results were discussed in terms of a model assuming that electromagnetic wave radiation from a small dipole antenna simulated that from the PD source. Consequently, the distance characteristics of the signal gain proved to agree well with the theoretical calculation in the frequency range from 35 MHz to 75 MHz. An attempt was also made to separately measure the electromagnetic spectrum caused by positive and negative PD pulses, according to AC applied voltage phase. A t the same time, PD pulses were measured with a computer‐aided measuring system. The relationship between the PD statistical characteristics and the electromagnetic spectrum has been discussed.