Effects of ambient conditions on partial discharges at very low frequency (VLF) sinusoidal voltage excitation

Effects of temperatures on corona discharges developed by needle/bowl electrode configuration at different frequencies are investigated. PD measurements are carried out under enclosed controlled air temperature range between 20°C and 40°C. The test chamber is airtight so the humidity is constant. Sinusoidal voltage waveforms in the frequency range of 0.05Hz to 50Hz are used to stress samples. There are evidences that PD behaviors at VLF and power frequency are dependent on ambient temperature in a similar manner. Nevertheless, there are still noticeable differences in PD patterns at VLF at various temperatures, especially in the phase position of PD events. These differences are discussed in details.