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Partial Discharge measurement for medium voltage cables using different voltage wave forms

Partial Discharge (PD) is the most important issue that arise when testing service aged and non-aged cables. For long time, High Voltage Direct Current (HVDC) was used to detect the occurrence of PD activity in cables. Due to technical reasons, the HVDC was replaced by the Very Low Frequency (VLF). Wide range of frequencies and wave forms were used for this purpose. This paper presents an evaluation to the ability of VLF to detect successfully the presence of PD. The study was based on laboratory testing data collected from medium voltage cable having artificial defects. PD was measured on healthy and unhealthy samples of 12/20 kV cables with VLF as well as with power frequency. Different wave forms such as sinusoidal and rectangular with different frequencies in the range from 0.01Hz to 0.1 Hz were used.