Partial Discharge Investigations on a High Voltage Generator Cable Insulation through TF Method

Partial discharge (PD) that occurs on the insulation of a high voltage (HV) generator bar has decisive influence over its operating condition and efficiency. So, it is vital to provide special attention while monitoring the PD activity of pertinent insulation arrangement. In particular, the occurrence of internal discharges that emerges due to micro-voids initiates PD which initially doesn't pose an immediate threat. Nevertheless, the prolonged internal discharges might cause permanent damage to the localized site insulation. The high operating temperature, electrical discharges and other adverse operating conditions aggravate the ageing phenomena which might result in premature failure of the generator. The modern maintenance procedures include periodical visual inspection and dielectric tests. Additionally, PD based monitoring systems are also installed to measure the level of PD and analyze the trend followed over a period of time. However, it is quite important to analyze the PD data from every aspect to understand the underlying phenomena and exercise a better maintenance procedure. In this regard, the present study resolves the PD that evolves in the micro-voids of mica based insulation of a HV generator bar. The PD levels of insulation coated on HV generator arrangement is measured, recorded and their respective phase resolved PD pattern (PRPD) is analyzed. Later, the measured PD signals are transformed into frequency domain and the possibilities and status of the sample bar is analyzed.