A study of three methodologies for the detection of partial discharge in OIP

High voltage bushing faults represent over one quarter of power transformer failures, therefore their reliability is crucial. The monitoring of partial discharge (PD) activity within a bushing to provide early identification of faults is well known. This paper provides a comparative analysis of three different techniques commonly used for PD measurements in bushings. Over time, concurrent PD measurements are made using phase resolved partial discharge pattern (PRPD), current pulse and radio frequency interference (RFI) methods. The progression of PD activity is tracked and the relationships between each of measurement methods are analysed and discussed. PRPD patterns are compared to patterns from known discharge types indicating PD typical of a cavity over three distinct stages. These experiments show a correlation in broadband spectral characteristic and proportional signal power uplift between the measured RFI and the current pulse power spectrum signals.