Statistical analysis of partial discharge data

Recently, considerable efforts were deployed at Hydro-Quebec to retrieve all partial discharge (PD) files recorded with the PDA-H instrument over the last 25 years and which were scattered all over in plant computers. These initial raw data files have been centralized on a corporate computer, where all new measurements are now systematically saved. The statistical analysis of the first 10000 files has served as a framework for establishing five levels of discharges severity. This paper presents the results of this statistical analysis which proposes a two dimensional classification of the discharge severity. It also attempts to compare the statistical distribution of the maximum discharge apparent amplitudes with what can be found in the industry. Finally, a description is given to show how the evolution of partial discharges over the years is used in a more general diagnostic process