Novel characterization of PD signals by real-time measurement of pulse parameters

Measurements of partial discharge (PD) are used to examine the insulation characteristics of HV equipment. This test method is also suitable for low-cost components in mass production. To monitor the quality of prefabricated parts, products and production processes, short test cycles and automatic classification are indispensable. In addition, it is desirable to acquire more information about the PD signals for classification. This can be achieved with an ultra wide band (UWB) measurement system. In this paper a new test method, based on analog capture of PD parameters which describe the PD waveform, in addition to the usual parameters, is proposed. The analog values are further processed employing a digital signal processing hardware and a PC. Measurements of frequently encountered PD pulse shapes and their frequency spectra are used to discuss problems which arise from the integration in the frequency domain. These problems are avoided using integration in the time domain, which is employed to determine the apparent charge with the described measurement system. Using the PD pulse duration as an example, measurements on artificially created test samples are presented, which show the influence of the defect dimensions on the PD pulse parameters. This is feasible for test circuit dimensions not extending to a certain value, which depends on the used frequency range of the measurement system.