Development of computer-based measurements and their application to PD pattern analysis

After referring briefly to the earlier developments of computer-based PD measurements in the 1970s, the paper outlines how the introduction of new technology has resulted in the design and production of a number of digital systems for use in test laboratories and on site. In order to avoid overgeneralization, the basis of the hardware required for detection and recording of the PD pulses is described by reference to a particular system, it being understood that many detailed variations are possible depending on the application. The paper describes a number of parameters that can be calculated by software and used to characterize the PD behavior. These include the IEC-270 integrated quantities, statistical moments and other fingerprints for recognizing the PD patterns within the power frequency cycle. Examples are given of the patterns obtained on equipment and samples. These are necessarily selective and are intended to indicate how the techniques may be applied. It is concluded that these new methods will become valuable in procedures for assessing the condition of electrical insulation, in particular faults or defects, but must be used in conjunction with existing techniques until improved confidence is achieved in interpreting results, especially in respect of the various phase-resolved distributions and calibration procedures