Collection: Instrumentation and measurement techniques for high voltage applications–Partial discharge echo measurement approach for high voltage insulation assessment

Abstract In this article, an original measurement methodology and detection approach, called partial discharge echo (PDE), applied to the electrical insulation systems of high voltage (HV) power devices is presented. This novel methodology and instrumentation extend the conventional partial discharge measurement approach, perceived as one of the crucial indicators of HV electrical insulation integrity. The application areas refer to electrical insulation in power grids, industrial network devices, and electrification in emerging transportation sectors such as electric vehicles, high-speed rail, propulsion in maritime vehicles, or more electric aircrafts. The experiments were carried out on the model specimens representing both a defect in HV polymeric power cable insulation and degradation of the motor winding insulation. The assessment was focused on PD echo characteristics, such as the echo decay time constant, duration of the echo cluster, inception level during base excitation and in echo period, and the charge magnitude attributes. Applying an analytical approach, the echo decay time constant was extracted from the PD phase-resolved patterns. A comparison of PD echo attributes in new and aged specimens revealed a clear dependence of the echo pattern on the condition of the dielectric surface. It was found in the research that, in the case of polyethylene specimen, the main PD echo attribute represented by the extracted decay time constant was reduced from 10.42 ms for the untreated sample to 1.04 ms for the electrically deteriorated sample. Simultaneously, the ratio of the echo peak magnitude to PD charge absolute magnitude has increased from 0.44 to 0.59 for the new and electrically aged specimen, respectively. In the case of twisted-pair motor winding insulation, the calculated PD echo decay time constant was 33.0 ms for new specimen and 6.1 ms for thermally deteriorated specimen. The PDE magnitude parameter yielded values of 0.18 and 0.19 in the above experiment. A reduction in the PD echo inception voltage from 1.4 kV to 1.2 kV was also observed. PDE is a non-invasive technique that may provide additional insight into the insulation surface conditions and charge-transport effects, offering new diagnostic attributes that expand the assessment of insulation conditions that are not possible by conventional PD measurements.