Correlation between PDIV and life distribution under different testing waveforms

Abstract

The implementation of underground distribution lines has grown significantly over the last decades due to the rapid increase of electric energy demands. But, the lifetime distribution of lines is strongly affected by the single or multiple stresses that could develop in the insulation system of the power cables. In this paper, the influence of applied voltage waveform on partial discharge activity and lifetime distribution of insulation material for power cables was investigated. In this sense, the Inverse Power Law-Weibull model was applied in order to develop a life model of the PD induced degradation processes under different voltage waveforms occurring in microcavities from the power cables insulation system. For the insulation design it is of great importance to assess the insulation threshold by using the voltage tests. As result, the step-up test method was used.

Investigation of Partial Discharge and Fracture Strength in Piezoelectric Ceramics

“…Studies suggest that PDs may be a source of fatigue degradation . To minimize this effect, relatively short time were set for the dwelling time (20 sec) in the PD test at each voltage step and the recording time (10 s) for the PD pattern . Moreover, to evaluate the influence of the PD test on the PZT ceramic, several tests were carried out.…”

“…[24][25][26][27] To minimize this effect, relatively short time were set for the dwelling time (20 sec) in the PD test at each voltage step and the recording time (10 s) for the PD pattern. 18 Moreover, to evaluate the influence of the PD test on the PZT ceramic, several tests were carried out. First, the surface structures of the PZT specimens were examined after polishing and after the PD test, once electrodes were removed, using an optical microscope; no obvious changes can be observed.…”

“…One group of PZT samples underwent PD testing. The test sequence used to detect the PD inception electric field is as follows . An AC voltage (in the same direction as the poling direction) was applied to the test object for 20 s. If there were no continuous observable PDs, the applied voltage was raised by an increment of approximately 80V.…”

“…The two‐parameter Weibull function for mechanical strength is as follows:where P f is the probability of mechanical failure, σ f is the flexure strength of material, m 1 is the Weibull modulus or Weibull shape parameter, which inversely reflects the strength distribution, and σ 0 is a scale stress, which is a measure of centrality (the center of the distribution). Similarly, the probability of the inception of partial discharge P I , can be expressed by the following equation: where m 2 is the Weibull modulus, E PD is the PDIE of the sample, and E 0 is a scale electric field …”

“…The test sequence used to detect the PD inception electric field is as follows. 18 An AC voltage (in the same direction as the poling direction) was applied to the test object for 20 s. If there were no continuous observable PDs, the applied voltage was raised by an increment of approximately 80V. This operation was repeated until repetitive PDs were detected and the voltage was recorded as the partial discharge inception voltage (PDIV).…”