Pulse sequence analysis on PD data from electrical trees in flexible epoxy resins

Abstract

This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent University of Leicester Department of EngineeringAbstract-The Pulse Sequence Analysis (PSA) was carried on PD data from electrical trees grown in flexible epoxy resins. The samples used for the electrical tree experiments were conditioned in environments with different relative humidity in the range 15-100% prior to the electrical tests and the corresponding moisture content in the samples was between 0.1 and 6.9%. The electrical treeing experiments were carried out at different temperatures in the range 20-70°C. The details of PD dynamics during the electrical tree growth have been found to change significantly with temperature and absorbed moisture. In this paper, it is shown that PSA could be successfully used to discriminate between PD data from electrical trees and runaway breakdown.

The role of bulk charge transport processes in electrical tree formation and breakdown mechanisms in epoxy resins

“…The simulations resemble closely the experimental data given in [34] and reproduced here in Figure 11. In the case of a lower conductivity of the bulk resin ( Figure 10a) the PDs occur in the first (Q1) and third (Q3) quadrants of the applied voltage and the PSA return map consists of six clusters, which have a similar appearance and alignment to the case of burst type behavior during an electrical tree growth, shown here on the left in Figure 11 and in [34]. The PD activity between the bursts is characterized by a significant scatter in the PSA clusters and it is not possible to simulate it using the equivalent circuit of Figure 9.…”

“…This is reflected in the corresponding PSA return map, where the clusters associated with positive and negative PD distributions extend along the 45° line. Similar return maps were observed in the cases of runaway growth, shown here on the right in Figure 11 and in [34]. The simulation therefore associates runaway growth with a high bulk conductivity for which the circuit model of Fig.9 applies throughout the discharging, i.e.…”

“…In the phase-resolved plots, the PD pulses are indicated by the green lines, the voltage across the spark gap is given in black, the voltage across the insulation (capacitor CB) in red and the applied sinusoidal voltage in blue. The differential ratio dU/dt was used to analyze the simulated data and to obtain the PSA plots in the same way as the experimental data presented in [34]. The simulations resemble closely the experimental data given in [34] and reproduced here in Figure 11.…”

“…The differential ratio dU/dt was used to analyze the simulated data and to obtain the PSA plots in the same way as the experimental data presented in [34]. The simulations resemble closely the experimental data given in [34] and reproduced here in Figure 11. In the case of a lower conductivity of the bulk resin ( Figure 10a) the PDs occur in the first (Q1) and third (Q3) quadrants of the applied voltage and the PSA return map consists of six clusters, which have a similar appearance and alignment to the case of burst type behavior during an electrical tree growth, shown here on the left in Figure 11 and in [34].…”

“…In the cases where thermal breakdown had occurred, no PD data were collected. At low temperature and low moisture the average values of both discharge rates and magnitudes are typical of those characterizing the PD activity during the electrical tree growth [33,34]. However, at high values of temperature and/or humidity the average PD magnitudes decrease, while the corresponding number of PDs per second increases significantly.…”