Acoustic emission measurement of partial discharges during electrical tree growth in XLPE cable insulation

Electrical treeing was initiated within XLPE insulation samples using a pin-plane electrode arrangement. The acoustic emission characteristics against test time until breakdown occurs, were investigated. Three dimensional φ-q-n patterns were used to present the discharge acoustic emission signals at different time periods during the breakdown process. Typical statistical operators, including skewness, kurtosis and cross correlation coefficients, were calculated. Obtained results indicate that a relationship may exist between skewness and the ageing process. Investigation also indicates that different experimental conditions such as pin tip radius,. pin-plane spacing and applied voltage, may determine the type of the resultant tree. The gas pressure within the tree channel and the space charge effect will also influence the breakdown process. The discharge signal magnitudes can vary significantly during the breakdown process, for this reason, breakdown cannot be predicted only by magnitude information