Partial discharge characteristics and development of typical XLPE power cable insulation defects

It is well known that preventive tests have been widely used as an important means to ensure reliable operation of the power cable. Nevertheless, in the early stages of insulation deterioration, the traditional preventive tests cannot effectively detect the faint abnormal signals caused by defects. As insulation failure usually starts with PD activities, which is not only one of the primary reasons to cause the insulation deterioration of the cable, but also the characteristic scalar to describe the insulation state of cable. Therefore, PD diagnosis is recommended by IEC, IEEE and CIGRE as an effective method to evaluate the properties of cable insulation condition. In order to study the PD characteristics of the typical defects in XLPE(Cross-Linked Polyethylene)power cable, two PD models as protrusion defect of cable joint and void defect in main insulation were designed, and then the PD measurement and analysis system based on the PDBase was established. The PD characteristics of typical defects were detected and compared, also the effects of the applied voltage on the phase-resolved PD (PRPD) pattern, waveform characteristic, discharge frequency, center-phase distribution and statistical features were investigated. The experimental results indicated that it has the high stability and repeatability of the discharge on the identical defect model under the same condition. The discharge development process, PRPD patterns, time domain waveforms, central phase changing of PD signals and statistical features had very similar distribution characteristics and those of different defect had different ones. So it provides a test basis for the pattern recognition of PD types and a deeper study on the PD mechanism of XPLE cable.