Partial discharge pattern Characteristic of MV Cable joints with artificial defect

Insulation failure of XLPE cable system, particularly in joints and terminations, mostly attributes to local defects resulted from inadequate manufacturing or poor installation workmanship. Since it is well-acknowledged that partial discharge (PD) has a relationship with the discharge source (fault or defect), PD detection and pattern recognition have been widely accepted as a means to provide information on both the type and severity of defects or potential failures, which is further expected to give advice on repair or replacement of cable accessories. Admittedly, it is absolutely not a simple task, thus a lot of current researches focus on this issue. This paper presents a laboratory experiment on 35kV XLPE cable joints with artificial defects and applies to a pattern classification method to distinguish different type defects. Seven artificial defects, including high-potential metal tip, semi conductor layer air gap, semi-conductor layer tip, semi conductor layer metal tip, insulation incision, mental particle on XLPE insulation, axial direction shift, are separately fabricated in 35kV XLPE cable joints to simulate field poor installation workmanship. The experiment setup and procedure are introduced subsequently. In regard to pattern classification, wavelet-based decomposition is applied to extract the distinguishing features of the gray-image of phase-resolved PD patterns. The result shows PD patterns of the artificial defects present dissimilarity, which can be utilized as samples for further on-site PD pattern recognition.