PD-testing of service aged joints in XLPE-insulated medium voltage cables at test voltages with variable shape and frequency

摘要

Joints with improper assembly may withstand service live for several years even with high PD stress. However, they fail far earlier then the expected service life of 10 to 20 years with a high probability. These joints may remain undetected by plain voltage withstand tests because they can withstand even high PD stresses much longer than usual testing times. By means of PD measurements the defective joints could be detected even under on-site conditions. In most cases the PD parameters like inception voltage, PD level and PD rate are nearly not dependent of test voltage shape and frequency. Therefore easy handling and transportability may become more important for the choice of a test voltage source.