PD detection of XLPE cables accessories on UHF

Monitoring the partial discharge (PD) on site in cables accessories is now a more effective method of cable tests. Meaningful PD measurement can obtain reliable information on the condition of sealing ends and joints after installation or several years of operation which can contribute to considerable overall reduction of error risk. The UHF (ultra high frequency) method is an effective PD detection method. It shows out the superiority in measurement sensitivity and suppressing interference. It has been confirmed that the frequency of the PD pulse generated in cables can reach up to GHz, while the frequency of background noise usually lies below 400 MHz. Experiments show that the UHF PD pulse can radiate from the disconnection between the shields in the sealing ends or the joints, and it can also radiate out along the ground wire or the cross-linked wire. Moreover, the detection by UHF sensor towards four different types of PD models have been done in laboratory, such as sliding discharge model, floating discharge model, protrusion discharge model and cavity discharge model. Mass of statistic results of these PD pulses indicate the distinct characteristics. It can help to do the pattern recognition research, even to do further research on fault diagnosis for XLPE cables.