Effective partial discharge measurement method for XLPE cables based on propagation characteristics of high frequency signal

Joints of power cable system have a possibility to include some defects due to long-term chemical reaction and deoiling of grease as well as on-site workmanship at their installation. The partial discharge (PD) measurement can be a powerful insulation diagnosis technology to confirm their soundness. PD is accompanied with a pulse current with its rise time of several nano-seconds, which propagates in the power cable. Thus its propagation characteristics are quite important to determine not only the objective frequency range but also the appropriate PD sensor installation. In this paper, the propagation characteristics of pulse signal in XLPE power cables are firstly discussed with empirical results. Then, the determining process of the objective frequency is proposed based on the frequency characteristics of the attenuation rate of the XLPE cable to measure the PD only at the both terminations.