Abstract
Partial discharge (PD) detection on live UHV/EHV power cables and accessories is one of the most important technique to prevent cable systems from serious troubles caused by slight mistakes in jointing the cables. New PD detecting method is proposed in this paper. REDI (Resonance Type Partial Discharge) sensor is developed for detecting PD occuring inside the joints of live XLPE insulated cables. This sensor pickes up the high frequency components of PD current pulses on the surface of live cables, so that the output signals can be clearly observed at the noiseless area (for example, 10_??_60MHz)
This new method was applied to the initial AC breakdown tests with three different types of joints of UHV/EHV power cables. PD pulse sequence was detected before their breakdown in all cases. The charge quantity and the number of pulses extremely increase just before the breakdown. In addition, the phase of PD pulse against the applied voltage (φ-q characteristics) changes with time or progress of deterioration. According to this experimental results, REDI sensor can be applied to the insulation diagnosis of live power cable joints.
