WATER TREE DETECTING METHOD FOR RUBBER*PLASTIC INSULATED POWER CABLE

摘要

PURPOSE:To realize a quick and accurate detection of the water tree, by applying the DC cut-wave between the conductor of the cable to be tested and the cable masking metal tape and at the same time giving a comparison of the DC leak current between the cables before after the area of application of the DC cut-wave. CONSTITUTION:The ball gap 2 is provided to the cable 1 to be tested and in parallel between the cable conductor 3 and the cable masking metal tape 4, and the DC high voltage generator 5 is connected to the gap 2. Then the fixed DC voltage V0 is applied to the cable 1 by the generator 5, and then the gap 2 is short- circuited. Thus the repetitive high voltage of the rectangular attenuation vibration wave having such waveform as shown in the figure and the cycle T is applied between the conductor 3 and the tape 4. And the electric tree is caused in case the water tree is caused in the insulator of the cable. Accordingly, the existence of the water tree can be detected by giving a comparison to the DC leak currents before and after application of the DC cut-wave.