DIELECTRIC BREAKDOWN TESTING METHOD FOR POWER CABLE MADE OF CROSSLINKED POLYETHYLENE

摘要

PURPOSE:To reduce the rush energy from the power source side after dielectric breakdown, and prevent the concentration of the electrostatic energy of the cable itself to the dielectrically broken hole of the cable by elevating the intrinsic resistance of an external semiconductor layer within a range where the evolution of heat is out of the question. CONSTITUTION:When a CV cable 1 causes dielectric breakdown, pulselike current flows in a coupling capacitator 9, and is detected by a detector 10. The output of the detector 10 is transmitted to a thyristor device 12 via a gate circuit 11. When the device 12 is turned on, the low voltage side of a transformer 5 for testing is short- circuited, and at the same time a signal is outputted to cut off the AC current by a breaker 8. Then, when dielectric breakdown occurs in the central part of the cable 1, the size of the broken down hole is kept 0.2mm.. In this case, the resistivity value of the external semiconductor layer of the cable 1 is 103OMEGA/m, the quantity of the evolved heat is about 0.2W/m in the ground part, and voltage drop is 350V which is negligible.