High Voltage Cable Sheath Fault Real-time Positioning System Research

With the increase of city power grid voltage cable running time, cable sheath damage phenomenon tends to be ordinary, sheath perforation, leading to formation of metal sheath grounding loop, circulation, so that the cable outer sheath of fever, reduce the cable transmission capacity; at the same time continuous discharge of the aluminum sleeve by galvanic corrosion, damage to the insulation of air and water the main insulation, resulting in increased the probability of water tree aging, easy to produce partial discharge and electrical tree, pose a threat to the long-term safe operation of cables, seriously affect the service life of the cable. Therefore, in order to prevent the cable sheath fault hidden trouble to expand the scope, reduce line outage occurs, the maximum protection of power system security and reliability of power supply, the research of cable sheath fault real-time positioning system, the defects of stem sheath in the bud, has very important significance.This paper established the determination of cross connection of cable fault location in the sheath circulation detection data, and through to the cable input pulse signal of high frequency, the research ideas by using the fault point of the original wave and reflected wave time difference to accurately locate the fault source location. Build the fault location system, the sheath current existing mature technology in monitoring system as the foundation, increases the sheath current fault location device and fault wave recording device. The difficulties in development of high frequency pulse generator sheath positioning system. Finally, through laboratory test, the fault section of cable sheath input frequency pulse electromagnetic wave, through the fault point method to find the time domain reflectometry is feasible, and the sheath positioning system can effectively detect the primary wave and reflected wave. The fault point, the data measured in the laboratory accuracy basically reached the expected requirements. However, field test in operation of transmission line 110 k V shore day II line, due to the relatively large internal interference, high frequency electromagnetic wave interference of this test, the test results are not up to the expected goal.The results of this study show that: through the electrode coupled to electromagnetic wave propagation in the outer sheath on the pulse frequency, when the outer sheath is damaged and the equivalent circuit, is the formation of discontinuities due to reflected here, the use of HFCT can be coupled to the primary wave and reflected wave, through the original wave and reflected wave time the difference can judge the fault location. This is the end reflection test in the laboratory, to prove that the theory is feasible. However, the cable sheath fault real-time positioning system the research also need to add more anti-interference methods in software and hardware, fault detection method and the electric field of cable in the existing technology conditions can not achieve long-term online, the system is far from the practical need to research, improvement.