Research On Non-contact Method Of Detecting Faulty Porcelain Suspended Insulators

With the development of electric power industry, a large number of insulators are used in power transmission system. The faulty insulator is dangerous to the safe operations of power system. There is no uniform standerd and convenient and reliable method to detect faulty insulator in the running state at home and abroad. Therefore, this paper studied three non-contact detection methods such as space electric field measurement method, infrared imaging method and ultraviolet imaging method to detect faulty insulators.Firstly, this paper analyzed the nature of the space electric field of the porcelain insulator string, and established a porcelain suspended insulator string simulation model by the finite element software Comsol 3.4. The influence of umbrella skirt types, transmission wires, towers, lightning line, insulator types, pollution, faulty insulators etc. to the space electric field of the porcelain insulator string were analyzed by simulation. The space electric field distribution characteristic of XP-160 type string (13 pieces) was measured by test, and those results were compared with the simulation results. According to the test and simulation results of space electric field distribution characteristic of the insulator string with and without faulty insulators, electric field distribution measurement based on sensitive insulator method was summarized, and also analyzed the influence of insulator type and pollution to its detection. The infrared imaging method and ultraviolet imaging method to detect faulty insulators were researched by the test in the State Key Laboratory of Power transmission Equipment & System Security and New Technology, Chongqing University. The infrared imaging method field test was taken in the part of 220kV and 500kV substations of Foshan Power Supply Bureau. The influence of pollution, faulty insulator position, insulator type, detection distance to the detection effect was analyzed by the test.The study has shown that, the wire, towers, insulator string types, pollution and other factors should be considered to calculate the space electric field of porcelain insulator strings. The surface maximum field strength of porcelain insulator is in the air near the surface of the umbrella skirt, when the insulator is faulty, the electric field value decreases. The influence of faulty insulators to the space axial electric field component is the most obvious, and the influence is related to the location of the faulty insulators, near high-voltage side and cross arm side is more obvious, near middle is less obvious. The electric field change rate of Multi-piece insulator continuous deteriorated is greater than the intermittent deterioration, and the influence of faulty insulator to the space electric field is noninterference. Analysing the axial electric field change rate of three porcelain insulator in the cross arm-side (d=0.3m) can determine whether the 220kV overhanging insulator strings contain zero value insulators. Pollution degree, insulator type has no influence to infrared imaging method to detect faulty insulator. Faulty insulator position, insulator surface color, type of insulator strings, detection distance has a certain effect on the detection. Infrared imaging method can detect whether there are faulty insulators in the insulator string and also can identify their locations. Dry pollution makes it detect faulty insulator easily, wet pollution will affect the accuracy of detection. Ultraviolet imaging method can detect whether insulator strings contain faulty insulator, but can not determine their locations. Corona of wire, end fitting and wet poulltion on insulator surface has obvious impact to the detection. Based on the above studies, a comprehensive method of detecting faulty insulators was summarized.This study concludes that the infrared imaging method and the electric field distribution measurement method could be used for detecting faulty insulators of the transmission line.