| With the development of power grid, cable has become an important part of power system. Modern production requires that cable must maintain a long-term, continuous and safe and stable operation. Thus the implementation of the state of the cable insulation online monitoring and control of cable insulation and running condition, discovering the latent dangers of cable equipment, guaranteeing that the cable run safely and reliably, has very important significance. Based on the current cable on-line monitoring of partial and local faults, This paper put forward to collect a variety of information to reflect the actual changes in cable insulation state by using fuzzy mathematics to scientific computing, and get the insulation state assessment, then based on the research the online monitoring system has developed. The main works are as follows:(1) This paper analyzed the reasons and the basic characteristics of partial discharge,based on the cause of cable insulation fault problems of urban power grid,. According to the actual structure data cable, the equivalent simulation model of the parts of cable was build for the simulation analysis of the electric field distribution characteristics of cable under different fault conditions distortion including air gap, water gap, steel nail knocked. According to the cable insulation fault mechanism this article selected the characteristics that monitoring system required including capacitor leakage current, frequency pulse current, ambient temperature and relative humidity, and analyzed the correlation of the selection of characteristic and cable insulation state in detail.(2) Considering the influence of the cable insulation state characteristic, using fuzzy comprehensive evaluation method for a comprehensive evaluation of cable insulation status, a evaluation method of cable on-line monitoring on the theory of fuzzy was proposed, which used fuzzy analytic hierarchy process for rational distribution of weights of cable evaluation factors, solved the problem of each evaluation factor’s membership degree with membership function and fuzzy set and completed the assessment of cable insulation condition.(3) Cable insulation online monitoring system was constructed on basis of the theory. Hardware module and software programming including capacitor leakage current, pulse current, environmental temperature and humidity data of online monitoring, remote communication and solar battery charging function was completed. Network real-time data transmission platform which achieved real-time continuous on-line monitoring for cable insulation status changes in three different levels of warning was set up.(4) The cable insulation online monitoring warning system was applied. On-line monitoring device was installed in the ten points selected to carry out effective field experiment. According to real-time data of three cables, data analysis and fuzzy evaluation of cable insulation state was conducted, The feasibility of fuzzy comprehensive evaluation method was validated by the analysis of the theoretical algorithm results and the actual measurement result. To verify the effectiveness of cable insulation status and feasibility of fuzzy comprehensive evaluation method, the theoretical algorithm results and the actual measurement status were analyzed, the results show that one of the cables was marked yellow warning by evaluation results and point of failure could be found through troubleshooting. |
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