Study On The Optimization Of Sheds Configuration Of35/110kV Composite Insulators Used At Icing Areas Based On Electric Field Distribution

More than twenty years’ using history of composite insulators in China shows that,compared to porcelain and glass insulators, their pollution flashover performance ismuch better, whereas the icing flashover performance isn’t so. Sheds configuration is akey factor that influences composite insulator’s icing flashover voltage. As the flashoverprocess of icing composite insulator is pretty complex, and the flashover voltage isclosely related to the electric field and potential distribution around the insulator,studying the flashover mechanism of icing composite insulators based on electric fielddistribution has always been the top priority of the research. Sheds configuration is themain factor that influences the flashover voltage, therefore, in order to increase theflashover voltage of composite insulators, studying the influence of sheds configurationon electric field distribution and finding out the best sheds configuration which letbe theoptimal electric field characteristics are of great importance.In the past study on the optimization of sheds configurition of iced compositeinsulators, researchers didn’t consider the difference between energized andnon-energized icing, and they generally considered the worst case, in which the iciclesstretch more than two-thirds of the distance of two adjacent big sheds or even bridge allof them, cause in this case, the electric field around the insulator would be distortedmost seriously. But for the composite insulators actually operated in the transmissionlines, their icing process are energized icing, the sheds at high voltage end are rarely tobe bridged by icicles. Furthermore, electric field has a significant impact on the icingvelocity, form, weight, density, etc. Therefore, compared to non-energized cases,energized icing tests and calculations of composite insulators are more approximate toactual situation. Contraposing the glaze icing which is most harmful to the powersystem, this paper is aimed at simulating the icing condition of composite insulatorsactually running in transmission lines. Non-energized and energized icing tests ofseveral35kV and110kV anti-icing composite insulators with different kind of shedsconfiguration were carried out in the multi-function artificial climate chamber.According to the experimental data, the icing models of insulators used in the testwere built up, the computed results are consistent with the experimental ones. The mainconclusions obtained from the tests and calculations are:â‘ The ice weight related to sheds configuration, energized or not and freezing water conductivity, and increases with the retio of creep distance and the arc distance（coefficient CF）;â‘¡Based on the basic purpose of reduction of icing, parameters characterizing thesheds configuration characteristics k₁, k₂, k₃were proposed in this paper, namely, shedsconfiguration optimization could be achieved by optimizing such parameters, and theoptimal value k₁, k₂, k₃and coefficient CF were obtained by calculation;â‘¢There are great influence of sheds configuration on Eav, and the flashovervoltage increases with the decrease of Eav;â‘£By electric field calculation, the inadequacies of the sheds configuration of Cand E, whose electric field characteristics were relatively better, were interpreted. Basedon the simulation of the electric field and the test results, sheds configuration of35kVand110kV insulators are optimized respectively at the last part of this paper. And thesimulation analysis shows that, by measures such as select the small （middle） sheds’diameter properly, ensure a suitable diameter difference of the big （middle） and smallsheds, choose the number of big sheds appropriately, adjust the distance of adjacent bigsheds at high voltage top, can achieve the purpose of optimization of shedsconfiguration. At the same icing conditions, the electric field performances of theoptimized insulators have been significantly improved.