Effects of ambient temperature on surface charge and flashover of heat-shrinkable polymer under polarity reversal voltage

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Abstract
DC transmission helps to solve the decentralization of distributed wind power generation and other renewable power sources to enhance system performance. But the existence of surface charges by the corona makes earlier insulation failure and plays an important role during the development of the surface flashover. The influences of the ambient temperature and the polarity reversal voltage on the surface charge and the flashover of the heat-shrinkable polymer are not completely clear. In this paper, the carrier mobility and the volume conductivity were employed to explain the temperature dependent surface charge decay results. The initial surface charge density and decay rates served for analyzing the effects of polarity reversal voltage. Furthermore, the flashover experiments of the samples charged by the polarity reversal voltage at different ambient temperatures were conducted. Obtained results show that the descending speed of the surface charge becomes faster at higher temperature. An obvious temperature dependence of the carrier mobility and the volume conductivity is observed. Moreover, the surface charges of the samples charged by the voltage with shorter reversal time decay more rapidly. The flashover voltage increases with the increasing ambient temperature because of less accumulated surface charges in this condition. Considering the accelerated surface charge decay by the increasing temperature and easier charge accumulation during the steady negative period, attentions should be paid to the design of DC insulation and the security of operation.

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