The hetero-polar charges on the spacer surface due to the gas ionization has been verified as one of the hazard charge sources threatening the safe operation of HVDC gas-insulated transmission line (GIL). This letter reports the differences in surface charging properties of spacers in SF 6 and C 3 F 7 CN/CO 2 gas mixtures, and a rigorous re-examination of environmental firendly gas assessment for DC GIL is introduced. The results show that when the maximum value of electrical field strength at the spacer surface is in 0.45 kV mm −1 , homo-polar surface potential in different insulating gases indicates a dominant charge originating from bulk injection. As the maximum value of electrical field strength at the spacer surface reaches 0.68 kV mm −1 , local hetero-polar surface potential areas are detected and the area ratio of these regions is higher in CO 2 gas, followed by 4% C 3 F 7 CN/96% CO 2...

中文翻译：

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环保C 3 F 7 CN / CO 2混合气中的本征异质表面电荷现象

已经验证了由于气体电离而导致的垫片表面上的异极性电荷是威胁HVDC气体绝缘传输线（GIL）安全运行的危险电荷源之一。这封信报道了SF 6和C 3 F 7 CN / CO 2气体混合物中隔离物的表面带电性能的差异，并引入了对DC GIL进行严格的环境气体评估的严格重新检查。结果显示，当间隔物表面处的电场强度的最大值为0.45kV mm -1时，不同绝缘气体中的同极性表面电势指示源自体注入的主要电荷。随着隔离物表面的电场强度的最大值达到0.68kV mm -1，