Charges due to ionization at conductors at low electric field serves as the main source of charge carriers that is responsible for surface charge enhancement, especially for hetero-polar charges on the convex surface side of spacers inside DC gas-insulated transmission lines (GILs). In this paper, simulation results of charge generation processes from gas side, including natural ionization, micro-discharge and field emission, are presented. The results show that for the case where the electric field strength is -6.548 kV/mm and the gas pressure is 0.4 Mpa, when conductor roughness Ra is lower than 24.16 µm, natural radiation ionization is the main cause of the dark current. When Ra is between 24.16 µm and 188.59 µm, the dark current is dominated by micro-discharge. The Fowler-Nordheim (F-N) field emission occurs when Ra exceeds 188.59 µm. Considering the roughness of the conductor in the actual GIL, the increase in the dark current due to local roughness is mainly due to micro-discharge rather than F-N field emission. The results in this paper provide an important part for further determining of conductor surface conditions in high voltage direct current (HVDC) GILs and serve as an important reference for completion of the surface charging model of spacers under DC.

中文翻译：

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HVDC GIL 的导体表面粗糙度相关气体传导过程 — 第 I 部分：模拟


低电场下导体电离产生的电荷是电荷载流子的主要来源，负责表面电荷增强，尤其是直流气体绝缘传输线 (GIL) 内间隔件凸面侧的异极电荷。本文给出了气体侧电荷产生过程的模拟结果，包括自然电离、微放电和场发射。结果表明，在电场强度为-6.548 kV/mm、气压为0.4 Mpa的情况下，当导体粗糙度Ra低于24.16 µm时，自然辐射电离是产生暗电流的主要原因。当Ra在24.16μm到188.59μm之间时，暗电流以微放电为主。当 Ra 超过 188.59 µm 时，会发生 Fowler-Nordheim (FN) 场发射。考虑到实际GIL中导体的粗糙度，局部粗糙度导致的暗电流增加主要是由于微放电而不是FN场致发射。本文的研究结果为进一步确定高压直流（HVDC）GIL中导体表面状况提供了重要的依据，并为完成直流下隔离件表面充电模型提供了重要参考。