Xue Jianyi, Chen Junhong, Dong Junhao, Deng Junho, Zhang Guan-Jun
State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, People's Republic of China.
Nanotechnology. 2020 Sep 4;31(36):364002. doi: 10.1088/1361-6528/ab938f. Epub 2020 May 15.
Surface flashover properties of alumina/epoxy spacers, involving a surface charge accumulation process, are critical for the safe and reliable operation of a high-voltage direct-current (HVDC) gas-insulated transmission line (GIL). This study reports surface charging behavior and flashover performance of alumina/epoxy spacers with different surface conductivity graded coating (SCGC) schemes in SF/N mixtures under DC stress. Four kinds of SCGC schemes, i.e. localized coating near high voltage (HV-coating), near grounded electrode (GND-coating), at the middle of spacer surface (SPM-coating) and near both high voltage and grounded electrode (HV-GND-coating), are designed by partially spraying SiC/epoxy composites on the spacer surface. Surface charge distribution patterns exhibit varied features with different SCGC schemes. The HV-coating and GND-coating schemes lead to aggravated homo-charge and hetero-charge accumulation respectively, whereas in the SPM-coating scheme surface charge shows a multi-tier distribution pattern with alternating polarity. A transition of the dominant surface charge mechanism from bulk conductivity to surface conductivity with increasing conductivity on the coated area is found. Flashover performance differs a lot with different SCGC schemes: the HV-coating and HV-GND-coating schemes increase the flashover voltage while the SPM-coating and GND-coating schemes degrade it. The optimal surface insulation strength is achieved in the HV-coating scheme with a coating width of about 10 mm. The impact of different SCGC schemes on flashover performance is revealed based on the electric field analysis by considering the effect of surface charges.
氧化铝/环氧树脂绝缘子的沿面闪络特性，涉及表面电荷积累过程，对高压直流（HVDC）气体绝缘输电线路（GIL）的安全可靠运行至关重要。本研究报道了在直流电压作用下，不同表面电导率分级涂层（SCGC）方案的氧化铝/环氧树脂绝缘子在SF₆/N₂混合气体中的表面充电行为和闪络性能。通过在绝缘子表面部分喷涂SiC/环氧树脂复合材料，设计了四种SCGC方案，即靠近高压端的局部涂层（HV涂层）、靠近接地电极的局部涂层（GND涂层）、绝缘子表面中部的局部涂层（SPM涂层）以及靠近高压端和接地电极的局部涂层（HV - GND涂层）。不同SCGC方案下的表面电荷分布模式呈现出不同的特征。HV涂层和GND涂层方案分别导致同极性电荷和异极性电荷积累加剧，而在SPM涂层方案中，表面电荷呈现出极性交替的多层分布模式。发现随着涂层区域电导率的增加，主导表面电荷机制从体电导率转变为表面电导率。不同SCGC方案的闪络性能差异很大：HV涂层和HV - GND涂层方案提高了闪络电压，而SPM涂层和GND涂层方案则降低了闪络电压。在涂层宽度约为10 mm的HV涂层方案中实现了最佳表面绝缘强度。通过考虑表面电荷的影响，基于电场分析揭示了不同SCGC方案对闪络性能的影响。
