Influence of Particle Properties on DC Breakdown Characteristics of Mineral Oil and Its Difference Reason Analysis
Hao Jian1, Dan Min1, 2, Liao Ruijin1, Li Jian1, Yang Lijun1
1. State Key Laboratory of Power Transmission Equipment & System Security and New Technology Chongqing University Chongqing 400044 China; 2. State Grid Chongqing Electric Power Co. Nan’an Power Supply Branch Chongqing 401123 China;
Abstract：The converter transformer is the most important equipment in the EHV/UHVDC transmission project. At present, impurity particles in insulation oil become a threat to the reliable operation of the converter transformer. In this paper, firstly, the effects of different concentrations and sizes of non-metallic fiber particles, copper particles, fiber and copper mixed particles on DC breakdown field strength of mineral were studied experimentally. Then the accumulation behavior of impurity particles in oil was simulated and analyzed using the particle dynamics model and the particle accumulation model. The particle accumulation and its effect on electric field distribution were analyzed. Finally, the differences and reasons of particle properties on DC breakdown of mineral oil were summarized. The results show that the particle properties determine the variation of DC breakdown voltage of insulation oil. The DC breakdown voltage of oil containing pure fiber or copper particles decreases linearly with the increase of particle concentration. The DC breakdown voltage of oil containing fiber and metal particles decreases exponentially with the increase of copper particle concentration. The deterioration degree of metal particles on oil insulation performance is greater than that of single particles, and the increase of fiber particle size further reduces the DC breakdown strength of oil. The results of experiment and simulation show that the bridge phenomenon of particle accumulation appears in the oil under the action of DC electric field. Particle accumulation greatly improves the conductivity of oil and leads to significant distortion of electric field distribution in oil. Compared with the DC breakdown voltage without preloading mode, the DC breakdown strength of oil decreases more than 30% due to the particle accumulation under the DC preloading mode.
郝建, 但敏, 廖瑞金, 李剑, 杨丽君. 颗粒属性对矿物绝缘油直流击穿特性的影响差异及原因分析[J]. 电工技术学报, 2019, 34(24): 5270-5281.
Hao Jian, Dan Min, Liao Ruijin, Li Jian, Yang Lijun. Influence of Particle Properties on DC Breakdown Characteristics of Mineral Oil and Its Difference Reason Analysis. Transactions of China Electrotechnical Society, 2019, 34(24): 5270-5281.
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2019, Vol. 34 
