含气泡缺陷环氧浇注绝缘管型母线电击穿机理研究

Investigation of Electrical Breakdown Mechanism of Epoxy Cast Insulated Tubular Bus with Bubble Defects

绝缘管型母线是一种新型的母线产品,有着优异的性能。但应用时间较短,研究不够深入,致使故障频发。文中设计与制备了含气泡缺陷环氧浇注绝缘管型母线真型样品,通过加压电破坏试验,研究其电击穿机理。在试验中首次发现了气体膨胀鼓包导致最终击穿的破坏方式。研究结果表明,电—机械击穿应为其击穿模式,其击穿过程可分为气体增强阶段和击穿临界阶段两个阶段,并得到了阶段特征与阶段变化判据。气隙内由局部放电导致环氧树脂分解所产生的气体气压超过气隙壁断裂韧性临界值,造成裂纹失稳扩展是击穿的主要原因。可以通过提高环氧树脂材料的抗局部放电能力或对环氧树脂进行改性提高其断裂韧性来增强绝缘管型母线的击穿性能;传统的检测手段难以判断击穿通道的发展状况。研究结果对于其他树脂浇注类绝缘电气设备也具有一定的参考价值。

Insulated tubular bus is a novel type of bus product with excellent performance. However, the period of its application is less two decades and its research is insufficient, which resulting in many accidents. In this paper, the full-scale model of epoxy cast insulated tubular bus was designed and fabricated, and its electrical breakdown mechanism was investigated by withstand voltage test. In the experiment, the failure mode of breakdown caused by gas expansion was found for the first time. The research showed that electrical-mechanical breakdown should be its breakdown mode, and the breakdown process could be divided into two stages: gas increase stage and breakdown threshold stage. The research also obtained the characteristics and the change criteria of the two stages. The gas in the bubble defects generated from epoxy decomposition which caused by partial discharge. When the gas pressure exceeds the critical fracture toughness of the bubble defects wall, the unstable crack extension occurs, therefore, improving the ability about resistance to partial discharge of epoxy resin or improving the fracture toughness of epoxy resin by modifying would enhance the breakdown performance of insulated tubular bus. The result also showed that it was difficult to judge the development status of breakdown channel by traditional testing method. The results of this research also have reference value for other epoxy cast insulated electrical equipment.