变压器油中阴极放电起始过程的气泡模型  

Bubble Model of Breakdown Initiation Process from Cathode in Transformer Oil

作　　者：王同磊 张乔根[1] 倪鹤立 袁炜雄 高萌[1] 李原[1] 

机构地区：[1]西安交通大学电气工程学院,西安710049

出　　处：《高电压技术》2017年第6期2042-2048,共7页High Voltage Engineering

摘　　要：为研究冲击电压下变压器油中阴极放电起始过程的物理模型,统计分析了不同冲击电压下稍不均匀场中变压器油的放电时延,利用Laue图获得了不同脉冲下的平均放电统计时延和放电形成时延,建立了稍不均匀场中阴极流注起始的"气泡"模型:阴极表面微凸起处的场致发射电流加热电极附近的液体;当液体达到一定过热度之后,过热液体内会产生气泡核心,气泡核心在场致发射电流的持续加热作用下会膨胀生长,直至气泡内放电产生。利用过热液体的汽化成核理论获得了成核时间的数学表达式,并结合F-N理论获得了放电统计时延和外施电场的关系式。结果表明,放电统计时延主要由电极附近过热液体的成核时间和气泡的膨胀形变时间组成,且成核时间占有主要部分;放电统计时延ts与间隙内电场E满足t_sE^3=ae^b/E。To study the physical model of streamer initiation from cathode under impulse voltages, the statistical characteristics of breakdown time lag in transformer oil are studied over a wide range of pulse width, and the statistical discharge time lag and the discharge formation time lag are calculated by the Laue＇s pattern. Then a ＇bubble model＇ for the discharge initiation process in quasi-uniform field is built. It is supposed that the field emission current generated by the small protrusion tips on the cathode surface could heat the liquid near the surface. When the liquid is superheated, nucleation sites would be generated. The nucleation sites would continue to expansion and elongate with the continuous heat supply until the gas in the bubble discharges. Moreover, the nucleation time is calculated based on the vaporization nucleation theory. A theoretical equation of the statistical discharge lag and the strength of the electric field is proposed based on the F-N theory. Results indicate that the statistical time is composed of the nucleation time and bubble distortion time. A relationship between the statistical time ts and electric field strength E is established by tsE^3=ae^b/E.

关 键 词：冲击电压 变压器油:放电统计时延 汽化成核理论 气泡模型 

分 类 号：TM41[电气工程—电器]