110 kV电缆中间接头的开/合闸过电压仿真

Overvoltage Simulation During Opening/Closing of 110 kV Cable Joint

110kV电缆线路近年发生过多起断路器跳闸检修后在再次合闸送电时电缆接头爆炸的事故,为寻找接头故障原因,研究了电缆中间接头在断路器开合闸过程中的过电压特性。首先建立中间接头的RLC等效模型,在PSCAD软件中搭建含有中间接头的电缆线路模型,分析开合闸相角、电缆长度和接头数量对接头过电压的影响,找出过电压最严重的接头;再利用ANSYS软件仿真过电压最严重的接头内部电场分布情况。仿真结果表明:B、C相线路60%~75%处的接头过电压较为严重;且开合闸过程中接头屏蔽层的电压含有超过40kHz的高频分量;接头内部硅橡胶与交联聚乙烯界面场强最大值和高压屏蔽管端部场强最大值均比没有过电压时增加1倍,界面场强最大值超过了安全阈值。在断路器跳闸后合闸送电的过程中,断路器的不同期合闸使得接头承受多次过电压造成的复合界面和高压屏蔽管端部场强的突增以及屏蔽层的高频振荡,容易引发接头故障。

In recent years, quite a few breakdowns of cable joints occurred due to closing of circuit breakers after tripping in the 110 kV cable line.To study the reason why cable joints break down, the transient behavior of cable joint under the condition of breakers opening and closing is studied in this paper.Firstly, a RLC equivalent model of cable joint is given and an 110 kV cable line is simulated by PSCAD, then the effect of closing or opening angle, the length of line and the number of joints on overvoltage of joint are analyzed, to find out the joints with the most serious over-voltage.Additionally, the internal electric field distribution of joint with serious overvoltage is simulated by ANSYS.The results show that the overvoltages of the joint at 60%~75% of B phase and C phase line are more serious than other joints;meanwhile there are more than 40 kHz high frequency components of overvoltage in joint shielding.What s more, the maximum electric field strength on the interface between silicone rubber and cross-linked polyethylene and the maximum field strength at the end of the high-voltage shielding tube are doubled than when there is no overvoltage, and the maximum interfacial strength exceeds the security threshold.In the process of breakers closing after tripping, the joints at 60%~75% of the line repeatedly suffer overvoltage, in which the increase of electric field strength at the end of high-voltage shielding tube and the high frequency oscillation in joint shielding both easily cause breakdown of joints.