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Analysis of Transient Characteristics in the 110kV Cable Joint System during Switch Closing

机译：开关合闸过程中110kV电缆接头系统的暂态特性分析

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In recent years, there occur quite a few breakdowns of cable joint when circuit breakers are closed in the 110kV cable lines. It's necessary to pay attention to the influence of cable joint in cable line without load during closing because of the different wave impedance between cable body and joint. In this paper, a RLC equivalent model of cable joint is established, and then an 110kV cable line including 14 joints is simulated by PSCAD. To study the effects of closing angle on overvoltage at cable joint core and metal shielding, the circuit breaker was closed 360 times in one power frequency cycle by using Multiple Run in PSCAD. Additionally, Fast Fourier Transform (FFT) is used to analyze the frequency characteristic of overvoltage at joint metal shielding. Then to study the effects of cable length on joint overvoltage, three different cable line lengths with the number of joint unchanged are simulated. Then electric field distribution inside the joint which suffered the most serious overvoltage is simulated by ANSYS. The simulation results show that cable line overvoltage is a 180° periodic function of the closing angle. The ideal closing angle and the closing angle matched the most serious overvoltage are both at the intersections of overvoltage curve of the phase B and the phase C. When breaker is closed at 0°, the maximum overvoltage of cable is 1.23p.u. While when breaker is closed at 90°, the maximum overvoltage of cable line is 1.85p.u. In addition, the shielding overvoltage of the 4 straight-through joints (3#, 6#, 9# and 12#) is more severe than that of other insulated joints. The maximum shielding overvoltage 5.23kV is at 6# joint of phase A with breaker closed at 90°. And FFT analysis of overvoltage at joint metal shielding shows that overvoltage at joint metal shielding contains high-frequency voltage component of 12 kHz to 14 kHz and 4 kHz with their amplitude below 70V. What's more, the line overvoltage increases with the increase of cable length, and the location of maximum overvoltage gradually moves from the end joint to the middle joint with the increase of the cable length when the cable line length is longer than 7500m. What's more, the electric field distribution inside two joints, the 6# joint whose metal shielding suffered the most severe overvoltage in all joints and the 12# joint whose core suffered the most severe overvoltage in all joints, are simulated by ANSYS. The results show that the maximum field strength in the joint 6# and 12# are more than that in joint without overvoltage, and the maximum field strength is always at the root of stress cone. The field strength at interface between silicone rubber and cable insulation in 12# joint is -1.4kV/mm, and the maximum field strength at the high-voltage shielding tube is 5.7kV/mm, both of which are doubled than those in joint without overvoltage.
机译：近年来，当110kV电缆线路中的断路器闭合时，电缆接头会发生相当多的故障。由于电缆主体与接头之间的波阻抗不同，在闭合过程中必须注意电缆接头在无负载的情况下对电缆线的影响。本文建立了电缆接头的RLC等效模型，然后通过PSCAD仿真了包括14个接头的110kV电缆线。为了研究闭合角度对电缆接头芯和金属屏蔽层上的过电压的影响，通过在PSCAD中使用Multiple Run，在一个工频周期中将断路器闭合了360次。此外，快速傅立叶变换（FFT）用于分析联合金属屏蔽处过电压的频率特性。然后，为了研究电缆长度对接头过电压的影响，模拟了三种不同接头长度不变的不同电缆线长度。然后用ANSYS模拟承受最大过电压的接头内部的电场分布。仿真结果表明，电缆线的过电压是闭合角的180°周期函数。理想的闭合角度和与最严重的过电压匹配的闭合角度均在B相和C相的过电压曲线的交点处。当断路器在0°闭合时，电缆的最大过电压为1.23p.u。当断路器以90°闭合时，电缆线的最大过电压为1.85p.u。此外，4个直通接头（3＃，6＃，9＃和12＃）的屏蔽过电压比其他绝缘接头更严重。在A相的6＃接点处最大屏蔽过电压5.23kV，断路器以90°闭合。接头金属屏蔽处的过电压的FFT分析表明，接头金属屏蔽处的过电压包含12 kHz至14 kHz和4 kHz的高频电压分量，其幅度低于70V。此外，当电缆长度超过7500m时，线路过电压会随着电缆长度的增加而增加，并且最大过电压的位置会随着电缆长度的增加而从端部接头逐渐过渡到中间接头。此外，ANSYS还模拟了两个接头内部的电场分布，其中金属屏蔽层在所有接头中承受的电压最严重的是6号接头，芯层所有接头中承受的电压最严重的12＃接头。结果表明，在6＃和12＃接头处的最大场强大于没有过电压的接头，并且最大场强始终处在应力锥的根部。 12＃接头中硅橡胶和电缆绝缘层之间的界面处的场强为-1.4kV / mm，高压屏蔽管处的最大场强为5.7kV / mm，与没有接头时的两倍。过电压。

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