铜屏蔽层间隔缠绕引发电力电缆过热的故障分析与仿真计算

Analysis and Simulation Calculation of Power Cable Overheating Fault Caused by Copper Shield Interval Winding

为了研究电力电缆因铜屏蔽层缠绕方式导致的过热故障甚至击穿问题,文中以某500 kV变电站35 kV交流侧融冰管母线的着火故障为例,通过分析交流耐压实验下的红外热图像和对地电流,建立铜屏蔽层缠绕结构的电路模型分析热故障机理。进一步建立35 kV单芯电缆的三维有限元仿真模型探讨铜屏蔽层间隔缠绕对电缆温度分布的影响。结果表明:外半导电层上流过的电流是导致电缆表面温度升高的主要原因,铜屏蔽层间隔缠绕将使间隔边缘与外半导电层接触位置流过的电流增大而引起过热故障,这种过热故障与外施电压的幅值、频率以及铜屏蔽层铜带缠绕间距之间的关系密切。

For the purpose of finding out the relationship between the fault （overheating fault or even breakdown fault） and the copper shielding layer winding type, an ignition fault occurred at the 35 kV ice melting tube bus in a 500 kV substation AC side has been introduced as an example in this paper. By analyzing the infrared thermal images and grounding current under AC withstand voltage experiments, a copper shielding layer winding circuit model has been estabhshed, which is used to analyze the principle of the overheating fault. In the further step, a three dimensional finite element model of 35 kV single core cable is established to study the effect of the copper shielding layer space which may affect the distribution of the cable temperature. The result shows that current flowing through the outer semi-conductive layer is a major cause of cable surface temperature rising, furthermore the interval winding of the copper shielding layer will lead to the current rising at the contact position of the edge and outer semi-conductive layer and the current rising will cause the overheating fault. This type of overheating fault has a close relationship with amplitude and frequency of the applied voltage and the winding space of the copper shielding layer.