考虑泄漏电流及层间耦合的高压电缆金属护套环流计算与分析

Calculation and Analysis of Circulating Current in Metal Sheath for HV Cable Considering Leakage Current and Interlayer Coupling

高压电缆线芯与金属护套间存在泄漏电流,当前护套环流的分析与计算中未准确计及其影响,为此提出了考虑泄漏电流及层间耦合的高压电缆金属护套环流计算方法。首先,建立了基于电缆双π集中参数模型的护套环流等值计算模型,在分析泄漏电流影响时,考虑线芯与护套、护套与护套之间的电磁感应作用;然后,运用叠加原理,推导了考虑泄漏电流及层间耦合的监测点与任意位置护套环流计算过程;最后,基于PSCAD/EMTDC仿真软件,搭建了不同排列方式及段长组合下的仿真模型,并结合工程案例进行结果验证,在此基础上,分析了负荷电流、段长组合以及排列方式对护套环流的影响。结果表明:采用该方法所得环流与仿真值的误差大都在1%以内,实例分析亦验证了其准确性;此外,工程中需注意轻载环流超标现象以及段长组合对护套环流的重要影响。以上方法及分析结果对电缆设计、运行监测、故障诊断与定位有一定的借鉴意义。

There is leakage current between the core and the metal sheath in high voltage(HV)cables.The current anal-ysis and calculation of sheath circulating current has not accurately accounted for its influence.Therefore,we propose a calculation method for circulating current of metal sheath in HV cables considering leakage current and interlayer cou-pling.Firstly,the equivalent calculation model of sheath circulating current based on the doubleπmodel of the cable with lumped parameter is established.When analyzing the effect of leakage current,the electromagnetic induction between the core and sheath and between different sheaths is considered.Then,the calculation process of sheath circulating current at the monitoring point and any position considering leakage current and interlayer coupling is deduced by the superposition principle.Finally,the simulation models under different arrangements and segment length combinations are built based on PSCAD/EMTDC,and calculation results are verified combined with an engineering cases.On this basis,the influences of load current,segment length combination and arrangement on circulating current of sheath are analyzed.The results show that the deviation between sheath circulating current obtained by this method and simulation value is mostly within 1%and the engineering case analysis also verifies its accuracy;in addition,attention should be paid to the phenomenon that circulating current exceeds the standard at light load and the important influence of segment length combination to sheath circulating current in projects.The above methods and analysis results have certain reference significance for cable design,operation detection,fault diagnosis and location.