考虑金属护层结构的电缆新型故障测距方法研究

Research on a new fault location method for cable considering metal sheath structure

单芯电力电缆的很多绝缘故障都和金属护层有关,只研究电缆导芯的简化结构模型不能进行护层相关故障的测距。基于分布参数模型,提出一种考虑电缆金属护层的新型故障测距方法。首先,使用分布参数理论分析计及金属护层的故障电缆等效分布参数电路,建立电压、电流方程;然后,通过边界条件求解电压、电流方程中的未知参数,得到故障点前、后的电压、电流值;最后,通过构建测距方程迭代搜索得到故障距离。该方法将复杂的相网络转化为相互独立的序列网络,使得该算法变得简单有效。大量仿真结果表明,该算法能实现护层相关故障(护层对地故障、芯—护层故障和芯—护层对地故障)的精确测距,测距误差基本不超过1.5%,且定位结果不受故障发生位置、故障类型以及过渡电阻的影响。

Many faults of single core cables are related to metal sheath.The simplified model that only considers the core cannot realize the sheath-related fault location.This paper proposes a novel fault location method considering the metal sheath of the cable basing on the distributed parameter model.First,based on the distribution parameter theory,the equivalent distribution parameter circuit of the fault cable of considering the metal sheath is analyzed,the voltage and current equations are established;then,the unknown parameters in the voltage and current equations are solved through boundary conditions,the voltage and the current value of both sides of the fault point are obtained;finally,the fault distance is obtained by iterative search of the ranging equation.The proposed method transforms the complex phase network into mutually independent sequence network,which makes the algorithm simple and effective.A large number of simulation results show that this algorithm can achieve the accurate distance measurement of sheath-related faults(sheath-to-ground faults,core-sheath faults,and core-sheath-to-ground faults),and the ranging error is within 1.5%.The results are not affected by the fault location,fault type and the transition resistance.