计及金属护层结构的电缆单端故障测距方法

Single-terminal Fault Locating Method of Cables Considering the Metal Sheath Structure

单芯电缆大部分故障均与金属护层相关,仅考虑导芯电气结构参数的模型无法实现护层的相关故障测距。基于双π模型,提出了计及电缆金属护层的单端故障测距方法。利用导芯及护层首端电气量得到线路沿线的电流值,根据非故障相对应故障点处前后电流故障分量相等的特征,可迭代搜索得到故障距离。该方法只需利用导芯及护层首端故障分量的相量值,能够实现护层对地故障、芯–护层故障以及芯–护层对地故障的准确测距。大量仿真结果表明,该方法测距精度高,且不受故障距离、故障类型、故障电阻、故障初相角以及电缆护层接地方式的影响。

Most faults of single core cables are related to metal sheath and the model that only considers the electrical structure parameters of the core fails to realize the sheath-related fault location. Based on the double PI model, this paper presented a fault location method considering the metal sheath. The current along the line can be obtained using the electrical quantities in the head of the conductor and sheath. Then the fault distance can be calculated through iteration according to the feature that fault current components before and after the fault point corresponding to the non-fault phase remain unchanged after the fault. The proposed method locates the fault point with only the phase value of the head end fault companent, which can locate the sheath-ground fault, core-sheath fault and core-sheath-ground fault accurately. A number of simulations indicate the method can get accurate results, without the influence of fault distance, fault type, fault resistance, fault initial angle and sheath grounding method.