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对存在预伏故障的低压待合闸线路进行送电会对相关人员及设备造成危害，为了减少此种危害的发生，根据故障特征，提出一种合闸前利用可控电压对线路进行检测的方法。将2个反向并联的晶闸管构成可控电压发生器，通过调节晶闸管导通角来实现待合闸线路上施加电压大小的可控。该可控电压施加于待合闸线路可以警示触碰线路导体的人员；而对回路阻抗参数的测试和比对，能够检测出可能对人身和设备安全造成危害或不利影响的预伏故障。仿真分析了当人体触碰待合闸线路故障导体时，可有效摆脱的可控电压大小，并针对单相非金属性故障判别困难的问题，通过模拟实验得到了单相非金属性故障的判据，结果表明该判据可有效地对单相非金属性故障和正常负荷进行识别。“,”It may bring hazard to people and equipment when a low-voltage power line with potential faults is energized. In order to reduce the risk, through analyzing the characteristics of potential faults, a detection method using controllable applying voltage was proposed. The controllable voltage generator is composed of two anti-parallel connected thyristors with power supply. The voltage applying to power lines can be controlled by adjusting the conduction angles of thyristors. The gradually increased voltage is able to warn persons against touching the de-energized power line. Meanwhile, comparison of the continuously measured impedances during the controllable applying voltage increase process is able to detect the potential faults existed on the de-energized power line. Simulation results determined the maximum voltage that can be extricated from when a human body touches the de-energized power line. The criterion of single-phase non-metallic faults, which is difficult to be identified, was also obtained and verified with experiments.