原理：接把一个高于正常工作的电压加在遮蔽线上，并持续一段规定的时间，如

Principle: access to a higher than normal operating voltage is applied to the shield line for a period of a predetermined period of time, if the insulation is good enough, the above voltage is applied to only produce a small leakage current. If the leakage current of the shielded wire held within a predetermined range within a predetermined period of time, by detecting the shielding lines, the alarm bell no response, on the contrary, will not pass, the warning light flashes rings.

原理：接把一个高于正常工作的电压加在遮蔽线上，并持续一段规定的时间，如果其绝缘性足够好，加在上面的电压就只会产生很小的漏电流。如果遮蔽线的漏电电流在规定时间内保持在规定的范围内，则该遮蔽线通过检测，警报铃无反应，反之,未通过检测，则警报灯响铃闪烁。

Principle: apply a voltage higher than the normal working voltage to the shielding line, and keep it for a specified period of time. If its insulation is good enough, the voltage applied on it will only produce a small leakage current. If the leakage current of the shielded wire is kept within the specified range within the specified time, the shielded wire passes the detection, and the alarm bell has no response; otherwise, if it fails to pass the detection, the alarm light rings and flashes.