To measure the insulation resistance of wires or electrical equipment, use a multimeter.
The so-called leakage of wires actually means that the insulation resistance of the wires or electrical equipment cannot meet the conditions for normal operation due to various reasons, causing the insulated wires and the earth to form a small resistance. For some cases where the insulation resistance value is equal to zero, it is not a simple leakage, but equivalent to a short circuit.
Here I will popularize the concept of insulation resistance; the so-called insulation is to use relatively non-conductive substances to isolate or wrap the charged body itself or the charged bodies with different voltage levels from each other. The function of insulation; ensuring the safe operation of electrical equipment and power supply lines, and preventing personal electric shock accidents.
The definition of insulation resistance is the resistance value of the insulation layer of electrical equipment under the action of DC voltage. There is no absolutely "insulating" material in the world. If a DC voltage is applied to both ends of an insulating material, there will always be current flowing through the medium, it's just the level of the voltage. The dielectric current is further divided into leakage current (leakage current, polarization capacitance current).
To put it simply, the leakage and ground current of wires is related to the moisture and aging of insulating materials, etc. The size of the leakage current is related to the applied voltage. The higher the voltage, the greater the leakage current. The volt-ampere curves between them are not linear.
Whether it is a digital multimeter or an analog multimeter, they are an auxiliary measurement tool commonly used by electricians. Strictly speaking, a multimeter cannot measure the leakage value of a wire. In fact, a practical multimeter can only initially determine whether the household electrical equipment or motor is powered on and whether there is leakage in the housing. At this time, the multimeter is just like a test pen.
If there is leakage in wire lines or electrical equipment, a megohmmeter should be used to measure it. Commonly used megohmmeters include 250v, 500v, and 1000v. As long as the insulation resistance is greater than 0.5 MΩ when shaken with a megger at 120 rpm, the insulation resistance is considered to be basically qualified and the appliance can be used with confidence.
Don't think that a multimeter is omnipotent. The internal batteries of general multimeters are 1.5v and 9v laminated batteries. It has no way to measure the insulation resistance of single-phase 220V or three-phase 380V AC lines or electrical equipment.
When conditions do not permit, the high resistance of a multimeter can be used to preliminarily determine the insulation resistance of wires or electrical equipment. This method is not easily recommended. Measuring the line grounding or measuring the grounding resistance with a multimeter is also a preliminary judgment measurement. The actual measurement of ground resistance is done using a single-arm or double-arm bridge.
