Use a multimeter to judge the insulation resistance of wires or electrical equipment
The so-called wire leakage actually means that the insulation resistance of the wire or electrical equipment cannot meet the normal working conditions due to various reasons, and the insulated wire and the earth form a resistance with a very small resistance value. 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 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. The role of insulation; to ensure the safe operation of electrical equipment and power supply lines, and to prevent personal electric shock accidents.
The definition of insulation resistance is; the resistance value of the insulating layer of electrical equipment under the action of DC voltage. There is no absolutely "insulating" substance in the world. If a DC voltage is applied across the insulating substance, the medium will always have a current flowing through it, but the voltage is high or low. The dielectric current is further divided into leakage current (leakage current, polarization capacitance current).
To put it simply, the leakage grounding current of the wire is related to the moisture and aging of the insulating material. The magnitude 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 a pointer multimeter, they are an auxiliary measurement tool commonly used by electricians. Strictly speaking, the multimeter cannot measure the leakage value of the wire. In fact, the practical multimeter can only preliminarily judge whether the household electrical equipment or motor is powered on, and whether there is leakage in the casing. At this time, the multimeter is equivalent to a test pen.
For the leakage of electric wires or electrical equipment, a megohmmeter should be used to measure. Commonly used megohmmeters are 250v, 500v, and 1000v. As long as the megohmmeter is shaken at a speed of 120 revolutions per minute, and its insulation resistance is greater than > 0.5MΩ, it is considered that the insulation resistance is basically qualified and can be used with confidence.
Don't think that a multimeter is omnipotent. Generally, the batteries used in the multimeter are laminated batteries of 1.5v and 9v. It has no way to measure the insulation resistance of single-phase 220V or three-phase 380V AC lines or electrical equipment.
If the conditions are not allowed, the high resistance of the multimeter can be used to preliminarily judge the insulation resistance of the wire or electrical equipment. This method is not easy to recommend. Using a multimeter to measure the line ground or measure the ground resistance is also a preliminary judgment measurement. The actual measurement of ground resistance is carried out using a single-arm or double-arm bridge.
