Judge the insulation resistance of wires or electrical equipment with multimeter.
The so-called wire leakage actually means that the insulation resistance of wires or electrical equipment can't meet the normal working conditions for various reasons, resulting in a small resistance between the insulated conductor and the earth. 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 introduce the concept of insulation resistance; The so-called insulation is to use relatively non-conductive substances to isolate or wrap the charged bodies themselves or charged bodies with different voltage levels. The role of insulation; Ensure the safe operation of electrical equipment and power supply lines and prevent personal electric shock accidents.
Insulation resistance is defined as; Resistance value of insulation layer of electrical equipment under DC voltage. There is no absolute "insulating" substance in the world. If a DC voltage is applied across the insulating substance, there will always be a current flowing through the medium, just the voltage level. Dielectric current is divided into leakage current (leakage current, polarization capacitance current).
Here, simply speaking, the leakage grounding current of wires is related to the moisture and aging of insulating materials. The magnitude of leakage current is related to the applied voltage. The higher the voltage, the greater the leakage current. Their volt-ampere curves are not linear.
Whether it is digital multimeter or pointer multimeter, they are an auxiliary measuring tool commonly used by electricians. Strictly speaking, the multimeter can't measure the leakage value of wires. In fact, the multimeter can only preliminarily judge whether the household electrical equipment or motor is electrified and whether there is leakage in the shell. At this time, the multimeter is equivalent to a electroprobe.
Whether there is electric leakage in wire lines or electrical equipment should be measured by megger. Commonly used megohmmeters are 250v, 500v and 1000v. As long as the megger is shaken at the speed of 120 revolutions per minute and its insulation resistance is greater than > ＞0.5MΩ, it is regarded as an electrical appliance with basically qualified insulation resistance and can be used safely.
Don't think that multimeter is omnipotent. The general multimeter internally makes the battery 1.5v and 9v laminated battery. It is impossible to measure the insulation resistance of single-phase 220 V or three-phase 380v alternating current lines or electrical equipment.
When the conditions are not allowed, the high resistance of multimeter can be used to preliminarily judge the insulation resistance of wires or electrical equipment, which is not easy to recommend. Measuring line grounding or measuring grounding resistance with multimeter is also a preliminary judgment measurement. The real measurement of grounding resistance should be carried out by using single-arm or double-arm bridge.
