To measure the insulation resistance of a wire or electrical equipment, use a multimeter.
The so-called wire leakage actually indicates that the insulation resistance of the wire or electrical equipment cannot meet the normal working conditions due to various reasons, resulting in a very small resistance between the insulated wire and the ground. For some cases where the insulation resistance value is zero, it is not simply a leakage, but rather a short circuit.
Here, I will popularize the concept of insulation resistance; The so-called insulation refers to the use of relatively non-conductive substances to isolate or encapsulate charged bodies themselves or charged bodies with different voltage levels from each other. The function of insulation; Ensure the safe operation of electrical equipment and power supply lines to prevent the occurrence of 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 absolute "insulating" substance in the world. If a direct current voltage is applied to both ends of an insulating substance, there will always be a current passing through the medium, only the voltage is high or low. The dielectric current is further divided into leakage current (leakage current, polarization capacitance current).
Simply put, the leakage grounding current of wires is related to factors such as moisture and aging of insulation materials. The magnitude of leakage current is related to the applied voltage, and the higher the voltage, the greater the leakage current. Their volt ampere curves are not linearly related.
Both digital multimeters and pointer multimeters are commonly used auxiliary measuring tools by electricians. Strictly speaking, a multimeter cannot measure the leakage value of wires. In fact, using a multimeter can only preliminarily determine whether household electrical equipment or motors are powered on and whether there is leakage in the casing. At this time, the multimeter is equivalent to a test pen.
A megohmmeter should be used to measure whether there is leakage in electrical wiring or equipment. Commonly used
There are several types of megohmmeters available, including 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 or greater than 0.5M Ω, it is considered that the insulation resistance is basically qualified and can be used with confidence.
Don't think that a multimeter is omnipotent. A typical multimeter uses stacked 1.5V and 9V batteries inside. It is impossible to measure the insulation resistance of single-phase 220V or three-phase 380V AC power lines or electrical equipment.
When conditions do not permit, using a multimeter with high resistance can preliminarily determine the insulation resistance of wires or electrical equipment, but this method is not recommended for use. Measuring the grounding of a circuit or measuring the grounding resistance with a multimeter is also a preliminary judgment measurement. The actual measurement of grounding resistance should be carried out using a single arm or double arm bridge.
