Although the grounding resistance and insulation resistance are also used to measure resistance, their functions are different. The grounding resistance is the resistance encountered when the current flows from the grounding device to the ground and then flows through the ground to another grounding body or spreads to a distant place; The insulation resistance is the resistance corresponding to the leakage current flowing through the dielectric after a certain time of polarization process by applying DC voltage to the dielectric; Secondly, the technical parameters are different. The unit of grounding resistance is ohm, and the unit of insulation resistance is megohm and above.
In terms of test purposes, the two are not exactly the same:
Grounding resistance: the main purpose is to determine whether the safety grounding wire can bear the fault current flow in case of product failure. The lower the grounding resistance value, the better, so as to ensure that once the product fails, the user can avoid the danger of electric shock before the input power switch is powered off.
Insulation resistance: it refers to the resistance value measured by applying the specified voltage to the insulation part under the specified temperature, humidity and pressure conditions to determine the insulation state of the product (whether the insulation is effective).
The resistance value is directly related to the safety of products or users.
The difference between the two: 1. The greater the insulation resistance, the better, generally more than millions of ohms (M Ω), while the smaller the grounding resistance, the better, generally less than 10 Ω. 2. The application fields of the two kinds of resistors are different. Insulation resistance refers to the resistance of the parts that should not conduct electricity, such as between the live parts in the product and the product shell, while the grounding resistance is to lead the current harmful to human body or equipment underground. 3. For the effect of current, the insulation resistance is blocked to block the current flow, and the grounding resistance is used to make the current flow smoothly. 4. The equipment for testing the grounding resistance is the grounding resistance tester, and the equipment for testing the insulation resistance is the insulation resistance tester.
Finally, the two test methods are different:
Grounding resistance: the A end is clamped at the input ground wire end, and the B end is clamped at the far end of the ground wire. The equipment is set with 25A current, and the test time is 2 minutes. The resistance of the protective connecting conductor shall not exceed 0.1 Ω, and the voltage drop shall not exceed 2.5V without being damaged.
Insulation resistance: between the two power supply levels and the output terminal, the equipment is set at 200V, and the insulation resistance measured one minute later shall not be less than 4M Ω.