Detailed introduction

1. Grounding resistance

It is the resistance encountered when the current flows from the grounding device into the ground and then flows through the ground to another grounding body or spreads far away. The grounding resistance value reflects the good degree of contact between the electrical device and the "ground" and reflects the scale of the grounding grid.

Grounding resistance is an important parameter used to measure whether the grounding state is good. It is the resistance encountered by the current flowing from the grounding device to the ground and then flowing to another grounding body or spreading to a distance. It includes the grounding wire and the grounding body itself. Resistance, the contact resistance between the grounding body and the resistance of the ground, and the ground resistance between two grounding bodies or the ground resistance from the grounding body to infinity. The size of the grounding resistance directly reflects the good degree of contact between the electrical device and the "ground", and also reflects the scale of the grounding grid. The concept of grounding resistance is only applicable to small grounding grids; as the area of grounding grids increases and soil resistivity decreases, the inductive component of grounding impedance becomes more and more important. Large-scale grounding grids should be designed with grounding impedance. The measurement of grounding resistance requires the right instrument to be selected to ensure the accuracy of the measurement results.

2. DC resistance

It is mainly for the DC resistance test of inductive loads, the measurement unit is mΩ. The measurement of DC resistance is also extremely important, such as the measurement of the DC resistance of transformer windings. The DC resistance of transformer windings is an indispensable test parameter after the transformer is handed over, overhauled and tap changer changed. By measuring the DC resistance of the transformer windings, you can check the welding or connection quality of the leads, whether the windings are short-circuited or open, and whether the tap switch is in good contact.

3. Loop resistance

Loop resistance is also a kind of resistance value. It is a main parameter for evaluating the performance of conductive loops. When its value is within the normal range, it is a parameter that characterizes the normality of the conductive loop. For different types of electronic products, it is Each has its own loop resistance value. If the loop resistance value exceeds the specified value, then a certain connection of the conductive loop is likely to have poor contact or damage. If we don't pay attention to this situation, then when a large current flows, the poor contact will begin to heat up locally. In a serious case, the conductive circuit will have a vicious circle, and the circuit will continue to be oxidized until it burns out.

The measurement of loop resistance is not allowed to be measured by the bridge method, and the DC voltage drop method specified in GB763 must be used. And the test current is greater than or equal to 100A. The loop resistance tester is used to measure the loop resistance of switching equipment such as high-voltage switches and on-load switches, which can directly reflect the contact status of the switch contacts.