Details of loop resistance
Loop resistance is also a kind of resistance value. It is a main technical parameter for evaluating the performance of the conductive loop system. When its value is within the normal range of society, it is a parameter that can characterize the normality of the conductive loop. For different data Each type of electronic product has its own loop resistance value. If the loop resistance value exceeds the value specified by the state, then a certain connection of the conductive loop is likely to have poor direct contact or damage. If we do not pay attention to this situation, then when a large current flows, contact with these bad places will begin to use local heating. In serious cases, the conductive circuit will have a vicious circle, and the circuit will continue to be oxidized until it burns. Bad.
For loop resistance measurement, the bridge method is not allowed, and the GB763 DC voltage drop method must be used. The test current is greater than or equal to 100A. The loop resistance tester is used to measure the circuit resistance of high-voltage switches, load switches and other switching equipment, which can directly reflect the contact status of the switch contacts.
Detailed analysis and introduction of grounding resistance
Grounding resistance is the resistance encountered when current flows from the grounding device to the ground, and then flows through the ground to another grounding body or spreads to a distance. The grounding resistance value reflects the good degree of contact between the electrical device and the "ground" and the scale of the grounding grid.
Grounding resistance is an important parameter to measure whether the grounding state is good. Grounding resistance refers to the resistance that current flows from the grounding device to the ground, and then flows through the ground to another grounding body or spreads to a certain distance. It includes the resistance between the ground wire and the grounding body itself, the contact resistance between the grounding body and the ground, and two The grounding resistance between the grounding bodies or the grounding resistance from the grounding body to infinity. The size of the grounding resistance directly reflects the degree of contact between the electrical equipment and the "ground", and also reflects the size of the grounding grid. The concept of grounding resistance is only applicable to small grounding grids. With the increase of grounding area of grounding grids and the decrease of soil resistivity, the role of inductive components in grounding impedance becomes more and more important. Large grounding grids should be designed with grounding impedance, but grounding impedance The measurement needs to select the correct instrument to ensure the accuracy of the measurement results.
Detailed DC resistance
The DC resistance is mainly for the DC resistance test of the inductive load, and the unit of measurement is mΩ. The measurement technology of DC resistance is also extremely important. For example, the DC resistance of transformer windings is measured. The DC resistance of transformer windings is an indispensable test design parameter after the transformer is handed over, overhauled and tap changer changed. By analyzing and measuring the DC resistance of the transformer windings, it is possible to check the welding or connection quality of the leads, whether there is an inter-turn short circuit or open circuit between the windings, and whether the tap changer's contact with society needs to be good.
The above is a detailed description of loop resistance, ground resistance, and DC resistance, but in fact these three values are measured values of resistance, but because the size and accuracy of the measured resistance are different, resistance testers are designed separately.