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What are the conditions for insulation resistance?

time:2020/9/3   source:华天电力  reading:237 time

In practical applications, we can select the appropriate measurement voltage according to the different gears of the insulation resistance test for the voltage levels of different measurement objects. So, how qualified is the insulation resistance?


Insulation resistance qualification standard: Insulation resistance refers to the ratio of the value of the DC voltage applied between two electrodes to the value of the leakage current flowing through the electrode. We take the insulation resistance of the outer sheath and inner lining of a rubber-plastic power cable as an example According to the preventive test specification, its insulation resistance value is not less than 0.5MΩ/km. It should be noted that the insulation resistance of different voltage levels and different cross-sectional areas are different.


Micro Ohmmeter.png


Classification of resistance:


1. Resistance can generally be divided into low-value resistance, median resistance and high-value resistance.


2. Low-value resistance refers to resistance less than 1Ω, such as circuit resistance of circuit breakers, bus resistance, and contact resistance of conduction joints. This type of resistance measurement should be measured with a loop resistance tester or an intelligent loop resistance tester.


3. The median resistance refers to the resistance between 1Ω and 1MΩ, such as the resistance of the high-voltage winding of the transformer, the winding resistance of the power transformer or the resistance of the closing coil of the high-voltage circuit breaker. For this type of resistance, we recommend the DC resistance test Instrument measurement


4. High-value resistance refers to the resistance value above 1MΩ, such as the insulation resistance of electrical equipment, etc. It is recommended to use an insulation resistance tester for measurement, and it also has the functions of measuring absorption ratio and polarization index.


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