Depending on the purpose, usage environment and voltage level of the equipment, the minimum detection standard value is greater than megohms, and generally the minimum is 2 megohms.
A measurement is required each year during normal operation:
1. The insulation resistance value is determined by yourself. If, under similar test conditions (temperature, humidity), the insulation resistance value drops below 1/3 of the normal value over the years, the reason should be identified.
2. The difference between the insulation resistance values of each phase or branch must not be greater than 100% of the minimum value
3. and drying rollers The absorption rate of mica insulation should not be less than 1.3 or the polarization index should not be less than 1.5; the absorption rate of epoxy powder mica insulation should not be less than 1.6 or the d indexe polarization should not be less than 2.0; ; additional instructions for water-cooled stator windings are stipulated by themselves 1) Rated voltage For voltages above 1000V, use a 2500V megger, and the range is generally not less than 10,000 MΩ.
The absorption rate is the difference between the insulation resistance value at 60 s and the insulation resistance value at 15 s measured with a 2500 V megohmmeter in the same test.
Compare.
Absorption rate refers to the ratio of insulation resistance at 60 seconds and 15 seconds when the measuring equipment is isolated from earth. Due to the different duration of application of DC voltage to the equipment, the impact on humidity and other conditions of the equipment is different, so comparing the ratios at two times can determine whether the resistance of equipment insulation is afaffected by humidity. When the insulation is damp, the minimum absorption rate is 1 and when humidity is affected. the insulation is dry, the absorption rates are both greater than 1. The absorption rate test is generally used for large capacity electrical equipment. The absorption rate must be considered based on the specific environment in which the equipment is located.
Reference for the above content: Baidu Encyclopedia-Absorption Report