Insulation resistance is the most basic insulation index of electrical equipment and electrical lines. During the handover test of low-voltage electrical devices, the insulation resistance of motors, distribution equipment and distribution lines should not be lower than 0.5MΩ at room temperature (the insulation resistance of running equipment and lines should not be lower than1mΩ/kV).
The insulation resistance of low-voltage electrical appliances and their connecting cables and secondary circuits should generally not be lower than1mω; ; In humid environment, it should not be less than 0.5MΩ；; The insulation resistance of small and medium buses in the secondary circuit should not be lower than10mΩ. The insulation resistance of Class I hand-held electric tools should not be less than 2M Ω.
Extended data:
When a certain DC voltage is applied to the measured material, the current on the measured material does not reach a stable value instantly, but has a decay process. At the same time of pressurization, a large charging current flows, followed by an absorption current that slowly decreases for a long time, and finally reaches a relatively stable conductance current. The higher the measured resistance, the longer it takes to reach equilibrium.
Therefore, in order to correctly read the measured resistance value in the measurement process, the value should be read after stabilization. According to the Test Method for Insulation Resistance of Communication Cables, the reading after charging 1 min is the measured value of cable insulation.
However, in practice, this method is somewhat inappropriate, because when DC voltage is applied to the measured material, the current on the measured material is capacitive current. Since it is a capacitive current, it is related to the capacitance of the cable. It takes a long time to charge the capacitor, especially when the cable is filled with ointment.