In general, the low voltage after new installation or overhaul should not be lower than 1MΩ；; The insulation resistance of low-voltage lines and equipment in operation shall not be less than 3m Ω/v; The insulation resistance of equipment and lines in wet situations should not be less than 2.5mΩ/v; The insulation resistance in the control line should generally not be less than 1MΩ, while the insulation resistance of high-voltage lines and equipment should generally not be less than 1MΩ.
Extended information:
Insulation can usually be divided into three categories: gas insulation, liquid insulation and solid insulation. Under the action of strong electricity, insulating substances may be broken down and lose their insulating properties. Due to corrosive gas, steam, moisture, conductive dust and mechanical operation, the insulation performance of insulating materials may be reduced or even destroyed. Moreover, the long-term effects of environmental factors such as sunlight, wind and rain can also make insulating materials age and gradually lose their insulating properties.
Reference: Insulation (physical term)-Baidu Encyclopedia