Before sending power, the insulation resistance test of all electrical lines (including exposed and concealed wires, cables) should be carried out. If the insulation requirements cannot be met, power supply is strictly prohibited. Purpose: to pass the insulation resistance test, The insulation of concealed wiring and low-voltage cables should be tested with a 500V megohmmeter (megger). Test requirements: After the electrical lines are installed, all electrical lines (including exposed and concealed wiring, and cables) should be tested before power is transmitted. The insulation resistance of the line is tested. If the insulation requirements cannot be met, power transmission is strictly prohibited. ． Purpose: Through insulation resistance testing, check and master the construction quality of line laying and electrical installation to avoid electrical safety accidents such as leakage and short circuit. Method: Insulation testing should be performed on exposed wiring, concealed wiring and low-voltage cables in electrical circuit laying. ? Fill out the insulation resistance test form carefully and ask the relevant department or owner for an acceptance visa. Loop number: system diagram of cables and wires (note that the system diagram has the corresponding loop number, such as: Line model, specification, laying method: Specifications and models are also shown on the system diagram, such as: laying method: direct burial, bridge, through Pipe, etc. Insulation resistance: A, B, C represent three-phase A-phase, B-phase, and C-phase. If it is single-phase A-C, A-B, etc., there is no need to fill in. N is the neutral line, and PE is the ground protection wire. The five phase wires must be filled in, but the resistance values ??are basically the same. Just copy and modify. The insulation resistance value of the cable is related to the type of cable, voltage level, temperature of the cable insulation, and air humidity. The rated voltage is 6KV and above. It should be no less than 100MΩ, and when the rated voltage is 1 to 3KV, it should be no less than 50MΩ. Generally, the neutral line and the ground wire are drawn from the same ground point, and under normal circumstances, they are connected to each other. The resistance value should be 0, but in special circumstances, the switch should be pulled open so that the zero-to-ground resistance should be very large. Otherwise, it means that the ground wire is not installed normally and correctly. The resistance value filled in the table should be the resistance value under special circumstances ( I am not very sure), so you should fill in a large resistance value.