1. Disconnect the power of the tested product, remove or disconnect all external connections, and discharge the tested product to ground. Use a tool such as an insulating rod when discharging, and do not touch the discharge wire with your hand.
2. The primary winding of the transformer is measured with a 2500V megohmmeter, and the secondary winding is measured with a 1000V megohmmeter. When measuring, the measured winding is shorted to the megohmmeter, and the non-test winding is short-circuited to ground.
3. Wipe off the dirt on the outer insulation surface of the test piece with a dry, clean and soft cloth. If necessary, wash it with a suitable detergent.
4. The terminal "E" on the megger is connected to the ground of the test object, "L" is connected to the high voltage end, and "G" is connected to the shield end. Use shielded wire and insulated shield rod for connection. Stabilize the megohmmeter horizontally. When the megohmmeter speed is still rotating at low speed, short-circuit the “L” and “E” terminals with the wire, and the pointer should be zero. When the circuit is open, the megohmmeter speed reaches the rated speed and its pointer should be “∞”. Then stop the megohmmeter, connect the ground end of the megohmmeter to the ground of the test object, connect the high-voltage end of the megohmmeter to the shielded connection line, and the other end of the connection line is suspended (not connected to the test sample), again When driving a megohmmeter or powering up, the indication of the megohmmeter should be no significant difference. Then stop the megohmmeter and connect the shielded cable to the measurement site of the test object.
5. Drive the megaohm to express the rated speed, or turn on the megohmmeter power supply. After the pointer is stable (or 60s), read the insulation resistance value.
6. After reading the insulation resistance, disconnect the connection line connected to the high voltage end of the test object, and then stop the megohmmeter.
7. Disconnect the test item after disconnecting the megohmmeter and ground it.
8. The temperature, humidity, weather conditions, test date and instrumentation of the equipment to be tested shall be recorded during the measurement.