How to detect the insulation resistance of the current transformer?

1. Preparation
Record environmental conditions: record the ambient temperature and humidity at the test site, as these factors will affect the measurement results of the insulation resistance.
Equipment discharge: fully discharge the current transformer under test and ground it to ensure safety.
Arrange safety measures: arrange a safety fence around the current transformer under test, hang a "Stop, high voltage danger" sign, and arrange for special personnel to monitor.
Check the instrument: check that the insulation resistance meter is normal.
2. Choose a suitable measuring instrument
Primary winding measurement: use a 2500V megohmmeter.
Secondary winding measurement: use a 1000V or 2500V megohmmeter.
3. Wiring and measurement
Primary winding insulation resistance test:
Ground the E end of the insulation resistance meter, and connect the grounding wire to the grounding end first, and then to the instrument end.
The test wire at the L end of the insulation resistance meter is first connected to the instrument end, then to the primary winding, and the secondary winding is short-circuited to ground.
Select the 2500V measurement voltage position on the insulation resistance meter, pressurize to the rated output voltage, and read the insulation resistance value at 60s.
Secondary winding insulation resistance test to ground:
When measuring the insulation resistance of the secondary winding to ground, the primary winding is short-circuited to ground.
Use a 1000V or 2500V megohmmeter for measurement.
4. Data analysis and judgment
Primary winding insulation resistance: Generally, it should be greater than 3000MΩ, and there should be no significant change compared with the last measurement value.
Secondary winding insulation resistance: It should not be lower than 1000MΩ.
End screen insulation resistance to ground: When the insulation resistance of the end screen to ground is less than 1000MΩ, the tanδ of the end screen to ground should be measured.
5. Precautions
Temperature influence: High temperature will reduce the insulation resistance. When measuring, the influence of ambient temperature on the result should be considered.
Test specification: After testing a large-capacity test product, the lead should be disconnected before stopping the instrument to avoid residual charge affecting the measurement accuracy.
Safe operation: The measurement should be carried out under conditions of sufficient light and dry air, and the recommended temperature is 20±5℃.
Fully discharge: After the measurement, the cable core wire should be fully discharged to prevent electric shock.