Suggestions on preventive testing items and cycles for power transformers

Suggestions on preventive testing items and cycles for power transformers

1、 Experimental project

The preventive testing projects for power transformers mainly include the following aspects:

1. Measure the insulation resistance and absorption ratio or polarization index of the winding.

2. Measure the leakage current of the winding.

3. Measure the winding's tg δ (dielectric loss tangent).

4. AC voltage withstand test.

5. Measure the TG δ value and capacitance value of the capacitive bushing.

6. Measure the insulation resistance values of the through core bolts and iron cores.

7. Measure the DC resistance of the winding.

8. Check the voltage division ratio of all tap connections in the winding.

9. Correct the group of three-phase transformers or the polarity of single-phase transformers.

10. Insulation oil test and chromatographic analysis of dissolved gases in oil.

11. Check the operation of the on load tap changer.

These test projects can comprehensively evaluate the insulation performance, electrical performance, and mechanical performance of power transformers, in order to promptly identify and address potential issues, ensuring the safe and stable operation of the equipment.

2、 Cycle suggestion

The recommended cycle for preventive testing of power transformers should be determined based on multiple factors such as equipment type, rated voltage, installed capacity, and commissioning time. Here are some general suggestions:

For high-voltage electrical equipment, especially 10KV indoor electrical equipment, preventive testing is usually required every two years. However, for equipment in substations and distribution rooms that have been in operation for more than 5 years, due to aging and other reasons, it is recommended to conduct equipment preventive tests once a year.

2. It is recommended to conduct tests on key items such as insulation resistance and coefficient ratio of power transformer windings every two years. However, for transformers that are important or operate in harsh environments, it may be necessary to shorten the testing cycle.

3. Lightning arrester equipment, whether it is 10KV or 0.4KV, should undergo a preventive test once a year to ensure its protective effect in thunderstorm weather.

4. For other insulation resistance tests such as power cables, it is recommended to conduct them once a year, while insulation tools (such as insulated shoes, insulated gloves, etc.) are recommended to be tested every six months.

In general, the cycle of preventive testing should be reasonably set according to the actual situation and operating environment of the equipment, ensuring the safe and reliable operation of the equipment while considering the cost and efficiency of the testing. At the same time, regular analysis and evaluation of the test results should be conducted to promptly identify and address any issues with the equipment.