What are the high voltage test projects of the main transformer in the overhaul of the power plant?

First of all, a high-voltage megohmmeter should be used to measure the insulation resistance and absorption ratio of the transformer winding, and then the DC resistance of the winding should be measured by a DC resistance fast tester, the voltage ratio of all taps of the winding should be measured by the automatic variable ratio group tester, the no-load current and no-load loss, short-circuit impedance and load loss of the transformer should be measured by the transformer no-load load tester, and the transition resistance, switching time and other parameters of the on-load tap-changer should be measured with the transformer on-load switch tester. The dielectric strength of transformer oil is measured by automatic insulating oil tester, the dielectric loss value of winding and capacitive conduit is measured by automatic anti-interference heterogeneous dielectric loss tester, and the chromatographic analysis of dissolved gas in transformer oil is carried out by chromatography analyzer.

After the above-mentioned obtained test parameters are comprehensively analyzed and confirmed to be qualified, the DC high-voltage generator or AC and DC high-voltage test transformer can be used to carry out the DC leakage test on the insulating conduit and winding of the transformer, and finally the power frequency AC high-voltage test transformer can be used to carry out the AC withstand voltage test on the transformer. So far, the relevant test project of power transformer has been completed!

One. Measure the DC resistance of the winding.

a.The purpose and content of the measurement.

1.Check the welding quality of wires and leads inside the winding;

2.Check whether the contact between the various positions of the tap changer is good;

3.Check whether the winding or lead wire is broken or broken;

4.Check whether the parallel branch is connected correctly, and whether there is one or several broken wires in the winding wound by several parallel wires;

5.Check the level for short circuits between turns.

Two. Measure the insulation resistance, absorption ratio and polarization index of the windings.

a.Purpose of the trial.

1.Preliminary judgment of the insulation performance of the transformer;

2.Identify whether the transformer insulation is damp in whole or locally;

3.Check whether the insulating surface is dirty, and whether there are penetrating concentrated defects caused by discharge or breakdown;

4.Check whether there is a cracking of the porcelain casing, the lead wire touching the ground, and the short circuit defect caused by the metallic bridge in the body;

5.The absorption ratio k and polarization index pi are not affected by the size and temperature of the material, etc., which is conducive to using the same judgment standard to measure whether it is qualified or not. PI is more reflective of the true insulation condition due to its longer absorption time.

k=r60s r15s greater than pi =r10 points r1 points greater than.

3) Measure the leakage current of the winding.

First, the purpose of measurement:

Measuring the leakage current of a winding transformer coil is similar to measuring insulation resistance, but is more sensitive and accurate than measuring insulation resistance. It can more effectively detect defects such as cracks and carbonization along the surface of pure porcelain casing.

When there is a defect inside the test sample, the leakage current will rise greatly with the increase of voltage, and even the phenomenon of surging the top meter.

4) Measure the loss angle of the medium tgδ

In order to improve the accuracy of the measurement and the sensitivity of defect detection, a decomposition test can be performed to determine the location of the defect if necessary.

The dielectric loss TGΔ of the winding is mainly to reflect the TGΔ of the paper insulation in the transformer insulation, and the insulation resistance is the series value of the paper and oil insulation, so the TGΔ is more effective than the insulation resistance of the transformer to reflect the overall insulation condition of the transformer. It is one of the main characteristics that reflect the moisture of transformer insulation.

The tests that should be carried out after the transformer overhaul are as follows:

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

2) Measure the leakage current of the winding along with the casing. Gross errors.

3) Measure the dielectric loss factor of the winding together with the casing.

4) AC withstand voltage test of winding together with casing.

5) Measure the dielectric loss factor of the impure porcelain casing.

6) Insulating oil test and chemical separation of insulating oil in transformer and bushing.

7) Insulation resistance of clamps and grommets.

8) DC resistance, conversion ratio, group (or polarity) of each winding.

9) Check the action and sequence of the on-load pressure regulating device.

10) Inspect the phase rock crust.

11) If necessary, carry out no-load characteristics, short-circuit characteristics test and measure partial discharge.

The regulations say that there are so many things to do, I haven't done 500 kV, 220kV generally do the first 18 items plus the last infrared temperature measurement, and the rest have not been done.

1. Chromatographic analysis of dissolved gases in oil.

2. Insulating oil test.

3. The winding points directly to the good current resistance.

4 Windings with the insulation resistance, absorption ratio or polarization index of the casing 5 Windings with the tanδ of the casing

6. AC withstand voltage test of winding together with casing.

7. Insulation resistance of iron core and clamp.

8. Partial discharge test.

9. The voltage ratio of all taps of the winding.

10. Check the polarity of the three-phase transformer or single-phase transformer.

11. Winding deformation test.

12. Current transformer test in casing.

13. Overall seal inspection.

14. No-load closing at full voltage.

15. Test and inspection of on-load tap-changers.

16. Calibration of temperature measuring device and its secondary circuit test.

17. Gas relay calibration and its secondary circuit test.

18. Calibration of pressure reducer and its secondary circuit test.

19. Inspection test of cooling device and its secondary circuit.

20 No-load current and no-load loss.

21. Short-circuit impedance and load loss.

22. Polymerization degree of insulating paper (board).

23. The moisture content of insulating paper (board).

24. Noise measurement.

25 box shell vibrating next to teasing.

26. Infrared temperature measurement.