Quality standards for the maintenance of power transformer cores.

Power transformers are now ubiquitous, and the quality standards for power transformer core maintenance are as follows:

1. The core should be flat, the insulating paint film should not peel off, the laminations should be tightly stacked, the silicon steel sheets on the sides should not be warped or wavy, the surface of all parts of the core should be free of oil and impurities, and there should be no short circuits or overlaps between the sheets. The gap between the joints should meet the requirements.

2. Good insulation should be maintained between the core and the upper and lower clamping plates, square iron, pressure plates, and base plates;

3. There should be a clear and uniform gap between the steel pressure plate and the core; the insulating pressure plate should remain intact, without damage or cracks, and have appropriate tightness;

4. The steel pressure plate should not form a closed circuit and should be grounded at one point;

5. After opening the connecting pieces between the upper clamping plate and the core, and the connecting pieces between the steel pressure plate and the upper clamping plate, measure the insulation resistance between the core and the upper and lower clamping plates, and between the steel pressure plate and the core, and compare it with previous measurements. The test results should show no significant changes compared to previous tests;

6. The bolts are tightened, and the positive and negative pressure pins and locking nuts on the clamping parts are not loose, making good contact with the insulating washers, with no signs of discharge burns, and the negative pressure pins have sufficient distance from the upper clamping parts;

7. The through-bolts are tightened, and their insulation resistance shows no significant change compared to previous tests;

8. The oil passages should be unobstructed, the oil passage spacers should not be detached or blocked, and should be neatly arranged;

9. The iron core is only allowed to be grounded at one point. The grounding plate should be a copper plate with a thickness of 0.5mm and a width of not less than 30mm, inserted between the 3rd and 4th layers of the iron core. For large transformers, the insertion depth should be no less than 80mm, and the exposed part should be insulated to prevent short-circuiting the iron core;

10. It should be securely fastened and have sufficient mechanical strength, with good insulation and no formation of a loop, and should not be in contact with the iron core;

11. Good insulation and reliable grounding.