Quality Standards For Iron Core Maintenance Of Power Transformers

GNEE Steel large power transformers

1. The iron core should be flat, the insulation paint film should not fall off, the laminations should be tight, the silicon steel sheets on the sides should not be raised or wavy, the surface of each part of the iron core should be free of oil stains and impurities, there should be no short circuits or overlapping between sheets, and the joint gap should meet the requirements;
2. Good insulation should be maintained between the iron core and the upper and lower clamps, square iron, pressure plate, and bottom foot plate;
3. There should be a clear and uniform gap between the steel pressure plate and the iron core; The insulation pressure plate should be intact, free from damage and cracks, and have appropriate tightness;
4. The steel pressure plate should not form a closed circuit, and there should be a point of grounding at the same time;
5. After opening the connecting pieces between the upper clamp and the iron core, as well as the connecting pieces between the steel pressure plate and the upper clamp, measure the insulation resistance between the iron core and the upper and lower clamps, and between the steel pressure plate and the iron core. There should be no significant changes compared to previous tests;

step down power transformer

single phase power transformer

three phase power transformer

6. Tighten the bolts, ensure that the positive and negative pressure nails and locking nuts on the clamp are not loose, have good contact with the insulation gasket, and have no signs of discharge burns. There is sufficient distance between the negative pressure nails and the upper clamp;
7. Tighten the through bolt, and there is no significant change in its insulation resistance compared to previous tests;
8. The oil circuit should be unobstructed, and the oil passage cushion blocks should not fall off or be blocked, and should be arranged neatly;
9. Only one point of grounding is allowed for the iron core. The grounding piece should be made of purple copper with a thickness of 0.5mm and a width of not less than 30mm, inserted between level 3-4 iron cores. For large transformers, the insertion depth should not be less than 80mm, and the exposed part should be wrapped with insulation to prevent short circuits in the iron core;
10. It should be tightened and have sufficient mechanical strength, with good insulation to form a loop and not in contact with the iron core;
11. Good insulation and reliable grounding.