1. Winding failure
There are mainly inter-turn short circuit, winding grounding, phase-to-phase short circuit, wire breakage and joint welding. The reasons for these failures are as follows:
① During manufacture or maintenance, local insulation is damaged, leaving defects;
② Due to poor heat dissipation or long-term overload during operation, sundries fall into the windings, causing the temperature to be too high and the insulation to age;
③ The manufacturing process is poor, the pressing is not tight, the mechanical strength cannot withstand short-circuit impact, and the winding is deformed and the insulation is damaged.
2. Casing failure
Such failures are common in explosions, flashovers, and oil spills, and the causes are:
① Poor sealing, poor insulation against moisture, or oil leakage;
② The respirator is improperly configured or the inhaled moisture is not dealt with in time;
③ The high-voltage side of the transformer (110kV and above) generally uses capacitor bushings, and there are trachoma or cracks due to poor porcelain quality;
⑤The casing is seriously fouled.
3. Core failure
① The insulation between the silicon steel sheets is damaged, causing the iron core to be partially overheated and melted;
② The insulation of the through-bolt clamping the iron core is damaged, causing the iron core silicon steel sheet and the through-bolt to form a short circuit;
③ Residual welding slag forms two-point grounding of the iron core;
4. Gas protection failure
The gas protection is the main protection of the transformer, the light gas acts on the signal, and the heavy gas acts on the tripping. The reasons and solutions for gas protection actions are analyzed below:
① The reason for the gas protection action may be that the air enters the transformer because the oil filter, refueling and cooling systems are not tight;
② The oil level decreases slowly due to temperature drop and oil leakage; or a small amount of gas is generated due to transformer failure;
6. Transformer catches fire
Transformer fire is also a dangerous accident. Because the transformer contains many combustible substances, it may explode or expand the fire if it is not handled in time.
The main reasons for transformer fires are:
① The casing is damaged and flashed off, and the oil flows out under the pressure of the oil pillow and burns on the top cover;
② The internal fault of the transformer ruptures the casing or the radiator, causing the burning transformer oil to overflow.
7. Faulty tap changer
Common failures are surface melting and burns, interphase contact discharge or individual joint discharge. The main reasons are:
(1) The connecting screws are loose;
(2) Bad and improper adjustment of the belt load adjustment device;
(3) Poor insulation of the tap insulation board;
(4) The joint solder is not satisfied, the contact is poor, the manufacturing process is not good, and the spring pressure is insufficient.
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