In order for the transformer manufacturer to handle the accident correctly, ① system operation mode, load status, load type, ② oil temperature, temperature rise, voltage of the upper part of the transformer, ③ meteorological conditions at the time of the accident, ④ maintenance around the transformer, etc., ⑤ Yes The operator is still ⑥ whether the system is running, ⑦ protection action, grasp the accident phenomenon, etc.
Common faults in transformer operation include windings, bushings, and tap switches. There are fewer failures of accessories such as iron cores and fuel tanks. The descriptions of several common main faults are as follows.
Coil failure mainly includes short circuit between coils, winding grounding, short circuit between phases, disconnection, joint welding, etc. The cause of the failure is as follows.
① Partial insulation damage during manufacturing or maintenance, leaving defects. ② During operation, due to poor heat dissipation or long-term overload, impurities are entangled, resulting in high temperature and deterioration of insulation. ③ The manufacturing process is not good, the pressing is not strict, and the mechanical strength cannot withstand the short-circuit impact, resulting in winding deformation and insulation damage. ④ The winding is damp, the insulation expands, and the oil circuit is blocked, causing local overheating. ⑤ Insulating oil and water are mixed and deteriorated, the contact area with air is too large, the oleic acid value is too high, the insulation level is reduced, the oil level is too low, and some windings are exposed to the air and cannot be treated immediately.
Due to the above-mentioned reasons, if insulation breakdown occurs during operation, it will cause winding short circuit or ground fault. The fault phenomenon of the short circuit between the lamps is that the temperature of the overheated oil of the transformer rises, the current on the power side increases slightly, the DC resistance of each phase is unbalanced, and sometimes there is the sound of rolling in the oil and the sound of foam. A slight short circuit between the lamps will cause the gas protection to operate, and in severe cases, it will cause the power supply side differential protection or overcurrent protection to operate. If you find a U-turn short hair, you must deal with it in time. Short circuit between windings may cause more serious faults such as single-phase grounding or short-circuit between phases.
