Troubleshoot Transformers Together

If the transformer fails, it will affect the safe and stable operation of the very important equipment in the power system. Once an accident occurs, it will cause great economic losses. Analyze various power transformer accidents, find out the reasons, sum up the methods to deal with the accident, control the accident loss to the minimum range, and minimize the damage to the system.

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;
②Due 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;
④ The winding is damp, and the insulation expansion blocks the oil passage, causing local overheating
⑤ The insulating oil is mixed with moisture and deteriorated, or the contact area with the air is too large, so that the acid value of the oil is too high, the insulation level is lowered or the oil level is too low, and some windings are exposed in the air and cannot be handled in time.
Due to the above reasons, once the insulation breakdown occurs during operation, it will cause a short circuit or ground fault of the winding. The fault phenomenon during the inter-turn short circuit increases the overheating oil temperature of the transformer, the current on the power supply side increases slightly, the DC resistance of each phase is unbalanced, and sometimes there is a creaking sound and a bubbling sound in the oil. A slight inter-turn short circuit can cause the gas protection action; in severe cases, the differential protection or the overcurrent protection on the power supply side will also act. If the inter-turn short circuit is found, it should be dealt with in time, because the inter-turn short circuit of the winding often causes more serious faults such as single-phase grounding or inter-phase short circuit.