Power transformer is a kind of power equipment that changes the size of AC voltage statically. It is one of the core equipment in the power system. In the process of electric energy transmission and distribution, power transformer is the core of energy conversion and transmission. The only way to the source of energy for thousands of households.
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.
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.
Such failures are common in explosions, flashovers, and oil spills, and the causes are:
① Poor sealing, poor insulation moisture ratio, 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;
④ There is a defect in the manufacture of the capacitor core, and there is a free discharge inside;
⑤The casing is seriously fouled.
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;
④The top and middle of the transformer oil tank, the upper part of the oil tank between the sleeve flange, the barrel skin and the sleeve. The internal iron core, winding clips, etc. heat up due to local magnetic leakage, causing insulation damage.
When the transformer in operation automatically trips, the operator should quickly take the following measures:
① When the circuit breaker on each side of the transformer automatically trips, operate the control switch of the trip circuit breaker to the position after the trip, and quickly put the backup transformer into operation, adjust the operation mode and load distribution, and maintain the operation system and its equipment in a normal state;
② Check what kind of protection action the dropped card belongs to and whether the action is correct;
③ Understand whether the system is faulty and the nature of the fault;
④ If it is in the following situations and approved by the leader, it can be tested without inspection: the circuit breaker is tripped by accidental touch protection; the protection is tripped by obvious malfunction; the transformer only operates under low-voltage overcurrent or time-limited overcurrent protection, and at the same time trips the next level of the transformer The equipment is faulty but its protection has not acted, and the fault has been removed, but the test transmission is only allowed once;
⑤ If it is the main protection action such as differential, heavy gas or current quick-break, and there is an impact phenomenon in the event of a fault, it is necessary to carry out a detailed inspection of the transformer and its system, power outage and measure the insulation. It is forbidden to put the transformer into operation until the cause has been identified. It must be pointed out that regardless of whether the system has a backup power supply, it is absolutely not allowed to force the transformer.
Transformer fire is also a dangerous accident, because there are many combustible substances in the transformer, 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.
When the transformer catches fire, the following measures should be taken promptly:
① Disconnect the circuit breakers on each side of the transformer, cut off the power supply on each side, and quickly put into the standby transformer to restore the power supply;
②Stop the cooling device operation;
③ When the main transformer and the high power plant are on fire, the generator should be disconnected first;
④If the oil burns on the top cover of the transformer, open the lower accident discharge throttle and drain the oil to the proper position. If the inside of the transformer catches fire, the oil cannot be drained to prevent the transformer from exploding;
⑤ Quickly put out the fire with the fire extinguishing device.
