1, winding fault
 
There are short-circuit, winding interturn ground, phase short circuit, disconnection and open solder joints and so on. The reasons for these failures are the following:
 
① in the manufacture or maintenance, local insulation damage, defects left behind;
 
② in operation or long-term due to poor thermal overload, there is debris falling inside the winding, so that the temperature is too high insulation aging;
 
③ poor manufacturing processes, repression is not tight, the mechanical strength can not withstand the impact of a short circuit, the winding insulation deformation damage;
 
④ winding is damp, insulation expansion clogging oil passages, causing local overheating
 
⑤ water is mixed into the insulating oil to deteriorate, or contact with air area is too large, the acid value is too high insulation level drop of oil or oil is too low, part-winding exposed in the air failed to deal with.
 
For all these reasons, in operation upon the occurrence of dielectric breakdown, it will cause a short circuit or ground fault winding. Symptom interturn short-circuit the transformer overheated oil increased, the power supply side current increases slightly each phase DC resistance unbalance, sometimes in the oil and Gulp bubble squeak sound. Inter-turn short circuit can cause slight gas protection action; severe jet lag or overcurrent protection will move the action on the supply side. Interturn short circuit was found to be in time, because among Windings often cause more serious phase or single-phase short circuit fault.
 
2, casing failure
 
This failure is common is blown up, the flash off and oil spills, the reasons are:
 
① poor sealing, insulation damp inferior ratio, or leakage;
 
② respirator misconfigured or not inhale water and timely treatment;
 
③ transformer high side (110kV and above) is generally used capacitor casing, due to poor porcelain and therefore have trachoma or cracks;
 
There ④ condenser core manufacturing defects, internal free discharge;
 
⑤ sleeve fouling serious.
 
3, the core failure
 
① between silicon insulation damage, causing localized overheating and melting of the core;
 
② clamping bolt mandrel core insulation damage, silicon and iron core mandrel bolt short-circuited;
 
③ residual slag formed two core ground;
 
④ transformer tank top and middle of the upper tank casing flange, barrel between skin and casing. Internal core, the winding clamps, etc. due to the local magnetic flux leakage and heat, causing damage to the insulation.
 
After running the transformer failure, as confirmed a winding or core failure should be hanging core examination. First measure the DC resistance of each phase winding and compared, such as large differences, for the winding fault. Then visual inspection of the core, and then the DC voltage, current meter measurement sheet between the insulation resistance. Such damage is not, in damage of the paint can.
 
4, gas protection fault
 
Gas protection is the main protection of transformer acts on the signal light gas, heavy gas acts on the trip. The following analysis of gas protection action causes and treatment:
 
① reason gas protection action may be due to oil filter, fuel and cooling system is not tight, causing air to enter the transformer;
 
② due to the temperature drop and resulting oil spill slowly lower position; or because of a transformer failure to produce a small amount of gas;
 
③ due to the occurrence of a short circuit, caused by crossing;
 
④ Since the secondary circuit fault protection device caused.
After light gas protection action signals. The reason: there are minor faults inside the transformer; the presence of air inside the transformer; secondary circuit failure. Operating personnel should immediately check, if no abnormality is found, the gas sampling and analysis should be carried out. Gas protection tripping when possible catastrophic failure inside the transformer, causing decomposition of large amounts of gas oil, may also be secondary circuit failure. Gas protection tripping occurs, it should be put into standby transformer and external checks. Check the oil pillow blast doors, each weld seam is split, the transformer housing is deformed; flammable gas last inspection.