Jiangsu Liwang Electric: Common three - coherence transforme

　Once the insulation breakdown occurs in the operation of three-coherent transformer, it will cause the winding short circuit or ground fault. In the case of inter-turn short circuit, the transformer overheating oil temperature is increased, the power side current is slightly increased, the dc resistance of each phase of the three-coherent transformer is unbalanced, sometimes there is a squeak and a bubbling sound in the oil. Slight interturn short circuit can cause gas protection action. Differential protection or overcurrent protection on the power side can also be activated in severe cases. Inter-turn short circuit should be dealt with in time, because inter-turn short circuit of winding will often cause more serious fault such as single-phase ground or inter-phase short circuit.

　　1. Winding failure

　　The three - coherent transformer mainly includes inter-turn short circuit, winding grounding, interphase short circuit, broken wire and joint open welding. The reasons for these failures are as follows:

　　(1) When manufacturing or maintenance, local insulation is damaged, leaving defects;

　　(2) in the operation due to poor heat dissipation or long-term overload, winding there is debris fall, so that the temperature is too high insulation aging;

　　(3) poor manufacturing process, pressing is not tight, mechanical strength can not withstand short circuit impact, so that the winding deformation insulation damage;

　　(4) the winding affected by moisture, insulation expansion plug oil channel, causing local overheating

　　The insulation oil mixed with water and deteriorated, or the contact area with the air is too large, so that the acid price of the oil is too high, the insulation level drops or the oil level is too low, part of the windings exposed to the air can not be timely treated.

　　2. Three-coherent transformer bushing failure

　　Such faults are commonly caused by explosions, flash drops and oil spills. The reasons are as follows:

　　(1) Poor sealing, damp insulation ratio, or oil leakage phenomenon;

　　3, three - coherence transformer core failure

　　(1) Insulation damage between silicon steel sheets, causing local overheating of the core and melting;

　　The top and middle of the transformer oil tank, between the casing flange, barrel skin and casing of the upper oil tank. The inner core and winding clamp are heated due to local magnetic leakage, which causes insulation damage.

　　If the transformer fails in operation, the winding or iron core should be checked. First, the dc resistance of each phase winding is measured and compared. If there is a big difference, it is the winding fault. Then the appearance of the core is checked, and the insulation resistance between the sheets is measured by dc voltage and ammeter. If the damage is not big, paint the damaged part of three - coherence transformer.

　　4, three coherent transformer gas protection fault

　　Gas protection is the main protection of transformer, light gas ACTS on signal, heavy gas ACTS on tripping. The following is the analysis of the reasons for the gas protection action and the treatment methods:

　　(1) Gas protection action may be due to the oil filter, refueling and cooling system is not strict, resulting in air into the transformer;

　　Signal after light gas protection action. The reasons are as follows: there is a slight fault inside the three-coherent transformer; There is air inside the transformer; Secondary circuit fault, etc. Operators should immediately check, if no abnormal phenomenon is found, should be carried out gas sampling analysis. When the gas protection action tri-coherent transformer tri-coherent transformer tri-coherent transformer tri-coherent transformer tri-coherent transformer tri-coherent transformer tri-coherent transformer is tri-coherent transformer. If gas protection action trip occurs, the standby transformer should be put in first, and then the external inspection should be carried out. Check the oil pillow explosion-proof door, whether the welding joints are cracked or not, and whether the transformer housing is deformed; Finally check the gas flammability.