Transformer abnormal operation and common faults - Solutions - Huaqiang

TP-IP4220CZ6 5V 0.35PF breakdown voltage 6V SOT

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

Photocoupler

1 Transformer abnormal operation and common faults
1.1 Abnormal conditions of transformer sound
1 Overload causes the transformer to emit a high and heavy "click" sound; 2 the internal contact of the transformer is poor, or the insulation is broken, the transformer emits a "beep" or "beep" sound, and the sound is close to the point of failure. Change; 3 when the grid occurs single-phase grounding or generates resonant overvoltage, the sound of the transformer is more sharp; 4 individual parts loose, such as the iron core of the core screw is not tightly clamped or missing parts on the iron core, the transformer is strong Uneven "noise" or sound of "hammering" and "blowing"; 5 When a large-capacity power plant is started, the load changes greatly, and the transformer sound increases. 
1.2 Under normal load and normal cooling mode, the transformer has a rising oil temperature
Short circuit between local windings or turns of the winding, internal contact fault, increased contact resistance, large resistance short circuit on the secondary line, etc., will also increase the oil temperature; due to eddy current or core for clamping the core Damage to the screw insulation will increase the oil temperature of the transformer. After the insulation of the core screw is broken, the insulation between the core screw and the silicon steel sheet is broken. At this time, a large current flows through the core screw, so that the screw heats up, and the oil temperature of the transformer also rises. 
1.3 The situation of oil injection in oil pillow or explosion-proof pipe
When the secondary system is suddenly short-circuited, and the protection is refused, or there is a short-circuit fault inside, and the air outlet and the explosion-proof pipe are blocked, the internal high temperature and high heat will cause the transformer oil to suddenly eject, and the oil surface will be lowered after the ejection, possibly Causes gas protection action. 
1.4 The situation of three-phase voltage imbalance occurs
1 Three-phase load imbalance causes neutral point displacement, so that the three-phase voltage is unbalanced; 2 system ferromagnetic resonance occurs, so that the three-phase voltage is unbalanced; 3 windings occur locally between turns and interlayers, causing three-phase voltage imbalance . 
1.5 The situation in which relay protection occurs 
The relay protection action generally indicates that there is a fault inside the transformer. Gas protection is the main protection of the transformer. It can monitor some of the faults inside the transformer. Usually, the light gas action first signals, and then the heavy gas acts to trip. When the external inspection does not find any abnormality in the transformer, the nature of the gas in the gas relay should be ascertained: 1 if the gas accumulated in the gas relay is non-flammable, and it is colorless and odorless, and the mixed gas is mainly inert gas. If the oxygen content is greater than 16% and the flash point of the oil does not decrease, it means that the air enters the gas relay. At this time, the transformer can continue to operate. 2 If the gas is flammable, it indicates that there is a fault inside the transformer, which should be accumulated according to the gas relay. The nature of the gas identifies the nature of the internal fault of the transformer; 3 uses gas chromatography to make appropriate judgments. When performing gas chromatography analysis, the internal fault of the transformer can be judged from the change in the contents of hydrogen, hydrocarbons, carbon monoxide, carbon dioxide, and acetylene. 
1.6 Flashover and explosion of insulated porcelain bushing
1 Due to the poor quality of the sealing rubber pad, the improper installation position, the nut is not pressed tightly, etc., the casing is not tightly sealed, and the insulation is damaged due to the intrusion or moisture intrusion; 2 the capacitive casing insulation layer gap exists. The free discharge formed inside; 3 the scale surface area of ​​the casing is severe, and there are large fragments and cracks on the casing, which will cause casing flashover and explosion accidents. 
2 Analysis of the cause of transformer failure
According to the reasons of transformer failure, it can be generally divided into circuit faults and magnetic circuit faults. Circuit faults mainly refer to wire loops and lead faults, etc. Common ones are: insulation degradation of the coil, moisture, poor contact of the switch, poor material quality and manufacturing process, overvoltage surge and fault caused by secondary system short circuit. Magnetic circuit faults generally refer to faults occurring between the iron core, yoke and clamps. Common ones are: short circuit of silicon steel sheet, insulation damage between core screw and yoke clamp and iron core, and discharge caused by poor grounding of iron core. . 
The above is only a preliminary, comprehensive induction and analysis of the faults of the transformer's sound, temperature, oil level, appearance and other phenomena. Since the transformer fault is not a reflection of a single factor, it involves many factors, sometimes even illusions. Therefore, if necessary, the characteristic test and comprehensive analysis of the transformer must be carried out in order to accurately and reliably identify the cause of the fault, identify the nature of the fault, and propose a more complete treatment to ensure the safe operation of the transformer. 
3 Avoid transformer failure during operation
In normal operation, the indication of the current, voltage, temperature, etc. of the monitoring transformer shall not exceed the specified value; when the transformer is overloaded, the number of times of recording shall be increased; ensure the safe operation of the transformer. For transformers in operation and standby, each shift should be inspected according to regulations; transformers after new installation or overhaul should be inspected every 2 hours within the first 8 hours of operation; transformers that are overloaded should be inspected thoroughly. 
3.1 Inspection items in transformer operation
Whether the sound is normal during the operation of the transformer, and whether there are other abnormal sounds; the oil level and oil color of the transformer oil storage tank and the oil-filled casing should be normal, and no oil leakage; whether the oil temperature and temperature rise of the transformer are normal, Whether the temperature meter indication and the telemetry thermometer indicate whether they are equal; whether the transformer bushing is clean, whether there are any broken cracks, discharge marks and other phenomena; whether the lead wires of the transformer, the cable have thermal discoloration and other abnormal phenomena; whether the transformer cooling device operates correctly , each submersible pump, cooling fan has no abnormal sound, whether the operation is normal, the oil flow relay indication is normal; the pressure release device or the safety air passage and the explosion-proof membrane should be intact; the gas relay should have no gas, the seal is good everywhere, no seepage Oil leakage phenomenon; the respirator is intact, the silica gel is dry and has no discoloration; the grounding connection of the transformer casing is firm and intact; the control box and the secondary terminal box should be closed and not damp; check the outer surface of the dry transformer should be free of dirt; Change the loaded tap and the control box in operation, no water leakage; the motor drive is intact, no damage; running teeth 
3.2 Special inspection items for transformers
1 After the thunderstorm, the outdoor transformer should be inspected for no discharge traces, the lead joints are not overheated, the number of counters of each arrester is counted, and the record is made; 2 windy days should check whether the lead wires of the outdoor transformer are violently oscillated, the upper part of the transformer and its surroundings There are no sundries; 3 snowy days, should check whether there is melting snow at the joints and lead connections of outdoor transformers, with or without ice slips; 4 foggy days, should check the outdoor transformer casing for spark discharge, pollution flash phenomenon ; 5 When the temperature suddenly changes, the oil level and oil-filled casing oil level, oil temperature and temperature rise should be checked. 6 When the load is overloaded, the load changes, the oil temperature and oil level change, the joint contact is good, and there is no overheating. The cooling system is operating normally.