Power transformers have a very important role in the power plant, however, due to its structure, process and operation and maintenance and other reasons, transformer failure occurs frequently in the power plant, greatly affecting the normal production of power plants.
Therefore, to strengthen the regular maintenance of the transformer, take effective measures to prevent the occurrence of transformer failure, to ensure the safe and stable operation of the transformer has important significance.
1, Transformer common fault phenomenon classification and reason
(1), the transformer itself factory when there is a problem. Such as loose head, pad loose, poor welding, bad core insulation, anti-short circuit strength and so on.
(2), line interference. Line interference is among the most important of all the factors that cause transformer accidents. mainly include:
The overvoltage generated at the time of closing, the peak voltage at the low load stage, the line fault, the flashover, and other anomalies. This type of failure in the transformer failure occupies a large proportion. Therefore, the transformer must be carried out on a regular impact test to detect the transformer anti-magnetizing current intensity.
(3), due to improper use of the transformer insulation caused by aging faster. General transformer life expectancy is only 17.8 years, much lower than expected for 35 to 40 years of life.
(4), caused by lightning over-voltage.
(5), overload. Overload refers to the transformer long-term over the nameplate power working state of the transformer. Overload often occurs in the power plant continued to slowly increase the load of the case, the cooling device is running properly, the transformer internal failure, etc., eventually resulting in transformer overload operation.
Resulting in excessive temperature will lead to premature aging of the insulation, when the transformer insulation paperboard aging, the paper strength decreased. Therefore, the impact of external failure may lead to insulation damage, and then failure.
(6), damp: If there is flood, pipeline leakage, roof leakage, moisture along the casing or accessories into the tank and the presence of moisture in the insulating oil.
(7), did not carry out proper maintenance.
2, transformer operation in the common fault analysis and treatment measures
(1), the main insulation of the winding and the inter-turn insulation fault.
Transformer windings of the main insulation and turn-to-turn insulation is prone to failure of the site. The main reason is:
Due to long-term overload operation, or poor heat dissipation conditions, or the use of a long life, so that the transformer winding insulation aging fragmentation, greatly reduce the strength of the transformer; transformer several times by the short-circuit impact, the winding force deformation, hidden insulation defects, There is voltage fluctuations may be insulated breakdown;
Transformer oil in the water so that the insulation strength greatly reduced and can not tolerate the allowable voltage, resulting in insulation breakdown; in the high-pressure winding reinforcement or low-voltage winding parts, due to insulation expansion, so that the oil block, affecting the heat, so that winding insulation Overheating and aging, the occurrence of breakdown short circuit; due to imperfect lightning facilities, the role of atmospheric over-voltage, the occurrence of insulation breakdown.
(2), transformer casing failure. Mainly casing flashover and explosion, the transformer high-pressure side of the general use of the capacitor casing, due to poor quality casing or trachoma and cracks, casing seal is not strict, there is oil leakage phenomenon; May cause flashover and explosion.
(3) core insulation failure. The transformer core is made of silicon steel sheet, and the insulating film is made of silicon steel sheet. As the silicon steel sheet is not fastened, so that the film damage caused by eddy current and local overheating.
Similarly, the core of the screw core screw, arm and other parts, if the insulation damage will occur overheating. In addition, if the transformer residue in the iron or slag, so that the core two or more ground, will cause the core failure.
(4), tap-changer failure. Transformer tap changer is one of the common faults of transformer. As the switch for a long time by pressure contact, there will be insufficient spring pressure, so that the switch connected part of the effective contact area reduced, and contact part of the silver layer wear off, causing the tap switch in the operation of heat damage.
Tap changer contact bad, can not withstand the impact of short circuit current caused by the tap switch burned and failure; in the load regulator of the transformer, tap the fuel tank and transformer fuel tank is generally not connected.
If the tap changer tank serious oil shortage, the on-load tap-changer in the switch will be short-circuit fault, so that the tap switch burned.
(5), gas protection failure. Gas protection is the main protection of the transformer, the light gas acts on the signal, the heavy gas acts on the trip. The following analysis of the reasons for gas protection action and approach:
First, the light gas protection action issued a signal. The reason is: a slight internal transformer failure; transformer internal air;
Secondary circuit failure. Operators should immediately check, if no abnormal phenomenon, should be carried out gas sampling analysis.
Second, the gas protection action trip, the transformer may be a serious internal failure, causing oil to break down a lot of gas, it may also secondary circuit failure. The occurrence of gas protection action trip, should be prepared to change, and then external inspection. Check the oil pillow explosion-proof door, the welding seam is split, the transformer shell is deformed; finally check the flammability of the gas.
(6), the transformer automatically trip processing. When the circuit breaker on each side of the transformer is automatically tripped, the control switch of the trip circuit breaker is first operated to the position after the trip and quickly put into the spare transformer, adjust the operation mode and load distribution, and keep the running system and equipment in the normal state.
Check the protection action and perform an external check. If the inspection is not an internal fault but is caused by an external fault (through fault) or malfunction of the person, it can be delivered without an internal check.
In the case of differential, heavy gas, quick break and other main protection action, the protection of the equipment within the scope of all the inspection. Do not put the transformer into operation until the cause is unchecked.
(7), transformer ignition is also a dangerous accident. Due to damage or flashover of the transformer casing, the oil in the oil under the action of oil pressure, and burned in the transformer roof; transformer internal failure, so that the oil burning and shell rupture.
Because the transformer has a lot of combustible material, not timely treatment may cause an explosion or to expand the fire. In the event of such an accident, the transformer protection should act to disconnect the circuit breaker.
If the circuit breaker is not disconnected, turn off the circuit breaker immediately and open the disconnect switch which may lead to the transformer power supply, and then quickly put into standby change, restore the power supply, stop the operation of the cooling equipment, fire. Transformers fire, the best use of foam-type fire extinguisher or dry powder fire extinguishers, if necessary, can be used to fire the sand.
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