(1) by phase:
(1) single-phase transformers: used for single-phase loads and three-phase transformer group.
(2) three-phase transformer: used for three-phase system step-up and step-down voltage.
(2) according to the cooling mode:
(1) dry-type transformer: rely on air convection for cooling, generally used for local lighting, electronic circuits and other small capacity transformers.
(2) oil-immersed transformer: rely on oil as a cooling medium, such as oil-immersed self-cooling, oil-immersed air-cooled, oil-immersed water-cooled, forced oil circulation.
(3) according to the use of:
(1) power transformer: used for transmission and distribution system voltage rise and fall.
(2) instrumentation transformers: such as voltage transformers, current transformers, for measuring instruments and relay protection devices.
(3) test transformer: can produce high voltage, high voltage test of electrical equipment.
(4) special transformers: such as furnace transformers, rectifier transformers, adjustment transformers.
(4) according to the winding form:
(1) double winding transformer: used to connect the two voltage levels in the power system.
(2) three winding transformer: generally used in power system regional substations, connecting three voltage levels.
(3) Autotransformer: used to connect power systems of different voltages. It can also be used as an ordinary step-up or step-down transformer.
(5) According to the iron core form:
(1) core transformer: used for high-voltage power transformers.
(2) shell transformer: used for high-current special transformers, such as furnace transformers, welding transformers; or for electronic instruments and TV, radio and other power transformers.
Editorials Comparison of transformers
Their respective operation and maintenance ：
Transformer, oil conservator, voltage tap changer
1, transformer operation in the abnormal phenomenon
(1)Transformer operation, such as leakage of oil, the oil level is too high or too low, the temperature is abnormal, the sound is not normal and the cooling system is not normal and so on, you should try to as soon as possible Eliminate.
(2) when the transformer load exceeds the allowable normal overload value, should be in accordance with the regulations to reduce the transformer load.
(3) transformer internal sound is very large, very abnormal, bursting sound; temperature is abnormal and rising; oil storage cabinet or safety airway oil spray; serious oil leakage makes the oil level drop below the limit of the oil level meter indication; oil color change too fast, the oil appeared in the carbon; casing has a serious breakage and discharge phenomenon, etc., should be immediately shut down for repair.
(4) when the transformer oil temperature is found to be high, and its oil temperature should be a significant reduction in oil level, should be immediately refueled. Refueling should be observed. If the oil level drops rapidly due to a large number of oil leakage, the gas protection should be changed to only act on the signal, must quickly take measures to plug the oil leakage, and immediately refueling.
(5) transformer oil level due to temperature rise and gradually rise, if the highest temperature when the oil level may be higher than the oil level indicator, the oil should be drained, so that the oil level down to the appropriate height, so as to avoid overflow of oil.
2, transformer operation check
(1) check whether the transformer upper oil temperature exceeds the allowable range. Each transformer load size, cooling conditions and different seasons, the operation of the transformer can not be based on the upper oil temperature does not exceed the allowable value, should also be running experience and the above situation with the last oil temperature comparison. If the oil temperature increases suddenly, should check whether the cooling device is normal, oil circulation is damaged, etc., to determine whether the transformer internal failure.
(2) check the oil quality, should be transparent, slightly yellow, which can determine the oil quality is good or bad. Oil level should be in line with the surrounding temperature standard line, such as oil level is too low should check whether the transformer oil leakage. Oil level is too high should check the use of cooling device, whether there is internal failure.
(3) transformer sound should be normal. Normal operation generally have uniform humming electromagnetic sound. If the sound has changed, should be carefully checked, and quickly report to the duty dispatcher and ask the maintenance unit to deal with.
(4) The casing should be checked for cleanliness, cracks and discharge marks, and the cooling device should be normal. The working and standby power supply and oil pump should meet the operating requirements, etc.
(5) When there is a change in weather, special inspection should be focused. When the wind, check the leads have no violent swing, transformer top cover, casing leads should be free of debris; snow days, the contacts after the snow, should not immediately melt or discharge phenomenon; fog days, the various departments have no spark discharge phenomenon and so on.
3, transformer accident handling
Correctly handle the accident, should grasp the following: ① system operation, load status, load type; ② transformer oil temperature, temperature and voltage; ③ accident weather conditions; ④ transformer around the maintenance and other work; ⑤ operator operation; ⑥ system operation; ⑦ what kind of protection action, accident phenomenon The situation and so on.
Transformer operation in the common fault is winding, casing and voltage tap changer failure, and core, tank and other accessories failure is less. The following will be common several major faults are described as follows:
3.1 Winding failure
Mainly turn-to-turn short circuit, winding, phase-to-phase short circuit, broken wire and joints welded and so on. These failures are caused by the following:
① Manufacturing or overhaul, local insulation is damaged, leaving defects. ② operation due to poor heat dissipation or long-term overload, debris falling into the winding, so that the temperature is too high insulation aging. ③ poor manufacturing process, the press is not tight, the mechanical strength can not withstand the short-circuit impact, so that the winding deformation insulation damage. ④ Winding moisture, insulation expansion blocking the oil channel, causing local overheating. ⑤ insulating oil mixed with water and deterioration, or too large a contact area with the air, so that the oil acid price is too high insulation level drop or oil level is too low, part of the winding dew air can not be dealt with in a timely manner.
All of the above reasons, once the insulation breakdown occurs in operation, it will cause the winding short-circuit or connection failure. Turn-to-turn short-circuit fault phenomenon is the transformer overheating oil temperature increases, the power side of the current slightly increased, the phase DC resistance imbalance, the oil has a squeak and goo goo goo goo bubbling sound. Slight turn-to-turn short circuit can cause gas protection action; serious differential protection or power side overcurrent protection will also act. Found that turn-to-turn short circuit should be dealt with in a timely manner, winding turn-to-turn short circuit often causes more serious single-phase connection or phase-to-phase short circuit and other faults.
3.2 casing failure
This kind of failure is common is blowing up, flash off and oil leakage, the causes are:
(1) poor sealing, insulation moisture inferior than;
(2) improper configuration of respiratory inhalation of moisture is not handled in a timely manner.
3.3 Tap changer failure
The common failures are surface melting and burns, phase-to-phase contact discharges or discharges at each joint. The main causes are:
(1) Loose connecting screws;
(2) Bad and improperly adjusted adjustment devices with load;
(3) Poor insulation of the tap changer insulating board;
(4) Dissatisfaction of soldering on the joints, poor contact, poor manufacturing process and insufficient spring pressure;
(5) Excessive acidity of the oil, which causes the contact surfaces of the tap changer to be corrosion.
3.4 Failure of the iron core
Most of the causes of iron core failures are caused by damage to the insulation of the iron core column
threading screws or iron wheel clamping screws, which may result in a two-point connection between the threading screws and the iron core iterative sheet, resulting in a circulating current that causes a localized heat generation, causing the iron core to locally melt down. May also cause the core iterative local short circuit, resulting in eddy current overheating, causing damage to the insulation layer between the iterative, so that the transformer no-load loss increases, the degradation of the insulating oil.
After the operation of the transformer failure, such as judgment is winding or core failure should be lifted core inspection. First of all, measure the phase winding DC resistance and comparison, such as the difference is large, it is the winding failure. Then the core appearance check, and then DC voltage, ammeter method to measure the insulation resistance between the pieces. If the damage is not big, the damage can be painted.
3.5 gas protection failure
Gas protection is the main protection of the transformer, light gas signaling, heavy gas tripping. The following analysis of gas protection action causes and treatment methods:
(1) light gas protection action signal. The reasons are: minor faults within the transformer; transformer internal storage air; secondary circuit failure. Operators should immediately check, such as not found anomalies, gas sampling should be analyzed.
(2) gas protection action trip, may be a serious fault within the transformer, caused by oil decomposition of a large number of gases, may also be a secondary circuit failure. Gas protection action trip, should first put into the backup transformer, and then external inspection. Check the oil pillow explosion-proof door, whether the weld is cracked, whether the transformer shell is deformed; finally check the gas flammability.
When the transformer automatically tripped, should identify the protection action, external inspection. After checking the internal faults external faults (crossing faults) or caused by personnel error, it can be put into the power supply without internal checking. If the differential protection action, the protection scope of the equipment should be all checked.
In addition, the transformer fire is also a dangerous accident, because the transformer has a lot of combustible material, treatment may not be timely explosion or fire expansion. Transformer fire is mainly due to: casing damage and flash off, oil pillow pressure outflow and burning on the top cover; transformer internal failure to make the shell or radiator rupture, so that the burning transformer oil overflow. When this type of accident occurs, the transformer protection should act to make the circuit breaker disconnect. If for any reason the circuit breaker is not disconnected, the application of manual to immediately disconnect the circuit breaker, pull open the transformer power supply isolation switch may lead to stop the cooling equipment to extinguish the fire. Transformer fire, it is best to use foam fire extinguishers, if necessary, sand extinguishing.