Common sense of transformer safe operation

1. What are the most basic items that should be paid attention to in transformer operation management?

First, the transformer is in operation

Before 1 is put into operation, all components of the transformer should be cleaned and wiped.

2 When no-load pressure regulating, the connectors of the pressure regulating tap shall be connected to the corresponding positions according to the identification on the nameplate;

For on-load voltage regulation, please refer to the instruction manual of on-load tap changer, and set the setting value of overcurrent protection in the on-load tap changer according to the rated current of high voltage side, and put it into operation after the tap changer is debugged normally.

When the transformer is equipped with a temperature control system, please refer to the operating instructions of the temperature control device.

5 The transformer should be put into operation with no-load switching, the peak value of switching inrush current can reach 8~ 10 times of rated current, and the setting value of transformer current quick-acting protection should be greater than the peak value of inrush current.

6 After all protection devices are put into operation, the transformer will be impacted by no-load closing for 5 times (every time interval 10 minute), and there should be no abnormality.

7 After the transformer is put into operation, the load should be changed from light to heavy, and the product should be checked for abnormal sound. It is forbidden to blindly put into heavy load.

After the transformer is out of operation, it can be put into operation again without taking other measures. However, if it is at high temperature and the transformer is condensed, it must be dried before the transformer can be put into operation again.

Second, the monitoring and maintenance of transformer

In order to ensure the normal operation of the transformer, it needs to be monitored and maintained regularly.

1 Always monitor the temperature display value of the thermostat, keep abreast of the operation of the transformer, and pay attention to the presence of abnormal sound and vibration.

2 When the three-phase load of the transformer is unbalanced, the maximum phase current and maximum phase temperature should be monitored, and the maximum allowable zero line current of the transformer connected by Yyn0 is 25% of the low-voltage line current. Dyn 1 1 The maximum allowable neutral current of the transformer can be the same as the low voltage line current.

3 When the transformer has the following conditions, such as abnormal fan operation; Abnormal temperature display; When the appearance of winding resin insulation has tiny cracks, it is not allowed to exceed the nameplate. Find out the reason or contact the manufacturing unit for confirmation.

4. Generally dry and clean places should be inspected once a year or for a little longer; On other occasions, such as running in dusty or turbid air, check it every three to six months. In heavily polluted areas, power outage maintenance and inspection must be carried out every month.

During the inspection, if excessive dust accumulation is found, it must be removed to ensure air circulation and prevent insulation breakdown. However, volatile cleaning agents are not allowed, and special attention should be paid to cleaning the top and bottom of transformer insulators and winding components, and using compressed air to blow off the dust in ventilation pipes. When the transformer is running, the flow direction of compressed air is opposite to that of cooling air.

6 Check whether fasteners and connectors are loose, whether conductive parts and other parts have traces of rust and corrosion, and observe whether the insulation surface has traces of carbonization and electrical corrosion. If found, corresponding measures should be taken to deal with it.

Third, safety precautions

1 The transformer, transformer shell or transformer isolation fence shall be well grounded with safety warning signs.

After the transformer is put into operation, it is forbidden to touch the transformer main body to prevent accidents, and it is forbidden to adjust the voltage with electricity without excitation.

Before the transformer high voltage test, the temperature sensor cable should be taken out of the temperature control box to prevent the temperature control box from being damaged. All temperature sensors, sensing wires and secondary control wires must not contact with live parts of the transformer! ! !

2. What is the safe operation procedure of transformer?

Safety operation procedures for transformers The cover flange bolts must be tightened symmetrically and evenly.

When checking the iron core of large transformer, scaffolding should be set up. It is forbidden to climb the lead frame up and down. Oil storage and oil treatment sites must be equipped with sufficient and reliable fire-fighting equipment, and a clear fire-fighting responsibility system must be formulated. The site shall be flat and tidy, and there shall be no kindling, inflammable and explosive materials within m range.

When transformer accessories are defective and need to be welded, the residual oil should be discharged to remove the oil on the surface and transported to a safe place. Insulation and isolation measures should be taken when poor welding of transformer leads needs to be repaired on site.

Repair welding is allowed for tiny leakage of oil-filled transformer. There should be an opening at the top of the transformer.

The welded part must be below the oil level. Open flame welding is strictly prohibited, and intermittent welding should be adopted.

The oil around the solder joint should be cleaned up. Appropriate safety and fire prevention measures should be taken and safety technical disclosure should be made to the participants.

Before transformer drying, safety technical measures and necessary management system should be formulated. The power supply and wires used in the drying transformer should be calculated, and the circuit should have an overload automatic cut-off device and an overheating alarm device.

When drying the transformer, thermometers should be installed on the iron core, winding or oil level according to the drying method, but mercury thermometers are strictly prohibited. .

3. What should be checked during the operation of the transformer?

(1) Whether the sound of the transformer is normal;

(2) Whether the oil color and oil level in the oil storage tank and oil-filled casing are normal and whether there is oil leakage;

(3) whether there is any damage on each side of the casing, whether there is any abnormal phenomenon such as discharge trace;

(4) Whether the cooling device is operating normally;

(5) the upper oil temperature indicator is correct, with or without exception;

(6) whether the diaphragm of explosion-proof pipe is in good condition and whether there is liquid accumulation;

(7) The discoloration degree of the mask discoloration selenium glue;

(8) Whether the gas relay is filled with oil;

(9) Whether there is leakage or oil leakage in the machine body and accessories;

(10) Whether the casing pile head and connecting line on each side are hot or discolored;

(1 1) Whether the surrounding environment and piles near the transformer may threaten the safe operation of the transformer.

4. How is the normal operation of the transformer operated?

Answer: Operating principle of transformer power failure: (1) When transformer power failure occurs, disconnectors must be replaced by circuit breakers, and so must no-load transformers.

The no-load current of transformer is very large, which is pure inductive current. The no-load current of large-capacity transformer is 0 of its rated current.

6%? 4%, small and medium capacity transformers reach 5% of the rated current? 1 1%。 The arc generated by cutting off the no-load current of transformer with disconnector may sometimes greatly exceed the natural arc extinguishing ability of disconnector, and even cause arc short circuit.

Therefore, try to connect or cut off the transformer circuit with a circuit breaker. When there is no circuit breaker in the transformer circuit, it is allowed to switch on and off the transformer with no-load current less than 2A with disconnector.

In order to cut off the no-load current of 20kV and above transformers, it is necessary to use the outdoor triple disconnector with arc suppression cover and mechanical transmission device. For transformers with 10kV/320kVA and below and 35kV/ 1000kVA and below, no-load current can be shunted by disconnectors.

For example, there is no high voltage circuit breaker in the distribution transformer below 400kVA, and the no-load current of the distribution transformer can be carried out by dropping the fuse. The role of the drop fuse is to protect the short circuit when it is short-circuited; During normal operation, the disconnector is used for switching operation.

When opening the brake, first divide the middle phase (phase B) and then pull both sides (phase A and phase C); In the case of wind, the headwinds will be pulled apart in turn. Closing is the opposite.

(2) the transformer stop sending operation sequence. When the transformer sends electricity, it will be sent to the power supply side first and then to the load side. If there is a power failure, the order is reversed.

This is because, when the power is transmitted in the above order, if the transformer fails, the protection device can act on the circuit breaker to trip and remove the fault, which is convenient for checking the fault according to the transmission range and judging and handling the fault. The above sequence of power failures will also prevent the transformer from charging in reverse.

Otherwise, stop the power supply side first, which increases the burden of the power supply side circuit breaker to cut off the circuit. At the same time, if there is a fault inside the transformer, it may cause misoperation or refusal of protection, prolong the fault removal time or expand the power outage range. (3) For distribution transformers with disconnectors on the high-voltage side and low-voltage circuit breakers or load switches on the low-voltage side, the high-voltage side should be connected first and then the low-voltage side; When the brake is opened, the situation is just the opposite.

(4) For the transformer connected to the generator-transformer group, the voltage should be raised from zero to the rated value as much as possible when sending power, and then tied with the system. In case of power failure, the order is reversed.

(5) When the transformer is put into operation or stopped, the neutral grounding isolating switch on each side should be closed first. On the one hand, neutral grounding disconnector can prevent overvoltage caused by single-phase grounding and avoid some operating overvoltage, and protect transformer windings from overvoltage damage; On the other hand, after the neutral grounding disconnector is closed, when single-phase grounding occurs, a grounding fault current flows through the transformer, which makes the differential protection and zero-sequence current protection of the transformer act and cuts off the fault point.

Therefore, before the transformer is put into operation or stopped, the neutral grounding isolating switch must be closed first. If the transformer is charged, the neutral grounding separator should also be in the closed position.

(1) Switching principle of disconnector with two transformers running in parallel and neutral grounded. When two transformers run in parallel, according to the needs of the system, the neutral point of one transformer is grounded and the neutral point of the other transformer is not grounded.

When it is necessary to switch the neutral grounding disconnectors of these two transformers, the neutral grounding disconnector of the ungrounded transformer should be closed first, and then the neutral grounding disconnector of the other transformer should be opened, and the zero sequence current protection should be switched. The reason is that if the disconnector of the neutral point of the grounding transformer is disconnected first, when the disconnector of the neutral point of another transformer is not closed, a single-phase short circuit will suddenly occur. As the large grounding system becomes ungrounded, the single-phase short circuit will actually become a single-phase grounding fault, and the phase voltage of the non-fault phase will be three times (the grounding insulation of the large current grounding system is designed according to the phase voltage). At this time, the neutral point of the transformer will also have a grounding voltage as high as the phase voltage.

This is very dangerous for equipment including transformers. Therefore, the switching principle of transformer neutral grounding disconnector in high current grounding system is to ensure that the power grid cannot lose the grounding point, that is, the operation method of first closing and then pulling is adopted: ① closing the standby grounding point disconnector; (2) turn on the isolating switch of work grounding point; ③ Switch the zero sequence protection to neutral grounding transformer.

(2) Principles of protection and use of transformers. Before power transmission, all protections of transformers should be put into use (protections that may malfunction or fail the test should be stopped with approval), and it is forbidden to transmit power and run unprotected transformers.

After the power failure of the transformer, it is not necessary to disconnect the protective connectors without affecting the standby equipment or operating equipment, or when there is no relay protection work on site. The protective connectors that need to be disconnected should be recorded in detail in the handover record book. (3) Switching of transformer tap changer.

Tap-changer is used for voltage regulation of transformer. By changing the tap changer and the tap position of the voltage transformer (that is, changing the ratio), the purpose of voltage regulation is achieved.

Tap-changer can be divided into on-load voltage regulation and off-load voltage regulation. The switching of no-load tap-changer should be carried out in the power failure state of transformer.

When the transformer is under load, the on-load tap changer can change the tap position manually or electrically. (4) When the double-winding transformer is put into operation, it should be connected to the power supply side first and then to the load side; Excision is the opposite.

(5) putting in a three-winding step-up transformer, first connecting the low-voltage side, then the medium-voltage side and finally the high-voltage side; Excision is the opposite. (6) put a three-winding step-down transformer, which is connected to the high voltage side, the medium voltage side and the low voltage side first; Excision is the opposite.

Note: For items (9), (10) and (1 1), there are different regulations on the switching-on sequence of transformers according to different conditions on site. (7) When switching transformers, it must be confirmed that the merged transformer has been loaded, and the transformer must be stopped.

When the standby transformer sends power, if the transmission mechanism of the circuit breaker is welded, the pull rod falls off or the isolating switch "misses", although the red light is on after the circuit breaker is closed, the primary circuit of the transformer is not actually connected. At this time, if you don't check whether the connected transformer is loaded, you will cut off the power supply of the running transformer in a hurry, which often causes accidents.

Therefore, when switching transformers, just take another look to check whether the combined transformers are loaded with current, and then operate them to plug the loopholes and avoid accidents. (8) Parallel operation principle of transformers.

The advantage of parallel operation of transformers is improvement.

5. Who knows some safety matters that need to be known in the production of power transformers?

Safety operation procedures. The operation of power transformer must meet the technical requirements specified in the transformer operation regulations.

2. Before the newly installed or overhauled transformer is put into operation, the following inspections shall be carried out: 1. Check the nameplate to see if its voltage level is consistent with the line voltage level. 2, transformer insulation is qualified, with 1000 or 2500 volts shaking table check, determination time is not less than 1 minute, so far the pointer is stable.

The insulation resistance is not less than 1 megohm per kilovolt, and the measurement sequence is high voltage to ground, low voltage to ground, and high and low voltage braking. 3. Whether the oil tank leaks oil, whether the oil level is within the range indicated by the oil standard, whether the oil gauge is unblocked, whether the breathing hole is ventilated, and whether the silica gel in the respirator is blue.

4, tap changer position is correct, good contact. 5, porcelain bushing should be clean, no loose.

Three, the power transformer should be regularly external inspection. Transformers in substations where people are often on duty should be inspected at least once a day and once a week at night.

Four, unattended transformer, the capacity of more than 3200 kva every 10 days at least once, and check before and after each put into use. If the capacity is greater than 320kVA but less than 3200kVA, it should be checked at least once a month, and it should be checked before and after each use.

Five, after overhaul or installed transformer began to run within 48 hours, each shift should be checked twice. Six, transformer operation under abnormal circumstances (such as high oil temperature, abnormal sound, oil leakage, etc.). ) monitoring should be strengthened and the number of inspections should be increased.

7. The following items should be inspected and inspected for the transformer in operation: 1, whether the sound is normal, and there is a uniform "buzzing" sound during normal operation. 2, the upper oil temperature should not exceed 85℃.

3, whether there is leakage, oil leakage, oil color and oil level indicator is normal. 4, whether the casing is clean, with or without damage, cracks, discharge marks and other phenomena.

5, explosion-proof pipe membrane without rupture, no oil leakage. 6, gas relay window oil level is normal, with or without gas.

Eight, transformer 1 allowed mode of action, the upper oil temperature in operation should not often exceed 85℃, and the highest should not exceed 95℃. 2. The voltage applied to the voltage tap shall not exceed 5% of the rated value.

3. The transformer can operate under normal overload and accidental overload, and the normal overload can be used frequently. The allowable value is determined by the technical personnel in charge of the unit according to the load curve of the transformer, the temperature of the cooling medium and the load before the overload of the transformer. When an accident occurs, it is allowed to run for two hours at 30% overload, but the upper oil temperature shall not exceed 85℃.

9. Transformers can run in parallel, but the following conditions must be met: 1, and the coil connection groups are the same. 2, the voltage ratio is equal, and the error is less than 0.5%.

3. The short-circuit voltages are equal, and the error is less than 10%. 4. The transformer capacity ratio is not more than 3: 1.

5. The phase sequence is the same. Ten, transformer parallel connection for the first time before the phase sequence inspection must be done.

11. Transformers without on-load voltage regulating devices are not allowed to be charged with back taps. For transformers above 320kVA, DC resistance should be measured before and after tap changer, and the integrity of loop and the uniformity of three-phase resistance should be checked.

12. When the transformer is put into operation or stopped, the following procedures must be followed: 1. When a transformer with oil switches and disconnectors on both high and low voltage sides is put into operation, all disconnectors on both sides of the transformer should be put into operation first, then the oil switch on the high voltage side should be put into operation to charge the transformer, and then the oil switch on the low voltage side should be put into operation to charge the low voltage bus. In case of power failure, the order is reversed. 2. When the transformer without oil switch on the low-voltage side is put into operation, first place the isolating switch on the high-voltage oil switch side, then place the oil switch on the high-voltage side to charge the transformer, and then place the circuit breaker and air switch on the low-voltage side to supply power to the low-voltage bus.

In case of power failure, the order is reversed. Thirteen, transformer operation found the following anomalies, immediately report to the leadership, and ready to put into standby transformer.

1, and the upper oil temperature exceeds 85℃. 2, shell oil leakage, oil level changes, oil level drops.

3. The casing is cracked and discharged. 14. When the transformer is in any of the following situations, it should immediately contact the power outage: 1. There is a loud noise inside the transformer and a discharge sound.

2. The temperature of transformer rises sharply. 3. The oil leakage is serious and the oil level drops rapidly.

15. When the following serious accidents happen to the transformer, the power shall be cut off immediately. 1, the explosion-proof pipe of the transformer is on fire, and the transformer itself is on fire.

2, transformer bushing burst. 3. The iron shell of the transformer body is broken, and a large amount of oil is sprayed out.

16, transformer fire, should first open the throttle, put the oil into the oil pool, at the same time with carbon dioxide, carbon tetrachloride fire extinguisher to put out the fire. After the transformer and surrounding power supply are all cut off, use foam extinguisher to put out the fire. It is forbidden to put out fires with water.

17. Check the transformer when the gas signal is light. If the oil level drops, the oil storage tank should be refueled when there is no oil.

If there is gas in the gas relay, observe the gas color and report it in time, and handle it accordingly. Eighteen, operating transformer and standby transformer oil, should be in accordance with the provisions, pressure test and simplified test.

19, standby transformer must be kept in good condition, ready to put into operation at any time.

6. What should be paid attention to in the operation, maintenance and overhaul of transformer?

Understanding the working principle and internal structure of transformer itself is the basic requirement for professional and technical personnel.

Before the maintenance work, the staff must be prepared, analyze possible problems, and prepare all kinds of materials and tools needed for maintenance. At the same time, contact welders, scaffolders, chemical oil handlers and other possible staff to help them do all kinds of cooperation work.

Before maintenance, the power supply should be cut off, so that the transformer is in a stopped state and adjusted as needed. Workers should also pay attention to their own clothes and other personal belongings when repairing. Don't wear clothes with many decorations and patterns, and don't carry other small instruments to ensure safety, so as to avoid affecting transformer maintenance due to mistakes or forgetfulness.

Everything is ready, and with the knowledge of transformers, skilled technology and proficient skills, and traveling lightly, the staff can start the maintenance work. Of course, we should always keep in mind the belief of "safety first" in the maintenance process.

7. Operation mode of transformer

Transformer zd consists of an iron core (or magnetic core) and a coil. The coil has two or more windings, of which the winding connected to the power supply is called a primary winding and the other windings are called secondary windings. It can transform AC voltage, current and impedance. The simplest core transformer consists of a core made of soft magnetic material and two coils with different turns sheathed on the core.

Transformer is an electrostatic appliance made by electromagnetic induction principle. When the primary coil of transformer is connected to AC power supply, alternating magnetic flux will be generated in the iron core, which is generally expressed by φ. The version φ in the primary and secondary coils is the same, and φ is also a simple harmonic function, which is expressed as φ = φ msin ω t.

Extended data:

Potential parameter

1, operating frequency

Transformer core loss has a great relationship with frequency, so it should be designed and used according to the use frequency, which is called working frequency.

2. Rated power

Under the specified frequency and voltage, the transformer can work for a long time without exceeding the output power of the specified temperature rise.

3. Rated voltage

Refers to the voltage allowed to be applied on the transformer coil, which should not be greater than the specified value when working.

4. Voltage ratio

Refers to the ratio of primary voltage to secondary voltage of transformer, which is different from no-load voltage ratio and load voltage ratio.

5. No-load current

When the secondary circuit of transformer is open, there is still a certain current in the primary circuit, which is called no-load current. No-load current consists of magnetizing current (generating magnetic flux) and iron loss current (caused by iron core loss). For 50Hz power transformer, the no-load current is basically equal to the magnetizing current.