Installation and debugging plan of oil-immersed transformer

Installation and commissioning plan of oil-immersed transformer

1. Power Performance and use of transformers:

1. Use a step-up transformer to increase the terminal voltage of the generator to tens of thousands of volts or hundreds of thousands of volts to reduce the transmission current and reduce energy loss on the transmission line without increasing the cross-section of the wire to transmit electricity over long distances.

2. Use Step-down transformer to reduce high voltage to low voltage suitable for electrical equipment, and convert high voltage of transmission line into various levels of voltage to meet the needs of various electrical loads.

3. Purpose: It is an electrical device that changes the AC voltage. This plan mainly discusses the installation and commissioning of a power transformer with a voltage of 10KV, a rated capacity of 1000KVA, and a frequency of 50HZ.

2. Composition and function of power transformer:

1. High and low voltage insulating bushing: It is the main insulating device outside the transformer box, with fixed leads and external circuits to connect the main components.

2. Tap changer: change the number of primary winding turns, adjust the secondary voltage, and adjust the voltage with or without load.

3. Gas Relay : It is connected with the control circuit to form a gas protection device.

4. Explosion-proof pipe: It is used for pressure protection when a fault occurs inside the transformer and the pressure increases dramatically.

5. Oil pillow: An oil storage device used to replenish the oil level during transformer operation. It has an oil mark tube to monitor the oil color and oil level, and is equipped with an oil filling hole and an air outlet flap on the top.

6. Respirator: Equipped with silica gel to absorb moisture. The silica gel is light blue when dry. When it is saturated with moisture, it turns light red. At this time, it can be taken out and replaced or dried at high temperature to restore it and still protect the original performance.

7. Radiator: Its function is to reduce the operating temperature of the transformer.

8. Oil tank, transformer casing, protective winding and core.

9. High and low windings: Made of insulated copper wire or aluminum wire, they are the circuit parts that establish the magnetic field and transmit electrical energy.

⒑ Iron core: The iron core constitutes the magnetic circuit of the transformer and is made of stacked silicon steel sheets.

⒒ Oil drain valve: The valve is at the bottom of the oil tank and is used for draining oil and taking oil samples.

⒓ Thermometer: monitors operating temperature, measures upper oil temperature, and has a thermometer socket.

3. The following work should be done before installing the transformer:

1. Labor time quota: (according to national quota standards) The total man-days required for the installation of the transformer body are 21 man-days. The work content includes: unpacking inspection, installation of the transformer body, body inspection, cleaning of bushings, oil pillows and radiators, oil column test, accessory installation, production and installation of pads and wheel stoppers, supplementary columns and overall sealing test after installation, grounding, repainting, etc. Whether the transformer needs to be dried during installation will be determined after inspection and judgment. If it needs to be dried, the iron loss drying method will take 20 man-days, and the oil filtration will take 3.38 man-days/ton. The man-days required for debugging will be calculated separately.

2. Installation site layout: Power transformer overhaul and assembly work is best carried out in the maintenance room. If there is no maintenance room, a temporary installation site needs to be selected. It is best to choose a place near the transformer foundation to put the transformer in place. It can also be installed on the foundation. There should be a tent at the outdoor site. The temporary installation site must be easy to transport, with a flat road and sufficient width. The ground should be solid, flat and dry, away from smokestacks and water towers, and the distance from nearby buildings must meet fire protection requirements.

3. Specify safety measures: ① Prevent accidents such as electric shock and falls. ② Prevent insulation overheating. ③ Prevent fire. ④ Prevent objects from falling into the oil tank. ⑤ Prevent accessories from being damaged. ⑥ Prevent the transformer from tipping over.

4. Formulate technical measures: ① Prevent the transformer core from getting wet. ② How to ensure good contact between all connected parts. ③ All parts must be well sealed without oil leakage. ④ How to ensure transformer insulation and oil insulation.

5. Basic procedures for installation work: ① Preparation work (tools, materials, equipment, drawings) ② Insulation inspection and judgment (mainly coils and cores) ③ Accessory inspection (should be complete and intact) ④ Hanging core inspection (to prevent moisture absorption and tools, parts, etc. from falling into the oil tank) ⑤ Accessory installation (appearance inspection, insulation measurement and strict test) ⑥ Ending work. ⑦ Handover test. ⑧ Trial operation.

6. Organization and division of labor of staff: ① General installation commander and technical person in charge ② Safety officer ③ Oil filter group ④ Lifting and transportation personnel ⑤ Test personnel ⑥ Installation personnel.

7. Requirements for transformer room: ① Level 1 fire protection ② Good ventilation ③ Sufficient safety distance ④ Solid foundation ⑤ In good condition for lifting facilities.

8. Preparation of tools and materials:

⑴Installation of machinery and tools (such as vacuum pumps, oil pumps, oil tanks, compressed air machines, oil filters, electric welders, running light transformers, valves, various wrenches, etc.)

⑵Testing instruments (such as megohmmeter, dielectric loss angle tester, step-up transformer, voltage regulator, ammeter , voltmeter , power meter, thermometer, etc.)

⑶ Lifting equipment (such as cranes, hangers, hanging beams, winches, wire ropes, pulleys, chain hoists, etc.)

⑷ Insulating materials (such as insulating oil, cardboard, cloth tape, bakelite insulating paint, etc.)

⑸ Sealing materials (such as resistant rubber gaskets, asbestos ropes, steel pads, shellac paint, nylon ropes, etc.)

⑹ Adhesive materials (such as epoxy resin, glue, cement, mortar, etc.)

⑺Cleaning materials (such as white cloth, alcohol, gasoline, etc.)

⑻Other materials (such as asbestos boards, square wood, wires, steel pipes, oil filter paper, vaseline oil, enamel, etc.)

9. Transformer external inspection: ① No mechanical damage to the inside

②The box cover bolts are intact

③The gasket is well sealed

④ No defects on the casing surface

⑤No oil seepage or leakage

⑥No rust, complete paint

⑦ All accessories are intact

⑧The wheel gauge of the roller is consistent with the gauge of the basic rail.

4. Conditions and requirements for transformer core inspection:

1. After long-distance transportation, the transformer will be subject to greater vibration and needs to be inspected. The transformer body inspection is divided into hanging core and hanging cover. Regardless of hanging core or hanging cover, the inspection content is the same. The hanging core inspection should be completed within one working day to speed up the inspection process.

2. Take the core inspection as an example: ⑴ The core of the transformer should be lifted indoors. If it is carried out outdoors, there should be a tent to prevent the core from being lifted in bad weather such as rain, snow, fog, wind and sand. ⑵ The temperature of the core should not be lower than zero degrees in winter, otherwise the transformer should be heated to make the core temperature 10℃ higher than the ambient temperature. ⑶ The shorter the time the core is exposed to the air, the better. It should not exceed 16 hours when the relative humidity is 65%, and should not exceed 12 hours when the relative humidity is 25%. The calculation time is from the start of oil draining to the end of oil filling. ⑷ When the relative humidity exceeds 75%, the core inspection is not allowed. ⑸ During the core inspection, special attention should be paid to prevent parts and tools from falling into the oil tank.

5. Preparation before transformer core hanging:

⑴ Preparation of tools and materials: such as oil storage tank, oil filter, complete set of wrenches, road book, oil-resistant rubber rope, white cloth, insulating cardboard, etc. ⑵ Preparation of lifting equipment: such as crane, fall chain, hand hoist, tripod, wire rope, etc. If the fall chain is used, the hanger must be set up according to the height and weight of the transformer. ⑶ Treatment of transformer oil, take oil samples for testing and testing, and make preparations for oil filtering, including oil filter paper. ⑷ Prepare the oil pan and put the wire core by hand.

The height of the hanger (h) should not hinder the lifting of the body. Therefore: h = h1 + h2 + h3 + h4 + h5 = h1 oil tank height h2 body height h3 lifting rope height h4 pulley (or fall chain) minimum distance h5 spare height (300 ~ 500mm) 1. Lifting beam 2. Pulley 3. Rope 4. Body 5. Oil tank

6. Core hanging steps:

⑴Choose the right position for the hanging core and add oil (place it below the plate)

⑵Remove the explosion-proof cylinder, oil pillow, gas relay

⑶Remove the large cover bolts

⑷ Use the balance iron to lift the iron core out and place it in the oil pan

⑸ Inspection: ① Wire core insulation

② Core insulation

③Through-core bolt insulation

④Tap changer contact insulation

⑤High and low voltage leads

⑥Fuel tank debris

⑦ Check whether the heat dissipation pipe is blocked

⑧Telemetry insulation resistance

⑨Measure DC resistance

⑹ If no problems are found after all items have been checked, reinstall the core in time and put it back into the oil tank.

⑺Strong large cover bolts

⑻ Install the removed accessories

⑼Inject qualified oil

⑽Perform a full set of pressure resistance test after standing still for 6-10 hours. ⑾On-site installation.

7. Transformer installation requirements:

1. The transformer foundation track should be horizontal, and the oil pillow should have a slope of 1-1.5%.

2. Transformer should be reinforced

3. The primary and secondary leads of the transformer should not put stress on the bushing.

4. The transformer housing is firmly connected to the neutral point and the grounding device to form a trinity 5. 800KVA (install gas relay )

8. Transformer trial operation:

1. The transformer can be put into trial operation only after all test items are qualified.

2. A comprehensive inspection of the transformer should be carried out before trial operation.

3. The transformer is subjected to five impulse tests (closing tests).

4. The no-load operation time is related to the transformer capacity and is generally not less than 24 hours.

5. After the no-load operation time is completed, the transformer is loaded again.

9. Transformer oil treatment:

1. Pressure filtration method: The insulating oil used in power transformers must have insulating and thermal conductivity properties (national standards). At the installation site, the pressure filtration method is often used to complete the general drying (removal of moisture) and purification (removal of dirt) of the insulating oil.

2. Open valves 8 and 11, then start the oil pump, and then open valves 6 and 7. When stopping the oil, first close valves 6 and 7, then stop the oil pump, and then close valves 8 and 11. ⑵ During normal operation, the pressure gauge is working normally under a pressure of 3*10 ~4*10 Pa. If impurities and oil paper are blocked, the pressure increases. When the pressure reaches 6*10 Pa, it must be stopped and the filter paper replaced. ⑶ Before using the filter paper, place it in an oven at 80-90℃ and dry it for 24 hours, and place it in a clean container. ⑷ The filter screen should be cleaned every 10~15 hours. At the beginning, within 3-5 minutes of filtering the oil, the oil outlet hole is sent back to the dirty oil tank through valve 10 for re-filtration. The oil accumulated in the oil filter is sent back to the dirty oil system through valve 9 and filtered again. The above filtered oil should be refined and dried many times until it is qualified.

3. Live oil filtering of transformer: ⑴ When the voltage is higher than 10V, live oil filtering should not be used. Because during filtering, more bubbles are generated, and bubbles will be freed under the action of higher voltage, which will deteriorate the insulation performance of the oil and cause internal discharge. When filtering oil with electricity, regularly release the gas released from the oil in the gas relay . ⑵ When filtering oil with electricity, the oil pipe and oil filter should be reliably grounded to protect the personal safety of the staff. The staff should be professional, supervised, and wear insulating supplies. ⑶ Operation: Connect the pressure oil filter buckle at the interface of the diagonal valves 4 and 5, and the oil is pumped out from valve 4 and returned to the oil tank from valve 5. After multiple cycles of filtering, it meets the standards.

10. Transformer test:

1. Remote measurement of insulation resistance : ⑴ Remote measurement items: high voltage to low voltage and ground (shell), low voltage to high voltage and ground (shell), ⑵ Select a 2500V megohmmeter, and conduct an appearance inspection on the megohmmeter. It should be in good condition, with complete external parts, flexible crank, no long resistance of the pointer, and no damage to the glass. ⑶ Conduct an open circuit test on the megohmmeter, separate the two test leads, shake the handle of the megohmmeter for 120 y/min, and the needle points to infinity (∞) for the best. Short circuit test: shake the handle of the megohmmeter, connect the two leads for a moment, and the needle points to "0" (zero), indicating that the megohmmeter is normal. ⑷ Qualified value: At a temperature of 20℃, the new transformer is not less than 450MΩ, and is not less than 300MΩ during operation. The current value shall not be reduced by 30% compared with the previous value. ⑸ Absorption ratio R60/R12 should be 1.3 times at 10-30℃.

2. DC resistance measurement: It can measure the welding quality of the internal wires and leads of the transformer, whether the parallel branches are connected correctly, whether there is a short circuit between layers or internal wire breakage, the tap switch, whether the contact between the bushing and the lead is good, etc.

3. Measurement method: If there is a bridge, the bridge can be used for measurement, which can read directly with high accuracy. If there is no bridge, the voltage drop method can be used. The voltage drop method measures the DC resistance of the wiring a) Measure small resistance b) Measure large resistance 1-coil under test 2-switch 3-battery 4-voltmeter 5- current meter DC resistance calculation formula: Where: U-voltmeter reading (mv) I-current meter reading (A) Transformers with tap switches should be measured at all tap positions during handover or overhaul. When a three-phase transformer has a midpoint lead-out line, the resistance of each phase line diagram should be measured. When there is no midpoint lead-out line, the line resistance can be measured.

When measuring, all lines not under test should be open circuited and not short-circuited. When measuring, you must wait for the current to stabilize before reading, and pay attention to personal safety.

4. Judgment standard: The difference between the DC resistance of each phase line diagram should not be greater than 2% of the average value of the three items. Compared with the previous measurement, the relative change should not be greater than 2%. In order to compare with the factory measurement value or the past measurement value, the DC resistance value should be converted to the value at the same temperature. The formula is as follows: Copper wire: Aluminum wire: Where: Re-DC resistance value measured at a temperature of Θ℃. Rt-DC resistance value at a converted temperature of t℃. Causes of failure: ⑴Poor contact of the tap changer ⑵Poor welding or breakage of the coil or lead wire, etc. ⑶Poor connection between the casing conductive rod and the lead wire ⑷Short circuit between coil turns or short circuit between layers.

5. Group test:

⑴ Single-phase transformer measurement polarity. The purpose of the three-phase transformer measurement group is to make the correct connection and determine whether the transformer can be operated in parallel .

⑵ Polarity measurement: It can be measured with DC or AC. Another introduction to DC measurement: For DC test wiring, select a 2-4V battery and a DC voltmeter with the zero position in the center. When the switch is closed, the needle swings to the positive direction, and when the switch is opened, the needle swings to the negative direction, which means the polarity is reduced. Otherwise, the polarity is increased.

⑶ There are two methods for measuring the connection group of three-phase transformer: DC method and AC method.