Power transformer installation

(1) Equipment and material preparation

The transformer should be equipped with a nameplate. The nameplate should indicate the name of the manufacturer, technical data such as rated capacity, primary and secondary rated capacity, primary and secondary rated voltage, current, impedance, voltage and wiring group. The capacity, specifications and model of the transformer must meet the design requirements. The accessories and spare parts are complete, and there are factory certificates and technical documents. Section steel: Section steel of various specifications should meet the design requirements and have no obvious corrosion. Bolts: Except for anchor bolts and anti-shock device bolts, galvanized bolts should be used and equipped with corresponding flat washers and spring pads. Other materials: welding rods, anti-rust paint, mixed paint, etc. should all meet the design requirements and have product certificates.

(2) Main machines and tools

Handling and lifting equipment: car cranes, cars, winches, hanging chains, three-step lifts, road wood, wire ropes, strap ropes, rolling bars; installation equipment: bench drills, grinding wheels, electric welders, gas welding tools, electric hammers, bench vises, Adjustable wrenches, hammerheads, wire sets; testing instruments: steel tape measure, steel ruler, spirit level, wire drop, shake meter, multimeter, electric bridge and testing instruments.

(3) Working conditions

The construction drawings and technical data are complete and correct; the civil engineering construction is basically completed.

(4) Operating technology

Equipment point inspection: Equipment point inspection should be carried out jointly by representatives of the installation unit, supplier unit and construction unit, and records should be kept. Check whether the specifications and models of the transformer body and accessory spare parts meet the requirements of the design drawings according to the equipment list, construction drawings and equipment technical documents. Whether it is complete and whether it is lost or damaged. The appearance of the transformer body was inspected for no damage or deformation, and the paint was intact and undamaged. Check whether the insulating porcelain parts and epoxy resin castings are damaged, defective or cracked. The secondary transportation of the transformer should be carried out by cranes with the cooperation of electricians. It is best to use a car crane for lifting, or a hanging chain for lifting. When transporting the transformer, care should be taken to protect the porcelain bottles. It is best to cover the high and low voltage porcelain bottles with cloth boxes or cartons to prevent them from being damaged. During the transportation of the transformer, there should be no impact or severe vibration. When using mechanical traction, the traction point should be below the center of gravity of the transformer to prevent tilting. The transportation tilt angle should not exceed 15° to prevent deformation of the internal structure. Before transporting or loading or unloading large transformers, the directions of the high and low voltage sides should be checked to avoid difficulties in changing directions during installation.

Stable installation of the transformer: When the transformer is in place, it can be thrown directly into the transformer room by a truck crane, or a temporary track can be set up with road wood, hoisted to the temporary track with a three-step lift and a hanging chain, and then pulled into a suitable position indoors with a hanging chain. When the transformer is in place, it should be noted that its orientation and distance from the wall are consistent with the drawings. The allowable error is ±25mm. If there is no mark on the drawing, it should be placed longitudinally according to the track. The horizontal distance from the wall should not be less than 800mm, and the distance from the door should not be less than 1000mm.

Installation of accessories; contents of transformer handover test: measure the DC resistance of the coil together with the bushing; check the transformation ratio of all tap transformers; check the wiring group of the three-phase transformer and the polarity of the lead wire of the single transformer; measure the sameness of the coil The insulation resistance of the bushing together; the AC withstand voltage test of the coil and bushing together. Inspection of the transformer before power transmission: A comprehensive inspection shall be carried out before the transformer is subjected to power transmission and trial operation, and it can only be put into operation when it is confirmed that it meets the conditions for trial operation. Before the transformer is put into trial operation, it must be inspected by the quality supervision department.

Inspection contents before the trial operation of the transformer: All handover test documents are complete and the data meets the requirements; the transformer should be cleaned and wiped clean, there is no debris left on the top cover, and the body and accessories are not defective; the primary and secondary leads of the transformer are in correct phase and insulated Good; the grounding wire is good; the ventilation facilities are installed and working normally; the signs are hung up and the doors are locked.

Transformer commissioning and operation

(1) Inspection before transformer power transmission and commissioning operation

Check whether the various handover test documents are complete, the phase and color of the primary and secondary leads of the transformer are correct, and the grounding wires are in good equal voltage contact. The transformer should be cleaned and wiped clean, with no debris left on the top cover, no defects on the main body and appendages, and no oil added. The ventilation facilities have been installed and working normally, the accident oil drainage facilities are intact, and the fire-fighting facilities are complete. The oil system throttle of the oil-immersed transformer should be opened, the throttle indication is correct, and the oil level is normal. The voltage switching position of the oil-immersed transformer is in the normal voltage range. The setting value of the protection device meets the specified requirements, and the operation and linkage test are normal.

(2) Transformer power transmission and commissioning operation

1. The transformer is put into impact test without load. When the transformer is put into operation for the first time, it can be switched on at full voltage for impact closing. When closing on impact, it can generally be switched on from the high voltage side. After the transformer receives power for the first time, the duration should be no less than 10 minutes without any abnormality.

2. The main method for checking the no-load operation of the transformer is to listen to the sound. When it is normal, it makes a buzzing sound, but when it is abnormal, the following situations may occur: when the sound is relatively loud and uniform, it may be that the applied voltage is relatively high; when the sound is relatively loud and noisy, it may be that the core is loose; there is a squeaking discharge. If there is a sound, it may be a flashover on the surface of the core and the casing; if there is a popping sound, it may be a breakdown of the core.

3. Transformer debugging and operation. After the no-load impact test, it can run without load for 24 to 28 hours. If no abnormality is confirmed, it can be operated with half load. After the transformer is energized at half load and debugged and runs in compliance with safe operation regulations, full load debugging will be carried out. The transformer is debugged and run at full load for 48 hours, and the temperature rise, oil level, oil leakage, and cooler operation of the transformer are checked again. After passing the full load test, the handover procedures can be completed before it can be put into operation.

Transformer acceptance

Acceptance plan: After the transformer starts to be energized, if there is no abnormality after 24 hours, acceptance procedures should be carried out; the following information and documents should be handed over during acceptance: design change certificate; product instructions, test report form, certificate and installation drawings and other technical documents; installation inspection and adjustment records.

The test adjustments and body inspection results of power transformers and their accessories must comply with the construction specifications. Defects such as crack damage and enamel damage on the surface of high and low voltage porcelain parts are strictly prohibited. The installation position of the transformer should be accurate, the surface of the transformer body should be clean, and the paint should be intact. The connection between transformer and line should meet the following requirements:

1. The connection is tight, the locking device of the connecting bolt is complete, and the porcelain casing is not subject to external force.

2. The neutral line is connected downward along the body of the device to the line segment of the grounding device, and is firmly fixed.

3. The wires connected between the accessories of the machine body are protected by protective tubes. The protective tubes and junction boxes are firmly fixed, and the box covers are complete.

4. The busbars leading to the transformer and their brackets, wire protection tubes and neutral wires should be easy to disassemble and not hinder their movement during transformer maintenance. The threads of the bolts used for each connection leaked 2 to 3 threads from the nuts, the protective tubes were of the same color, and the brackets were completely anti-corrosion.

5. The outer shell of the transformer and its accessories and other non-live metal parts should be grounded and comply with relevant requirements.

Conclusion

Power transformers play an extremely important role in the power system. The quality of their operation, inspection and maintenance is directly related to the economic benefits, social image and users' power quality of power supply enterprises, as well as to the power quality of the majority of users. to the security of the entire system. Therefore, it has attracted great attention from the power system. During the actual on-site operation and maintenance process, due to the limitations of usage conditions, operating environment, operation cycle, and maintenance personnel's sense of responsibility and skill level, the actual operating level reflected varies widely.

S11-M-1600 Oil-Immersed Transformer