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Oil filled distribution Transformer Body Assembly Instructions

April 10, 2019

Transformer body assembly operation guide for oil filled type.

1.Scope of application

This process is suitable for insulation assembly of oil-immersed power transformer body with capacity of 2000KA and 10KV. This process is a general process. Except for the special requirements in the drawings, it is operated according to this process.

Oil filled transformer tank with corrugated fins cooler walls are not detailed state here.

transformer tank leakage test

transformer tank leakage test

2.Main equipment and tools

  • 2.1 Equipment: crane, assembly table, etc.
  • 2.2 Tools: hangers, ropes, hammers, flat pads, inserting knives, scissors, etc. 

3.Transformer Body Material:

coil, insulator, wrinkle paper, straight ribbon, compact ribbon, etc. 

4.Process preparation:

  • 4.1 Check parts such as cores, coils and insulators according to drawings.
  • 4.2 Clean up assembly area and remove dust.
  • 4.3 Insulators should be placed on the assembly table to check whether the iron core foot is flat.  

5.Technological process:

5.1. Remove clamp and yoke.

  • 5.1.1 Loosen the yoke screw on both sides and remove the upper clamp and the insulation of the clamp.
  • 5.1.2 Remove yoke from outside to inside on one side, remove main stage and then from outside to inside on the other side until it is finished.

5.2. Set coil for Transformer body

  • 5.2.1 The hook is symmetrically placed under the coil pad, but the coil must be tied up by two ropes to ensure safety before lifting. Manual lifting of the suit is allowed for smaller and lighter coils.
  •  5.2.2 Insulate all parts of insulation assembly with yoke balancing pad. (The shrinkage after drying should be considered in installation. Generally, the balance pad is 2-3 mm higher than the yoke. Where the height is above this range, the thickness of the gasket should be adjusted) and the yoke insulation and oil guide pipe should be installed.
  • 5.2.3 packages of low-pressure paper cylinder (core column insulated paper cylinder) must be packed tightly. After the paper cylinder is packed, the outer diameter should be measured to ensure that the low-voltage winding can be sleeved in tighter conditions. High and low voltage windings. 
  • 5.2.4 Install yoke insulation, starting from the upper end of the high voltage winding, inserting angle rings and putting insulation end rings. Then put the winding pressure plate in place. (The pressure plate of the super-large transformer is made of non-metallic materials.
  • 5.2.5 insertion board; before insertion board, the passageway at the upper end of winding must be blocked with cloth or sheet of paper, and then covered with paper or cloth to prevent foreign bodies from falling into it. When inserting the board, the edges of the insertion should be aligned, and the edges should be clamped with a“∏”shaped clamp, which should be tightened reliably. Fix the clamp between 1-2mm.
  • 5.2.6 slightly screw the clamp bolt and pull out the “∏”clamp, install all fasteners after shaping, then clamp the yoke, and pay attention to the insulation between the clamp and the core to meet the quality standards.  
  • 5.2.7 Install winding shield, yoke shield, phase spacer, grounding wire, etc. Vacuum and blow again. Then to test ratio.

5.3 Lead wire Assembly:

  • 5.3.1 Lead wire preparation; cutting wires according to drawing size or measured size, such as cable, thin copper circle and so on, and preparing for welding, can be pre-welded before paper wrapping.  
  • 5.3.2 Wire erection, with lead wire support and fixed bracket mounted on the lifting body
  • 5.3.3 Welding of lead wire, welding between winding outlet and lead wire, or welding between winding outlet wire. When the wires are installed, arrange the winding to go out, clear the paint film, bend, cut, then weld, deburr and carbide.
  • 5.3.4 insulation bandage. At the end of welding, metal shielding paper and insulating paper should be wrapped in the welding part, and then partitions, grooves, forming insulating parts, etc. Installation of overhead wires. After wrapping, it should be smooth and smooth.
  • 5.3.5 Finishing and fastening. All the lead wires should be orderly arranged, beautiful, clamped firmly and reliably, and the cleanliness and insulation distance of the lead wires should be checked comprehensively.

5.4 Lead wire inspection and test. (Test resistance, check bandage)

5.5 Transformer Body Drying:

  • 5.5.1 preheating stage. The maximum allowable temperature of Class A insulation of oil-immersed transformer shall not exceed 115 degrees Celsius. The preheating stage shall be completed only when the uniform temperature of each part of the body reaches 105-110 degrees Celsius.
  • 5.5.2 Low vacuum stage. Two methods are used in the low vacuum stage. One is the breaking vacuum method, but dry air is needed to solve the vacuum. Secondly, the step-by-step vacuum method is adopted, that is, the vacuum degree is gradually raised in three stages, each stage lasts for two hours, but it is allowed to prolong the time in the stage of insulating a large amount of water. Otherwise, the rapid increase of the vacuum degree will affect the effluent because of the rapid evaporation of water and the decrease of the surface temperature. 
  • 5.5.3 In the high vacuum stage, the temperature should be kept at the uniform maximum allowable temperature. The vacuum degree can reach 133.2-133.32 Pa according to different capacities and voltage grades, and there is no water continuously. Generally, according to the capacity size, continuous anhydrous 4-10 hours, can be considered that drying treatment has been completed.

5.6 Transformer Body Finishing and Compression:

  • 5.6.1 After finishing and pressing the transformer body, a comprehensive inspection should be carried out. After there is no residue and other problems in the validator body and in the crevice, the sorting work can be started.
  • 5.6.2 Fasten all fasteners of upper and lower yokes.
  • 5.6.3 Finish the pad, align it up and down to meet the requirements specified in the quality standard.
  • 5.6.4 Adjust the height of each winding under the same pressure coil so that each winding can be tightened reliably.
  • 5.6.5 Compression winding, tightening lead splint, check all lead size and position. Then tighten.
  • 5.6.6 Finally, do a comprehensive cleaning work.

5.7 Transformer Body lower box and wiring.

  • 5.7.1 After finishing the body and cover, adjust the height and size of the cover to ensure that the body will not be suspended and will not withstand. Then the high and low pressure porcelain bushing is connected reliably, and other relevant wiring is connected as required.
  • 5.7.2 Sealing flange holes in lower tank, semi-vacuum or full vacuum oil injection in tank, all flange holes should be sealed. As far as possible, ensure that the oil surface height after oil injection exceeds all insulating parts, and when necessary, install a rising seat to ensure the oil surface height. Pay attention to the device body when damp can not come down the tank to inject oil.

5.8 Feeding oil to Transformer tank:

  • 5.8.1 low voltage small capacity product refueling under atmospheric pressure can be injected from the bottom of the tank, the top of the tank to deflate. After filling up, stop for a few hours, then deflate, when the oil is insufficient to fill up. The temperature of oil injection should be 50-70 degrees Celsius. Oil speed is unlimited, oil pressure tolerance requires more than 40 kilo-volts.
  • 5.8.2. 110 kilo-volt products use semi-vacuum refueling, half-vacuum 4H left of the tank. Right, and then from the bottom of the oil. Oil temperature 50-70 degrees Celsius, oil speed does not exceed 4T/H, control insulation resistance during refueling is not less than 300 mega ohm, refueling end to continue semi-vacuum degassing 8-10H oil withstand voltage over 50KV.
  • 5.8.3 110KV large transformer using full vacuum refueling, can also be re-baked room full vacuum refueling. The main process includes heating, vacuum pumping, vacuum pumping and other procedures. The vacuum residual pressure should be less than 0.5*133.2Pa and the oil pressure should be no less than 55KV. For 500KV products, the whole vacuum refueling process is basically similar to the above, but requires higher requirements, such as vacuum residual pressure less than 0.1*133.2Pa, oil pressure 60 KV and water content less than 10*10-6


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