Production of Transformer Bushings

Production process of transformer bushing

  Transformer bushing is an important component of a transformer, used to connect the internal windings of the transformer with the external circuit, while also serving as insulation and support. The production process usually includes the following key steps:

• Raw material preparation

1. Conductive materials

  Core conductive components are generally made of copper, aluminum, or silver copper alloys, which require high conductivity, mechanical strength, and corrosion resistance.

2. Insulation materials

(1) Main insulation material:

  Porcelain: Used for outdoor casing, resistant to aging and has high mechanical strength (such as voltage levels of 110kV and above).

  Epoxy resin composite insulation: composed of epoxy resin, glass fiber, etc., commonly used in medium and high voltage bushings, with excellent insulation performance and small volume (such as voltage levels of 35kV and below).

  Oil immersed paper insulation: The core insulation layer of traditional oil paper sleeves needs to be used in conjunction with transformer oil.

(2) Auxiliary insulation materials: mica tape, silicone rubber (used for umbrella skirt anti fouling flash), etc.

3. Structural materials

  Metal flanges (stainless steel or cast iron), seals (rubber or polytetrafluoroethylene), pressure equalization rings (aluminum alloy or copper alloy), etc.

• Core manufacturing process

1. Core production

  Conductive rod treatment: Cut and polish the conductive rod, weld the wiring terminals (ensuring that the welding points are free of virtual welding and have good conductivity).

2. Insulation layer winding:

3. Oil paper sleeve: Wrap insulation paper layer by layer on the conductive rod, apply insulation oil and vacuum dry to form an "oil paper insulation layer".

4. Epoxy sleeve: It is made of glass fiber cloth soaked in epoxy resin, wound and formed on the conductive rod, and then cured at high temperature to form a complete insulation layer.

5. Shell manufacturing

Ceramic sleeve production:

  Raw material mixing (porcelain clay, quartz, feldspar) → molding (extrusion or compression molding) → high temperature sintering (above 1200 ℃) → secondary glazing sintering → inspection (without cracks or bubbles).

Composite casing shell: Through mold injection molding or winding process, silicone rubber or epoxy resin is compounded with glass fiber to form a shell with umbrella skirt.

• Testing and experimentation

1. Appearance and dimensional inspection

Check whether there are defects in the porcelain sleeve/composite shell, and measure whether the umbrella skirt spacing, flange aperture, etc. meet the design requirements.

2. Electrical performance testing

3. Insulation resistance measurement: Use a megohmmeter to test the insulation performance of the sleeve.

4. Dielectric loss factor (tan δ) test: Evaluate the degree of aging of insulation materials.

5. Power frequency withstand voltage test: Apply a power frequency voltage higher than the rated voltage to check for breakdown.

6. Lightning impulse test: Simulate lightning overvoltage to verify the ability of the casing to withstand transient high voltage.

7. Mechanical performance testing

8. Bending test (simulating short-circuit electrodynamic force) and compression test (flange load-bearing capacity).

9. Environmental testing

10. Temperature rise test (current carrying and heating situation of conductive rod), aging resistance test (UV, humid and hot environment simulation).

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