What is the function of the transformer bushing?
2026-05-09
The Transformer bushing is a crucial component that allows the high-voltage lines to pass through the transformer oil tank while providing insulation and fixation.It has four main functions
1.Insulation isolation: The conductive leads extend out of the transformer oil tank through the outer casing, separating the high-voltage live conductor from the grounded oil tank casing, preventing ground breakdown and leakage.
2. Support and fixation: Secure the high-voltage and low-voltage leads firmly to the wall of the transformer box, to withstand the tension of the leads and the vibrations of the equipment.
3.Wire connection: As a channel for connecting the internal and external circuits, the winding leads are led from the interior of the oil tank to the exterior, and connected to the busbars and lines.
4. Sealing and Anti-leakage: The pipe of the meter is sealed with the flange of the oil tank to prevent the leakage of transformer oil and the intrusion of external moisture and dust into the tank, thereby protecting the oil quality and the internal insulation.
Common types of pipe and the corresponding scenarios of their usage
1.Pure porcelain bushing is also known as ceramic bushing.
Features: Overall porcelain material, simple structure, low price, average stain resistance.
Usage scenario: Low-voltage Distribution Transformer, a conventional small-capacity transformer with a voltage ratio of 10/35kv; Indoor conditions with clean environment and no severe dust pollution; Old-fashioned oil-immersed type
2.Oil-paper capacitive bushing
Features: Internal oil-paper insulation combined with capacitor voltage-sharing structure, featuring high insulation strength, low partial discharge, and resistance to high voltage.
Application scenarios: 110kv, 220kv, 500kv large-scale high-voltage power transformers; main transformers in substations, main line transformers in power grids; high-voltage scenarios requiring low partial discharge, stable operation, and long-term full-load operation.
3Dry-type composite bushing (silicone / epoxy resin composite bushing)
Features: Oil-free, maintenance-free, strong anti-flashover performance, explosion-proof, lightweight, good hydrophobicity Usage scenario
Special for dry-type transformers (most standard configuration)
High pollution, chemical plants, coastal salt fog, and large amounts of dust in mining environments
High-fire-prevention requirements in indoor places such as high-rise buildings, shopping malls, subways, and computer rooms
High outdoor anti-pollution grade requirements in medium and high voltage scenarios
4.Gas-filled bushings (SF6 gas bushings)
Features: Using SF6 gas as insulation, small in size, extremely strong insulation performance, and capable of withstanding high voltage Usage scenario
Ultra-high voltage, extra-high voltage 500kV/750kV/1000kV large main transformers
Transformers for GIS (Gas Insulated Switchgear) combined electrical equipment
Spaces limited, ultra-high voltage level substations