What Is a Transformer Bushing?
A transformer bushing is a component that provides electricity while supporting electric wires using transformer insulation.
Electric wires need to be supported because they are affected by gravity, but if they are supported by metal parts, they will cause ground faults and short circuits. Therefore, they must be robustly supported by insulators, resin, or other insulating materials. Transformer bushings play a crucial role in supporting and insulating the wires, as well as transmitting electrical energy.
It has high insulation performance and can insulate both the high-voltage side and the low-voltage side in a transformer. Generally, bushings with larger isolation distances are used on the high-voltage side.
With proper maintenance and inspection, transformer bushings are long-lasting and highly reliable components. They contribute to the stability and supply reliability of the power infrastructure.
Applications of Transformer Bushings
Transformer bushings are used in transformers and peripheral equipment. Peripheral equipment includes bus ducts and anti-collision plates. Applications include power distribution plants and substations.
1. Electric power distribution plants
Power distribution plants are facilities that branch power lines and distribute power. They often have transformers, which convert high-voltage lines to low-voltage lines for easier handling. Transformer bushings are used at the junction points of high-voltage transmission lines and low-voltage distribution lines to provide isolation in the transmission and distribution of power.
2. Receiving substations
Transformer substations are facilities that receive high-voltage power from transmission lines, convert it to low-voltage power, and supply it to general consumers. Transformer bushings ensure the insulation performance of transformers and prevent ground faults and short circuits in transformers. This improves the safety and reliability of the receiving substation.
Principles of Transformer Bushing
Transformer bushings are components that efficiently and safely transmit electric power while insulating electric wires. Its structure is based on a combination of insulators and conductors.
The most important function of a transformer bushing is to completely insulate the charging section. This prevents electrical ground faults and short circuits. Insulation is provided by insulating materials, which typically include ceramic, glass, and polymers (plastics). Transformer bushings have conductors inside to transmit electrical energy from the high-voltage side to the low-voltage side.
These conductors are made of highly conductive materials such as copper or aluminum to ensure reliable current transmission. Transformer bushings are attached to the transformer itself or to equipment at the receiving substation to establish a power transmission path. The high voltage side is often connected to transmission lines or transformers, while the low voltage side is connected to the power distribution system.
How to Select a Transformer Bushing
When selecting a transformer bushing, several important factors should be considered. The following are transformer bushing selection factors:
1. Operating Voltage
The voltage level of the transformer bushing should be selected to match the voltage level of the wires to which it will be connected. It is important to comply with the voltage range designed for safe operation within the specification voltage range. Bushings for high voltage and special high voltage are sold, with special high voltage bushings available for 66kV, 154kV, 275lV, and other types.
2. Insulator Material
The insulating material of the bushing is important to insulate the charging section. Common insulating materials include ceramic and polymer (plastic). Ceramic insulators are robust and less susceptible to contamination, while polymer insulators are easier to mass produce and process.
3. Allowable Current
The allowable current of a bushing indicates its performance with respect to current loading. It is necessary to select a bushing that matches the design current of the transformer and has the allowable current capacity to handle the load.
4. Dimensions
The dimensions of the bushing must match the design of the transformer and peripheral equipment. It is important to select bushing dimensions for the high voltage side and the low voltage side and plan to fit into the installation space.
5. Contamination Resistance
When used outdoors, the bushing’s resistance to contaminants is important. Especially in salt-affected areas, it is necessary to minimize the adhesion of contaminants by surface treatment of the bushing. Transformer bushings for protection against salt damage are also available.