Transformer’s Key Component: Exploring What is LV Bushing and Its Impact

A low-voltage (LV) bushing is a critical component of a transformer that provides electrical insulation and a connection point for the low-voltage winding to external circuits. It is typically located on the transformer’s tank and serves as a termination point for the outgoing low-voltage conductors.

Functions of LV Bushing

The primary functions of an LV bushing in a transformer are:

• Electrical Insulation: The bushing provides electrical insulation between the live conductors inside the transformer and the grounded tank or external environment.
• Mechanical Support: The bushing mechanically supports the low-voltage conductors and provides a secure connection to the external circuit.
• Environmental Protection: The bushing protects the low-voltage winding from moisture, dust, and other environmental factors.

Construction of LV Bushing

LV bushings are typically constructed using the following components:

• Porcelain Body: The porcelain body is the main insulating component of the bushing. It is made of high-quality porcelain with excellent electrical and mechanical properties.
• Conductor: The conductor is a copper or aluminum bar that carries the current from the low-voltage winding to the external circuit.
• Capacitance Graded Insulation: Capacitance grading is used to reduce the electric field stress within the bushing. This is achieved by using a series of insulation layers with different dielectric constants.
• Metal Flange: The metal flange is attached to the porcelain body and provides a connection point for the external conductors.
• Sealing Gaskets: Sealing gaskets are used to ensure a watertight seal between the porcelain body and the metal flange.

Types of LV Bushing

LV bushings are classified into two main types based on their construction:

• Solid Core Bushing: In a solid core bushing, the conductor is embedded in a solid porcelain body.
• Hollow Core Bushing: In a hollow core bushing, the conductor is located inside a hollow porcelain body.

Selection of LV Bushing

The selection of an LV bushing for a transformer is based on the following factors:

• Voltage Rating: The voltage rating of the bushing must match the voltage of the low-voltage winding.
• Current Rating: The current rating of the bushing must be sufficient to carry the load current without overheating.
• Mechanical Strength: The bushing must be able to withstand the mechanical forces acting on it during operation.
• Environmental Conditions: The bushing must be suitable for the environmental conditions where the transformer will be installed.

Installation of LV Bushing

The installation of an LV bushing in a transformer requires careful attention to the following steps:

• Preparation: The bushing should be inspected for any damage before installation. The mounting surface on the transformer tank should be cleaned and prepared.
• Mounting: The bushing is mounted on the transformer tank using bolts or studs. The bolts or studs should be tightened to the specified torque.
• Connection: The conductors from the low-voltage winding are connected to the bushing terminals. The connections should be made using the appropriate connectors and tools.
• Sealing: The sealing gaskets should be properly installed to ensure a watertight seal.

Maintenance of LV Bushing

Regular maintenance of LV bushings is essential to ensure their proper operation and extend their lifespan. Maintenance activities include:

• Visual Inspection: The bushing should be visually inspected for any signs of damage, such as cracks, chips, or discoloration.
• Electrical Testing: Electrical tests, such as insulation resistance and capacitance measurements, should be performed to ensure the bushing’s electrical integrity.
• Cleaning: The bushing should be cleaned to remove any dirt, dust, or moisture that could compromise its insulation.

Troubleshooting LV Bushing Problems

Common problems associated with LV bushings include:

• Electrical Breakdown: This can be caused by excessive voltage stress, moisture ingress, or insulation damage.
• Mechanical Failure: This can be caused by improper installation, excessive mechanical forces, or thermal expansion.
• Leakage: This can be caused by damaged sealing gaskets or cracks in the porcelain body.

Basics You Wanted To Know

Q: What is the primary function of an LV bushing in a transformer?
A: An LV bushing provides electrical insulation and a connection point for the low-voltage winding to external circuits.

Q: What are the different types of LV bushings?
A: LV bushings are classified into solid core and hollow core bushings based on their construction.

Q: How is an LV bushing installed in a transformer?
A: The bushing is mounted on the transformer tank, the conductors are connected to the bushing terminals, and the sealing gaskets are installed.

Q: What are the common problems associated with LV bushings?
A: Common problems include electrical breakdown, mechanical failure, and leakage.

Q: How can LV bushing problems be prevented?
A: Regular maintenance, including visual inspections, electrical testing, and cleaning, can help prevent problems.