Components of a Padmount Transformer - Part 1 Primary compartment

February 9, 2024

This article will go over the components found inside a Padmount Transformer compartment. Part 1 will go over the components on the Primary section of the Padmount Transformer compartment and Part 2 will go over the components that make up the Secondary section.

Components of a Padmount Transformer Compartments Diagram
Components of a Padmount Transformer Compartments Diagram

Bay-O-Net Fusing: is a protective system in pad-mounted transformers, designed to prevent damage by cutting off excessive electrical current. It includes a main fuse that can be replaced when necessary and a backup fuse (Current Limiting Fuse) for additional safety. This dual-layer protection ensures the transformer operates safely, even under high current situations.

Oil Injection Port: allows for easy oil top-up or replacement, ensuring optimal insulation and cooling. It’s accessible for quick maintenance, supporting the transformer’s efficient and safe operation.

Drip Shield: The drip shield prevents any oil that would come out of the Bay-O-Net fusing from dripping onto the High-Voltage terminals. It is angled in such away to stop oil from pooling and directs any flow away from the High-Voltage terminals.

Tap Switch: is a device used to adjust the transformer’s voltage output to match the required level for the distribution system. It is operated off-circuit and is designed to be used when the transformer is not energized. The switch allows for selecting different voltage settings, ensuring the transformer can adapt to varying electrical loads and maintain stable voltage supply. The voltage settings are typically in increments of 2.5% and voltage settings also know as tap settings’ can go above and below the nominal voltage.

High-Voltage Bushing Wells: High-voltage bushing wells in pad-mounted transformers provide secure connections to the electrical distribution system, supporting dead-front operations with separable insulated connectors. They handle specified continuous and short-circuit currents and come with protective caps for safety. Configurations include three wells for radial feed and six for loop-feed units.

Parking Stand: Parking stands in pad-mounted transformers safely hold electrical connections, like load break elbows, when not in use. They prevent accidental contact with live parts and support both radial and loop feed setups, enhancing safety and maintenance efficiency.

Ground Bus: Also known as the grounding assembly, the ground bus in a pad-mounted transformer serves the critical purpose of providing a path for fault currents to safely dissipate into the ground, thereby preventing electrical hazards and minimizing damage to the transformer and surrounding equipment. It helps to ensure system reliability and personnel safety by effectively grounding the transformer enclosure and associated components.

Ground Bus Connection: This connection is typically a wire conductor that connects the ground bus of the primary compartment to the ground bus of the secondary compartment. Some pad-mounted transformers utilize a continuous ground bus between the primary and secondary compartments.

There are other non-standard components of a pad-mounted transformer that are used depending on the requirements of the end-user and the application. We will discuss these in a future article.

Check in for Part 2 where we will go over the components found in the secondary compartment.