Understanding Submersible Transformers: Key Features and Considerations

Submersible transformers play a crucial role in modern electrical systems, particularly in areas where traditional overhead installations are not feasible. With a secondary voltage of 480Y/277-V, these transformers come in a range of sizes from 75 to 2500 kVA, making them versatile for various applications. Their design allows them to function efficiently underwater, which is essential in specific industrial and utility settings.

These transformers incorporate various protection options to ensure safety and longevity. For example, dry-well current-limiting fuses with interlocked switches prevent the fuses from being removed while energized, providing an added layer of security. Submersible bayonet fuses are another safety feature, often found in concrete boxes with removable covers, allowing for maintenance and access without compromising safety.

Material selection for these transformers is vital for performance and durability. Smaller units can be made from 400-series stainless steel, which is cost-effective, while larger units typically utilize mild carbon steel due to material availability issues. Although 300-series stainless steel offers superior performance, its higher cost often restricts its use in larger models. Understanding these material properties can help engineers and utilities make informed decisions based on budget and environmental conditions.

Temperature ratings are another key aspect of submersible transformers. They are designed to handle an average winding temperature rise of 55°C and a maximum of 70°C, using insulation systems similar to those in overhead and pad-mounted transformers. This design allows them to operate reliably in varied ambient temperatures, although utilities may impose stricter loading limits compared to other transformer types.

Maintenance of submersible transformers is essential for their continued operation. Keeping enclosures and air vents free from debris can prevent issues like anaerobic corrosion, which can compromise the transformer’s integrity. Additionally, emerging regulations around water pumping from these enclosures necessitate careful management of any collected water, especially in urban environments where runoff can introduce contaminants.

Finally, innovations like solid insulation transformers are becoming increasingly relevant. These are specifically designed for subsurface applications and help mitigate common problems associated with underground installations. With encapsulated designs that resist corrosion and contamination, solid insulation transformers offer a reliable alternative for environments where traditional transformers may struggle.