Corrosion problems and the high cost of installation have minimized the use of __________ transformers.

• A. Vault-type
• B. Pad-mount
• C. Submersible
• D. Pole-mount

Answer: (C)

When choosing how to install a transformer, environment and maintenance costs are major factors. Submersible transformers are designed to go into underground, moisture-prone spaces, sometimes even submerged in oil or water. That constant exposure to moisture accelerates corrosion of metal parts and seals, and it requires highly specialized, tightly sealed construction and connection methods. All of that adds up to higher initial costs and ongoing maintenance expenses.

Because of these durability and cost concerns, utilities limit their use and favor options that are easier and cheaper to install and protect from moisture, such as pad-mount transformers on a concrete pad or pole-mounted units mounted above ground. Submersible designs simply aren’t as economical or practical in many situations, so their use has diminished relative to other configurations.