Which transformer type is described as being internally protected by a current limiting fuse and a circuit breaker on the secondary side?

• A. CSP
• B. Conventional
• C. Auto
• D. Pad-mounted

Answer: (A)

The concept being tested is how protective devices are arranged in a transformer design, specifically where protection on the low-voltage (secondary) side is integrated. When a transformer has a current-limiting fuse and a circuit breaker located on the secondary side inside the unit, it’s designed to limit fault current and quickly disconnect the load-side circuit right at the transformer. This built-in secondary protection is a hallmark of the CSP type, which emphasizes integrated protection in a compact, enclosed package.

This arrangement helps improve safety and reliability by containing faults close to the source, reducing arc flash risk, and minimizing damage to downstream equipment. Other transformer types typically rely on external protection devices or different protection schemes, so they don’t feature this exact combination of internal secondary-side current-limiting fuse and circuit breaker.