Which transformer type is described as having internal protection by a current limiting fuse and a circuit breaker that energizes the secondary side?

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

Answer: (A)

This question is about how some transformers are protected internally. A design that includes a current-limiting fuse and a circuit breaker on the secondary side uses built‑in protection to quickly limit fault energy and to energize the secondary in a controlled way. The current-limiting fuse clamps down fault currents, protecting both the transformer and the connected equipment by interrupting high-energy faults fast. The secondary-side circuit breaker allows safe energization and isolation of the secondary circuit, giving protection coordination and selective disconnect capability.

This combination describes a CSP-type transformer—one that is self-protected with internal devices. Other types rely more on external protection or differ in their fundamental configuration (for example, auto transformers have a different winding arrangement with no isolation, and pad-mounted refers to form factor rather than a specific protection scheme).