What is the protective fused device for a conventional transformer called?

• A. Cutout or Switch
• B. Fuse
• C. Lightning Arrestor
• D. Core

Answer: (A)

The key idea is identifying the protective device that both guards the transformer from faults and provides a means to disconnect it from the line. On a conventional transformer, that role is fulfilled by a cutout assembly, also known as a fuse cutout or drop-out fuse. It mounts at the transformer terminal, contains a fuse link, and will open the circuit if a fault or overload occurs. Because it combines protection (the fuse) with a switching/disconnect function, it’s described as a cutout or switch.

The other concepts don’t fit as the primary protective device for the transformer: a fuse by itself is just a protective element but isn’t typically the mounted transformer protection and isolation device; a lightning arrestor protects against voltage surges; and the core is a structural part of the transformer, not a protective disconnect.