Which type of transformer is described as having an internal fuse?

• A. CSP transformers
• B. Conventional transformers
• C. Oil-filled transformers
• D. Dry-type transformers

Answer: (A)

Internal protection inside a transformer is a feature that provides immediate isolation of fault current by a fuse placed inside the unit. When a fault or overload occurs, the internal fuse blows and disconnects the transformer from the circuit, helping to prevent further damage to windings and reducing the risk of fire.

CSP transformers are designed with this internal fuse as part of their protection scheme, so they have built-in fast fault- interruption. Other types—oil-filled, dry-type, and conventional transformers—usually rely on protective devices located in external switchgear or protection systems rather than an integrated fuse inside the transformer itself.