Which device is used to energize or de-energize the transformer?

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

Answer: (A)

Opening and closing the circuit to energize or de-energize a transformer is done with a cutout or switch. This device serves as the controllable disconnect between the transformer and the power line, allowing energization when closed and safe de-energization when opened for maintenance or fault isolation. It is designed to handle high voltage and current and can be operated manually or remotely. The other components have different roles: a lightning arrestor protects against voltage surges, insulating fluid cools and insulates the transformer, and the core is part of the magnetic circuit rather than a switching device.