Protection Relay

• A. A distribution transformer
• B. Equipment in cubicles designed to detect faults and initiate circuit interruption.
• C. Metering Cubicles
• D. Voltage Range for Distribution Transformers

Answer: (D)

Protection relays are the devices that monitor electrical conditions and trip circuits to prevent damage when something abnormal occurs. In a distribution system, a key protective function is keeping the transformer operating within a safe voltage range. If voltage deviates outside that range, insulation stress, overheating, or other faults can develop, so the relay acts to open the circuit and isolate the transformer. This focus on safeguarding the transformer by enforcing its voltage limits is why selecting the voltage range for distribution transformers best fits the concept being tested. The other descriptions describe the transformer itself, the cubicles where different equipment may be housed, or general fault-detection purposes, but they don’t capture the protective boundary that a protection relay is specifically ensuring.