What is the function of a protective relay in a circuit?

A protective relay plays a critical role in ensuring the safety and stability of electrical systems by monitoring the operating conditions of a circuit and providing isolation during faults. When a fault, such as an overload or short circuit, occurs, the protective relay identifies the abnormal condition and triggers protective devices, like circuit breakers, to disconnect the affected section from the electrical supply. This action helps to prevent equipment damage, reduces the risk of fire, and protects personnel by minimizing the potential for electrical shock hazards.

In contrast, the other options relate to functions that protective relays do not specifically address. While monitoring current flow is a feature of some protective relays (specifically those designed to measure and assess electrical parameters), the primary function regarding circuit integrity during faults is to isolate and protect rather than just monitor. Similarly, enhancing energy efficiency and increasing voltage levels pertain to different aspects of electrical design and circuit management that are not the focus of a protective relay's functionality.