In circuit breakers, what is the purpose of an overcurrent relay?

The primary function of an overcurrent relay in circuit breakers is to detect excessive current flowing through the circuit. This occurs when the electrical current exceeds a preset limit, which can lead to overheating and potential damage to electrical devices and wiring. By identifying these excessive current levels early, the overcurrent relay activates the circuit breaker to interrupt the flow of electricity, thereby protecting the system from faults such as overloads and short circuits. This crucial role in monitoring current levels helps maintain the safe operation of the electrical system.

In contrast, the other options describe functions that are not specifically managed by an overcurrent relay. Preventing short circuits is a broader goal that encompasses various protective devices. Controlling voltage levels is the role of voltage regulators or transformers, while monitoring power distribution is typically done by devices like power meters or monitoring systems, rather than an overcurrent relay.