What is the purpose of protective relays in substations?

Protective relays are critical components in substations primarily designed to detect faults in the electrical system and ensure safe operation. When a fault occurs—such as a short circuit or overload—the protective relay identifies the abnormal condition and responds by initiating protective actions, typically disconnecting the affected section of the network. This helps to prevent equipment damage, maintain system reliability, and protect personnel from hazards associated with electrical faults.

In contrast to this, the other options focus on functions that are not the primary purpose of protective relays. Monitoring energy efficiency, for instance, pertains more to management and optimization rather than immediate fault detection and isolation. Enhancing power generation and controlling voltage output are tasks associated with different devices, such as controllers or regulation equipment, rather than protective relays whose main role is safety and protection within the system.