Digital protective relays represent a significant leap forward in power system protection, moving from older electromechanical and static designs to a computer-based system. These modern relays use a microprocessor to analyze and interpret electrical data, such as voltage and current, to detect faults in a power system. They are often called microprocessor-based relays and are a key component of a modern relay protection system.

The core of a digital relay is its ability to process complex data. It takes in analog signals from instrument transformers, converts them into a digital format, and then uses software-based algorithms to analyze the data. This allows them to perform a variety of protection functions that would have required multiple separate devices in the past. Beyond fault detection, they can also provide metering, communication, and self-test functions, making them a versatile tool for grid operators. Digital relays can be programmed with user-configurable logic, allowing them to adapt to changing grid conditions and provide more precise protection. The ability to record event data, including oscillographic records, is also a major advantage, as it helps engineers analyze the root cause of a fault and improve system reliability.