A digital relay, also known as a microprocessor protective relay, is a computer-based device used in power systems. It uses software-based algorithms to detect electrical faults. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions. Engineering use: Relays are used on feeders, transformers, buses, motors, generators, and transmission lines to protect equipment and improve system reliability. What controls it: Relay performance depends on the protected zone, CT/PT inputs, pickup settings, time delay, breaker clearing time, trip. Selectivity is a mandatory requirement for all protection, but the importance of it depends on the application. For example, unselective protection operation during a medium voltage network fault will cause an outage for an unnecessarily large number of consumers. While this is bad, It's not a. Today, digital relays provide features such as self-testing, waveform analysis, and rapid fault response, which far surpass the capabilities of early devices. The following table illustrates the shift in relay protection, highlighting how digital relays outperform electromechanical types in speed. In utility and industrial electric power transmission and distribution systems, a numerical relay is a computer-based system with software-based protection algorithms for the detection of electrical faults.
