Digital relays can emulate functions of many electromechanical relays in one device. This allows for more simplified protection and maintenance.
These devices are designed to trip a circuit breaker, within a thousandths of a second, when a fault is detected.
Relays are load breaking units with a limited short-circuit making and breaking capacity for applications with high switching rates up to 3 million operating cycles.
The earlier designs were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over current, reverse power flow, over-frequency and under-frequency.
Microprocessor based digital protection relays can replace the functions of electromechanical instruments. These relays convert voltage and currents to digital form and process with results measuring the usage of microprocessor. Digital relays can emulate functions of many electromechanical relays in one device. This allows for more simplified protection and maintenance.