History
The digital/numeric relay was introduced in the early 1980s, with AREVA, ABB Group's forerunners and SEL making some of the early market advances in the arena, but the arena has become crowded today with many manufacturers. In transmission line and generator protection, by the mid-1990s the digital relay had nearly replaced the solid state and electromechanical relay in new construction. In distribution applications, the replacement by the digital relay proceeded a bit more slowly. While the great majority of feeder relays in new applications today are digital, the solid state relay still sees some use where simplicity of the application allows for simpler relays, which allows one to avoid the complexity of digital relays.
Read more about this topic: Digital Protective Relay
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