Intelligent electronic device
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An Intelligent Electronic Device (IED) is a term used in the electric power industry to describe microprocessor-based controllers of power system equipment, such as circuit breakers, transformers, and capacitor banks.
[edit] Description
IEDs receive data from sensors and power equipment, and can issue control commands, such as tripping circuit breakers if they sense voltage, current, or frequency anomalies, or raise/lower voltage levels in order to maintain the desired level. Common types of IEDs include protective relaying devices, load tap changer controllers, circuit breaker controllers, capacitor bank switches, recloser controllers, voltage regulators, etc.
Protection relays being manufactured these days are primarily IEDs. This is due to the fact, that with the available microprocessor technology a single unit can perform several protective, control etc. functions. Whereas before the microprocessor technology a single unit would contain only one protection function, if several protection functions were required one would have to combine a number of different units of protection relay.
A typical IED can contain around 5-12 protection functions, 5-8 control functions controlling separate devices, an autoreclose function, self monitoring function, communication functions etc. Hence, they are aptly named as Intelligent Electronic Devices
