2013. — 10 c.
Localized protection and control functions within modern microprocessor-based relays directly measure the required data representing the present state of the power system, without the aid of communications assistance. This is achieved by performing analog-to-digital conversion on low-level analog signals directly wired into relay input contacts from field contacts and instrument transformers physically monitoring power system apparatus. Communications-assisted localized protection and control functions collect data from a second intelligent electronic device (IED) that measures values associated with other field contacts and instrument transformers. IEDs specialized for power system applications and now migrating to other mission-critical applications are referred to as protection, control, and monitoring (PCM) IEDs because they are designed to do all three functions simultaneously. The values of these field signals from the second IED, as well as other calculated quantities, are acquired as contents of digital messages via various communications mediums. The contents of the digital messages are combined with the local measurements in the relay to provide a larger pool of values to use within protection and automation logic. Presently, the process to move data from a data provider IED to a data consumer IED includes data change detection; message creation, publication, transfer, reception, and verification; and parsing and mapping of message contents into virtual data locations in the relay.
