The Protective Relay IED In The Automation World

William J. Ackerman, Consultant John Popiak, ABB, Inc. BACKGROUND The primary function of protective relays is simply to do that; protect power system circuits, generators, transformers, etc. With advancing capabilities of protective relays, now being referred to as Intelligent Electronic Devices (IEDs), the addition of this functionality MUST NOT compromise protection. As the IED information is required by larger parts of the utility infrastructure, lED performance (timeliness and reliability of this data) will become paramount to the optimal operation of the power system. The communications design in most IEDs has evolved as the information requirements have increased. Being on the forefront of the substation automation explosion and the capabilities Utility Communication Architecture (UCA 2.0) affords, product design and implementation must treat the automation requirements equal to that of the system protective abilities. Since most of today's products did not anticipate the information requirements, the communications are lower priority relative to the protective relay functions and had not been part of the original product architecture. Most protective relays use three basic approaches to fulfill the information requirements: localized, command interpreter, or data sharing: