The International Electrotechnical Commission (IEC) is currently working on a new series of standards that covers the functional requirements of measuring relays and related equipment used to protect electrical transmission and distribution systems. Selectivity is a mandatory requirement for all protection, but the importance of it depends on the application. For example, unselective protection operation during a medium voltage network fault will cause an outage for an unnecessarily large number of consumers. While this is bad, It's not a. Protective relays and devices have been developed over 100 years ago to provide “last line” of defense for the electrical systems. The selection and applications of. Alex Apostolov, John R. Boyle, Patrick Carroll, David Hart, Gerald Johnson, Gary Kobet, Mukesh Nagpal, Krish Narendra, Dan Nordell, Russell W. Patterson, Tarlocman Sidhu, Eric Udren, Miguel A.
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