Transformer Overcurrent Protection (N.E.C. Review), 1998 Process Control, Electrical & Info. Conference Proceedings

Since the 1981 Edition of the National Electrical Code
(NEC
or Code) ANSI/NFPA 70], there have been more than 10,000 revisions to the Code and even more suggestions to revise the wording and intent of various Articles within the Code. With all the revisions that have occurred, it is difficult for engineers--who are inundated with administrative tasks, records keeping, and either providing design and support to, or overseeing the design and support for, multiple, concurrent projects--to keep up with them. Further, the accelerated schedules to which projects are subjected leaves the project electrical engineer having to resort to experience, to "Rules-of- thumb," and, sometimes, to intuition. All these certainly speed the design along, but can you say that you are right? Has the Code changed since you gained your experience or developed your "Rules?" Or does your intuition align with the wording and intent found in the Code? This paper will explore the requirements for Overcurrent Protection of Multi-winding Transformers found in the NEC, 1996 Edition. Additionally, this will (in a few short paragraphs) update your experience, allow you to modernize your "Rules," and educate your intuition through sound knowledge (with references!).