Automated coordination programs do not make correct results automatic

Abstract

The availability of computer programs which aide in protective device coordination studies has led to the assignment of coordination problems to those who are computer literate rather than protection literate. For those put in this unfortunate situation, some of the finer points of time current coordination are presented which are often not learned until after the news of that first false trip. This paper is intended as an addendum to, rather than a replacement for a typical time current coordination seminar. It covers: delta-wye transformers, instantaneous relays, protective device tap ranges, transformer damage curves, and combination starters.