Which of the following protection curves is represented as CO-6 according to IEEE standards?
Correct Answer: Definite minimum
Help: Inverse Time Overcurrent Relays and Curves Explained
As far as I know, IEEE C37.112 is the only IEEE standard that defines protection curves. I checked the 2018 and 1996 book years and neither one represents anything according to the ABB type CO relay numbers. Also, definite minimum is not one of the IEEE curves. The only curves in C37.112 are Moderately Inverse, Very Inverse, and Extremely Inverse. All of these curves include a definite minimum time component, which in electromechanical relays is the part of the trip curve where the induction element would be saturated.
