Answering questions that may arise related to the meaning of portions of an IEEE standard concerning specific applications.

IEEE Standards Interpretation for IEEE Std 1015™-1997 IEEE Recommended Practice for Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems

Copyright © 2004 by the Institute of Electrical and Electronics Engineers, Inc., 3 Park Avenue, New York, New York 10016-5997 USA. All Rights Reserved.

This is an interpretation of IEEE Std 1015-1997.

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3 August 2004

Interpretation Request #1
Topic: Determining the minimum instantaneous overcurrent tripping value Relevant Clause: Subclause 7A.6.5, Instantaneous Overcurrent Trip Test

In the following equation for minimum final adjustment setting, found in 7A.6.5 of IEEE 1015-1997, should the expression on the second line represent the calculations in the equation on the first line? If so, there seems to be an inconsistency in the expression. How should we interpret the necessary calculation?


MIN = _____ + ( _____ x _______) = _______A

Interpretation Response #1
The text in the second line was in fact intended to be a representation of the calculation in the prior equation. As such, it seems that both lines should read


MIN = _____ -- ( _____ x _______) = _______A

This is providing the low end tolerance for the instantaneous trip test. The equations above these are providing the high end tolerance for the instantaneous trip test. By performing the 2 calculations you now have the range at where the circuit breaker should function.

This information will be passed on to the IEEE Working Group responsible for this standard for consideration during any revision or amendment to the standard.