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

IEEE Standards Interpretation for IEEE Std 1048™-1990 IEEE Guide for Protective Grounding of Power Lines

Copyright © 2005 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 1048-1990.

Interpretations are issued to explain and clarify the intent of a standard and do not constitute an alteration to the original standard. In addition, interpretations are not intended to supply consulting information. Permission is hereby granted to download and print one copy of this document. Individuals seeking permission to reproduce and/or distribute this document in its entirety or portions of this document must contact the IEEE Standards Department for the appropriate license. Use of the information contained in this document is at your own risk.

IEEE Standards Department, Copyrights and Permissions, 445 Hoes Lane, Piscataway, New Jersey 08855-1331, USA

January 2005

Interpretation Request #1
Relevant Figure: Figure 8 - Fusing Current vs. Time for Copper Conductors Topic: Clarification

On X-axis it just states Current in Amperes; however, it is a log scale, hence, how would one know whether x10, x100, x1000 and/or x10000?

Interpretation Response #1
The plot shown in Figure 8 in Std 1048-1990 is a portion of the Fusing current time for copper conductors curves. These are based on the Onderdonk formula found in the Standard Handbook of Electrical Engineering.

The curves in the Handbook are: Y Axis 0.1 X Axis 1

The portion of this curve as found in IEEE Std 1048-1990 is the later portion for large conductors.

IEEE Std 1048-1990 Figure 8 curves are: Y Axis 0.1 X Axis 10,000

Interpretation Request #2
Numbers on both X and Y axis are not very legible, especially at the beginning (where X and Y meet). Is it (3,1), (0, 0.1)?

Interpretation Response #2
See Interpretation #1.