1、IEEE Standards Interpretations for IEEE Std C37.20.7 -2007 IEEE Guide for Testing Metal-Enclosed Switchgear Rated Up to 38 kV for Internal Arcing Faults Copyright 2009 by the Institute of Electrical and Electronics Engineers, Inc. Three Park Avenue New York, New York 10016-5997 USA All Rights Reserv
2、ed. This is an interpretation of IEEE Std C37.20.7-2007. Interpretations are issued to explain and clarify the intent of a standard and are not intended to constitute an alteration to the original standard or to supply consulting information. Permission is hereby granted to download and print one co
3、py 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
4、Department Copyrights and Permissions 445 Hoes Lane, P. O. Box 1331 Piscataway, New Jersey 08855-1331, USA November 2009 Interpretation Request #1 Topic: Ignition Clause, Subclause, Annex, Figure, or Table: Clause 6.1, Criterion 4 An interpretation of 6.1, Criterion 4 of IEEE Std C37.20.7-2007 is re
5、quested. Under what conditions does ignition of indicators due to glowing particles constitute a FAILURE and when is it a PASS? Criterion 4 states that: “Indicators ignited as a result of the burning of paint or labels, glowing particles, and so on, are excluded“ i.e. it is a PASS when indicators ig
6、nite as a result of glowing particles. Criterion 4 continues with: “Holes in horizontally mounted indicators caused by particles that do not ignite the indicator are ignored.“ This implies that if indicators are ignited by glowing particles it is a Page 1 of 3IEEE Std C37.20.7-200712/4/2009http:/sta
7、ndards.ieee.org/reading/ieee/interp/C37.20.7-2007.htmlFAILURE and contradicts the earlier statement in Criterion 4. An interpretation of term “ignition“ is requested. It is assumed that the definition of “ignition“ in this context requires the presence of a flame which consumes cloth beyond that aff
8、ected by the passing particle. Interpretation Response #1 The following is the C37.20.7 Working Group response to this request for interpretation. The request was reviewed and it was concluded that the Guide is correct as written. A line-by-line explanation is as follows: Q: Under what conditions do
9、es ignition of indicators due to glowing particles constitute a FAILURE and when is it a PASS? Criterion 4 states that: “Indicators ignited as a result of the burning of paint or labels, glowing particles, and so on, are excluded“ i.e. it is a PASS when indicators ignite as a result of glowing parti
10、cles. A: The intent of the indicator is to monitor for burning gases. Glowing particles are specifically excluded provided it can be positively shown that the ignition was caused by a glowing particle and not by escaping gases. Q: Criterion 4 continues with: “Holes in horizontally mounted indicators
11、 caused by particles that do not ignite the indicator are ignored.“ This implies that if indicators are ignited by glowing particles it is a FAILURE and contradicts the earlier statement in Criterion 4. A: The working group disagrees with the above interpretation of this sentence. Stating that holes
12、 in the horizontally mounted indicators caused by falling particles are ignored does not imply that ignition by glowing particles is a failure. It clearly states that both conditions, ignition by a glowing particle and small holes created by non-glowing particles, do not constitute a failure in the
13、horizontal indicators only. For vertical indicators, glowing particle ignition is ignored, but holes in the indicators are cause for failure as they indicate part ejection in the assessment area as defined by Criterion 2. Q: Please also confirm the following interpretation of the term “ignition.“ It
14、 is assumed that the definition of “ignition“ in this context requires the presence of a flame which consumes cloth beyond that affected by the passing particle. A: The working group agrees with this interpretation of the term “ignition.” Page 2 of 3IEEE Std C37.20.7-200712/4/2009http:/standards.iee
15、e.org/reading/ieee/interp/C37.20.7-2007.htmlBack to Available IEEE Standards Interpretations Online Copyright IEEE-SA Contact IEEE-SA For questions or comments, please contact the IEEE-SA Webmaster. Page 3 of 3IEEE Std C37.20.7-200712/4/2009http:/standards.ieee.org/reading/ieee/interp/C37.20.7-2007.html
