ML20036B497
| ML20036B497 | |
| Person / Time | |
|---|---|
| Issue date: | 08/12/1992 |
| From: | Rosa F Office of Nuclear Reactor Regulation |
| To: | Treece B AFFILIATION NOT ASSIGNED |
| References | |
| NUDOCS 9305240275 | |
| Download: ML20036B497 (1) | |
Text
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August 12. 1992 Mr. B. G. Treece, Chairman DC Auxiliary Power Task Force 807 South We-Go Trail Mount Prospect, Illinois 60056
Subject:
Ground Detection in Ungrounded DC Systems
Dear Mr. Treece:
Recently I had an opportunity to review the IEEE document P946/D5.
I have the following comments for Appendix C of this document.
Appendix C covers calculation of the ground fault detector setting based on t
I the minimum permissible value of ground fault resistance that will eliminate spurious pickup or dropout of any device in a dc system when multiple ground l
faults occur in the dc system. However, the methodology presented in Appendix 4
l C has not covered the effects of the resistance introduced by the on-line
)
ground fault detector.
l In addition, this Appendix has not covered the aspect of a permissible upper bound of the ground fault resistance. An upper bound value should be i
established which is below the maximum leakage resistance of the de system.
Then to eliminate spurious ground alarms, the setting of the ground fault detector alarm should be well within these upper and lower bounds.
Your task force may even be able to recommend a few standard ranges to which the ground fault detectors should be set based on cable leakage resistance data from a few power plants and in consultation with the manufacturers of the ground fault detectors.
If you need additional information, please contact S. Mazumdar (301-504-2783) of my staff.
Sincerely,
- 0riainal ALsmed pg6 Faust Rosea.-
Faust Rosa,',' Chief Electrical Systems Branch Division of Systems Technology Distribution:
A. Thadani F. Rosa D. Thatcher J. Knox S. Mazumdar SELB Rdg. File
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