IEEE-1125-1993-R2005.pdf

The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright © 1994 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 1994. Printed in the United States of America. IEEE is a registered trademark in the U.S. Patent & Trademark Office, owned by the Institute of Electrical and Electronics Engineers, Incorporated. Print: ISBN 1-55937-432-2 No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. IEEE Std 1125-1993 (R2005) IEEE Guide for Moisture Measurement and Control in SF6 Gas-Insulated Sponsor Insulated Conductors Committee of the IEEE Power Engineering Society Reaffirmed February 2, 2005 Approved December 2, 1993 IEEE-SA Standards Board Abstract: Guidelines for moisture level measurement, moisture data interpretation, and moisture control in gas-insulated transmission class equipment (GIE) are provided. Keywords: circuit breakers, gas-insulated equipment (GIE), gas-insulated substations (GIS), mois- ture measurement, SF 6 Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=IHS Employees/1111111001, User=O'Connor, Maurice Not for Resale, 04/28/2007 23:21:10 MDTNo reproduction or networking permitted without license from IHS -,-,- IEEE Standards documents are developed within the Technical Committees of the IEEE Societies and the Standards Coordinating Committees of the IEEE Standards Board. 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Provided by IHS under license with IEEELicensee=IHS Employees/1111111001, User=O'Connor, Maurice Not for Resale, 04/28/2007 23:21:10 MDTNo reproduction or networking permitted without license from IHS -,-,- iii Introduction (This introduction is not part of IEEE Std 1125-1993, IEEE Guide for Moisture Measurement and Control in SF 6 Gas- Insulated Equipment.) The objectives of this guide are to introduce the importance of moisture in the design, manufacture, installa- tion, operation, and maintenance of transmission class gas-insulated equipment and to provide guidance for measurements of moisture in gas-insulated equipment. This guide was prepared by working group 5-12 of the Insulations Subcommittee of the Insulated Conduc- tors Committee, consisting of the following members: S. J. Dale, Chair F. Y. Chu, Chair, Moisture Task Force P. BolinJ. DoddsR. Jackson R. Matulic The following persons were on the balloting committee: T. J. Al-Hussaini P. Alex R. W. Allen, Jr. W. O. Andersen, Jr. R. H. Arndt T. P. Arnold T. A. Balaska Anthony Barlow C. W. Blades Vincent J. Boliver R. R. Borowski Ken. E. Bow John E. Bramfi tt M. D. Buckweitz R. R. Burghardt John I. Carlson Paul L. Cinquemani Wayne E. Cole E. J. DAquanno S. J. Dale J. M. Daly James C. Dedman Joseph A. Di Costanzo C. Doench J. P. DuPont G. S. Eager, Jr. R. M. Eichhorn Hussein El Badaly J. S. Engelhardt S. L. Fitzhugh A. Fitzpatrick E. O. Forster R. W. Foster Ronald F. Frank R. D. Fulcomer J. B. Gardner P. Gazzana-Priaroggia R. B. Gear S. M. Gilbert A. Godoshian Stan V. Harper R. Hartlein H. C. Hervig, Jr. S. V. Heyer R. W. Higginbottom Lauri J. Hiivala C. V. Johnson J. Jurcisin F. E. Kimsey Joel Kitchens H. T. Knox Frederick B. Koch Donald E. Koonce M. Kopchik, Jr. S. Kozak F. E. La Fetra F. E. La Gase Carl Landinger J. S. Lasky Jack H. Lawson Raoul H. Leuteritz T. H. Ling John V. Lipe G. Ludasi R. Luther G. J. Luzzi Jeffrey P. Mackevich M. A. Martin, Jr. I. J. Marwick S. G. Mastoras F. M. McAvoy A. R. McCulloch E. J. McGowan A. L. McKean W. J. McNulty J. D. Medek John E. Merando, Jr. David J. Mintz J. A. Moran, Jr. D. J. Nichols J. J. Pachot Cutter D. Palmer Keith A. Petty Jan S. Pirrong Gary A. Polhill J. B. Prime, Jr. Paul F. Pugh John O. Punderson Peter Ralston Greg P. Rampley Robert A. Resuali R. B. Robertson Ralph W. Samm E. L. Sankey John F. Shimshock Bynum E. Smith Joseph H. Snow T. F. Stabosz D. R. Stein Joseph L. Steiner George A. Straniero Mike D. Sweat Keith W. Switzer John Tanaka James W. Tarpey Frank A. Teti H. D. Thomas W. A. Thue Austin C. Tingley William Torok Duc B. Trinh S. E. Turner Jack R. Tuzinski Donald A. Voltz C. F. Von Hermann, Jr. Steven P. Walldorf E. M. Walton Roland H. W. Watkins A. C. Westrom Charles A. White W. D. Wilkens Robert O. Wilkinson J. A. Williams William G. Wimmer Clarence Woodell J. T. Zimnoch Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=IHS Employees/1111111001, User=O'Connor, Maurice Not for Resale, 04/28/2007 23:21:10 MDTNo reproduction or networking permitted without license from IHS -,-,- iv When the IEEE Standards Board approved this guide on December 2, 1993, it had the following membership: Wallace S. Read, Chair Donald C. Loughry, Vice Chair Andrew G. Salem, Secretary Gilles A. BarilJim IsaakDon T. Michael* José A. Berrios de la PazBen C. JohnsonMarco W. Migliaro Clyde R. CampWalter J. KarplusL. John Rankine Donald C. FleckensteinLorraine C. KevraArthur K. Reilly Jay Forster*E. G. “Al” KienerRonald H. Reimer David F. FranklinIvor N. KnightGary S. Robinson Ramiro Garcia Joseph L. Koepfi nger*Leonard L. Tripp Donald N. HeirmanD. N. “Jim” LogothetisDonald W. Zipse *Member Emeritus Also included are the following nonvoting IEEE Standards Board liaisons: Satish K. Aggarwal James Beall Richard B. Engelman David E. Soffrin Stanley I. Warshaw Stephen J. Huffman IEEE Standards Project Editor Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=IHS Employees/1111111001, User=O'Connor, Maurice Not for Resale, 04/28/2007 23:21:10 MDTNo reproduction or networking permitted without license from IHS -,-,- v Contents CLAUSEPAGE 1.Overview 1 2.Scope 1 3.Purpose. 2 4.Definitions 2 5.Conversion of measurement units 2 5.1 Parts per million by volume (PPMV)2 5.2 Parts per million by weight (PPMW). 2 5.3 Conversion from PPMV to PPMW 2 5.4 Dew point. 3 5.5 Relative humidity (RH) (%). 4 6.Measuring instruments. 4 6.1 Absolute humidity instruments 5 6.2 Relative humidity hygrometers 5 6.3 Operation 6 7.Pressure and temperature effects on moisture measurements 6 7.1 Pressure effects 6 7.2 Temperature effects . 7 8.Moisture control. 8 8.1 Adsorbed and absorbed moisture. 8 8.2 Effect of vacuuming. 10 8.3 External moisture sources 11 8.4 Application of desiccant 11 9.Acceptable moisture limits and moisture check intervals 11 10.Summary 13 11.Bibliography 14 Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=IHS Employees/1111111001, User=O'Connor, Maurice Not for Resale, 04/28/2007 23:21:10 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=IHS Employees/1111111001, User=O'Connor, Maurice Not for Resale, 04/28/2007 23:21:10 MDTNo reproduction or networking permitted without license from IHS -,-,- 1 IEEE Guide for Moisture Measurement and Control in SF 6 Gas-Insulated Equipment 1. Overview Moisture measurement and control constitute a major part of an effective maintenance program for gas-insu- lated equipment (GIE). Moisture, particularly in the liquid phase, affects the dielectric withstand strength of GIE B9. 1 Therefore, moisture in GIE shall be maintained at a level such that it does not condense into liq- uid for the entire range of the expected operating temperatures. Additionally, excessive moisture in the enclosed equipment accelerates the formation of hydrofl uoric (HF) acid, a result of reactions between SF 6 arc by-products and water B2, B6. Because of the importance of moisture in controlling insulation strength and aging mechanisms of the epoxy insulating spacers, most users periodically measure moisture levels in their SF 6 insulated equipment. However, results of a North American survey conducted in 1984 by the IEEE Insulated Conductors Committee indicate that utility personnel have experienced diffi culties in carrying out moisture measurement and interpretation in GIE B6, B3. The experience has shown that although hygrometry is an established science, techniques and procedures for moisture measurement in GIE are not well understood. As a result, there is considerable confusion among engineers and fi eld personnel on how to properly measure moisture (particularly under high-pressure conditions), interpret the results, and control the moisture levels. Compounding the problem of moisture measurement in GIE is the fact that moisture inside the GIE system can exist in either the vapor or adsorbed phase on the surface of the enclosure, or in the absorbed phase inside the polymeric solid insulator. The distribution of moisture in the various phases can signifi cantly affect the dielectric strength and the measurement results. For example, moisture measurements taken in the winter would tend to be lower than moisture measurements taken in the summer, since more surface- adsorbed water exists during periods of low temperature. Elucidation of the moisture sources and migration phenomena is the key to designing an effective moisture measurement and control program. The objective of this guide is to provide adequate information about the techniques and know-how needed to conduct a successful moisture measurement and control program for GIE. 2. Scope This document establishes guidelines for moisture level measurement, moisture data interpretation, and moisture control in gas-insulated transmission class equipment. 1 The numbers in brackets correspond to those of the bibliography in clause 11. Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=IHS Employees/1111111001, User=O'Connor, Maurice Not for Resale, 04/28/2007 23:21:10 MDTNo reproduction or networking permitted without license from IHS -,-,- IEEE Std 1125-1993IEEE GUIDE FOR MOISTURE MEASUREMENT 2 3. Purpose Because of the importance of moisture in the design, manufacture, installation, operation, and maintenance of GIE, guidelines are necessary to establish an acceptable range of moisture levels depending on equipment design, measurement procedures, and data interpretation. The purpose of these guidelines is to provide guidance and promote understanding among users of GIE. More specifically, the objective is to communicate general knowledge and sufficient understanding so as to ensure successful operation of the equipment. 4. Defi nitions 4.1 parts per million by volume (PPMV): One million times the ratio of the volume of water vapor present in the gas to the total volume of the gas (including water vapor). 4.2 parts per million by weight (PPMW): One million times the ratio of the weight of water vapor present in the gas to the total weight of the gas (including water vapor). 4.3 dew point: The temperature at which the water vapor in the gas begins to condense, expressed in degrees Fahrenheit (ºF) or Celsius (ºC). 4.4 relative humidity (RH): The ratio between the amount of water vapor in the gas at the time of measure- ment and the amount of water vapor that could be in the gas when condensation begins, at a given temperature. 5. Conversion of measurement units Moisture measurements in GIE are generally reported in PPMV, PPMW, or dew point in ºF or ºC since most available instrumentation is calibrated in these units. Relative humidity, expressed in percent, is often used to represent moisture content in the gas, but it is rarely measured directly by an instrument. Instrumentation to measure PPMV, PPMW, and dew point is discussed in the following subclauses. 5.1 Parts per million by volume (PPMV) PPMV is the most commonly used system of units in North America. If the moisture level is 300 PPMV, fo