1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-22429-5 SANS 60076-12:2009 Edition 1 IEC 60076-12:2008 Edition 1SOUTH AFRICAN NATIONAL STANDARD Power transformers Part 12: Loading guide
4、for dry-type power transformers This national standard is the identical implementation of IEC 60076-12:2008 and is adopted with the permission of the International Electrotechnical Commission. Published by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001 Tel: +27 1
5、2 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS This standard may only be used and printed by approved subscription and freemailing clients of the SABS. SANS 60076-12:2009 Edition 1 IEC 60076-12:2008 Edition 1 Table of changes Change No. Date Scope National foreword This South African standard w
6、as approved by National Committee SABS SC 67E, Electricity distribution systems and components Electricity distribution, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This SANS document was published in March 2009. This standard ma
7、y only be used and printed by approved subscription and freemailing clients of the SABS. IEC 60076-12 Edition 1.0 2008-11 INTERNATIONAL STANDARD NORME INTERNATIONALE Power transformers Part 12: Loading guide for dry-type power transformers Transformateurs de puissance Partie 12: Guide de charge pour
8、 transformateurs de puissance de type sec INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE V ICS 29.180 PRICE CODE CODE PRIX ISBN 2-8318-1015-2 Registered trademark of the International Electrotechnical Commission Marque dpose de la Commission Electrotechnique Int
9、ernationale SANS 60076-12:2009This standard may only be used and printed by approved subscription and freemailing clients of the SABS. 2 60076-12 IEC:2008 CONTENTS FOREWORD.4 INTRODUCTION.6 1 Scope.7 2 Normative references .7 3 Terms and definitions .7 4 Effect of loading beyond nameplate rating 8 4
10、.1 General .8 4.2 General consequences8 4.3 Effects and hazards of short-time emergency loading8 4.4 Effects of long-time emergency loading .9 5 Ageing and transformer insulation lifetime 9 5.1 General .9 5.2 Lifetime .9 5.3 Relation between constant continuous load and temperature 10 5.4 Ageing rat
11、e11 5.5 Lifetime consumption 11 5.6 Hot-spot temperature in steady state.11 5.7 Assumed hot-spot factor12 5.8 Hot-spot temperature rises at varying ambient temperature and load conditions12 5.9 Loading equations.12 5.9.1 Continuous loading12 5.9.2 Transient loading.13 5.10 Determination of winding t
12、ime constant .14 5.10.1 General .14 5.10.2 Time constant calculation method14 5.10.3 Time constant test method.15 5.11 Determination of winding time constant according to empirical constant 15 5.12 Calculation of loading capability 15 6 Limitations17 6.1 Current and temperature limitations.17 6.2 Ot
13、her limitations 17 6.2.1 Magnetic leakage field in structural metallic parts17 6.2.2 Accessories and other considerations17 6.2.3 Transformers in an enclosure 18 6.2.4 Outdoor ambient conditions .18 Annex A (informative) Ageing rate .19 Annex B (informative) Examples of lifetime consumptions for 3 l
14、oad regimes.24 Annex C (informative) List of symbols33 Bibliography35 Figure A.1 Molecule structure of an epoxy .19 Figure A.2 Thermal endurance graph.22 Figure B.1 Step change loading curve25 Figure B.2 Hot-spot temperature rise and life consumption 27 SANS 60076-12:2009This standard may only be us
15、ed and printed by approved subscription and freemailing clients of the SABS.60076-12 IEC:2008 3 Figure B.3 Load current and winding hot-spot temperature rise30 Figure B.4 Ageing rate versus time 30 Table 1 Constants for lifetime equation10 Table 2 Maximum hot-spot winding temperature 16 Table 3 Curr
16、ent and temperature limits applicable to loading beyond nameplate rating.17 Table B.1 Lifetime consumption calculations26 Table B.2 Life consumption calculations for varying load .29 Table B.3 Life consumption calculation 31 SANS 60076-12:2009This standard may only be used and printed by approved su
17、bscription and freemailing clients of the SABS. 4 60076-12 IEC:2008 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ POWER TRANSFORMERS Part 12: Loading guide for dry-type power transformers FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization co
18、mprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International St
19、andards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this pr
20、eparatory work. International, governmental and non- governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two org
21、anizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees. 3) IEC Publications have the for
22、m of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpreta
23、tion by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or re
24、gional publication shall be clearly indicated in the latter. 5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with an IEC Publication. 6) All users should ensure that they have the latest edition of this p
25、ublication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indire
26、ct, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications. 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the
27、correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 60076-12 has been prepa
28、red by IEC technical committee 14: Power transformers. This standards cancels and replaces IEC 60905 (1987). This first edition constitutes a technical revision. The text of this standard is based on the following documents: FDIS Report on voting 14/584/FDIS 14/590/RVD Full information on the voting
29、 for the approval of this standard can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. SANS 60076-12:2009This standard may only be used and printed by approved subscription and freemailing clients of
30、the SABS.60076-12 IEC:2008 5 A list of all parts of IEC 60076 series, under the general title Power transformers, can be found on the IEC website. The committee has decided that the contents of this publication will remain unchanged until the maintenance result date indicated on the IEC web site und
31、er “http:/webstore.iec.ch“ in the data related to the specific publication. At this date, the publication will be reconfirmed; withdrawn: replaced by a revised edition; or amended. SANS 60076-12:2009This standard may only be used and printed by approved subscription and freemailing clients of the SA
32、BS. 6 60076-12 IEC:2008 INTRODUCTION This part of IEC 60076 provides guidance for the specification and loading of dry type power transformers from the point of view of operating temperatures and thermal ageing. It provides the consequence of loading above the nameplate rating and guidance for the p
33、lanner to choose appropriate rated quantities and loading conditions for new installations. IEC 60076-11 is the basis for contractual agreements and it contains the requirements and tests relating to temperature-rise figures for dry type power transformers during continuous rated loading. It should
34、be noted that IEC 60076-11 refers to the average winding temperature rise while this part of IEC 60076 refers mainly to the hot-spot temperature and the latter stated values are provided only for guidance. This part of IEC 60076 gives mathematical models for judging the consequence of different load
35、ing, with different temperatures of the cooling medium, and with transient or cyclical variation with time. The models provide for the calculation of operating temperatures in the transformer, particularly the temperature of the hottest part of the winding. This hot-spot temperature is used for esti
36、mation of the number of hours of life time consumed during a particular time period. This part of IEC 60076 further presents recommendations for limitations of permissible loading according to the results of temperature calculations or measurements. These recommendations refer to different types of
37、loading duty continuous loading, short-time and long time emergency loading. An explanation of ageing fundamentals is given in Annex A. SANS 60076-12:2009This standard may only be used and printed by approved subscription and freemailing clients of the SABS.60076-12 IEC:2008 7 POWER TRANSFORMERS Par
38、t 12: Loading guide for dry-type power transformers 1 Scope This part of IEC 60076 is applicable to dry-type transformers according to the scope of IEC 60076-11. It provides the means to estimate ageing rate and consumption of lifetime of the transformer insulation as a function of the operating tem
39、perature, time and the loading of the transformer. NOTE For special applications such as wind turbine application transformers, furnace transformers, welding machine transformers, and others, the manufacturer should be consulted regarding the particular loading profile. 2 Normative references The fo
40、llowing referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60076-11, Power transformers Part 11: Dry-type tran
41、sformers IEC 60216-1, Electrical insulating materials Properties of thermal endurance Part 1: Ageing procedures and evaluation of test results IEC 61378-1:1997, Convertor transformers Part 1: Transformers for industrial applications 3 Terms and definitions For the purposes of this document, the foll
42、owing terms and definitions apply. 3.1 long-time emergency loading loading resulting from the prolonged outage of some system elements that will not be reconnected before the transformer reaches a new and higher steady state temperature 3.2 short-time emergency loading unusually heavy loading of a t
43、ransient nature (less than one time constant of the coil) due to the occurrence of one or more unlikely events which seriously disturb normal system loading 3.3 hot-spot if not specifically defined, “hot-spot” means the hottest-spot of the winding 3.4 relative thermal ageing rate for a given hot-spo
44、t temperature, the rate at which transformer insulation ageing is reduced or accelerated compared with the ageing rate at a reference hot-spot temperature SANS 60076-12:2009This standard may only be used and printed by approved subscription and freemailing clients of the SABS. 8 60076-12 IEC:2008 3.
45、5 transformer insulation life time the total time between the initial state for which the normal transformer insulation life time is considered new and the final state when due to thermal ageing, dielectric stress, short-circuit stress, or mechanical movement, which could occur in normal service and
46、 result in a high risk of electrical failure 3.6 AN cooling cooling by natural air ventilation 3.7 AF cooling method of cooling to increase the rated power of the transformer with fan cooling 4 Effect of loading beyond nameplate rating 4.1 General Normal life expectancy is a conventional reference b
47、asis for continuous duty under design ambient temperature and rated operating conditions. The application of a load in excess of nameplate rating and/or an ambient temperature higher than specified ambient temperatures involves a degree of risk and accelerated ageing. It is the purpose of this part
48、of IEC 60076 to identify such risks and to indicate how, within limitations, transformers may be loaded in excess of the nameplate rating. 4.2 General consequences The consequences of loading a transformer beyond its nameplate rating are as follows: the temperatures of windings, terminals, leads, ta
49、p changer and insulation increase, and can reach unacceptable levels; enclosure cooling is more sensitive to overload leading to a more rapid increase in insulation temperature to unacceptable levels; as a consequence, there will be a risk of premature failure associated with the increased currents and temperatures. This risk may be of an immediate short-term character or may come from the cumulative effect of thermal ageing of the insulation in the transformer over many year
