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Iec 60726 Dry Type Power Transformers Pdf Download

Specifies requirements for dry-type power transformers (including auto-transformers) having values of highest voltage for equipment up to and including 36 kV. The following small and special dry-type transformers are not covered by this standard:-instrument transformers (covered by IEC 60185 and 60186);-transformers for static convertors (covered by IEC 60084, 60119 and 60146).Where IEC standards do not exist for other special transformers, this standard may be applicable as a whole or in part.

iec 60726 dry type power transformers pdf download

3 IEC:1993+A1: CONTENTS FOREWORD... 7 Page Clause 1 Scope and service conditions Scope Service conditions Normative references Definitions General Terminals and neutral point Windings Rating Tappings Losses and no-load current Short-circuit impedance and voltage drop Temperature rise Insulation Connections Kinds of tests Meteorological data with respect to cooling Rating Rated power Loading cycle Preferred values of rated power Operation at higher than rated voltage and/or at disturbed frequency Requirements for transformers having a tapped winding General Notation of tapping range Tapping voltage tapping current. Standard categories of tapping voltage variation. Maximum voltage tapping Tapping power. Full-power tappings reduced-power tappings Specification of tappings in enquiry and order Specification of short-circuit impedance Load loss and temperature rise Connection and phase displacement symbols for three-phase transformers Rating plates Information to be given in all cases Additional information to be given when applicable Miscellaneous requirements Dimensioning of neutral connection Oil preservation system Load rejection on generator transformers Tolerances... 55

4 IEC:1993+A1: Clause 10 Tests General requirements for routine, type and special tests Measurement of winding resistance Measurement of voltage ratio and check of phase displacement Measurement of short-circuit impedance and load loss Measurement of no-load loss and current Measurement of the harmonics of the no-load current Measurement of zero-sequence impedance(s) on three-phase transformers Tests on on-load tap-changers Electromagnetic compatibility (EMC) Page Annex A (normative) Information required with enquiry and order Annex B (informative) Examples of specifications for transformers with tappings Annex C (informative) Specification of short-circuit impedance by boundaries Annex D (informative) Three-phase transformer connections Annex E (normative) Temperature correction of load loss Annex F (informative) Bibliography Figure 1a) Constant flux voltage variation CFVV Figure 1b) Variable flux voltage variation VFVV Figure 1c) Combined voltage variation CbVV Figure 2 Illustration of 'clock number' notation three examples Figure C.1 Example of specification of short-circuit impedance by boundaries Figure D.1 Common connections Figure D.2 Additional connections Figure D.3 Designation of connections of three-phase auto-transformers by connection symbols. Auto-transformer Ya Figure D.4 Example of three single-phase transformers connected to form a three-phase bank (connection symbol Yd5)... 85

6 IEC:1993+A1: POWER TRANSFORMERS Part 1: General 1 Scope and service conditions 1.1 Scope This part of International Standard IEC applies to three-phase and single-phase power transformers (including auto-transformers) with the exception of certain categories of small and special transformers such as: single-phase transformers with rated power less than 1 kva and three-phase transformers less than 5 kva; instrument transformers; transformers for static convertors; traction transformers mounted on rolling stock; starting transformers; testing transformers; welding transformers. When IEC standards do not exist for such categories of transformers, this part of IEC may still be applicable either as a whole or in part. For those categories of power transformers and reactors which have their own IEC standards, this part is applicable only to the extent in which it is specifically called up by cross-reference in the other standard. * At several places in this part it is specified or recommended that an 'agreement' shall be reached concerning alternative or additional technical solutions or procedures. Such agreement is to be made between the manufacturer and the purchaser. The matters should preferably be raised at an early stage and the agreements included in the contract specification. 1.2 Service conditions Normal service conditions This part of IEC gives detailed requirements for transformers for use under the following conditions: a) Altitude A height above sea-level not exceeding m (3 300 ft). b) Temperature of ambient air and cooling medium A temperature of ambient air not below 25 C and not above +40 C. For water-cooled transformers, a temperature of cooling water at the inlet not exceeding +25 C. * Such standards exist for dry-type transformers (IEC 60726), for reactors in general (IEC 60289), for traction transformers and reactors (IEC 60310), and are under preparation for static convertor transformers.

7 IEC:1993+A1: Further limitations, with regard to cooling are given for: oil-immersed transformers in IEC ; dry-type transformers in IEC c) Wave shape of supply voltage A supply voltage of which the wave shape is approximately sinusoidal. NOTE This requirement is normally not critical in public supply systems but may have to be considered in installations with considerable convertor loading. In such cases there is a conventional rule that the deformation shall neither exceed 5 % total harmonic content nor 1 % even harmonic content. Also note the importance of current harmonics for load loss and temperature rise. d) Symmetry of three-phase supply voltage For three-phase transformers, a set of three-phase supply voltages which are approximately symmetrical. e) Installation environment An environment with a pollution rate (see IEC and IEC 60815) that does not require special consideration regarding the external insulation of transformer bushings or of the transformer itself. An environment not exposed to seismic disturbance which would otherwise require special consideration in the design. (This is assumed to be the case when the ground acceleration level a g is below 2 m/s.) * Provision for unusual service conditions Any unusual service conditions which may lead to special consideration in the design of a transformer shall be stated in the enquiry and the order. These may be factors such as high altitude, extreme high or low temperature, tropical humidity, seismic activity, severe contamination, unusual voltage or load current wave shapes and intermittent loading. They may also concern conditions for shipment, storage and installation, such as weight or space limitations (see annex A). Supplementary rules for rating and testing are given in other publications for: Temperature rise and cooling in high ambient temperature or at high altitude: IEC for oil-immersed transformers, and IEC for dry-type transformers. External insulation at high altitude: IEC and IEC for oil-immersed transformers, and IEC for dry-type transformers. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of IEC At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this part of IEC are encouraged to investigate the possibility of applying the most recent edition of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. * See IEC

8 IEC:1993+A1: IEC 60050(421):1990, International Electrotechnical Vocabulary Chapter 421: Power transformers and reactors IEC :1991, Environmental testing Part 3: Guidance. Seismic test methods for equipments IEC :1993, Power transformers Part 2: Temperature rise IEC :1980, Power transformers Part 3: Insulation levels and dielectric tests IEC :1987, Power transformers Part 3: Insulation levels and dielectric tests. External clearances in air IEC :1976, Power transformers Part 5: Ability to withstand short circuit IEC 60137:1984, Bushings for alternating voltages above V IEC 60354:1991, Loading guide for oil-immersed power transformers IEC 60529:1989, Degrees of protection provided by enclosures (IP Code) IEC 60551:1987, Determination of transformer and reactor sound levels IEC 60606:1978, Application guide for power transformers IEC 60726:1982, Dry-type power transformers IEC 60815:1986, Guide for the selection of insulators in respect of polluted conditions IEC 60905:1987, Loading guide for dry-type power transformers ISO 3:1973, Preferred numbers Series of preferred numbers ISO 9001:1987, Quality systems Model for quality assurance in design/development, production, installation and servicing 3 Definitions For the purpose of this part of IEC 60076, the following definitions shall apply. Other terms use the meanings ascribed to them in the International Electrotechnical Vocabulary (IEV). 3.1 General power transformer a static piece of apparatus with two or more windings which, by electromagnetic induction, transforms a system of alternating voltage and current into another system of voltage and current usually of different values and at the same frequency for the purpose of transmitting electrical power [IEV , modified]

INTERNATIONAL STANDARD IEC 60076-11 First edition 2004-05 Power transformers Part 11: Dry-type transformers This English-language version is derived from the original bilingual publication by leaving out

Technical Information Requirement for MV transformers and transformer for internal power supplies for SUNNY CENTRAL SC_Trafo-TI-en-62 Version 6.2 ENGLISH Table of Contents SMA Solar Technology Table of

This document applies to medium power transformers from 25 kVA up to 3 150 kVA with highest voltage for equipment up to 36 kV, or in low voltage (LV) networks with highest voltage for equipment of up to 1,1 kV equipped with voltage regulating devices. 350c69d7ab


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