AS 2374.1-1997

1 - AS 2374.1-1997 POWER TRANSFORMERS - GENERAL
4 - PREFACE
6 - CONTENTS
9 - 1 Scope and service conditions
9 - 1.1 Scope
9 - 1.2 Service conditions
9 - 1.2.1 Normal service conditions
10 - 1.2.2 Provision for unusual service conditions
11 - 2 Normative references
12 - 3 Definitions
12 - 3.1 General
12 - 3.1.1 power transformer
12 - 3.1.2 auto-transformer
12 - 3.1.3 booster transformer:
12 - 3.1.4 oil-immersed type transformer:
12 - 3.1.5 dry-type transformer:
12 - 3.1.6 oil preservation system:
12 - 3.2 Terminals and neutral point
12 - 3.2.1 terminal:
12 - 3.2.2 line terminal:
12 - 3.2.3 neutral terminal:
13 - 3.2.4 neutral point:
13 - 3.2.5 corresponding terminals:
13 - 3.3 Windings
13 - 3.3.1 winding:
13 - 3.3.2 tapped winding:
13 - 3.3.3 phase winding:
13 - 3.3.4 high-voltage winding*:
13 - 3.3.5 low-voltage winding*:
13 - 3.3.6 intermediate-voltage winding*:
13 - 3.3.7 auxiliary winding:
13 - 3.3.8 stabilizing winding:
14 - 3.3.9 common winding:
14 - 3. 3.10 series winding:
14 - 3.3.11 energizing winding:
14 - 3.4 Rating
14 - 3.4.1 rating:
14 - 3.4.2 rated quantities:
14 - 3.4.3 rated voltage of a winding
14 - 3.4.4 rated voltage ratio:
14 - 3.4.5 rated frequency
15 - 3.4.6 rated power
15 - 3.4.7 rated current
15 - 3.5 Tappings
15 - 3.5.1 tapping:
15 - 3.5.2 principal tapping:
15 - 3.5.3 tapping factor (corresponding to a given tapping):
16 - 3.5.4 plus tapping:
16 - 3.5.5 minus tapping:
16 - 3.5.6 tapping step:
16 - 3.5.7 tapping range:
16 - 3.5.8 tapping voltage ratio (of a pair of windings):
16 - 3.5.9 tapping duty:
16 - 3.5.10 tapping quantities:
16 - 3.5.11 full-power tapping:
16 - 3.5.12 reduced-power tapping:
16 - 3. 5.13 on-load tap-changer:
17 - 3.6 Losses and no-load current
17 - 3.6.1 no-load loss:
17 - 3.6.2 no-load current:
17 - 3.6.3 load loss:
17 - 3.6.4 total losses:
17 - 3.7 Short-circuit impedance and voltage drop
17 - 3.7.1 short-circuit impedance of a pair of windings:
18 - 3.7.2 voltage drop or rise for a specified load condition:
18 - 3.7.3 zero-sequence impedance (of a three-phase winding):
19 - 3.8 Temperature rise
19 - 3.9 Insulation
19 - 3.10 Connections
19 - 3.10.1 star connection (Y-connection):
19 - 3.10.2 delta connection (D-connection):
19 - 3.10.3 open-delta connection:
19 - 3.10.4 zigzag connection (Z-connection):
19 - 3.10.5 open windings:
19 - 3.10.6 phase displacement of a three-phase winding:
19 - 3.10.7 connection symbol:
20 - 3.11 Kinds of tests
20 - 3.11.1 routine test:
20 - 3.11.2 type test:
20 - 3.11.3 special test:
20 - 3.12 Meteorological data with respect to cooling
20 - 3.12.1 monthly average temperature:
20 - 3.12.2 yearly average temperature:
20 - 4 Rating
20 - 4.1 Rated power
21 - 4.2 Loading cycle
21 - 4.3 Preferred valves of rated power
21 - 4.4 Operation at higher than rated voltage and/or at disturbed frequency
22 - 5 Requirements for transformers having a tapped winding
22 - 5.1 General – Notation of tapping range
22 - 5.2 Tapping voltage – tapping current. Standard categories of tapping voltage variation. Maximum voltage tapping
25 - 5.3 Tapping power. Full-power tappings – reduced-power tappings
26 - 5.4 Specification of tappings in enquiry and order
26 - 5.5 Specification of short-circuit impedance
27 - 5.6 Load loss and temperature rise
28 - 6 Connection and phase displacement symbols for three-phase transformers
30 - 7 Rating plates
30 - 7.1 Information to be given in all cases
31 - 7.2 Additional information to be given when applicable
32 - 8 Miscellaneous requirements
32 - 8.1 Dimensioning of neutral connection
32 - 8.2 Oil preservation system
32 - 8.3 Load rejection on generator transformers
32 - 9 Tolerances
35 - 10 Tests
35 - 10.1 General requirements for routine, type and special tests
36 - 10.2 Measurement of winding resistance
37 - 10.3 Measurement of voltage ratio and check of phase displacement
37 - 10.4 Measurement of short-circuit impedance and load loss
38 - 10.5 Measurement of no-load loss and current
38 - 10.6 Measurement of the harmonics of the no-load current
39 - 10.7 Measurement of zero-sequence impedance(s) on three-phase transformers
39 - 10.8 Tests on on-load tap-changers
41 - Annex A - Information required with enquiry and order
41 - A.1 Rating and general data
43 - A.2 Parallel operation
44 - Annex B - Examples of specifications for transformers with tappings
44 - Example 1 – Constant flux voltage variation
44 - Example 2 – Variable flux voltage variation
45 - Example 3 – Combined voltage variation
46 - Annex C - Specification of short-circuit impedance by boundaries
47 - Annex D - Three-phase transformer connections
50 - Annex E - Temperature correction of load loss
51 - Annex F - Bibliography
52 - APPENDIX ZZ - LIST OF VARIATIONS BETWEEN THIS STANDARD AND IEC 76-1
55 - APPENDIX ZA - POWER RATINGS AND METHODS OF COOLING COMMONLY USED IN AUSTRALIA
55 - ZA1 POWER RATINGS
55 - ZA2 METHODS OF COOLING
56 - APPENDIX ZB - TRANSFORMER CONNECTIONS IN GENERAL USE
56 - ZB1 THREE-PHASE TRANSFORMERS
56 - ZB2 EXAMPLE OF THREE SINGLE-PHASE TRANSFORMERS CONNECTED TO FORM A THREE-PHASE BANK
56 - ZB3 MISCELLANEOUS TRANSFORMER TYPES
63 - APPENDIX ZC - DESIGNATION OF WINDINGS, ASSIGNMENT OF LETTERS AND NUMBERS TO WINDING ENDS AND TAPPINGS, MARKING AND POSITION O
63 - ZC1 DESIGNATION OF WINDINGS
63 - ZC2 DESIGNATING LETTERS AND NUMBERS
65 - ZC3 SUBSCRIPT NUMBERS FOR WINDING ENDS AND TAPPINGS
66 - ZC4 MARKING OF TERMINALS
69 - ZC5 ARRANGEMENT AND SEQUENCE OF TERMINALS
69 - ZC6 PHASE DISPLACEMENT DIAGRAM AND SYMBOLS
69 - ZC7 TERMINAL MARKING PLATES
69 - ZC8 CONNECTION DIAGRAM DRAWINGS

Specifies the technical requirements for single and three-phase power transformers, including auto transformers, but excludes single-phase transformers rated at less than 1 kVA, three-phase transformers rated at less than 5 kVA, and certain special transformers such as instrument, starting, testing and welding transformers, transformers for static converters and those mounted on rolling stock. Based on but not equivalent to and has been reproduced from IEC 76-1:1993. Includes Australian variations such as commonly used power ratings and preferred methods of cooling, connections in general use, and details regarding connection designation.

This part of International Standard IEC 76 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 76 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.

First published as part of AS C61-1931.
Second edition 1946.
Third edition 1963.
Fourth edition 1970.
Revised and redesignated in part as AS 2374.1-1982 and AS 2374.4-1982.
AS 2374.1-1982 and AS 2374.4-1982 revised, amalgamated and designated AS 2374.1-1997.