• AS 2374.7-1997

    Superseded A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

    Power transformers - Loading guide for oil-immersed power transformers

    Available format(s):  Hardcopy, PDF 1 User, PDF 3 Users, PDF 5 Users, PDF 9 Users

    Superseded date:  30-10-2017

    Language(s): 

    Published date:  01-01-1997

    Publisher:  Standards Australia

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    Table of Contents - (Show below) - (Hide below)

    1 - AS 2374.7-1997 POWER TRANSFORMERS - LOADING GUIDE FOR OIL-IMMERSED POWER TRANSFORMERS
    4 - PREFACE
    6 - CONTENTS
    7 - Section 1: General
    7 - 1.1 Scope
    7 - 1.2 Object
    8 - 1.3 Definitions
    8 - 1.3.1 Distribution transformer
    8 - 1.3.2 Medium power transformer
    8 - 1.3.3 Large power transformer
    9 - 1.4 General limitations and effects of loading beyond nameplate rating
    9 - 1.4.1 Effect of loading beyond nameplate rating
    11 - 1.4.2 Transformer size
    12 - 1.4.3 Current and temperature limitations
    13 - 1.5 Specific limitations for distribution transformers
    13 - 1.5.1 Rating limitation
    13 - 1.5.2 Current and temperature limitations
    13 - 1.5.3 Accessory and other considerations
    13 - 1.5.4 Indoor transformers
    13 - 1.5.5 Outdoor ambient conditions
    13 - 1.6 Specific limitations for medium power transformers
    13 - 1.6.1 Rating limitations
    13 - 1.6.2 Current and temperature limitations
    14 - 1.6.3 Accessory, associated equipment and other considerations
    14 - 1.6.4 Short-circuit withstand requirements
    14 - 1.6.5 Voltage limitations
    14 - 1.7 Specific limitations for large power transformers
    14 - 1.7.1 General
    15 - 1.7.2 Current and temperature limitations
    15 - 1.7.3 Accessory, equipment and other considerations
    15 - 1.7.4 Short-circuit withstand requirements
    15 - 1.7.5 Voltage limitations
    16 - Section 2: Determination of temperatures
    16 - 2.1 Symbols
    16 - 2.1.1 Basic symbols
    16 - 2.1.2 Prefixes
    16 - 2.1.3 Exponents
    17 - 2.1.4 Suffixes (general)
    17 - 2.1.5 Specific suffixes relating to oil temperatures
    17 - 2.2 Direct measurement of hot-spot temperature
    17 - 2.3 Assumed thermal characteristics
    17 - 2.3.1 Simplifications made
    20 - 2.4 Steady-state temperature equations
    20 - 2.4.1 ON cooling
    20 - 2.4.2 OF cooling
    21 - 2.4.3 OD cooling
    21 - 2.4.4 Equation corrections
    21 - 2.5 Transient temperature equations
    22 - 2.6 Thermal ageing of transformer insulation
    22 - 2.6.1 Law of thermal ageing
    23 - 2.6.2 Relative thermal-ageing rate
    23 - 2.6.3 Loss-of-life calculation
    24 - 2.7 Ambient temperature
    24 - 2.7.1 General
    24 - 2.7.2 Weighted ambient temperature
    25 - 2.7.3 Ambient temperature for hot-spot calculation
    25 - 2.7.4 Continuously varying ambient temperature
    27 - 2.8 Computer program
    27 - 2.8.1 Logic diagram
    28 - 2.8.2 Example of calculation
    35 - Section 3: Loading tables
    35 - 3.1 Limitations applicable to loading tables
    35 - 3.2 Method of representing an actual load cycle by an equivalent two-step rectangular load cycle
    35 - 3.2.1 Use of guide
    36 - 3.2.2 Load cycle with one peak
    36 - 3.2.3 Load cycle with two peaks of equal amplitude and different duration
    37 - 3.2.4 Load cycles with peaks in close succession
    37 - 3.3 Normal continuous loading
    37 - 3.4 Normal cyclic loading
    47 - 3.5 Emergency cyclic loading
    72 - Annex A - Equivalent rating for auto-transformers
    74 - Annex B - Alternative method for determining the winding oil average temperature rise from temperature-rise test measurement
    78 - Annex C - Information to be supplied with enquiry and order
    79 - Annex D - Calculation of parameters for sinusoidal variation of ambient temperature
    85 - Annex E - Example of simplified application of the guide
    87 - APPENDIX ZZ - VARIATIONS FROM IEC 354 FOR AUSTRALIAN CONDITIONS
    88 - APPENDIX ZA - DETERMINATION OF THE THERMAL TIME-CONSTANT OF A TRANSFORMER UNDER STEADY LOAD CONDITIONS
    89 - APPENDIX ZB - INDIRECT MEASUREMENT OF WINDING HOT-SPOT TEMPERATURE

    Abstract - (Show below) - (Hide below)

    Provides guidance on determining the acceptable relationship between transformer rating and proposed load cycle when considering the effect of operating temperatures on life expectancy due to insulation deterioration and thermal ageing. Includes recommendations for loading above the nameplate rating and guidance for choosing appropriate rated quantities and loading conditions for new installations. It applies to the same range of transformers complying with AS 2374.1-1997. This Standard is technically equivalent to and reproduced from IEC 354:1991 and includes Australian informative appendices on determination of the thermal time-constant and indirect measurement of winding hot-spot temperature.

    Scope - (Show below) - (Hide below)

    This guide is applicable to oil-immersed transformers complying with IEC 76. It indicates how, within limits, transformers may be loaded above rated conditions. For furnace transformers, the manufacturer should be consulted in view of the peculiar loading profile.

    General Product Information - (Show below) - (Hide below)

    Committee EL-008
    Document Type Standard
    Publisher Standards Australia
    Status Superseded
    Superseded By
    Supersedes
    Under Revision

    History - (Show below) - (Hide below)

    First published as AS CC10-1965.Revised and redesignated AS 1078.1-1972.Revised and redesignated AS 1078-1984.Revised and redesignated AS 2374.7-1997. First published as AS CC10-1965. Revised and redesignated AS 1078.1-1972. Revised and redesignated AS 1078-1984. Revised and redesignated AS 2374.7-1997.

    Standards Referenced By This Book - (Show below) - (Hide below)

    AS 2374.2-1997 Power transformers Temperature rise
    AS 2374.5-1982 Power Transformers Ability To Withstand Short-Circuit
    AS 2374.1-1997 Power transformers General

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    AS/NZS 60137:2008 Insulated bushings for alternating voltages above 1000 V (IEC 60137, Ed. 5.0 (2003) MOD)
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    AS 2374.8-2000 Power transformers Application guide
    AS 60214.2-2006 Tap-changers - Application guide
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