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INTERNATIONAL STANDARD Power transformers – Part 11: Dry-type transformers INTE

INTERNATIONAL STANDARD Power transformers – Part 11: Dry-type transformers INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS 29.180 ISBN 978-2-8322-5967-2 ® Registered trademark of the International Electrotechnical Commission ® Warning! Make sure that you obtained this publication from an authorized distributor. IEC 60076-11 Edition 2.0 2018-08 REDLINE VERSION colour inside This is a preview - click here to buy the full publication IEC 60076-11:2018/ISH1:2020 – 1 – © IEC 2020 ICS 29.180 INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________ IEC 60076-11 Edition 2.0 2018-08 POWER TRANSFORMERS – Part 11: Dry-type transformers I N T E R P R E T A T I O N S H E E T 1 This interpretation sheet has been prepared by IEC technical committee 14: Power transformers. The text of this interpretation sheet is based on the following documents: DISH Report on voting 14/1052/DISH 14/1054/RVDISH Full information on the voting for the approval of this interpretation sheet can be found in the report on voting indicated in the above table. ___________ 14.3.2 Temperature-rise test Question The independent certification body in Poland "Instytut Energetyki" carries out the testing of transformers or its inspectors witness this testing at the manufacturers' premises. The description of resistance measurement during the temperature rise test has caused a dispute between a manufacturer and the inspector on where exactly the resistance should be measured. The inspector requested that the resistance be measured on "winding lead exits" inside the enclosure, while the manufacturer argued for the measurement to be made on "winding terminals" which in its opinion were the bushings on the enclosure cover. IEC 60076-11:2018-08/ISH1:2020-07(en) This is a preview - click here to buy the full publication – 2 – IEC 60076-11:2018/ISH1:2020 © IEC 2020 Subclause 14.3.2.1 General, states: The winding temperature rise shall be established by the rise in resistance method or by superposition method. For the determination of the average winding temperature rise the measured temperatures of the cooling air or of the water intake of the cooling equipment shall be used. For three-phase transformers, the resistance measurements shall be made between the central and an outer phase line terminals. NOTE When the temperature rise is performed it is advisable to measure the windings resistance close to the windings. Where should the measurements be made? Interpretation Testing of the winding resistance at transformer terminals (bushings) includes leadwork or busbars and often also multiple connections. Because of this, the tested winding resistance and its change due to heating is affected by the resistance of all these leads and connections. Consequently, the derived winding temperature rise if measured at the transformer terminals could be lower than if the winding resistance were tested directly on the winding lead exits. That is why the standard suggests (in the NOTE) that measurement of the windings' resistance be carried out close to the windings. That way, the accuracy of the indirect winding temperature measurement by resistance is higher. In the case of dry-type transformers without enclosures, it is possible to have access close to the winding lead exits and not only to the transformer line terminals. Therefore, measurements shall normally be made at such locations. On the other hand, if the dry-type transformer is equipped with an enclosure, the resistance measurement close to the winding lead exits requires opening the enclosure to have access to carry out the test (hence, affecting the normal cooling efficiency of the unit). Nevertheless, the advice to measure the resistance normally close to the winding lead exits holds. Limiting the enclosure opening by using special through elements for the cabling and/or by closing the required opening by temporary means as well as possible will minimize the impact on the normal cooling efficiency. This is a preview - click here to buy the full publication – 2 – IEC 60076-11:2018 RLV © IEC 2018 CONTENTS FOREWORD ......................................................................................................................... 6 1 Scope ............................................................................................................................ 8 2 Normative references..................................................................................................... 8 3 Terms and definitions .................................................................................................... 9 4 Service conditions ....................................................................................................... 10 4.1 General ............................................................................................................... 10 4.2 Normal service conditions ................................................................................... 10 4.3 Electromagnetic compatibility (EMC) .................................................................... 12 5 Rating and general requirements ................................................................................. 12 5.1 General ............................................................................................................... 12 5.2 Rated power ....................................................................................................... 12 5.2.1 General ....................................................................................................... 12 5.2.2 Operation Definition of the rated power with fans cooling or heat exchangers .................................................................................................. 13 5.2.3 Transformer IP00 (without enclosure) ........................................................... 13 5.2.4 Operation in an Transformer with enclosure .................................................. 13 5.2.5 Preferred values of rated power .................................................................... 14 5.2.6 Loading beyond rated power ........................................................................ 14 5.3 Provision for unusual service conditions .............................................................. 14 5.4 Transportation and storage conditions ................................................................. 15 5.4.1 Transport limitation ...................................................................................... 15 5.4.2 Transport acceleration ................................................................................. 15 5.4.3 Temperature and environment conditions for transport and storage ............... 15 5.5 Rated voltage and rated frequency ...................................................................... 15 5.5.1 Rated voltage .............................................................................................. 15 5.5.2 Rated frequency ........................................................................................... 16 5.6 Operation at higher than rated voltage ................................................................. 16 5.7 Highest voltage for equipment Um and dielectric tests levels ................................ 16 5.8 Identification according to cooling method ........................................................... 16 5.8.1 General ....................................................................................................... 16 5.8.2 Identification symbols ................................................................................... 16 5.8.3 Arrangement of symbols ............................................................................... 17 5.9 Guaranteed temperature rise at rated conditions .................................................. 17 5.10 Additional information required for enquiry ........................................................... 17 5.11 Sound level ......................................................................................................... 17 5.12 Components and materials .................................................................................. 17 6 Tappings ..................................................................................................................... 17 7 Connections ................................................................................................................ 18 8 Ability to withstand short circuit .................................................................................... 18 9 Rating plate ................................................................................................................. 18 9.1 Rating plate fitted to the transformer .................................................................... 18 9.2 Rating plate fitted to the transformer enclosure .................................................... 19 10 Temperature-rise limits ................................................................................................ 19 10.1 Normal temperature-rise limits ............................................................................. 19 This is a preview - click here to buy the full publication IEC 60076-11:2018 RLV © IEC 2018 – 3 – 10.2 Reduced temperature rises for transformers designed for high cooling air medium temperatures or special air cooling medium conditions ............................ 20 10.3 High altitude temperature rise correction .............................................................. 20 11 Insulation levels ........................................................................................................... 21 11.1 General ............................................................................................................... 21 11.2 Transformers for use at high altitudes .................................................................. 22 12 Climatic, environmental and fire behaviour classes ....................................................... 23 12.1 Climatic classes .................................................................................................. 23 12.2 Environmental classes ......................................................................................... 24 12.2.1 Transformers for indoor application with or without enclosure and for outdoor application with enclosure ................................................................ 24 12.2.2 Dry-type transformers without enclosure for outdoor application .................... 25 12.3 Fire behaviour classes ........................................................................................ 25 12.4 Test criteria for climatic, environmental and fire behaviour classes ....................... 25 13 Seismic ....................................................................................................................... 26 13.1 General ............................................................................................................... 26 13.2 General seismic class approach .......................................................................... 27 13.2.1 Generalities ................................................................................................. 27 13.2.2 The standard amplitude method ................................................................... 27 13.2.3 The calculated amplitude method ................................................................. 28 14 Test ............................................................................................................................ 29 14.1 General requirements for tests ............................................................................ 29 14.2 Routine tests ....................................................................................................... 30 14.2.1 Measurement of winding resistance .............................................................. 30 14.2.2 Measurement of voltage ratio and check of phase displacement .................... 30 14.2.3 Measurement of short-circuit impedance and load loss ................................. 30 14.2.4 Measurement of no-load loss and current ..................................................... 31 14.2.5 Separate-source AC withstand voltage test Applied voltage test (AV) ............ 31 14.2.6 Induced AC withstand voltage test Induced voltage withstand test(IVW) ........ 31 14.2.7 Partial discharge measurement .................................................................... 31 14.3 Type tests ........................................................................................................... 33 14.3.1 Full wave lightning impulse test (LI) .............................................................. 33 14.3.2 Temperature-rise test ................................................................................... 34 14.4 Additional procedure test (Special tests) .............................................................. 38 14.4.1 Partial discharge measurement for transformers operated under a single phase line-to-earth fault condition ....................................................... 38 14.4.2 Measurement of sound level ......................................................................... 38 14.4.3 Short-circuit test........................................................................................... 39 14.4.4 Climatic tests ............................................................................................... 39 Thermal shock test for C1 class transformers .................................................. Thermal shock test for C2 class transformers .................................................. 14.4.5 Environmental test ....................................................................................... 41 14.4.6 Fire behaviour test ....................................................................................... 44 14.4.7 Seismic test ................................................................................................. 51 14.4.8 Special test for transformers equipped with amorphous core ......................... 52 15 Tolerances .................................................................................................................. 53 16 Protection against direct contact .................................................................................. 53 17 Degrees of protection provided by enclosures .............................................................. 53 This is a preview - click here to buy the full publication – 4 – IEC 60076-11:2018 RLV © IEC 2018 18 Earthing terminal ......................................................................................................... 53 19 Information required with enquiry and order .................................................................. 53 Annex A (informative) Installation and safety of dry-type transformers ................................. 54 A.1 Manuals .............................................................................................................. 54 A.2 Installation .......................................................................................................... 54 A.2.1 General ....................................................................................................... 54 A.2.2 Intrinsic safety ............................................................................................. 54 A.2.3 Installation precautions ................................................................................ 55 A.2.4 Installation design ........................................................................................ 55 Annex B (informative) Environmental test for evaluation of outdoor transformers without enclosure ................................................................................................................ 56 B.1 General ............................................................................................................... 56 B.2 Salt-fog and UV-radiation chamber test ............................................................... 56 B.2.1 Test description ........................................................................................... 56 B.2.2 Acceptance criteria: ..................................................................................... 58 B.3 Core and clamp coating test ................................................................................ 58 B.3.1 Test description ........................................................................................... 58 B.3.2 Acceptance criteria ...................................................................................... 58 B.4 Field test ............................................................................................................. 58 B.4.1 Test description ........................................................................................... 58 B.4.2 Acceptance criteria ...................................................................................... 59 Annex C (normative) Cooling of transformer in naturally ventilated room ............................. 60 C.1 Assumptions ....................................................................................................... 60 C.2 Data for the calculation of ventilation ................................................................... 61 C.3 Output ................................................................................................................ 61 C.4 Numerical application for a 1 000 kVA transformer ............................................... 62 Annex D (normative) Calculation of the losses with different reference temperatures and/or winding material ....................................................................................................... 63 Bibliography ....................................................................................................................... 66 Figure 1 – Basic measuring circuit for the partial discharge test for a single-phase transformer ......................................................................................................................... 32 Figure 2 uploads/Geographie/international-iec-60076-11-2018.pdf