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International iec 60076 11 2018

This is a preview - click here to buy the full publication INTERNATIONAL STANDARD IEC - Edition - REDLINE VERSION colour inside Power transformers ?? Part Dry-type transformers INTERNATIONAL ELECTROTECHNICAL COMMISSION ICS ISBN - - - - Warning Make sure that you obtained this publication from an authorized distributor Registered trademark of the International Electrotechnical Commission CThis is a preview - click here to buy the full publication IEC - ISH ? IEC ?? ?? INTERNATIONAL ELECTROTECHNICAL COMMISSION IEC - Edition - POWER TRANSFORMERS ?? Part Dry-type transformers INTERPRETATION SHEET This interpretation sheet has been prepared by IEC technical committee Power transformers The text of this interpretation sheet is based on the following documents DISH DISH Report on voting 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 Temperature-rise test Question The independent certi ?cation 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 - - ISH - en ICS CThis is a preview - click here to buy the full publication Subclause General states ?? ?? IEC - ISH ? IEC 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 a ?ected 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