DIN EN 60076-2:2012-02

The new version of DIN EN 60076-2 (VDE 0532-76-2) deals with liquid-immersed power transformers according to their cooling methods, which are designated by a coding method made up of four letters (for instance, ONAN, ONAF, OFAF, OFWF, etcetera). It specifies temperature rise limits and provides methods for temperature rise tests. With respect to DIN EN 60076-2 (VDE 0532-102):1997-12, along with a complete editorial revision of the standard, the scope has been expanded to include liquid-immersed transformers, the subjects cooling and temperature rise measurements have been extensively revised and the annexes for the determination of the hot-spot, hot-spot measurement with optical fibre sensors and for gas analysis have been supplemented. In IEC 60076-1 indicates that the usual ambient temperature limits for power transformers are between -25 °C and +40 °C. With regard to the usual temperature rise requirements, the temperatures at the intended installation site are taken into account in this standard and the permissible temperature rises for transformers are specified taking into account options: These include requirements for continuous operation with rated power as well as additional requirements which refer to a loading cycle. These additional requirements are mainly applicable to large system transformers for which emergency loading conditions require particular attention. They should not regularly be used for small and medium-size standardized transformers. The standard describes methods for determination of temperature and temperature rise values during the factory test as well as methods for reproduction of operational load by way of equivalent test procedures. During the temperature rise measurements the transformer shall be equipped with its protective equipment (for instance, Buchholz relays). For this purpose, each response of this equipment shall be recorded during the test and the causes investigated. For transformers with multiple values for the rated power, principally, a temperature rise measurement is performed for each rated power. For large system oil-filled transformers in which magnetic leakage flux represent possible risk factors, the analysis of the gases dissolved in oil can lead to the detection of possible local overheating. The analysis should, if this has been agreed upon between the manufacturer and the purchaser, be performed as a special test before and after the temperature rise measurement. The details of the test method and the acceptance criteria for evaluation of the analysis results are provided in an annex of the standard. The responsible committee is K 321 "Transformatoren" ("Transformers") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.