Transformer monitoring
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Till Sybel Transformer monitoring according to IEC 60354 Christian Schobert Special edition Edition 06/2007 02/2006 from Transformer Vol. 105 (2006) Heft 6

Basic Information and Implementation Possibilities Transformer Monitoring according to IEC 60354 High and middle voltage transformers are particularly important components in electrical energy supply networks. This statement is true even without considering network breakdown situations (blackouts). Electricity is required to sustain our comfortable standard of living, and without electricity it would not be possible to remain competitive. As a result, transformers deserve special attention. General information The following document describes a method for optimising the load on a...

However, the deciding factor for the quality of the insulation - and thereby for the transformer‘s service life - is the hot spot or the hot spot temperature (P). The hot spot is determined by the parameter H· gr (H · gr = hot spot to top oil temperature difference). This is also a transformer constant and can be determined from the temperature difference between the oil (measured in the upper oil layer (A)) and the hottest spot of the transformer (P). This temperature occurs on the inside of the coil and can also be considered to be the sum of the oil temperature and a temperature...

Determining the absolute lifetime consumption If a transformer operates for one day with a hot spot temperature of 116 °C, it ages by 8 days (V= 8, Table 1) during this time. However, in practice, eq. (3) cannot be used, since the surrounding temperature and the load level of the transformer change continuously. Therefore, the following integration should be used for a given operating time T. (4) with T t1- t2 t1 Start time t2 End time. Cooling of the transformers It is recommended to control the hot spot temperature using appropriate cooling measures because this has the largest influence...

Figure 3. Basic functional schematic of transformer monitoring module TMM Figure 4. Advanced control circuit for calculating the hot spot temperature according to IEC 60354 with intelligent (“smart”) fan control Load factor I / In Hot spot to top oil temperature difference Hot spot temperature Coil exponent Measured oil temperature Hot spot temperature increase Expected hot spot tempera

Intelligent fan control Intelligent or “smart” fan control refers to pre-emptive control of the fan. The time delay component in Figure 4 is switched off to allow the hot spot temperature control to be determined. Using this process, the hot spot temperature immediately stops increasing when the load current increases and the fans are activated without delay. This results in a lower hot spot temperature and thereby a lower lifetime consumption. However, the time component remains active when calculating the lifetime consumption, since the hot spot can only be modelled realistically when the...

Figure 6. Extended basic functional schematic of transformer monitoring module TMM to play an important role in future concepts for medium and high voltage transformers. For the first time it is possible to input an important variable - the hot spot temperature - into the voltage regulator to enable optimal transformer operation. DIN VDE 57536: Belastbarkeit von Öltransformatoren. [Load on oil transformers] VDE Verlag, 1977. IEC Loading Guide for Mineral Oil Immersed Power Transformers. IEC Std 60354, September 1991. IEC Loading Guide for Mineral Oil Immersed Power Transformers. IEC Std...

Dipl.-Ing. (TU) Till Sybel Sales manager, A. Eberle GmbH & Co. KG, Nuremberg E-Mail: till.sybel@a-eberle.de www.a-eberle.de www.regsys.de Dipl.-Ing. (FH) Christian Schobert, Coordination for customer support and special programming, A. Eberle GmbH & Co. KG, Nuremberg E-Mail: christian.schobert@a-eberle.de