Experimental Study of Clamping Pressure during Step Loading of Power Transformer with and without Prior Energisation

Inge Madshaven (), Henrik Enoksen, Lars E. Lundgaard, Stefan Jaufer, Christoph Krause, Borut Prašnikar and Asgeir Mjelve
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Inge Madshaven: SINTEF Energy Research, 7034 Trondheim, Norway
Henrik Enoksen: SINTEF Energy Research, 7034 Trondheim, Norway
Lars E. Lundgaard: SINTEF Energy Research, 7034 Trondheim, Norway
Stefan Jaufer: Weidmann Electrical Technology AG, 8640 Rapperswil, Switzerland
Christoph Krause: Weidmann Electrical Technology AG, 8640 Rapperswil, Switzerland
Borut Prašnikar: Kolektor Etra d.o.o., 1231 Ljubljana-Crnuce, Slovenia
Asgeir Mjelve: Elvia AS, 0275 Oslo, Norway

Energies, 2024, vol. 17, issue 12, 1-12

Abstract: The electrification of society, increasing renewable energy sources and mobility charging lead to new loading patterns for power transformers. Dynamic load conditions induce enhanced mechanical stress on the transformers’ windings, potentially causing degradation of the solid insulation over time and compromising the transformer’s short-circuit withstand capability. Thermal expansion of the windings, caused by losses in the copper conductors, occurring as the transformer is loaded, increases the stress. Conversely, magnetic losses in the core and tie plate expansion contribute to a reduction in stress. This paper presents the effect of step changes in core losses and copper losses by on-line measurements of the clamping pressure, to better understand the mechanical stresses acting upon the solid insulation cellulose materials. Energisation is found to decrease the clamping pressure following warming up of the transformer, and loading the transformer increased the pressure as the windings increased in temperature. The converse effect was found when unloading and de-energising. The on-line monitoring system provides a new and important step towards ensuring the short-circuit performance of power transformers.

Keywords: power transformer; clamping pressure; transformer energisation; transformer loading; short-circuit performance; on-line measurements (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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