Measurements show need for transformer core joint details in finite element modelling of GIC and DC effects
ISSN: 0332-1649
Article publication date: 8 May 2018
Abstract
Purpose
This paper aims to improve the finite element modelling of transformers subjected to DC excitation, by including core joint details.
Design/methodology/approach
Geomagnetically induced currents (GICs) or leakage DC can cause part-cycle, half wave saturation of a power transformer’s core. Practical measurements and finite element matrix (FEM) simulation were carried out using three laboratory-scale, untanked single-phase four limb transformers resembling real power transformers in terms of the core steel and parallel winding assemblies. “Equivalent air gaps” at the joints, based on AC measurements, were applied to the FEM models for simultaneous AC and DC excitation.
Findings
Measurements confirm that introducing equivalent air gaps at the joints improves the FEM simulation of transformers carrying DC.
Research limitations/implications
The FEM simulations based on the laboratory transformers are exemplary, showing the difference between modelling core joints as solid or including equivalent air gaps. They show that, for more representative results, laboratory transformers used for research should have mitred core joints (like power transformers).
Originality/value
This research shows why joint details are important in FEM models for analysing transformer core saturation in the presence of DC/GICs. Extending this, other core structures of power transformers with mitred joints should improve the understanding of the leakage flux during half-wave saturation.
Keywords
Acknowledgements
Powertech Transformers, South Africa, provided the power transformer data and simulation facility for the preliminary FEM study. The test transformers and the material and design information were provided by Royal Smit Transformers, The Netherlands. Infolytica Corporation supplied an academic license and support for FEM simulation. Eskom Holdings, Brackenfell provided the testing facilities. Small equipment and instruments were supplied by the University of Cape Town.
This paper forms part of a special section “The 5th Advanced Research Workshop on transformers (ARWtr2016)”, guest edited by Xose M. Lopez-Fernandez.
Citation
Chisepo, H.K., Borrill, L.D. and Gaunt, C.T. (2018), "Measurements show need for transformer core joint details in finite element modelling of GIC and DC effects", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 37 No. 3, pp. 1011-1028. https://doi.org/10.1108/COMPEL-11-2016-0511
Publisher
:Emerald Publishing Limited
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