Comparison of different iron core models of three‐phase core‐type transformers

• Matjaz Dolinar ^[1] ; Drago Dolinar ^[2] ; Gorazd Stumberger ^[2] ; Bostjan Polajzer ^[2]
  1. [1] University of Ljubljana

     University of Ljubljana

     Eslovenia

     
  2. [2] University of Maribor

     University of Maribor

     Eslovenia

     
• Localización: Compel: International journal for computation and mathematics in electrical and electronic engineering, ISSN 0332-1649, Vol. 26, Nº 4 (Selected papers from the 19th Symposium on Electromagnetic Phenomena in Nonlinear Circuits 2006), 2007, págs. 1049-1062
• Idioma: inglés
• Enlaces
  • Texto completo
• Resumen

  • Purpose – The majority of three‐phase dynamic transformer models used in commercially available electric power system transient simulation programs offer only saturated three‐phase transformer models built from three single‐phase transformer models. This paper sets out to deal with the modelling and transient analysis of a saturated three‐limb core‐type transformer.

    Design/methodology/approach – Three iron core models I‐III are given by the current‐dependent characteristics of flux linkages. In the first model, these characteristics are given by a set of piecewise linear functions, which include saturation. In the second model, the piecewise linear functions are replaced by the measured nonlinear characteristic. The more complex third model is given by a set of measured flux linkage characteristics.

    Findings – The behaviour of transformers used in electric power applications depends considerably on the properties of magnetically nonlinear iron core. The best agreement between the calculated and measured results is obtained by use of the most complex iron core model III, which takes into account magnetic cross‐couplings between different limbs, caused by saturation.

    Research limitations/implications – Measurement of the current‐dependent flux linkage characteristics of the 0.4 kV, 3.5 kVA laboratory transformer requires corresponding excitation of windings by three independent linear amplifiers. Current‐dependent flux linkage characteristics of the larger power transformer can be determined either by similar measurement with linear amplifiers of an appropriate power or by extracting them from the calculated magnetic field, which is done by the finite element method.

    Practical implications – A three‐phase dynamic transformer model with the obtained iron core model III is suitable for the numerical analysis of nonsymmetric transient states in power systems.

    Originality/value – This paper presents a three‐phase dynamic transformer model with an original iron core model III, which accounts for magnetic cross‐couplings between different limbs, caused by saturation.