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Electromechanical stress in transformers caused by inrush and short circuit currents

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Journal of the Brazilian Society of Mechanical Sciences and Engineering Aims and scope Submit manuscript

Abstract

The purpose of this paper is to present two methodologies, one being analytic in nature and the other computational, both with the objective of producing a diagnostic of the electromagnetic forces, along with the electromechanical stresses which occur in transformers due to inrush and short circuit currents. To reach the desired outcome, a computational model was developed using the finite element method in its three-dimensional version. The computational package used was FLUX 3D. It should be noted that this platform permits the study of inter-relationships between the electrical, magnetic and mechanical magnitudes. The electromagnetic and electromechanical results obtained through these computational simulations will be analyzed side by side with those self-same magnitudes, which have had their origin drawn from analytical calculations or project values. It should also be noted that these studies can be used as a benchmark when reaching a management and/or technical decision as to the best time to preventatively repair and/or substitute a transformer. Lastly, it should be highlighted that the procedures investigated here in are based upon fundamentals which should be used to guide the project as well as the construction of the transformer, especially when concerning those points linked directly to the windings’ mechanical support structure.

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Abbreviations

a c :

Conductor cross sectional area (m2)

b :

Axial height of conductor (m)

B :

Leakage flux density (T)

c :

Manufacturers constant for equivalent thickness

d 0 :

Duct width (m)

d 1 :

Equivalent duct width (m)

d e :

Radial thickness of outer winding (m)

d i :

Radial thickness of inner winding (m)

D m :

Diameter of the winding (m)

D mt :

Mean diameter of transformer (m)

e :

Radial thickness of the conductor (m)

E :

Modulus elasticity of the material (N/m2)

Espa :

Number of axial supports

E(δ):

Incremental modulus of elasticity at the critical value (N/m2)

f :

Volumetric density of the magnetic force (N/m3)

h :

Height of the winding (m)

I max :

Asymmetrical current of short circuit or inrush (A)

J :

Superficial current density (A/m2)

L ax :

Distance between the axial supports (m)

L rad :

Distance between radial supports (m)

n :

Number of turns on the winding

q :

Turns expressed as a fraction of the ampere-turns of one winding

s :

Width of radial spacers (m)

w :

Conductor axial dimension plus insulation (m)

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Acknowledgments

The authors would like to express their thanks for the financing of the strategic project by P&D of ANEEL: “Estresse Eletromecânico em Transformadores Causado pelas Altas Correntes de Energização (Inrush) e de Curtos-circuitos Passantes” with support and financial aid from Chesf-Companhia Hidroelétrica do São Francisco-Recife-PE-Brazil.

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Authors and Affiliations

  1. Faculdade de Engenharia Elétrica, Universidade Federal de Uberlândia, Uberlândia, Brazil

    Ronaldo Guimarães, Antônio C. Delaiba, Arnaldo J. P. Rosentino Jr., Elise Saraiva & José C. de Oliveira

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  1. Ronaldo Guimarães
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  2. Antônio C. Delaiba
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  3. Arnaldo J. P. Rosentino Jr.
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  4. Elise Saraiva
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  5. José C. de Oliveira
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Correspondence to Ronaldo Guimarães.

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Technical Editor: Fernando Forcellini.

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Guimarães, R., Delaiba, A.C., Rosentino, A.J.P. et al. Electromechanical stress in transformers caused by inrush and short circuit currents. J Braz. Soc. Mech. Sci. Eng. 37, 243–253 (2015). https://doi.org/10.1007/s40430-014-0150-2

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  • DOI: https://doi.org/10.1007/s40430-014-0150-2

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