T. Keikko, T. Sauramäki, S. Kuusiluoma, and L. Korpinen (Finland)
Transmission lines; Magnetic field;Approximation methods.
The aim of this paper was to study magnetic field under the transmission lines with different calculation methods. Analytical method (accurate), FEM and approximated method developed by Kaune and Zaffanella were used. The sensitivity and suitability of the approximated method for transmission line calculations were studied by comparing the results to the calculation results of other methods. First the general situation (phases positioned horizontally) was calculated. The results of maximum magnetic flux density for a 20 kV horizontally positioned line (current 100 A) was 1.1 µT, 3.4 µT for 110 kV transmission line (299 A) and 14 µT for 400 kV transmission line (777 A). Then different line geometries were studied and magnetic flux densities were lower than for horizontally positioned lines. In addition, a special environment example (transmission line above the water) was modeled and calculated. The accuracy of the approximated method was good enough for 20 kV (maximum error -5.4 - +4.7%) and 110 kV (-5.6 - +10%) lines in practical calculations but not for 400 kV lines.
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