Monitoring and supervision of overhead power lines have become essential actions in Electrical Power Systems since the introduction of the Smart Grid concept. In order to monitor overhead power lines, simple non-invasive devices are mounted on support poles, which detect line abnormalities and faults by measuring magnetic field originating from power line conductors. Measured signals are also used to determine various electrical and non-electrical line parameters. In this paper a new

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... model for magnetic flux density vector components of the overhead power lines suitable for real-time conductor sag estimation is presented. In the proposed model, catenary-shaped power line conductors are approximated with tilted straight line conductors, and the approximate model is calibrated by tuning model coefficients to match flux density vector components as in the case of real catenary-shaped conductors. The accuracy of the proposed model is verified by measurements on three-phase overhead power line model scaled to laboratory conditions. As a conclusion, an adaptive method for possible practical implementation based on the approximate model is considered.