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Abb Technology Ag

Lassi Toivonen

Kari Rautiainen

Tero Talvitie

Olavi V&auml;h&auml;m&auml;ki

A power supply arrangement, especially in connection with a conductor ( ) of a medium-voltage overhead line, which arrangement comprises a power supply ( ) and a first and second element ( ) made of an electrically conductive material, which are connected electrically to the power supply for feeding energy to the power supply. The first element ( ) of the power supply arrangement is arranged to be close to the conductor ( ) and has a capacitance (Ce) to an element in a second potential, the capacitance being arranged to charge itself by effect of an electric field generated by the voltage of the medium-voltage conductor, and said second element ( ) is arranged to have a galvanic or capacitive connection with the conductor ( ) for feeding energy to the power supply ( ) from the potential difference between said first and second elements.

Power supply arrangement

This invention relates to a method for measuring the electrode-related electric quantities of an AC electric-arc furnace. The method is based on observing the mutual correlation between electrode currents and total power supplied into a furnace by utilizing the fast, natural fluctuation of currents and power supplies into a furnace, and on estimation observations. The information required in estimation is collected by performing a plurality of successive current and voltage measurements at adjacent instants and at various energy distributions of a furnace. The measurement results are used to calculably determine the estimates for electrode-related voltages, impedances and powers. It is further possible to split the electrode-related powers and voltages on the one hand in the electric-arc power and voltage and on the other hand in the power and voltage loss caused by resistive conduction. The effect of mutual impedances is automatically taken into account in estimation. If desired, the estimation can be performed independently at those frequencies, i.e., at the power system fundamental frequency and at harmonic and interharmonic frequencies which experience a significant transfer of energy. The method is useful in measuring both a furnace with neutral power connection and a furnace without neutral power connection. The measurements can be performed in the primary or secondary of the furnace transformer.

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Espoo, Finland

Lassi Toivonen