The Finnish high tech company Real Time Systems has recently developed an advanced electrode control system that compared with conventional systems offers substantially higher productivity and reduced specific energy consumption in electric arc furnaces.

The first version of the system was tested in 2008 in a full scale trial during normal steel production on a Swedish arc furnace with an active power of 70 MW and currents of 60 kA.

Dr Lassi Toivonen at Real Time Systems said that "By examining the results we came to the conclusion that it would have been possible for the mill to produce about 45,000 tonnes more steel per year just by installing our system. At the same time the energy consumption per steel tonne was reduced by over 3%."

Since then RTS has developed the system further. The new computation unit is significantly more powerful and can track the process quantities in real time. The electrodes are moved more smoothly, which leads to reduced fluctuation of current and power, and also gives the actuators a longer life cycle.

According to Dr Toivonen, the new system was recently tested in a 120 MVA furnace of a Finnish steel mill with good results. He said that "We have developed the estimation methods for process quantities so that it’s now possible to obtain reliable electrode resistances, which has not been possible before. It also allowed us to implement an electrode resistance control that is superior over the conventional impedance control. This makes it possible to predict the mutual interaction of electrode resistances when the electrodes are moved and compensate for the resistance changes. Due to this there is no need for the endless and sometimes uncontrolled chain of subsequent adjustments that often take place in conventional electrode control."

He explained that "Normally, when you adjust one electrode, its effect on other electrodes must be compensated for. Then you have to re adjust the first electrode again to compensate for the control actions made on the other electrodes and so on. As our system adjusts the electrodes as an entity, we are able to achieve more stable currents and power than it is possible with conventional electrode control systems."