This work presents the results of observing the oxidation stage of steelmaking in EAF-135 with the help of an automated control system of electrical characteristics. The workspace of the furnace has three main zones which differ by the physical state of materials in them: arc discharge, melt and foamed slag. The data on the distribution of electric power over the furnace zones are given. It is shown that the main factors impacting the melt and slag resistances are oxygen blowing and motion of electrodes. The influence of magnesia flux feeds on the melt resistance is studied. It is noticed that these feeds correspond to a sharp increase and subsequent gradual decrease in the resistance, whereas the dope congestion time does not exceed one minute. The average electrical parameters of the workspace zones are given for single heats in EAF-135. The nature of the change in the arc discharge power and the change in the melt temperature are compared. It is noted that the profiles of changes in these characteristics match one another, and the rise in the arc power corresponds to the rise in the melt temperature. An attempt to correlate the FeO content in slag with the arc power has not given a positive result. It is noted that the control of this parameter by changes in the electrical parameters of the arc and the slag zone due to the overwhelming influence of intense oxygen blast, melt mixing and electrode motion does not meet the reliability criterion. However, this method should be checked at the refining of steel in the ladle-furnace unit.