In the case of three-phase arc furnaces, two types of asymmetry can be distinguished: constructional and operational. The structural asymmetry is related to the construction of high-current circuits supplying the arc furnace. The knowledge of the parameters of the high-current circuit allows to determine the operating characteristics of the arc device. The author proposed a method for calculating the real values of the resistance and reactance of the high-current circuit. For this purpose, tests were made to short-circuit the electrodes with the charge. During the short-circuit, with the use of a power quality analyzer, measurements of electrical indicators were carried out, which allow to determine the parameters of the high-current circuit. A new method for determining voltage operational unbalance is also presented in this paper. The theoretical considerations presented in the article were verified in industrial conditions.