Monitoring power system response to UHP arc furnace operations

Electric arc furnaces of the ultra-high-power (UHP) design range have ratings from 20 to over 100 MW. UHP are furnaces, with their large connected loads, are frequently the largest single power consumer in a given section of a power grid. Their operation, therefore, is of serious concern to the power utility. The refiring period at maximum power level is what has been identified as the area of main concern. During this period, the arc tends to cause distortions of the voltage and current waveforms. The combination of the nonlinear arc resistance and the relatively large but linear external reactance results in distortions to the supply voltage at the point of common coupling (PCC). A PC-based data acquisition system has been developed. This was used to measure the voltage and current waveforms at the PCC during various furnace operational modes. From the data acquisition system, the instantaneous and RMS values in the power system were measured at 100000 samples per second and displayed. The operation of a 40 MW arc furnaces at maximum power causes no serious problems on the electric system. However, during the ramping up stage and for loss of a furnace while operating at maximum load, there are measurable changes in the voltage and current profile.<>