Ferro-resonance in a series capacitor system supplying a submerged-arc furnace

This paper addresses a ferro-resonance problem encountered at two 30 MVA submerged-arc furnaces resulting in unnecessary furnace downtime. The electrical supply system under consideration includes a series capacitor battery system in conjunction with a step down furnace transformer. A mathematical model is used to explain how the electrical supply system brings about saturation in the core of the furnace transformer and then describes how the electrical system reacts to this phenomenon. The typical submerged-arc furnace characteristics that triggers the ferro-resonance response is identified and explained in order to furnish an understanding of the severity of the problem.