A Laboratory Investigation of Ferroresonance in Cable-Connected Transformers

Results of a full scale laboratory investigation into the ferroresonance phenomenon are presented. The investigation consisted of energizing and de-energizing three-phase 13-kV padmounted distribution transformers with single-phase cutouts. Applied cable lengths ranged from 100 to 5000 feet. In addition to three- phase switching, the application of resistive loading from 1 to 4 percent was also investigated as a preventive measure. Results indicate that three-phase switching, the use of a wye-wye transformer with both neutrals grounded, and the presence of secondary load are all effective in the control of ferroresonant overvoltages.