A new method in reducing the overcurrent protection response times at high fault currents to protect equipment from extended stress

This paper describes a new method for protecting power equipment from extended stresses during high fault current conditions. This was achieved using a universal protection device with a software platform that can facilitate designing time-current characteristic (TCC) curves of different shapes, all in the same hardware. When combined, recloser control and relay response times are faster and more accurate than with conventional means. Reduced device response times are achieved by combining different overcurrent TCCs. A coordination example is presented for a typical distribution system loop scheme containing new multifunction relays and reclosers. The advantages of using integrated device functions over standard overcurrent relays and recloser controls are illustrated. A comparative analysis is presented to quantify the reduction in let-thru I/sup 2/t values and equipment stress that can be realized using this method during high fault current conditions.