New technology for looped distribution feeders

Two distribution feeders, each with one or more midline overcurrent protective devices, can be tied together through a normally-open tie point to restore service to unfaulted sections of line, creating a ldquoloopedrdquo distribution system. This practice provides an alternate source of supply and reduces the impact of faults, thereby improving electric service reliability.Conventional looped distribution systems rely on overcurrent coordination to ensure that the correct device in a loop clears a particular fault. However, properly coordinating a large number of devices in series has practical limitations. This paper outlines a new technology - referred to as pulse closing - that enhances the conventional loop system concept by testing the line for a fault without actually reclosing into the fault. This reduces thermal and mechanical stresses on substation transformers and other power system equipment by eliminating the repeated occurrence of high-magnitude fault currents. Pulseclosing can be used to expand a distribution loop into an almost unlimited number of series overcurrent protective devices by overcoming the coordination constraint since faults are detected without using Time-current characteristic (TCC) curves. Maximum system restoration will be achieved within seconds of the initial fault detection. These advancements are all achieved without requiring communication between devices.