The Simulation of Loop Flow in Radial Distribution Analysis Programs

Distribution systems are typically composed of radial feeders. Radial means that there is only one path of current flow to each of the loads on the feeder. There are times when it becomes necessary to form a loop in a feeder by closing switches. This may be because of an outage or a new load that will cause the radial current to exceed the conductor current rating or violate the American National Standards Institute voltage requirement. This paper will present a method for simulating the loop flow using an injection current technique. A simple single-phase circuit is used to demonstrate the steps in the simulation. Following that, the IEEE 13 bus test feeder will be studied as it is right now, followed by the addition of a new three-phase load at one bus and a new single-phase load added at another bus. Both of these loads are going to require the addition of new lines and the capability of operating the feeder with one or two closed loops. The process for simulating the closed loops will be presented.