  The feeder reconfiguration problem chooses the on/off status of the switches
in a distribution network in order to minimize a certain cost such as power
loss. It is a mixed integer nonlinear program and hence hard to solve. A
popular heuristic search consists of repeated application of branch exchange,
where some loads are transferred from one feeder to another feeder while
maintaining the radial structure of the network, until no load transfer can
further reduce the cost. Optimizing each branch exchange step is itself a mixed
integer nonlinear program. In this paper we propose an efficient algorithm for
optimizing a branch exchange step. It uses an AC power flow model and is based
on the recently developed convex relaxation of optimal power flow. We provide a
bound on the gap between the optimal cost and that of our solution. We prove
that our algorithm is optimal when the voltage magnitudes are the same at all
buses. We illustrate the effectiveness of our algorithm through the simulation
of real- world distribution feeders.
