  An electric power distribution system is operated in several distinct radial
topologies by opening and closing of system's sectionalizing and tie switches.
The estimation of the system's current operational topology is a precursor to
implementing any optimal control actions (during normal operation) or
restorative actions (during outage condition). This paper presents a
mathematical programming approach to estimate the operational topology of a
three-phase unbalanced power distribution system under both outage and normal
operating conditions. Specifically, a minimum weighted least absolute value
estimator is proposed that uses the line flow measurements,
historical/forecasted load data, and ping measurements and solves a
mixed-integer linear program (MILP) to estimate the operational topology and
any outaged sections simultaneously. We thoroughly validate the accuracy of the
proposed approach using IEEE 123-bus and a 1069-bus three-phase multi-feeder
test system with the help of numerous simulations. It is observed that the
approach performs well even at high percentages of measurement errors.
