  Accurate network topology information is critical for secure operation of
smart power distribution systems. Line outages can change the operational
topology of a distribution network. As a result, topology identification by
detecting outages is an important task to avoid mismatch between the {topology
that the operator believes is present and the actual topology}. Power
distribution systems are operated as radial trees and are recently adopting the
integration of sensors to monitor the network in real time. In this paper, an
optimal sensor placement solution is proposed that enables outage detection
through statistical tests based on sensor measurements. Using two types of
sensors, node sensors and line sensors, we propose a novel formulation for the
optimal sensor placement as a cost optimization problem with binary decision
variables, i.e., {to place or not place a sensor at each bus/line}. The
advantage of the proposed placement strategy for outage detection is that it
incorporates various types of sensors, is independent of load forecast
statistics and is cost effective. Numerical results illustrating the placement
solution are presented.
