  This paper considers the problem of fault detection and localization in
active distribution networks using PMUs. The proposed algorithm consists in
computing a set of weighted least squares state estimates whose results are
used to detect, characterize and localize the occurrence of a fault. Moreover,
a criteria to minimize the number of PMUs required to correctly perform the
proposed algorithm is defined. Such a criteria, based on system observability
conditions, allows the design of an optimization problem to set the positions
of PMUs along the grid, in order to get the desired fault localization
resolution. The performances of the strategy are tested via simulations on a
benchmark distribution system.
