  This paper presents an innovative approach to micro-phasor measurement unit
(micro-PMU) placement in unbalanced distribution networks. The methodology
accounts for the presence of single-and-two-phase laterals and acknowledges the
fact that observing one phase in a distribution circuit does not translate to
observing the other phases. Other practical constraints such as presence of
distributed loads, unknown regulator/ transformer tap ratios, zero-injection
phases (ZIPs), modern smart meters, and multiple switch configurations are also
incorporated. The proposed micro-PMU placement problem is solved using integer
linear programming (ILP), guaranteeing optimality of results. The uniqueness of
the developed algorithm is that it not only minimizes the micro-PMU
installations, but also identifies the minimum number of phases that must be
monitored by them.
