This project presents a linear zed, three-phase, and distribution class state estimation algorithm for applications in smart distribution systems. Unbalanced three-phase cases and single-phase cases are accommodated. The estimator follows a complex variable formulation and is intended to incorporate synchronized phasor measurements into distribution state estimation. Potential applications in smart distribution system control and management are discussed. Index Terms in this project are Distribution management systems, distribution system monitoring and control, distribution system state estimation, power distribution engineering, synchronized phasor measurements, three-phase unbalance.