  The ever-increasing deployment of distributed resources and the opportunities
offered to loads for more active roles has changed the previously
unidirectional and relatively straight-forward operating profile of
distribution systems (DS). DS will be required to be monitored closely for
robustness and sufficient power quality. State estimation of transmission
systems has consistently served as a monitoring tool, which drives system-wide
control actions and, thus, ensures the operational integrity of the electric
grid. An update to the classic state estimation for the case of DS is offered
in this work, based on a power flow formulation for radial networks that does
not require measurements or estimate of the voltage angles.
