  The needs for improving observability of medium and low voltage distribution
networks has been significantly increased, in recent year. In this paper, we
focus on practical approaches for placement of affordable Measurement Devices
(MDs), which are providing three phases voltage, current, and power
measurements with certain level of precision. The placement procedure is
composed of a state-estimation algorithm and of a greedy placement scheme. The
proposed state-estimation algorithm is based on the Distflow model, enhanced to
consider the shunt elements (e.g., cable capacitances) of the network, which
are not negligible in low voltage networks with underground cables. The greedy
placement scheme is formulated such that it finds the location of minimum
required number of MDs while certain grid observability limits are satisfied.
These limits are defined as the accuracy of state-estimation results in terms
of voltage magnitudes and line currents over all nodes and lines, respectively.
The effectiveness of the proposed placement procedure has been validated on a
realistic test grid of 10 medium voltage nodes and 75 low voltage nodes, whose
topology and parameters were made available from the Distribution System
Operator (DSO) of the city of Geneva, Switzerland.
