  Sensing and measurement systems are quintessential to the safe and reliable
operation of electric power grids. Their strategic placement is of ultimate
importance because it is not economically viable to install measurement systems
on every node and branch of a power grid, though they need to be monitored. An
overwhelming number of strategies have been developed to meet oftentimes
multiple conflicting objectives. The prime challenge in formulating the problem
lies in developing a heuristic or an optimization model that, though
mathematically tractable and constrained in cost, leads to trustworthy
technical solutions. Further, large-scale, long-term deployments pose
additional challenges because the boundary conditions change as technologies
evolve. For instance, the advent of new technologies in sensing and
measurement, as well as in communications and networking, might impact the cost
and performance of available solutions and shift initially set conditions.
Also, the placement strategies developed for transmission grids might not be
suitable for distribution grids, and vice versa, because of unique
characteristics; therefore, the strategies need to be flexible, to a certain
extent, because no two power grids are alike. Despite the extensive literature
on the present topic, the focus of published works tends to be on a specific
subject, such as the optimal placement of measurements to ensure observability
in transmission grids. There is a dearth of work providing a comprehensive
picture for developing optimal placement strategies. Because of the ongoing
efforts on the modernization of electric power grids, there is a need to
consolidate the status quo while exposing its limitations to inform
policymakers, industry stakeholders, and researchers on the
research-and-development needs to push the boundaries for innovation.
