Abstract—High penetration levels of distributed energy resources (DER) and active loads in the distribution grid can change the traditional grid from a slower-changing radial network to a multi-source network with faster dynamics. Although overall system reliability and quality of supply can in principle be improved under this paradigm, new control and protection challenges could arise that may not be adequately addressed using the traditional approaches. The conventional control and management of the distribution grid where only voltage magnitudes are measured and utilized at the control center could undermine these new dynamics and may potentially lead to severe complications in grid operation. A system-wide dynamic analysis and control of the distribution grid therefore seems crucial for optimal system operation. This would require new phasor data, coming from Phasor Measurement Units (PMU), to be incorporated into the functions of Distribution Management System (DMS). This paper discusses the potential applications within the DMS that can benefit from PMU data. Index Terms—Phasor Measurement Unit, Synchrophasor, Distributed Energy Resource, Distribution Management System, Microgrid, Smart Grid. I. INTRODUCTION HASOR Measurement Units (PMU) have been in use in the power transmission system (110kV and above) in order to provide accurate voltage phasor measurements, to be used in various control, protection, and monitoring applications. Traditionally at the distribution level (34.5kV and below), and in the absence of a widespread penetration of DER and active loads with dynamics (e.g., demand responsive loads, electric vehicles), the bus voltages are denoted by their magnitudes only, and the phase angle measurements, often due to their generally small values, have not been of great interest to the utility engineers. However, with the projected penetration (in excess of 30% in some areas) of DER and active loads under the Smart Grid paradigm things are likely to change. New dynamics are introduced in the distribution grid, especially in the stand- alone applications of Microgrids, which did not exist before. Rotating machine based DERs, with their corresponding power angle and rotor speed, introduce additional dynamics into the grid. Non-dispatchable energy resources such as small scaled J. Sexauer is with PJM Interconnection in Valley Forge, PA, 19403, USA (e-mail: sexauj@pjm.com). At the time of this work, he was with the Electrical Engineering and Computer Science Department, Colorado School of Mines, Golden, CO 80401, USA. P. Javanbakht and S. Mohagheghi are with the Electrical Engineering and Computer Science Department, Colorado School of Mines, Golden, CO 80401, USA (e-mail: pjavanba, smohaghe@mines.edu). wind turbines and rooftop photovoltaic panels –if deployed in large numbers– are likely to introduce a higher level of fluctuations in the voltage, power, and perhaps even frequency in specific islanded operation modes. In addition to all this, a high penetration level of DER in the grid –dispatchable or non-dispatchable– will transform the distribution system from a traditionally radial network to one with multitude of doubly- fed lines and bidirectional flow of power. All this could introduce new challenges in planning, monitoring, control, management and protection of the distribution grid, which would require a dynamic analysis and control of the grid taking into account not just the voltage magnitudes, but the phase angles as well. This situation would therefore justify the need for measuring voltage and current phasors in the distribution grid. Accurate phasor measurement can be achieved by deploying dedicated PMUs across the distribution grid, or utilizing the built-in phasor measurement functionality of many protective relays. The new dynamic snapshot of the system developed in this way can now be incorporated into the distribution management system (DMS) in order to provide monitoring, control, energy management and protection schemes more suitable for this new situation. The focus of this paper is on potential applications of PMUs at the distribution level, and the benefits gained from their deployment in the grid. Some case studies are also provided on the IEEE 34-bus system to show how penetration of renewable energy resources can change the quasi-steady-state nature of the distribution grid. II. PHASOR MEASUREMENT UNIT Steady state sinusoidal quantities of the power system are best represented through phasors. A sinusoidal function x(t) with magnitude X m and phase angle δ can be expressed as a phasor X: ) . cos( ) ( δ ω + = t X t x m δ . ) 2 / ( . j m i r e X X j X X × = + = (1) The concept of synchronized phasor, also commonly referred to as synchrophasor, was then introduced as a phasor calculated from data samples using a standard time signal as the reference for the measurement [1]. A phasor measurement unit (PMU) is a device that measures the voltage and/or current waveforms at the point of connection to the grid, using synchronized sampling by means of a common time reference for all locations, commonly facilitated through the Global Phasor Measurement Units for the Distribution Grid: Necessity and Benefits Jason Sexauer, Student Member, IEEE, Pirooz Javanbakht, Student Member, IEEE Salman Mohagheghi, Member, IEEE P