Xen Lab

Motivation and Challenge

Recent decline in the reliability of the energy grid have led to a major thrust to modernize the grid. The new technologies aim to create a power deliver network which is distributed, self healing, able to seamlessly incorporate renewable resources, and promotes consumer involvement. New control methodologies, modeling techniques, networks, and sensor technologies aim to make the grid “Smart”.

Hence, ‘Network Clock Synchronization’ has quickly become a critical component in developing reliable monitoring systems. The ability to take measurements and be aware of the position and time at which the measurement was taken allows information systems to reconstruct wide area snapshots of the condition of the grid in close to real-time. Disturbances can be identified before they become critical and control actions can be taken based upon this extra information.

IEEE 1588 Precision Time Protocol (PTP) is the clock synchronization technique that will push technology forward. It provides synchronization within a microsecond, the limit needed for critical sequence of event recording and accurate wide area measurement of system dynamics. While the technology exists, in many cases the potential of PTP has yet to be realized and there is a major thrust to determine the best implementations of the protocol.

Overview of the Work

The Xen (eXperimental Energy Networks) Lab at the University of Michigan specializes in testing IEEE 1588 implementations and developing best practices for the power industry. The current focus is on the simulation and integration of PMUs (Phasor Measurement Units) into substation topologies.
This includes two thrusts:

  • Test-bed to test integration of devices
  • OPNET simulation to create realistic networks and background traffic

The simulation will extend by creating a realistic background network in terms of nodes, distance, and traffic loads. The test-bed will then be used to examine the performance of various devices under substation and wide area network loads.


  • Develop test metrics to test device performance with respect to IEEE 1588.
  • Develop models of real world devices for use in simulation.
  • Create test methodology to replicate real world networks in simulation.
  • Integrate physical devices into simulation backbone.
  • Evaluate device and network performance based upon testing metrics.
  • Note best practices for future reference.

Preliminary Results

  • Evaluation of transparent clock performance in conjunction with NIST (National Institute of Standards and Technology) test-bed.
  • Demonstrated difference in IEEE 1588 slave device clock drift and synchronization performance
  • Evaluation of current IEEE 1588 technologies and implementations.

Current Status

  • The network simulation environment is currently under development. First stages involve identifying existing OPNET libraries related to IEEE 1588 and Smart Grid technologies. Models will be created to represent the missing devices.
  • The test-bed has been integrated with additional devices at NIST to expand the number of nodes available for testing.

Future Milestones

  • Testing of metrics on a realistic simulation.
  • Integration of device test-bed and OPNET simulation.
  • Testing of device performance with simulation background.
  • Report on device performance, metrics, and best practices.
  • Develop control methodologies based upon experiences.


  • Identify issues with clock synchronization.
  • Evaluate device performance in realistic settings.
  • Better understanding of control with clock synchronization.
  • Reduce the need for dedicated GPS servers.
  • Utilize existing Ethernet networks for clock synchronization when possible.


  • Evaluation of existing OPNET models related to the research.
  • Characterization of additional devices which require modeling.
  • Presentation to IEEE PSRC/PSSC WG H7/SubC7 regarding clock synchronization.
  • Testing metrics for IEEE 1588.
  • Internship at NIST in 2010.
  • Simulation framework for future network testing.

The Xen lab uses software sponsored by OPNET Technologies. Click here to find out how OPNET software is being used in the Xen lab.

Contact Information

Dr. James Moyne

Associate Research Scientist

P| 734-516-5572

F| 734-615-6575

E| [email protected]

Jeff Fletcher

Graduate Student Researcher

Engineering Research Center for Reconfigurable Manufacturing Systems

2350 Hayward Street

1531 HH Dow Ann Arbor, Michigan 48109-2125

P| 734-764-4336

F| 734-763-5700

E| [email protected]