Certifying Precision Timing in the Smart Grid

power magazine logo

Utilities deploying precise timing in their networks have an additional choice in evaluating solutions based on whether or not the devices are IEEE certified for compliance to the appropriate IEEE 1588 Power Profile. To reach this point, years of effort from the IEEE, International Electrotechnical Commission (IEC), National Institute of Standards and Technology (NIST), and the University of New Hampshire InterOperability Laboratory (UNH-IOL) have come together to enable this option now going through pilot testing.

The distribution of precise timing across common networking infrastructure is ubiquitous in many applications, including power, automotive, industrial, and telecommunications. Common underlying timing standards such as IEEE 1588 for Precision Time Protocol (PTP) have thus gained in popularity, as various PTP profiles of the IEEE 1588 address the market-specific needs. For the smart grid, standards development organizations such as IEC and IEEE have recently completed updates for their IEEE 1588 Power Profiles to aid utility companies in the specification of their timing networks.

How, though, does a utility or a supplier know if their product meets the expectations of the standard and its profiles? The NIST Smart Grid Program seeks to ensure that standards relevant to the smart grid have associated testing and certification programs to provide confidence to utilities that implementations conform to the requirements with appropriate oversight of an industry test program operator.

With the recent publications of the PTP Power Profiles, the IEEE-SA Conformity Assessment Program (ICAP) has established a path toward certification for the power industry. Through grant support from NIST, and review and assistance from a committee of experts organized by the ICAP, the UNH-IOL has produced the Test Suite Specification (TSS) test plan to govern the initial certification program. A committee of experts, known as the Conformity Assessment Steering Committee (CASC) includes representatives from NIST, UNH-IOL, IEEE-SA, the Oak Ridge National Laboratory, as well as utilities, such as Bonneville Power Administration and AltaLink.

Distributed energy resources such as solar and wind are just one example of the evolving grid. Such microgrids need to synchronize their inverters with the grid. Similarly, the use of synchrophasors to monitor grid health over a large geographic area continues to expand. Such Phasor Measurement Units (PMUs) require clock synchronization accuracy in microseconds to minimize errors in the phase-angle measurement. Fault detection tools benefit from precision clock synchronization to pinpoint transmission line faults to within hundreds of meters. Event data recorders similarly need to log in a common time base over large regions.

By way of these brief examples, precise time is used in today’s smart grid to monitor the health of the current grid, enabling automation of control decisions in dynamic environments. In the event of fault, event logs will more rapidly find and remedy grid failures. For such reasons, utilities benefit from deploying certified equipment, allowing for the potential consideration of intelligent electronic devices from various suppliers with greater confidence in their underlying functionality and interoperability.

To this end, the UNH-IOL’s IEEE 1588 Testing Service has developed the TSS, as well as a conformance test tool to aid in automating the required validation. Working closely with ICAP and NIST, the UNH-IOL is also hosting a pilot program that is currently open and continues to welcome participants (Figure 1). These tests are designed to validate the conformance of an implementation to the IEC/IEEE 61850-9-3 standard, and to the additional requirements of the IEEE C37.238 standard, if supported by the device under test.