Among the many important, yet weak, satellite signals that can be disrupted by space weather, the Global Positioning System (GPS) is undoubtedly the most important and the weakest. Two recent public discussions have highlighted the challenges this poses for the national electrical grid, both today and going forward.
In March 2016, the MITRE Corporation released information on “Smart Grid Use of GPS Time.” The posted presentation stated that, “(The) Power Grid has a vital dependence on precise time for:
Time-stamping of operational data (e.g., supervisory control and data acquisition – SCADA)
Wide area situational awareness
Synchronization of operations
Grid management and control
System and asset protection”
MITRE’s most recent effort built upon a 2013 paper that specifically enumerated all the places where GPS timing information was used by electrical grids such as fault detection, substation control, and in SCADA systems.
In May 2016, Alison Silverstein of the North American SynchroPhasor Initiative (NASPI) spoke to the National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board. As part of a presentation with Netinsight, Silverstein downplayed the use of GPS time in the grid today, but indicated that it was going to be increasingly important going forward. She did acknowledge, though, that the grid is critically dependent on telecommunications and information technology networks, and that those networks are critically dependent on GPS time. Several examples of problems with the GPS signal, such as the January 2016 SVN23 anomaly (when half of the GPS satellites’ time transmissions were off by 13.7 microseconds) and faulty installations – and their impact on electrical grids – were discussed. Going forward, she said, the electric power industry would be looking for more reliable, stable sources for wide-area synchronized time signals.
At the same PNT Advisory Board meeting, Andy Proctor, lead for satellite navigation at Innovate UK and chair of the UK Government PNT Group, mentioned that his country was keeping eLoran on the air to provide timing for critical infrastructure and other uses. Theea is to combine eLoran, GPS, and Europe’s Galileo satellite navigation and timing system signals as a way of providing trusted time to electrical, telecommunications, and information technology networks.
Pairing eLoran and GPS signals has currency in the United States as well. In December 2015, Department of Defense Deputy Secretary Robert Work and Department of Transportation Deputy Secretary Victor Mendenz told the U.S. Congress that the administration would build an eLoran timing system to help protect critical infrastructure. Unfortunately, little appears to have been done so far.
Dana A. Goward
Dana A. Goward is the president of the Resilient Navigation and Timing Foundation, a scientific and educational charity in northern Virginia. He spent several decades as a first responder piloting Coast Guard helicopters, and was serving as the maritime navigation authority for the United States when he retired from federal service.