Electricity grid operators must carefully balance the flow of power from generators to homes, which they do with the help of time-stamped measurements of voltage and current, taken at substations.
These synchronised data points help track supply and demand, and support coordinated responses to faults – for example, if a power line goes down, sensors and switches must act in unison to protect the network and reroute electricity flows.
Managing electricity grids depends on access to a shared clock, with synchronised time signals delivered to every substation, so that a time stamp is the same at any given substation.
Today, those time signals mostly come from atomic clocks on GNSS satellites, but as demand increases, alternative time sources can provide valuable backup options.
The Innovate UK-funded NTOL (NPL Time Over eLoran) project brought together Chronos Technology and the University of Strathclyde to demonstrate that traceable time signals from the National Physical Laboratory (NPL) could be broadcast over radio waves, using one of the UK’s eLoran transmitters. Electricity substations were chosen as the demonstration case to show how such signals could be received and used by industry.
The eLoran transmitter sends out high-power, low-frequency radio waves. The high power makes it harder to jam, whilst the low frequency means it can penetrate buildings, reaching places where signals from satellites might struggle. That gives it a very different profile to high-frequency, low-power satellite signals, making it a robust and complementary method of transmitting timing signals.
Linking radio transmissions to UK time
The project used time signals from NPL’s Innovation Node at Strathclyde – established through the National Timing Centre (NTC) programme’s research and development phase. This node hosts a caesium clock, synchronised to the national time scale, UTC(NPL).
The team used a satellite link to compare Strathclyde’s clock to the eLoran transmitter’s clocks, with a correction then sent to the eLoran clocks to anchor it to NPL’s time. Whilst satellites were used to calibrate the eLoran clocks, those clocks are accurate enough to maintain reliable time during a temporary loss of the satellite link.
Distributing traceable time signals to substations
The NPL-linked time signal was then tested in a real substation environment in Strathclyde’s Power Networks Demonstration Centre (PNDC). Substations equipped with eLoran receivers successfully used the signals to synchronise key monitoring and protection systems. Comparisons between existing approaches and this new approach showed no discernible difference in system performance.
In delivering these time signals via eLoran, the project had to overcome several technical challenges around integrating timing components with legacy equipment, managing signal reception in noisy electrical environments, and ensuring NPL traceability through an offset calculation.
The impact
The project proved the concept of an end-to-end timing chain that can deliver trusted signals from NPL clocks to end users in industry sectors – in this case energy – via the eLoran broadcast, all using existing timing and transmission equipment.
This architecture could ultimately be used to distribute resilient timing to end users through eLoran, or other terrestrial radio transmission methods.
This will strengthen the resilience of infrastructure and other time-dependent industries. It also supports the UK government’s ambition – led by the Department for Science, Innovation and Technology – to build a sovereign, resilient timing infrastructure, and position the UK as a leader in timing systems that could be adopted internationally.
“We have shown that we can adapt and integrate existing technologies to deliver a resilient UK timing signal to critical industries. This was made possible thanks to the NPL traceable time signals at the Strathclyde Innovation node as well as the power and timing expertise at Strathclyde and NPL.”
Calum Dalmeny, Technical Director – Chronos
“This is a strong example of the UK leading the way on timing innovation. Provision of an NPL traceable time source available at the Innovation Node offers a compelling value proposition for those developing and benefitting from resilient timing applications. These timing signals provide the foundation for timing innovations that are hugely valuable to industry, and that has been showcased here through a collaborative project with complementary expertise.”
Ibrahim Abdulhadi, Lead R&D Engineer – PNDC, University of Strathclyde
