A sub-μs accuracy GPS alternative using electrical transmission grids as precision timing networks

Robson, Stephen ORCID: https://orcid.org/0000-0003-3156-1487 and Haddad, Manu Abderrahmane ORCID: https://orcid.org/0000-0003-4153-6146 2024. A sub-μs accuracy GPS alternative using electrical transmission grids as precision timing networks. Scientific Reports 14 , 8696. 10.1038/s41598-024-56296-8

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Abstract

It is widely recognised that over-reliance on GNSS (e.g GPS) for time synchronisation represents an acute threat to modern society, and a diversity of alternatives are required to mitigate the threat of an outage. This paper proposes a GNSS alternative using time dissemination over national scale transmission or distribution networks. The method utilises the same frequency bandwidth and coupling technology as established power line carrier technology in conjunction with modern chirp Spread Spectrum modulation. The basis of the method is the transmission of a time synchronised chirp from a central substation, coupled into the aerial modes of the transmission line. During GNSS operation, all substations can estimate the time of flight by correlating the received chirp with a time-synchronised local copy. During GNSS outage, time sychronisation to the central substation is maintained by correcting for the precalculated time of flight. It is shown that recent advances in chirp spread spectrum allow for a computationally efficient algorithm with the capacity to compute hundreds of thousand of chirp correlations every second, facilitating timing accuracy which satisfies the majority of smart grid applications. ATP-EMTP simulations of the method on large transmission networks demonstrate sub-μs timing accuracy even in the presence of low SNR and impulsive noise. An FPGA prototype demonstrates experimentally sub-μs accuracy for time dissemination over a distance of 700 m. Averaging over time is shown to facilitate satisfactory performance down to -20dB, which could extend the range of the system to a national scale and a time dissemination network invulnerable to wireless spoofing and jamming attack vectors.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Engineering
Additional Information:	License information from Publisher: LICENSE 1: URL: http://creativecommons.org/licenses/by/4.0/, Type: open-access
Publisher:	Nature Research
Funders:	EPSRC
Date of First Compliant Deposit:	16 April 2024
Date of Acceptance:	5 March 2024
Last Modified:	17 Jun 2024 12:09
URI:	https://orca.cardiff.ac.uk/id/eprint/168008

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