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Reference Number NIA_NGTO025
Title Substation Time Synchronisation to Safeguard the Network
Status Completed
Energy Categories Other Power and Storage Technologies(Electricity transmission and distribution) 100%;
Research Types Applied Research and Development 100%
Science and Technology Fields ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering) 100%
UKERC Cross Cutting Characterisation Not Cross-cutting 100%
Principal Investigator Project Contact
No email address given
National Grid Electricity Transmission
Award Type Network Innovation Allowance
Funding Source Ofgem
Start Date 01 November 2018
End Date 01 November 2019
Duration ENA months
Total Grant Value £91,110
Industrial Sectors Power
Region London
Programme Network Innovation Allowance
Investigators Principal Investigator Project Contact , National Grid Electricity Transmission (100.000%)
  Industrial Collaborator Project Contact , National Grid Electricity Transmission (0.000%)
Web Site
Objectives To fulfil the resilience requirement, the project investigates alternative timing solutions that could deliver external time references into substations.One source of time is based on satellite systems, e.g. GPS – a global navigation satellite system that provides geolocation and time information to a GPS receiver anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. It requires the installation of a high-quality GPS receiver and antenna at the substation site. Depending on the receiver type, it could also receive Global Navigation Satellite System (GNSS) time signals from GLONASS, Compass and Galileo constellations. GPS is the most commonly used GNSS constellation, as GLONASS has until recently not been fully operational and the other GNSS services are under development and have not yet been fully standardised. This study will review the option to include other GNSS constellations as well as GPS, and methods to increase resiliency of the GNSS-based solution. Although GNSS is a widely used source of accurate time, the signals are weak at the Earths surface and are vulnerable to jamming and spoofing attacks which can result in errors in the received time. For a robust timing system, a second ground-based source of time should be transmitted into substations.The proposed second source of time is based on optical fibre delivery of the UK time scale UTC using the IEEE 1588 Precision Time Protocol (PTP) v2, which allows high-accuracy time for P&C applications to be disseminated over compatible Ethernet. To implement this technique, a communication link between a remote PTP time server and slave devices at substations is required. The study will investigate the feasibility of using available optical fibre communication networks for time delivery from external IEEE 1588 time servers to substations, e.g. station master clocks. A station master clock is able to internally distribute timing signals via PPS, IRIG-B, SNTP and PTP formats depending on device compatibility. As well as the two time sources, the project will review the option to install a high-performance clock (as a master clock) at the substation as a holdover solution to loss of GPS signals. Various types of clock will be considered, for example rubidium and caesium atomic clocks. A commercial rubidium standard could provide holdover of ±1 μs to Coordinated Universal Time (UTC) over 1 day, while a caesium clock would potentially achieve better than 10 ns to UTC over 1 day. The scope of work is to carry out feasibility studies to assess the viability of adopting the following three options to improve the resilience of delivering time references into substations. Enhanced GNSS-based time synchronisation, considering a combined use of GPS, Galileo, GLONASS and Compass Signals to improve resilience against service jamming and spoofing. PTPv2 based time transfer over an optical fibre network between independent IEEE 1588 time servers at remote locations and PTP slave devices at substations. Installation of holdover clocks (as master clocks) at substations, which can keep time drift within protection requirements in case of GPS signal loss. The implementation challenges, security issues, timescales and full costings for each of the above options will be analysed throughout the study. The requirements and implementation of automatic switchover among the three options will also be studied. The project aims to investigate the benefits, costs and challenges of using alternative technologies (i.e. multi-GNSS, IEEE 1588 based time dissemination over optical fibre, and holdover clocks) to reduce security risks and enhance resilience of the existing GPS-based solution for substation time synchronisation.
Abstract Substation protection and control systems require each device to be synchronised to UTC (Co-ordinated Universal Time), which is currently achieved using Global Positioning System (GPS). Recent studies on GPS use and dependency have highlighted the vulnerabilities of GPS signals, and a robust solution for time synchronisation based on more diverse sources of time should be developed. This project investigates alternative timing solutions that could deliver independent time references into substations, minimising the risk of a single source failure.
Publications (none)
Final Report (none)
Added to Database 02/12/22