This project aims to examine three different problems associated with the earthing of the T-pylon assets. The project will investigate the earthing performance of innovative T-pylons and the induced effects of the T-pylons and the associated energised lines. Induced voltages and induced currents will be measured and compared with the computational results to establish recommendations on earthing and induced effects. In addition, the project will examine the most recent computational (XGSLab) and measurement techniques to compare the computations with the existing techniques (CDEGs). Comparative computations of software will be conducted under variable frequency and transient currents will be injected into ground. Conducrete will also be explored to improve the earthing performance. Such low resistance materials will reduce the earth impedance and materials will act as an enlarged earth electrode size increasing the ability to dissipate more earth fault currents.
Benefits
The benefit of this project is based on an assumption that NGET will achieve earthing performance safety of its assets. A new computational software will also be explored which will reduce the capital and the yearly renewal cost as well. If this project is successful, over a 20-year period, we assume that health and safety will be improved for live T-pylon assets and lives of two on field personnel and 10 injuries can be saved resulting in generation of societal value created with a net benefit of £1.9m.
Learnings
Outcomes
2023/24
The tower base earth resistance for the T-pylon is low enough, making the rise of earth potential safe under normal operating conditions. However, step potential may need further mitigation in the areas above the corners of the concrete base.
2024/25
1-Detailed circuit model in ATP-EMTP of the 400 kV hybrid power network for investigating the induced effects (voltage and current) along the tower position.
2-Measurements on the performance of conducrete, soil survey for characterization of soil and future simulations.
3-Investigation of the performance of XGSLAB in comparison with CDEGS, applied to simple and T-pylon’s earthing system characterizing the harmonic impedance, developed earth potentials and time-domain responses.
4- Empirical equation for induced voltages on the objects on electrical substations.
Recommendations for further work
None at this stage.
Lessons Learnt
The derived analytical expression and results arising from comparison showed enhanced compatibility of using CDEGS earthing software. The earthing Technical Specifications will change and allows the usage of CDEGS as well.
Dissemination
2023/2024
"Bulletin Board: Report on the 16th UHVnet Colloquium, May 9–10, 2024," in IEEE Electrical Insulation Magazine, vol. 40, no. 5, pp. 48-52, September/October 2024, doi: 10.1109/MEI.2024.10646176.
M. Mokhtari et al., "An Analytical Model for Low Frequency Earthing System of the T-Pylon Transmission Tower," 2024 59th International Universities Power Engineering Conference (UPEC), Cardiff, United Kingdom, 2024, pp. 1-5, doi: 10.1109/UPEC61344.2024.10892483.
A. R. Justo de Araújo et al., "Quantification of Induced Effects on T-pylon Transmission Lines," 2024 59th International Universities Power Engineering Conference (UPEC), Cardiff, United Kingdom, 2024, pp. 1-6, doi: 10.1109/UPEC61344.2024.10892566.
2024/2025
- A paper and a keynote speech at the 17th UHVNet in Liverpool from 2–3 June 2025.
- A paper accepted to the 24th ISH, from 24-29 August 2025 in Karuizawa, Japan.
- A paper is being elaborated to the 60th UPEC, Brunel University from 2–5 September 2025.