| Author: | Li, Zhe |
| Title: | Modeling and assessment of grounding systems for power distribution networks under fault conditions |
| Advisors: | Du, Yaping (BEEE) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Subject: | Lightning protection Electric power distribution Electric currents -- Grounding Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Building Environment and Energy Engineering |
| Pages: | 137 pages : color illustrations |
| Language: | English |
| Abstract: | This thesis explores the modeling and evaluation of grounding systems in power distribution networks, with a particular focus on addressing the challenges posed by lightning transients and fault conditions. As modern infrastructures become increasingly reliant on sensitive electronic systems, the risks associated with lightning strikes and fault currents have grown significantly, as these systems are more vulnerable to damage. Lightning events can induce high-voltage surges that affect both the power grid and sensitive equipment, while fault conditions, particularly in low-voltage distribution systems, can create hazardous touch voltage levels, leading to potential electrocution risks. Given the growing dependence on electrical and electronic systems in urban environments, ensuring effective grounding solutions is critical for both protecting equipment and ensuring human safety. This research investigates these issues in depth, aiming to provide a better understanding of the behavior of grounding systems under lightning strikes and fault scenarios, with a view to enhancing protective measures and improving overall safety in power distribution networks. The first part of this research focuses on simulating lightning strikes, a major risk for power distribution networks, particularly in areas with tall structures such as wind turbines. This research introduces a novel Nonlinear Charge Simulation Method (NCSM) to model the charge dynamics in downward negative lightning leaders. This method offers a more accurate representation of the complex electrical interactions that occur during lightning strikes, providing critical insights for improving lightning protection measures in sensitive and critical infrastructure. A hybrid model combining Transmission Line (TL) theory and Partial Element Equivalent Circuit (PEEC) methods is proposed to simulate the interaction between lightning channels and such structures. This model accounts for electromagnetic coupling effects that are often neglected in conventional lightning simulation approaches. The model not only improves the understanding of lightning-induced transients but also helps in evaluating the performance of lightning protection systems, such as grounding electrodes and surge arresters, in mitigating the effects of lightning strikes on tall structures. This is particularly significant as the size and number of tall structures like wind turbines continue to increase globally, demanding better protection strategies to prevent equipment damage and ensure operational reliability. In the second part of the thesis, the focus shifts to fault conditions, with an in-depth evaluation of the risks posed by touch voltage and fault potential in low-voltage (LV) distribution systems, particularly in older residential communities with outdated grounding configurations. In such environments, traditional grounding systems often fail to provide adequate protection, increasing the risk of electrocution during faults. This research uses the PEEC method to model various grounding configurations, including TT, TT(M)-C-S, and TX(M)-C-S, assessing their ability to mitigate the risks of electrocution in fault scenarios such as phase-to-ground and line-to-neutral faults. The simulations reveal how different grounding designs affect touch voltage levels and fault potential, highlighting the critical role that grounding configurations play in reducing safety hazards, particularly in areas where modern protective devices are difficult or costly to retrofit. The results from this research demonstrate that specific grounding configurations can significantly reduce the touch voltage levels, making it safer for residents, especially in aging urban communities with outdated electrical infrastructure. Furthermore, the study emphasizes the importance of distributed grounding points along network paths to enhance safety in low-voltage distribution systems, suggesting that such designs can help mitigate the risks of electrocution and improve the overall safety of the electrical system. In conclusion, the research presents significant advancements in the modeling and assessment of grounding systems, providing a robust framework for understanding and mitigating the risks associated with lightning strikes and electrical faults. These contributions are essential for the development of more resilient, fault-tolerant infrastructures, particularly in aging urban environments, and provide critical guidance for the design of improved grounding solutions that ensure both human safety and equipment protection in modern power distribution systems. |
| Rights: | All rights reserved |
| Access: | open access |
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