Lightning study in mixed overhead-underground transmission lines using rigorous formulations for computing earth-return parameters.

• Grant number: 24/14472-6
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: January 07, 2025
• End date: July 06, 2025
• Field of knowledge: Engineering - Electrical Engineering - Power Systems
• Principal Investigator: Jose Pissolato Filho
• Grantee: Jesus Enrique Guevara Asorza
• Supervisor: Theofilos Papadopoulos
• Host Institution: Faculdade de Engenharia Elétrica e de Computação (FEEC). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Institution abroad: Aristotle University of Thessaloniki (AUTh), Greece
• Associated to the scholarship: 23/05066-1 - Study of transient overvoltages in underground and submarine transmission lines considering rigorous models for calculating ground-return parameters, BP.MS

Abstract

In response to the growing demand for energy in recent years, it is imperative to continue supplying it through transmission lines while enhancing system reliability. In densely urbanized areas, connecting electrical substations using solely overhead transmission lines is impractical and almost impossible due to limited space for towers or pylons. If there is any space, generally, it is occupied by trees and parks. Consequently, underground transmission lines have been increasingly constructed inside the cities. When it is necessary to connect to another city, the underground lines transition to overhead lines when there is sufficient space (generally on the outskirts of the town), only to revert to underground lines upon entering another city and connecting to the substation therein, giving rise to mixed transmission lines. In some cases, where the city is not too urbanized, it is possible to have overhead and underground lines in some parts. Thus, mixed lines have become more prevalent in recent years. One of the critical challenges with mixed lines is protecting against lightning strikes that enter the cable through the overhead line. The existing literature includes studies that simulate this event using an Electromagnetic Transients (EMT)-type platforms. However, these studies often employ simplified models for mixed transmission lines, grounding systems, insulators, and other components. Additionally, they do not account for the real-world limitations of such lines, such as space constraints and urban grounding systems. Simplified models can lead to inadequate design of protective elements like Surge Voltage Limiters (SVL) and surge arresters. Such inadequate design could result in cable faults, leading to transmission service disruptions. Moreover, it is necessary to calculate the Ground Potential Rise (GPR) for the grounding system associated with the transition tower and those from the underground line. The calculation must be as precise as possible to ensure an accurate assessment of potential risks, safeguarding the lives of humans and animals in the vicinity, as these grounding systems are located in accessible areas. Therefore, this research aims to employ the most rigorous frequency-dependent power system models to accurately simulate this phenomenon and highlight the discrepancies compared to studies typically conducted using internal EMT-type platforms formulations.