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Two-layer soil effects on backflashover rate in overhead transmission lines

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Author(s):
Asorza, Jesus E. Guevara ; De Azevedo, Walter Luiz Manzi ; De Araujo, Anderson Ricardo Justo ; Colqui, Jaimis Sajid Leon ; Papadopoulos, Theofilos A. ; Filho, Jose Pissolato
Total Authors: 6
Document type: Journal article
Source: Electric Power Systems Research; v. 254, p. 10-pg., 2025-12-19.
Abstract

This paper examines the impact of two-layer earth modeling on the electromagnetic behavior of overhead transmission lines (OHTLs), particularly emphasizing the backflashover rate (BFR) and associated transient responses. The study focuses on a 220-kV OHTL subjected to lightning strikes, analyzing key responses such as insulator overvoltages, sky wire overcurrents, and Ground Potential Rise (GPR) at the tower base. The generalized two-layer earth model is considered as reference in the analysis. To approximate this configuration, two Equivalent Homogeneous Earth Models (EHEMs) are employed: the first utilizes the equivalent propagation constant (sigma(eq)), and the second applies the equivalent conductivity (sigma(eq)). Additionally, two homogeneous earth models are included in the analysis, corresponding to the resistivities of the upper and lower soil layers, respectively. The results indicate that the BFR remains nearly unchanged between the two-layer earth model and its corresponding EHEM. However, appreciable differences arise compared to the extreme cases represented by homogeneous soils with resistivity of the upper and bottom layer. Regarding transient behavior, the backflashover inception time is significantly influenced by the soil stratification model, highlighting the importance of accurately representing subsurface conditions. Furthermore, results show that higher soil resistivity reduces lateral current flow to adjacent towers, increasing current injection into the local grounding system and GPR, which lowers the insulator string overvoltage. (AU)

FAPESP's process: 21/11258-5 - Engineering Research Center for the Aerial Mobility of the Future (ERC-AMF)
Grantee:Domingos Alves Rade
Support Opportunities: Research Grants - Applied Research Centers Program
FAPESP's process: 19/01396-1 - Modelling conventional and tall transmission towers directly in time domain for electromagnetic transient analysis
Grantee:Anderson Ricardo Justo de Araújo
Support Opportunities: Scholarships in Brazil - Post-Doctoral
FAPESP's process: 23/05066-1 - Study of transient overvoltages in underground and submarine transmission lines considering rigorous models for calculating ground-return parameters
Grantee:Jesus Enrique Guevara Asorza
Support Opportunities: Scholarships in Brazil - Master
FAPESP's process: 24/14472-6 - Lightning study in mixed overhead-underground transmission lines using rigorous formulations for computing earth-return parameters.
Grantee:Jesus Enrique Guevara Asorza
Support Opportunities: Scholarships abroad - Research Internship - Master's degree