Doctoral Thesis Defense Session No. 55 of PPGEEC - Evaluation of the Transient Response of Concrete-Encapsulated Grounding in Transmission Lines

STUDENT: GABRIEL VIDAL NEGREIROS BEZERRA

DATE: 12/13/2024

TIME: 2:00 PM

LOCATION: https://conferenciaweb.rnp.br/sala/fernando-augusto-moreira

TITLE: Evaluation of the Transient Response of Concrete-Encapsulated Grounding in Transmission Lines

KEYWORDS: Concrete-Encapsulated Grounding; Ground Frequency Dependence; Atmospheric Discharges; Transmission Lines; Impulsive Impedance; Electromagnetic Transients;

ABSTRACT: The correct dimensioning of the grounding system ensures reliability and safety in the operation of transmission lines under atmospheric discharge conditions. In this regard, over time, efforts have been made to seek new techniques to improve the transient response of grounding, especially for high resistivity soils. In this sense, one of the long-known techniques is the use of low resistivity materials around the grounding electrodes, such as bentonite and concrete. However, despite the time that has passed, few studies in the literature carry out an in-depth study on the characterization of the transient response of concrete-encapsulated groundings, which would be especially important in evaluating them for use in grounding transmission line towers. In view of the above, and aiming to contribute to the state of the art, in this work, the transient response of concrete-encapsulated grounding electrodes is investigated. For this, simulations were performed using the finite element method, considering a rigorous Full-Wave electromagnetic modeling. Concrete encapsulated grounding systems of the vertical electrode (rod) type with 3 and 30 m, as well as horizontal electrode (counterweight) with 15, 30, 45 and 60 m, were analyzed. Impulsive current excitations of first discharge and subsequent discharge were considered. The effect of frequency dependence of soil parameters was considered. In addition, soils with low, medium and high resistivities (300 Ω.m to 4000 Ω.m) were evaluated. Different lengths of concrete casing were taken into account in order to verify situations of partial or total encapsulation. For all these cases, the harmonic impedance (from 60 Hz to 4 MHz) was simulated, and the respective potential rise in the grounding and the impulsive impedance were calculated. In total, 150 different grounding systems were evaluated, each one subjected to two discharges, totaling 300 impulsive responses. The results indicate that the concreting of the electrode in medium and high resistivity soils produced average reductions in impulsive impedance of up to 40% for the 3 m vertical rod, considering the first and subsequent discharges. For the horizontal electrodes, the reduction in impulsive impedance in medium and high resistivity soils was up to 22% for the first discharge, while for subsequent discharges the results varied considerably between 10% and 26%, depending on the electrode length and soil resistivity.

MEMBERS OF THE BOARD:

FERNANDO AUGUSTO MOREIRA (ADVISOR)            UFBA

FELIPE MENDES DE VASCONCELLOS                      UFBA

VITALY FELIX RODRIGUEZ ESQUERRE                    UFBA

ALEXANDRE PIANTINI                                          USP

ANTÔNIO CARLOS SIQUEIRA DE LIMA                   UFRJ

TARSO VILELA FERREIRA                                      UFS

Em 06/12/2024