Modeling of multiphase transmission lines considering frequency-dependent soil parameters: transient analysis via ATP software

Abstract

This document presents the proposal for an international research internship by the researcher Tainá Fernanda Garbelim Pascoalato at the University of Lisbon - Instituto Superior Técnico, in Lisbon, Portugal, under the supervision of Prof. Dr. Maria Teresa Nunes Padilha de Castro Correia de Barros with a BEPE grant from the São Paulo Research Foundation (FAPESP). The objective of this research is to improve the classical model known as Universal Line Model (ULM) to represent the multiphase transmission lines (TLs), when subjected to lightning discharges for the adequate analysis of the electromagnetic transients directly in the time domain using the Alternative Transient Program (ATP) software. This improvement consists of calculating the TL parameters accurately (considering the suitable models to obtain the ground-return impedance and admittance), taking into account the frequency effect on the soil electrical parameters, homogeneous and/or stratified soils, the water content of the soil, the presence of shield wires at the top of the tower and other characteristics. Once this model is developed and validated, the transient responses generated by different types of disturbances (switching maneuver- energization, faults, and lightning strikes) will be analyzed directly in the time domain. Thus, overvoltages and induced voltages will be accurately calculated for these disturbances in transmission lines under these phenomena. These facts are important because the exact value of the transient responses will allow the specification of the string of insulators to be designed accurately and the protection systems to operate properly. As a consequence, the possibility of erroneous predictions is mitigated, and the transmission reliability and the quality of electricity supplied to consumers are increased. In addition, this research internship will bring several other benefits to your research group at the Department of Electrical Engineering (DEE) of São Paulo State University (UNESP), such as new research topics, improvement of existing models for electrical components in electrical systems and new tools to be implemented in programs for the analysis of electromagnetic transients in power systems. (AU)