Análise comparativa entre duas metodologias de estudo de coordenação de isolamentos para surtos atmosféricos em uma subestação de 500 kV da CHESF.

Abstract

This work presents a comparative analysis between two component modeling methodologies in the Alternative Transients Program - ATP for studies of fast-front electromagnetic transients, associated with lightning strikes in transmission lines affecting an Extra High Voltage substation. For this purpose, a case study in a CHESF 500 kV substation was carried out considering a simplified modeling methodology (surge modeling by a voltage source) and currently used in Brazil, as well as a methodology that considers the most detail of the transmission line struck by lightning (surge modeling by a current source). for the latter, a reference case was defined in which some proposed models were selected for the return current, transmission line, towers, supportability of the insulator chain and grounding. A correlation between the front time and the amplitude of the discharge current was considered in the reference case. For the two methodologies analyzed, the main results obtained in the simulations are presented and their impacts on the coordination of substation insulation are commented. Finally, sensitivity analyzes are carried out in relation to parameters and models of some components of the transmission line affected by lightning, in order to better assess the impact of each one on the maximum overvoltages verified inside the 500 kV substation. The analyzes indicate that the modeling of the surge by a voltage source produces conservative results in relation to those observed in the modeling of the surge by a current source, being able to burden the design of a substation with regard to its insulation coordination.