Lightning overvoltage investigation due to a backflashover event in transmission lines: A realist modeling proposal

This paper presents a study about the lightning performance of transmission lines using advanced electromagnetic models to perform a realistic representation of the first stroke current. Based on the measurement data obtained at the Morro do Cachimbo/MG Station, it was possible to synthesize first stroke current waveforms with single- an double-peak in a realistic way. In addition, the investigation involves an analysis with a model implemented in ATP-Models to reproduce the first stroke current recommended by CIGRÉ methodology. The breakdown process was represented through a Leader Progression Model able to represent accurately the physical process established along the perimeter of the insulator strings, during a backflashover event. The results allowed an investigation of the waveforms and amplitudes of the resulting overvoltages across the insulators. The computational modeling developed permits to identify the amplitude of the overvoltage that produces the backflashover and the instant of time that the breakdown occurs.