Residual current method of grounding resistance measurement in transmissions towers with earth wire - Part 1: Study of residual current in transmition towers

The characterization and the best understanding of residual currents, that circulate from the earth wire to the grounding system through the structures of transmission towers, promote the development of different methods of grounding resistance measurement. One of these methods is based on the use of the residual current as current injection source in the measurements of grounding resistance. This method allows better analysis of the grounding system of transmission towers through the analysis of phenomena that originate this residual current. Therefore, this study aims at carrying out the computational modeling of these currents based on information and measurements of a real transmission line. This modeling considers not only the induced current, but also other effects like the unbalance currents, and also demonstrates that the induced current is the most significant portion. Besides that, the behavior of the residual current along the transmission line model was evaluated by different systems conditions, showing the load current as the major factor that affects the magnitude of residual currents. The results of this study are the basis of the development of a measurement system. This development and several measurement campaigns are the study object of our next paper (Part II).