A method to evaluate voltages to earth during an earth fault on a HV network in a system of interconnected earth electrodes of MV/LV substations

An easy and fast method to evaluate, in a system of interconnected earth electrodes, earth potentials on earthing systems of medium voltage/low voltage (MV/LV) substations, in event of single-line-to-earth fault on a high voltage/medium voltage (HV/MV) station, is presented. The paper shows the results of simulations, done on network with different extensions and characteristics, organized in easy-to-read graphs and tables. A comparison of these results with the values obtained according to the procedure. explained in the IEC-Standard 60909-3, and a study on the accuracy of the method has been done. Moreover, in the paper, some considerations on safety aspects in global earthing system (GES) including HV/MV stations are done.