Question How can I find out the currents that are circulating in the grid in HIFREQ?
Answer The currents flowing into every conductor in the grid are printed in the program's output file. Two values ("Entering" and "Leaving") are provided for the longitudinal current in the F09 file (as well as in Output Toolbox Configuation plots). This is because, generally speaking, the current is not constant over the conductor segments. The "Entering" value is the value of the current at the origin of the conductor (defined by the first X-Y-Z coordinates of the conductor) and the "Leaving" value is the value of the current at the other end of the conductor. The difference between those two quantities is the "Surface Current Leaking In", or "Leakage Current".
Either the "Entering" or the "Leaving" value can be used as a measure of the current circulating in a conductor, as long as they are not too different. If the values are very different, a better value could be the average current over the conductor (you can assume that the current varies linearly over the conductor).