Lightning-originated overvoltages in a multi-circuit HV-MV line

The analysis of lightning-originated flashovers occurring on a multi-circuit high voltage (HV)-medium voltage (MV) overhead line, from indirect and direct lightning, is presented in the paper. We focus on the protection of a 15-kV line with compact configuration that shares the same concrete poles of a 69-kV transmission line. For the indirect lightning performance analysis, the electromagnetic coupling between the lightning electromagnetic field and the multi conductor system is calculated using a version of the LIOV-EMTP-RV tool adapted for the non-conventional line configuration. The HV line increases the incidence of direct strikes but the prevailing effect, as thoroughly discussed in the paper, is the shielding of the MV line by the above HV line. Lightning-originated voltages from both direct and indirect events are presented in the time domain for each conductor of the n-conductor line, with particular focus on the occurring flashover phenomena. The analysis of the overvoltages transferred to the LV systems through distribution transformers is presented too.