Analysis of phenomena, that affect the distance protection

This article presents the impact of changes in distance protection reach and zone changes when performing simplifications in certain calculations, such as fault impedances, mutual impedances of sequence zero, grounded line in both sides and the other line in service, effect infeed and changes in sequence zero impedance because of resistivity of the ground. It also illustrates the consequences of failure to carry all zero sequence currents from other circuits coupled. These considerations are of special interest in lines without differential protection and/or with transfer trip (POTT/PUTT). Analyses were performed with a software package which illustrates the capabilities of these tools.