The objective of this paper is to study the possibility of voltage instability on the border section between Italy and Slovenia. At present, the Italian and Slovenian power systems are interconnected by two overhead lines, one at the nominal voltage of 380 kV and the other at 220 kV. Referring to the classic voltage stability analysis, the paper investigates possible large overload conditions on the 220 kV interconnector, caused by an outage of the 380 kV interconnector when the power flows between the two countries are at their highest level. After a brief description of the characteristics of the power system in the considered section, the real network is approximated to match the model used in the classic analysis of voltage stability. The performed load-flow calculations relevant to the (real) power system under heavy operating conditions allow for an evaluation of the effects of the used approximations and validation of the results of this study.
