Identification and influence of the external elements on the transmission system operator´s responsibility area

In this paper is presented a methodology to identify and evaluate the influence of the external elements on the Transmission System Operator´s (TSO) responsibility area. The algorithm is based on the influence factor approach and is described for this purpose. This algorithm offer a concrete support in the determination of the observability area, which at the end remains in the responsibility of a single TSO. The influence factor is a numerical value used to quantify the greatest effect of the outage of an external network component on any internal network branch. The proposed methodology was applied to identify and to assess the influence of the external elements on the Portuguese transmission network. All simulations of the Portuguese and Spanish systems were performed using the computational software package PSS/E of Siemens/PTI. The results obtained with the proposed methodology are compared with the solutions produced by the horizontal network methodology.