The Ossanna's theorem for educational purposes: Impact of distributed parameter transmission lines on power systems

This paper faces a challenge in power education: how to teach the students the impact of different transmission lines on the power system at power frequency. More specifically, the paper exploits the very effective and elegant Ossanna's theorem in order to make clear which are the allowable electrical regimes of different transmission line typologies in terms of power losses, voltage drops, transmissible powers and the conditions for the voltage collapse. Moreover, the formulation of the complex power at the sending-end of the power transmission line inferred from the Ossanna's theorem, which has never been shown in technical literature, is clearly presented. It is worth noting that although the paper is focused on high and extra-high voltage transmission lines, the presented didactical approach can be indifferently applied to any voltage level.