Application of phase shifting transformers for a secure and efficient operation of the interconnection corridors

In the liberalized energy markets, TSOs are more and more required to have a better control of network power flows in order to maintain a secure and efficient operation of the system. The paper describes the phase shifting transformer (PST) model implemented in the CESI programs and the analyses performed, on behalf of the Italian ISO (GRTN), for assessing the installation of PSTs on the Italian east border interconnection. In this case, the control action of the PSTs aims at mitigating uncontrolled "parallel flows" and unbalanced sharing of power among circuits. Three different solutions with increasing number PSTs were identified and simulated. Furthermore, a precontingency bucking angle is calculated for the PST installed in the weakest circuit in order to alleviate the post-contingency overload and to avoid the untimely intervention of line protections.