An investigation of controlled power system separation of the Uruguayan network

The Uruguayan power system is highly dependent on two 500 kV transmission lines connecting the largest generation site (Salto Grande) and the Argentinean interconnection in the North, to the largest loading area in the South. Actual occurrences, where both 500 kV lines tripped, lead the system to widespread blackouts including the critical area of Montevideo, the nation´s capital district. This paper presents an investigation of a controlled separation of the Uruguayan network into two stable islands, using power swing blocking (PSB) and out-of-step tripping (OST) protection functions. The investigation is based on transient stability studies using comprehensive models and, on the role of PSB and OST covering many possible protection strategies. The study specifically compares the amount of load shedding necessary to achieve similar transient performance with and without a controlled islanding scheme. The results show first that the required load shedding is relatively high (about 500 MVA), and that the controlled islanding scheme allows similar transient performance with 20% saving of load curtailment.