The Brazilian interconnected system: a study on transfer limits, reactive compensation and voltage collapse

On April 1999 the S+SE (~40 GW load) and N+NE (~12.5 GW) systems in Brazil were interconnected over a single-circuit 500 kV line. The line has been operating with an average transfer of 600 MW and peak loading of almost 1000 MW. In order to improve reliability and increase transfer capability the interconnection will be expanded in 2002 with a second parallel line (North-South) and a new Southeast-Northeast 500 kV line. This paper summarizes results of studies conducted to determine the compensation and/or reinforcements that are necessary to secure those benefits. The results show that voltage stability is the most limiting constraint, with transient stability a distant second. The paper shows how OPF techniques were employed to develop compensation strategies to increase transfer capability from 1000 to 3000 MW. Steady-state results demonstrating voltage collapse conditions were confirmed using long-term dynamic simulation. That analysis demonstrated the possibility of utilizing mechanically switched capacitors instead of more expensive compensation alternatives