On reverse operating conditions identification

This paper investigates some aspects of reactive power and voltage control. In general, load tap changers, local shunt compensation and reactive power generation help to enhance the system voltage level. In some cases, however, these actions deteriorate the system, leading to a voltage instability scenario. To diagnose the problem and prevent voltage collapse, this paper supports the idea that relationships of terminal voltage versus reactive power and terminal voltage versus internal voltage in synchronous machines should both be analyzed in a complementary way. The main idea and the factors that may influence the analysis are discussed with the help of a test system. The Brazilian system with all limits considered is also studied.