Effect of Load Restoration on an Integrated Autonomous Protection System Against Voltage Instability

An integrated autonomous protection system against voltage instability based on monitoring the secondary (controlled) voltages of bulk power delivery transformers is modified in this paper to include also firm load shedding. The performance of the proposed protection scheme is investigated in the presence of self-restoring loads using a small test system consisting of 9 buses. Simulations on this test system show adequate performance of the protection in two cases of severe and marginal voltage instability respectively.