Analysis and solutions for bulk system voltage instability

The phenomenon of voltage instability and its effects are described in some detail. It is argued that controls that can steer a system away from voltage instability are feasible and badly needed. Among the control possibilities discussed are: load tap changers between the bulk and distribution systems, which play a key role in the voltage collapse process, sometimes contributing to collapse, sometimes helping avoid it; the use of generator reactive overload capability (a few extra VArs from a generator can save a system from collapse or give operators time to restore a secure state); and undervoltage load shedding.<>