Tracking maximum loadability conditions in power systems

This paper deals with the problem of identifying emergency conditions during system operation in the case of voltage instability. A novel detection scheme is proposed based on measurement of the controlled voltage of bulk power delivery transformers equipped with load tap changers. The detection is based on the comparison of successive post-tap-change voltages. The detection scheme is purely local, even though it senses a system-wide emergency condition. It is shown that the condition detected is a precursor to maximum loadability and voltage instability.