A smart and adaptive scheme for generator out of step protection

The present day power system comprises of extra high voltage network, transmitting power from large generating stations over long distances. The modern day generators are built with higher rating and better cooling techniques, resulting in larger machine impedances. The closely knit transmission network has resulted in decreased system impedance. These changes have increased the chances of occurrence of out of step condition with swings passing through the generator impedance circle. This paper describes an adaptive out of step protection scheme for detecting this condition. The new scheme proposed uses both impedance and power measurement to obtain a comprehensive protection scheme which uses locally available information and does not require extensive simulation studies for setting the relay. Adaptive swing classifier logic is introduced to differentiate between stable and unstable swings. The performance of the proposed scheme is compared with the conventional single blinder scheme by testing it on a multi-machine system.