A Real-Time Out-of-Step Protection Strategy Based on Instantaneous Active Power Deviation

Out-of-Step (OOS) protection against severe grid disturbances is one of the most serious concerns of the power industry. Many methods have been proposed to identify the OOS condition in which impedance-based relays are one of the most widely used ones. However, some problems have been reported associated with the performance and application of these techniques. Therefore, to alleviate some of these problems, this paper presents a new real-time approach based on the active power deviation to estimate the instability of a single synchronous generator in the multi-machine power system. The angular velocity and acceleration data obtained from the instantaneous active power are continuously calculated to determine whether or not the generator experiences an unstable condition. The instability can be distinguished by monitoring the polarity of extracted angular velocity and acceleration data during the power swing. The instantaneous active power is computed locally using voltages and currents measured at the terminals of each generator. Additionally, this method does not require such information as fault clearing time and network parameters. The reliability of the presented approach and its independence from the network configuration are successfully investigated by simulating various scenarios. Furthermore, simulation results demonstrate the straightforward and satisfactory application of this method.