Rate of Change of Active Power as a Power Swing Blocking Function of Distance Relays

Power swings may cause undesired trips of protection relays and, consequently, shutting down power utility equipment, leading to the outage of loads. This paper presents a procedure for detecting power swings based on the rate of change of active power. When a power swing occurs, the derivative of the active power can be modeled as a sinusoidal function and, therefore, it is possible to estimate the frequency oscillation. The proposal takes advantage to this theoretical concept to detect power swings on transmission systems. Simulation results show that the developed algorithm has good performance, including research scenarios against low and large power swings. The protection relay is unblocked upon the occurence of a short-circuit. The proposed technique is simple to implement and can be employed as a Power Swing Blocking (PSB) function to avoid misoperation of distance protection relays.