It is critical to estimate voltage sag parameters fast and exactly.The paper presented a novel detection method of voltage sag based on novel Teager energy operator(NTEO) and RMS algorithm for voltage sag detection and measurement accurately.It introduced a resolution parameter i to improve the performance of TEO,then obtained NTEO,which had better anti-noise performance.First,it used the NTEO algorithm to locate the starting and ending time of voltage dip disturbances,and then using the RMS algorithm to me...