Precision enhancement of the traditional sub-synchronous analysis by using frequency components of instantaneous magnetic flux

Sub-synchronous resonance (SSR) is a great danger to the stable and safe operation of the synchronous generator and power network. Detecting this condition in a fast and precise method is very important for power engineers. During the last decade, many methods have been proposed for SSR detection. The most famous of these methods use shaft speed analysis. On the other hand, it is noteworthy that SSR is a phenomenon that needs the use of both mechanical and electrical quantities for its analysis. Therefore, if both kinds of the signal are used, the protection system reliability can be enhanced significantly and its trip is more efficient and consistent. Subsequently, to enhance the precision and sensitivity of the SSR detection, this paper proposes the use of frequency analysis of the magnetic flux linkage of the generator as an electrical signal along with the shaft speed as a mechanical signal. The magnetic flux is a local index that is available at the relay location and does not require a communication channel to transmit. This index contains a lot of useful information about the performance of the machine. However, the main disadvantage of this index is its accessibility, which requires invasive sensors.