Power grids have recently become more susceptible to sub-synchronous control interactions (SSCI) due to the increasing penetration of renewable resources and series-compensated lines. SSCI is a purely electrical and fast-growing phenomenon. Therefore, without an expeditious detection and mitigation solution, it can cause serious damage to renewable and transmission facilities, consequently leading to cascading outages. This paper proposes an effective algorithm to detect SSCI within 45 ms and reliably send a trip signal within 95 ms. First, a comprehensive SSCI analysis is suggested to improve the preprocessing of the measured signal. Then, the proposed algorithm utilizes mode identification approaches in conjunction with a moving fast fourier transform (FFT) to capture and process the frequency and magnitude of oscillations to issue a reliable trip command in the case of an SSCI event. To evaluate the algorithm, a portion of the Electric Reliability Council of Texas (ERCOT) grid with relatively high penetration of renewable generation resources is utilized. The proposed detection algorithm is implemented on a real-time target device and is tested with an SSCI signal from the ERCOT grid under real-time operating conditions. The results indicate the efficiency and accuracy of the method with successful detection within the acceptable time frame.