Hilbert Huang Transform Based Online Differential Relay Algorithm for a Shunt-Compensated Transmission Line

A differential protection scheme, based on real-time analysis of a time-frequency based technique, is proposed for a transmission line with a midpoint-connected static synchronous compensator (STATCOM). The first intrinsic mode function obtained from the decomposition of current signals from both ends of the transmission system, processed through an ensemble empirical mode decomposition technique, is used to estimate the discrete Teager energy (DTE) through online Hilbert-Huang transformation. The differential DTE from both ends of the line is used to detect the exact faulty phase. For analysis, a midpoint STATCOM compensated transmission line model is considered and simulated using EMTDC/PSCAD. Test cases, such as high fault resistance, fault inception angle, reverse power flow, current transformer saturation, and variation in source impedance, are generated for different operating modes of the STATCOM. The method is also tested for a cross-country fault in a double-circuit transmission system. Comparative assessment reports with other conventional approaches verify the reliability, speed, and feasibility of the proposed method.