Enhancing Backup Protection Of Series Compensated Lines Using Wavelet Packet Transform

Ibrahim, D. K., M. M. Abdel Aziz, N. M. Abdel Fattah, and A. Ramadan, "Enhancing Backup Protection Of Series Compensated Lines Using Wavelet Packet Transform", Proceedings of the 15th International Middle East Power Systems Conference, MEPCON 2012; Alexandria, Egypt, December, 23-25, 2012., 2012.


Series compensated lines present challenges for directional, distance, and differential elements because the transient response of the series capacitor is not readily predictable. This paper presents a directional overcurrent relay that used as a backup protection for distance relays in series compensated lines. Wavelet Packet Transform (WPT) technique is used for proper fundamental RMS value calculating of current and voltage signals since it can preserve both time and frequency information with high resolution by decomposing a waveform into uniform frequency bands, and measuring individual harmonic components. The proposed scheme demonstrates its feasible performance in detecting nonlinear high impedance faults with low voltage and current variation for maximum trip time required of 2 cycles. In addition, the proposed scheme examines the load current continuously and changes the relay pick up value adaptively. Characteristics of the proposed scheme are fully analyzed by extensive ATP/EMTP simulation studies that clearly reveal that the proposed scheme has an efficient performance insensitive of the variation of different fault conditions that may occur in double ended transmission lines with series capacitors at the middle of the line.