A protection scheme of transmission line based on nature frequency

This paper proposes a protection scheme for transmission lines based on nature frequency of fault-generated travelling wave. The fault component of current signals are first computed and decoupled into their modal components, and then the mode spectrums are computed by FFT to extra the fundamental frequency of nature frequencies, through comparing the fundamental frequency at both ends of lines to identify internal and external faults. The scheme operates rapidly, reliably and is immune to CT saturation, operation mode and transient resistance; it can endure the influences of various fault inception angles, fault location, The performance of scheme is investigated for various faults on a typical Electro-Magnetic Transient Program/Alternative Transients Program (EMTP/ATP) simulated transmission feeder.