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The paper outlines a new method of distance protection that has been developed to provide true ultra-high-speed tripping for transmission line faults in both 50 Hz and 60 Hz systems. Techniques are described for deriving and comparing signals that are specially developed finite Fourier transforms, which are particularly well suited to real-time implementation using finite impulse response transversal filter functions. A particularly economical hybrid realisation using charge-coupled devices and a 16-bit microprocessor is described, and methods for retaining directional stability and dynamic accuracy are given. The paper concludes with a presentation of the results of studies to determine the performance of the new relays when used in conjunction with a conventional capacitor voltage transformer.