New ultra-high-speed directional comparison technique for the protection of e.h.v. transmission lines

The basis of a new ultra-high-speed transmission-line protection scheme is described. Analogue processing is performed using charge-coupled devices to extract the fault or superimposed components impressed on a power system following a disturbance. The new arrangement is designed for use in conjunction with carrier blocking communication equipment and tripping times of typically 2 to 4 ms are shown to be feasible for most faults. The results of an cxtensive series of laboratory tests are given and the paper concludes with a consideration of the performance of the new scheme following very high resistance single phase-to-earth faults.