New high-voltage directional and phase selection protection technique based on real power system data

Traditional directional power and current protection requires the current and the voltage to be measured. The directional current protection equipment is only capable for tripping the faulty incomer. While the direction in which the fault occurs is detected by measuring the direction of current flow, or in other words the phase displacement between the current and voltage. This study introduces a directional protection technique with phase selection based on measuring the current only. The correlogram function principle is applied on two successive current cycles. The two cycles are based on the pre- and post-fault current signals. The ability to differentiate between a fault in one direction and others is obtained using the sign of correlogram coefficients while its magnitude is used to identify the faulted phase. A proposed directional relay characteristic with correlogram coefficients calculated pre- and during the fault are also introduced. Different cases of non-symmetrical faults have been studied on a real recorded fault data for 240-kV transmission system at the province of Alberta-Canada. The results showed that the proposed technique is simple and reliable not only to identify the fault direction but also to select the faulted phases.