Abstract: Waveform information is transmitted from the ends of a protection zone by first compressing the information using a lossy compression technique such as wavelets and then compressing the lossy compressed waveform information using a loss-less compression technique such as the Burrows-Wheeler transform. Status information is transmitted from the ends of the protection zone by compressing that information using the loss-less technique. The time for transmission can be less than, equal to or greater than the time for one cycle of the power line frequency.

Abstract: Waveform information is transmitted from the ends of a protection zone by first compressing the information using a lossy compression technique such as wavelets and then compressing the lossy compressed waveform information using a loss-less compression technique such as the Burrows-Wheeler transform. Status information is transmitted from the ends of the protection zone by compressing that information using the loss-less technique. The time for transmission can be less than, equal to or greater than the time for one cycle of the power line frequency.

Abstract: A measure of the current through a first terminal of a device in a three-phase power system is obtained for each phase of the system. A measure of the current through a second terminal is also obtained for each phase. To compensate for any changes in phase introduced by the device between the first and second terminals, the measured currents obtained for each phase at those terminals are normalized using a novel, generalized normalization transform having the form: G(&thgr;)=cos(&thgr;)U+sin(&thgr;)J where U represents a unit zero degree phase shift with zero sequence components removed, and J represents a unit ninety degree phase shift with zero sequence components removed. From the normalized currents, a differential current is then calculated for each phase.