The traditional current differential protection cannot be applied to UHV AC transmission line with high voltage shunt reactor

so this paper describes a novel solution of traveling-wave differential protection. Firstly the three-phase voltage and current transients are calculated

it means that system fault if the module components of traveling-wave current are obtained after decoupling transformation. In order to distinguish the internal faults or external faults

the integral value of initial wave fronts at both terminals for tens milliseconds is taken as eigenvalues which compose the novel action criterion. This criterion can avoid transient unbalance differential currents under the system normal operation and external faults. It also has high sensitivity for all internal faults.Theoretical analysis and MATLAB simulation show that the solution operates reliably and rapidly. The protection has high practical value and low demands for sampling rate

communication system and computer technology. It could be realized by existing technique.