Abstract：In traditional current protection，the effective value of current is compared with the setting value to

identify the fault which is the typical protection scheme for the transmission lines of the power distribution systems.

The current is calculated by the fast Fourier transform algorithm. As the calculation of the effective value of current

requires a long time，the speed of the current quick break protection is reduced. In this regard，a fast current

protection algorithm based on the discrete setting-value was presented to solve this problem. The main emphasis

was placed on the construction of the discrete sequence of setting-value and the protection criterion. The protection

startup criterion and action criterion were constructed based on comparisons between discrete sequence of settingvalue and sampling-value of the current fault component. The operation characteristics and reliability of the fast current protection were analyzed. The performance of the novel fast current protection algorithm was compared

with that of the conventional current protection through simulations based on PSCAD/EMTDC. The results verify

that the novel fast current protection algorithm has good operation characteristics under different fault conditions.

      Key words：power distribution systems；fast current protection；discrete setting-value；current fault component