A fast current relaying algorithm for distribution systems based on discrete setting value

The traditional current protection uses the RMS value of the current to compare with a setting-value to identify faults, which is the typical protection scheme for the transmission lines of the power distribution systems. The current is calculated by the fast Fourier transform (FFT) algorithm. As the calculation of the RMS 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 is presented in this paper to solve this problem. The main emphasis is placed on the construction of the discrete sequence of setting-value and the protection criterion. The protection startup criterion and action criterion are constructed based on comparisons between discrete sequence of settingvalue and sampling values of the current fault component. The operation characteristics and reliability of the fast current protection are analyzed. The performance of the novel fast current protection algorithm is compared with that of the conventional current protection through simulations based on PSCAD/EMTDC. The results verified that the novel fast current protection algorithm has good operation characteristics under different fault conditions. (C) 2022 The Author(s). Published by Elsevier Ltd.