Based on the analysis of fault current characteristics of distribution network branch with DG, matrix algorithm for fault location is optimized. The branch contained with distributed generations is improved. To begin with, fault associated area is located by the initial mutations quantity from sum of positive-sequence component and negative-sequence component rms. What’s more, fault line is located by comparing both sides of the line current amplitude variation characteristics. Comprehensive amplitude is simplified, protection scheme is improved for distributed generations branch, and other branches remain unchanged in order to reduce equipment, keep cost saving, and locate fault line. The typical model is built on PSCAD/EMTDC platform for proving the protection algorithm in both symmetric and asymmetric fault. The simulation results of different fault type results show the effectiveness of this scheme.

The transient based protection becomes one of the main research areas for HVDC transmission lines protection.This paper firstly analyzed the frequency characteristics of HVDC transmission line and line boundary,and proposed the boundary protection principle criterion to discriminate the internal-faults and external-faults.Then the fault-induced transient current amplitude of certain frequency was extracted by fast improved recursion wavelet transformation(IRWT),which was also used to construct the practical algorithm of boundary protection.A large number of simulations were conducted by PSCAD.Testing results showed that the proposed protection algorithm can distinguish the internal-faults and external-faults accurately,and the protection performance is not affected by the fault position,fault type and fault transition resistance.