Abstract:

To address the challenge of insufficient sensitivity in line protection within novel distribution systems,a distribution network line protection scheme based on impedance parameter identification of two-port network model is put forward.A key feature of this scheme is its immunity to power source characteristics.The distribution line,bounded by the protection installations at both ends,is modeled as a linear network equivalent without independent power sources.The characteristics of network impedance parameters under normal operation,external fault conditions and internal fault conditions are analyzed,and key identification parameters are extracted.This enables effective discrimination between different operating states of the distribution line.Simulation results demonstrate that the proposed scheme accurately operates during internal faults,effectively avoids mal-operation during external faults and system oscillation conditions,and enhances the reliability and sensitivity of distribution protection devices.The scheme is well-suited to meet the line protection requirements of novel distribution systems with extensive integration of distributed generation.

Key words: distribution line protection, distributed generation (DG), two-port network model, impedance parameter identification, transition resistance