Impedance Protection for Transmission Line T-Connected With Inverter Interfaced Distributed Generations

With Inverter Interfaced Distributed Generations (IIDGs) access to the distribution lines in a T-connected way, dual-terminal impedance differential protection is no longer applicable. A protection method based on impedance characteristics for T-connected lines is proposed. First, the measured impedance characteristics of the three ends of the T-connected line are analyzed. Then, based on the measured impedance of the three ends and the line impedance of the T-connected line, characteristic impedances are constructed. The faulty branch is identified by utilizing the relative relationships of characteristic impedances during faults in different branches. Subsequently, based on the result of the faulty branch, different differential impedances and restraint impedances are constructed, and the relative relationships between them are used to determine the fault location. A model of IIDG T-connected lines is built in PSCAD, and simulation results verify the effectiveness and superiority of the proposed protection method.