Improved Distance Relay Protection Considering High Proportion of New Energy Sources

Because of non-linearity and limitation control of overall new energy sources, the short-circuit current and residual voltage are reduced during a fault occurred on the line, which will become more evident in the future. Extremely, if the fault point is near start of line, the measured residual voltage at protection site is near zero. Furthermore, if error and noise of measurement is considered, the obtained impedance will be deviated by traditional distance protection method. So, an improved distance protection method is proposed. Internal potential information of equivalent generator is adopted, which is high and relatively constant. Then, the fault component of generator output is considered, which is inverse to fault distance and can be separated from the short-circuit current through an established equivalent source model. Finally, based on obtained internal potential and internal resistance and fault output component of the generator, the distance between protection site and short circuit point can be calculated. The correctness and applicability of this improved method are verified through the analysis and comparison of cases.