Directional element for VSC-HVDC transmission lines based on model identification

As the impact of the large shunt capacitor on both terminals of the HVDC transmission lines in VSC-HVDC, the system impedance can be equivalent to shunt capacitor impedance in high frequency domain. According to this characteristic, a directional protective scheme based on model identification method for VSC-HVDC transmission lines is proposed. The scheme detects transmission line fault by comparing difference of the model error, inductance and capacitance calculated in two different models and the real values using time domain algorithm in high frequency band. The simulation results show that the method is not affected by fault type, fault location and transition resistance, and it can identify the fault reliably and rapidly in any condition.