When fault distance is greater than a certain value, attenuation of high frequency fault signal over the line is greater than what the DC line boundary is subject to. To sensitively detect a fault and improve the reliability of UHVDC (Ultra High Voltage Direct Current) transmission line protection, a new protection scheme based on wavelet based direction element is proposed, where directional element and attenuation of high frequency energy are used to identify an internal fault. Extensive simulation results show that the proposed protection scheme is able to sensitively detect high impedance faults, identify the faulty pole.
