A Novel Zero Sequence Directional Element Based on Fault Type

Grounded faults occur on transmission lines, may cause malfunction of currently available zero sequence directional element when zero sequence voltage can’t meet the sensitive requirement. By analyzing the phases’ relation between zero sequence voltage and voltage of faulted-phase, a novel directional element based on faulty type is proposed in this paper to overcome the defects above. When the zero sequence voltage is below the threshold, this element adopts the recorded voltage of the faulted-phase to replace the zero sequence voltage, and then determine the zero sequence power direction. The simulations use recorded fault data show that this element is correct and reliable. The element proposed has been applied into 750kV transmission line digital relaying