Pilot protection of flexible DC line based on Jaccard similarity integration criterion

Abstract

The flexible DC line protection based on the double-ended method with large communication and long action time is greatly affected by factors such as noise, which makes it difficult to set. Based on this, a pilot protection method of flexible DC line based on Jaccard similarity integration criterion is proposed. Firstly, the fault characteristics of voltage and current change rate in the case of internal and external faults of flexible DC lines are analyzed, and the conversion relationship between analog quantities and logical quantities is constructed respectively. Then a Jaccard similarity model based on the comparison of logical quantities under the 0.5 ms data window is proposed. The integrated criterion is constructed with high similarity to realize fault type identification, and fault starting and fault pole selection criteria are not required. Finally, the double-ended longitudinal protection scheme based on the comparison of logical quantities realizes the rapid protection of the flexible DC line. The scheme is easy to be implemented, because the protection principle of that is simple with fast action speed. Using the four-terminal flexible straight model built by PSCAD/EMTDC, the protection effectiveness in various scenarios such as different fault types, high-resistance grounding, and noise interference inside and outside the zone were verified.

Keywords

• four-terminal flexible dc transmission system
• flexible dc line
• jaccard similarity
• integration criterion
• pilot protection
• fault type identification