The Identification of Internal and External Faults for ±800kV UHVDC Transmission Line Based on S-Transform and SVM

Abstract

There is a smoothing reactor and DC filter between the inverter and the direct current line to form a boundary in the HVDC transmission system. Since this boundary presents the stop-band characteristic to the high frequency transient voltage signals, the high-frequency transient voltage signal caused by external faults through boundary will be attenuated and the signals caused by internal faults will be unchanged. In this paper, a new technique in which the combination of the S–transform and support vector machine (SVM) is used to analyze the transient signals, is proposed for distinguishing internal faults from the external faults based on the significantly difference of high-frequency transient voltage on the point of protection.