A Transient Current Waveform Feature Based Novel High-speed Differential Protection

With the development of large-scale AC/DC hybrid systems, the problems caused by system faults become more and more serious. So higher requirements are placed on the performance of the relay protection. The line fault transients contain a wealth of fault information. Through the research on the transient differential current of the fault component, it is found that the fault phase appears as a power frequency under internal fault. The non-fault phase of internal fault and each phase of the external fault appear as a high-frequency, and there is a theoretical minimum frequency. Therefore, a new pilot protection principle based on transient current waveform was proposed. The least squares fitting method is used to extract the frequency information and the corresponding protection criterion was constructed. Through simulation verification, the proposed protection can reliably and sensitively identify various internal and external faults, effectively improve the protection action speed, and has strong resistance to transition resistance and high frequency noise interference. The proposed protection has low requirements on sampling frequency, which has certain practical value. © 2020 Chin. Soc. for Elec. Eng.