A Novel Bus Differential Protection Method Based on the Frequency-Dependent Evolution Mechanism of Fault-Current Traveling Waves

The time-domain fault signal data window provided by the new energy source is short. Certain existing bus protection methods may operate incorrectly when there are loud noise interference and high-resistance fault. Here, a novel differential bus protection method is proposed by using the fault-current traveling wave (FCTW) frequency domain. Changes in the reflection coefficient and the refraction coefficient with respect to the frequency of FCTWs (when they are reflected to the fault line and refracted to the nonfault line through the bus) are theoretically deduced. The frequency-dependent evolution mechanism of FCTWs on buses and transmission lines is revealed. Characteristic differences in the FCTW spectrum waveforms that occur between the power lines when internal and external faults occur in the bus system are accurately identified. A protection criterion is constructed using the Tanimoto coefficient (TC) because the TC construction mode and the corresponding characteristics can reliably identify the spectral waveform change trend, making the criterion largely unaffected by noise and fault resistance variations. PSCAD/EMTDC simulation results reveal that the proposed method is faster and more sensitive than the existing protection method, particularly for protecting against internal high-resistance faults and external faults with loud noise interference. Laboratory testing verifies the effectiveness of the proposed method and it is suitable to realize the industry application with new energy access.