A New Method of Hybrid Cascaded DC Line Protection Based on the Two-Dimensional Judgment Plane

The interelectrode hybrid transmission mode of the Baihetan - Jiangsu UHVDC transmission project realizes large capacity and multi-terminal transmission, and reduces the risk of commutation failure. However, its transmission distance is long, the fault probability is high and the fault characteristics are more complex. Therefore, from the perspective of protection, this paper deduces the complex frequency domain expression of the fault electricity volume under different protection areas and concludes that there are differences in the waveform characteristics of the measured terminal voltage when the fault is located in the area and outside the area. Then, principal component analysis (PCA) is used to quantify and amplify the difference of fault electrical volume in the fault area and outside the area, and a new method of interelectrode hybrid cascade DC line protection is constructed by using Euclidean distance to construct protection criteria. A large number of simulation data tests show that the protection method can identify line faults reliably and quickly, and has high resistance to transition resistance.