Analysis of anonymous phase grounding fault and tripping strategy optimization for double-circuit transmission lines on the same tower

The fault detection technology and tripping strategy for single circuit high-voltage transmission lines of 220 kV and above have gradually matured, but for the particularity of faults in double-circuit transmission lines, further research is needed on fault characteristics and detection methods. In this article, a fault analysis is conducted on double-circuit transmission lines with anonymous phase grounding fault, to determine the failure mode and the entire process of fault development. At the same time, a detailed analysis of the action behaviour of the phase selector was conducted based on the principle of relay protection, and it was pointed out that for the faults of double circuit transmission lines on the same tower, the distance phase selector may not be able to correctly distinguish the fault phase. In addition, in response to the shortcomings of tripping two single-circuit transmission lines due to double-circuit transmission line faults, this article proposes a tripping strategy suitable for cross-country faults in double-circuit transmission lines, which can further improve the stability of power system.