RLS-Based Time Delay Control Method for Distributed Asynchronous Sheath Current Sensing in Underground HV Cable Systems

Distributed sheath current sensing in HV cable systems is vital for grounding fault detection. However, the signal is occasionally lost in underground sensing applications with previous synchronized methods based on satellite time transfer. In this paper, a time delay control method based on parallel Smith estimation and the coupling law between cables via RLS (Recursive Least Square) is proposed for asynchronous sheath current sensing in underground HV cable systems. This method is verified by the field test on the primary side high voltage cable of the traction transformer of 220 kV high-speed railway. The result shows that the proposed method converges to the minimum residual value point, the average residual is 0.321 A, the accurate time delay is 5.22 s, and the synchronization of distributed sheath current sensing can be realized.