Synchronization Method of Sheath and Load Current Distributed Online Monitoring in Cross-Bonded Cable Systems

This article puts forward a method to address the issue of time synchronization in distributed current sensing for underground high-voltage (HV) cable systems. In the context, the detection of distributed sheath currents and load currents is crucial for diagnosing sheath grounding faults. To solve the problem of time synchronization without relying on external time references, the method is based on the coupling relationship between distributed sheath currents and core currents in cross-bonded high-voltage cables. It introduces a recursive-least-squares method for estimating the time delays among multiple current sensors. The estimation aims to obtain the time offset compensation that minimizes the residuals, using the short-time invariance of capacitive currents as a stability criterion. The proposed method is experimentally validated on a 220 kV high-speed railway traction transformer's primary side high-voltage cable distributed current sensing system. The experimental results demonstrate that the method converges to the point of minimum residuals, with an average residual of 0.30 A and an accurate time delay measurement of 3.93 s. Therefore, the method achieves time synchronization for distributed sheath current sensing.