On-line insulation monitoring method for converter transformer valve side bushings based on time series correlation of leakage current

Valve-side bushings in converter transformers are critical components that are subjected to various transient over voltages and complex high-order harmonic voltages during normal operation. The insulation state of these bushings faces significant challenges. Existing offline inspection methods have limitations in terms of real-time performance and applicability, and they cannot fully simulate real operating conditions. Therefore, this study investigates the amplitude and phase distribution patterns of the direct voltage, power frequency, and harmonic voltages in valve-side bushings. It establishes the mapping relationship between the time series correlation of leakage current and the insulation state. Based on this, an on-line insulation monitoring method based on time series correlation of leakage current is proposed, which ensures real-time performance through data-driven approaches and applicability through mutual supervision, while maintaining the realism of operating conditions through online implementation. The results of simulation experiments demonstrate that this method could accurately identify early-stage degradation of insulation in valve-side bushings. It exhibits higher sensitivity compared to existing methods and holds significance for ensuring the safety and stability of direct current transmission systems.