Ultraviolet-spot distribution and photon-count variation characteristics in direct current partial discharge

To address the challenges of ultraviolet (UV) imaging technology for partial discharge (PD) in high-voltage direct current (HVDC) converter stations (equipment), a comprehensive UV image processing methodology has been developed, and a needle–needle electrode experimental platform has been established. The dynamic characteristics of UV photon counts and spatial distribution patterns of UV spots during PD processes were systematically investigated. Our research reveals that there is an inverted U-shaped distribution between UV photon counts and applied voltage. This demonstrates how discharge mechanisms evolve from molecular excitation to atomic ionization. Furthermore, probability distribution analysis identified distinctive spatial features of DC PD and elucidated the correlation between discharge modes and spatial distribution patterns. Based on these findings, a hierarchical monitoring strategy is proposed, which could optimize integration time and probability thresholds synergistically, enabling complete process monitoring from corona inception detection through discharge development tracking to precise source localization. This research provides fundamental insights and practical methodologies for UV-based monitoring and diagnostics of PD in HVDC converter stations (equipment).