Time Resolved Analysis of Corona Discharge in SF 6 Alternative Gases under LCC Rectification Harmonic Voltage Impact

Implementing pilot SF 6 -free DC gas insulated switchgear connected to the rectifier station poses challenges due to the combination of discharge severity metrics, harmonic control, and gas characteristics. This paper examines the impact of DC harmonic voltages produced by line-commutated converters rectification on corona discharge phenomena in gas insulated switchgear. With a focus on the various types of harmonic distortions that present electric field fluctuations, this study evaluates corona discharge behaviour in C 4 F 7 N mixture, CO 2 and technical air under overstressing ripple voltages. Comprehensive descriptions of the methodology encompass: (i) reproducing representative DC terminal voltages of a generic line-commutated converter in a laboratory setting, and (ii) correlating the harmonics impact of these harmonics with discharge analytics using updated time-resolved analysis. Compared with pure DC voltage, it is found that the line-commutated converter harmonic discharge results demonstrate a non-monotonic increase in discharge inception voltage with increasing firing angles under fixed overlap angles. A strong correlation between voltage rate of change and discharge pulse sequence patterns is seen for the three gases. The concepts derived from pulse-pulse correlation are explored as indicators of the influence of commutation control logic in discharge generation, emphasising their utility in diagnosing DC gas insulated switchgear in rectifier stations.