Dissolved Gas Generation Characteristics of Dielectric Liquids Under Partial Discharges and Breakdown Sparks

ABSTRACT With the growing interest in monitoring and diagnostic techniques for assessing transformer condition, dissolved gas analysis (DGA) stands out as a crucial diagnostic tool to detect electrical and thermal faults in liquid‐immersed transformers. Laboratory‐based DGA studies have primarily focused on detecting gas concentrations and patterns under simulated fault conditions in different types of insulating liquids. To understand the significance of dissolved gas values it is invaluable to establish the quantitative relationship between the gas generation amount and the electrical energy associated with the fault. This study aims to systematically investigate the correlation between gas generation characteristics and the electrical energy associated with either partial discharges (PD) or breakdown sparks (BD) in a mineral oil (MO) and a synthetic ester (SE). An in‐house designed experimental setup was developed, and various influencing factors were explored. The results of DGA‐PD tests indicated that PD magnitude influences the fault gas volume per unit energy (GVPUE, μL/J) generated in both liquids. The GVPUE in MO was found to be higher than that in SE for the same PD magnitude. The results of DGA‐BD tests showed that larger breakdown gap distances lead to a higher GVPUE and a lower H 2 /C 2 H 2 gas ratio. The findings bring new insights on fault gas generation mechanisms in transformer liquids.