The Effect of Selected Experimental Conditions on DGA Key Gas Ratios During Simulated Thermal Faults in a Bench-Top Test Rig

Dissolved gas analysis (DGA) is the most widely used technique for monitoring transformer conditions and detecting early-stage faults. The quantity and type of gases produced by transformer faults and dissolved in the insulating liquid provide valuable insights into the nature and severity of the fault. A previous simulation of thermal faults using a lab-scale test rig yielded key gas ratios that consistently indicated a high-temperature fault. However, inconsistencies in the predicted fault type were observed depending on whether IEC 60599 or Duval triangles were applied. This study investigates the influence of headspace volume and hotspot material on key gas ratios at simulated thermal faults at 550°C for mineral oils. Reducing the headspace volume and incorporating copper in the hotspot improved the agreement between experimental data and observed field data.