What does the CO2/CO ratio in transformer oil indicate?

The CO2/CO ratio in transformer oil is an indicator of the condition of the paper insulation within the transformer. A high ratio of carbon dioxide (CO2) to carbon monoxide (CO) generally suggests that the paper insulation is aging normally, with slow, natural degradation. Conversely, a low CO2/CO ratio may indicate more severe or accelerated insulation degradation, possibly due to thermal stress or overheating. Monitoring this ratio through dissolved gas analysis (DGA) helps in assessing the health of the transformer and predicting potential issues before they lead to failure.