Influence of paper insulation on acceptable gas-in-oil levels in transformers

Abstract

The influence of cellulose on acceptable gas-in-oil levels in high-voltage transformers as indicated by the value of the CO/sub 2//CO ratio is assessed by means of dissolved-gas analysis. The results presented here are based on 6932 gas-in-oil analyses on 1320 Hydro-Quebec transformers over a period of 20 years. Preliminary results indicate that C/sub 2/H/sub 4/ levels are affected by cellulose participation for both arcing and hot spots. The effect can be felt starting from CO/sub 2//CO ratios <6 for arcing and <2 for hot spots. These results suggest that the acceptable and dangerous levels of dissolved C/sub 2/H/sub 4/ in power transformers must be greatly reduced as the CO/sub 2//CO ratio in the oil decreases.<>