# Development of an Online Detection Setup for Dissolved Gas in Transformer Insulating Oil
## 4 Experiment and Discussion
### Dissolved Gas Analysis  
In order to determine the operating status of the transformer, dissolved gases in the detected oil samples are analyzed. The total hydrocarbons (THC) and CO\({}_{2}\)/CO value of the oil samples are shown in Table 5.  
According to the guidelines of the electric power industry (IEEE Std C57.104-2019 and IEC60599), the acetylene concentration is used as the criterion. The attention value is 5 \(\upmu\)L/L. When it reaches 35 \(\upmu\)L/L, it indicates that the transformer will malfunction if it continues to operate. Some scholars [6; 26; 32] have measured acetylene and provided early warning to the transformer. However, acetylene can only be used as a caution indicator for judging the state of the transformer. When the concentration of acetylene is between the caution value and the serious warning value, it is impossible to further analyze the state of the transformer (such as the fact that the concentration of acetylene in No.1 oil sample is about 10 \(\upmu\)L/L). At this time, only the measurement of acetylene does not meet the requirements. Therefore, it is necessary to measure other characteristic gases to analyze the further state of the transformer. \begin{table}
\begin{tabular}{c c c c c} \hline
**Oil Sample Number** & **Type of Gas** & **Measurement Result (\(\upmu\)L/L)** & **Standard Value (\(\upmu\)L/L)** & **Error Value (\(\upmu\)L/L or \%)** \\ \hline \multirow{4}{*}{1} & CO & 12.1 & 15.5 & 3.4 \\  & CO\({}_{2}\) & 735.6 & 711.5 & 3.4 \\  & CH\({}_{4}\) & 11.9 & 12.7 & 0.8 \\  & C\({}_{2}\)H\({}_{4}\) & 37.8 & 36.2 & 1.6 \\  & C\({}_{2}\)H\({}_{6}\) & 88.7 & 91.1 & 2.4 \\  & C\({}_{2}\)H\({}_{2}\) & 9.6 & 10.8 & 1.2 \\ \hline \multirow{4}{*}{2} & CO & 236.7 & 234.2 & 2.5 \\  & CO\({}_{2}\) & 1127.3 & 1263.1 & 10.8 \\  & CH\({}_{4}\) & 67.9 & 70.2 & 2.3 \\  & C\({}_{2}\)H\({}_{4}\) & 93.2 & 91.4 & 1.8 \\  & C\({}_{2}\)H\({}_{6}\) & 159.7 & 161.2 & 1.5 \\  & C\({}_{2}\)H\({}_{2}\) & 53.1 & 54.5 & 1.4 \\ \hline \multirow{4}{*}{3} & CO & 3906.1 & 3755.6 & 4.0 \\  & CO\({}_{2}\) & 11,920.3 & 10,510.3 & 13.4 \\ \cline{1-1}  & CH\({}_{4}\) & 841.9 & 851.2 & 1.1 \\ \cline{1-1}  & C\({}_{2}\)H\({}_{4}\) & 793.7 & 780.2 & 1.7 \\ \cline{1-1}  & C\({}_{2}\)H\({}_{6}\) & 803.2 & 823.7 & 2.6 \\ \cline{1-1}  & C\({}_{2}\)H\({}_{2}\) & 821.8 & 811.4 & 1.3 \\ \hline \end{tabular}
\end{table} 
Table 4: Comparison result of experimental setup measurement data and standard oil sample. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**Oil 1**} & \multicolumn{2}{c}{**Oil 2**} & \multicolumn{2}{c}{**Oil 3**} \\ \cline{2-7}  & **Measurement** & **Standard** & **Measurement** & **Standard** & **Measurement** & **Standard** \\ \hline CH\({}_{4}\) (\(\upmu\)L/L) & 11.9 & 12.7 & 67.9 & 70.2 & 841.9 & 851.2 \\ C\({}_{2}\)H\({}_{4}\) (\(\upmu\)L/L) & 37.8 & 36.2 & 93.2 & 91.4 & 793.7 & 780.2 \\ C\({}_{2}\)H\({}_{6}\) (\(\upmu\)L/L) & 88.7 & 91.1 & 159.7 & 161.2 & 803.2 & 823.7 \\ C\({}_{2}\)H\({}_{2}\) (\(\upmu\)L/L) & 9.6 & 10.8 & 53.1 & 54.5 & 821.8 & 811.4 \\ THC (\(\upmu\)L/L) & 148 & 150.8 & 373.9 & 377.3 & 3260.6 & 3266.5 \\ CO (\(\upmu\)L/L) & 12.1 & 15.5 & 236.7 & 234.2 & 3906.1 & 3755.6 \\ CO\({}_{2}\) (\(\upmu\)L/L) & 735.6 & 711.5 & 1127.3 & 1263.1 & 11,920.3 & 10,510.3 \\ CO\({}_{2}\)/CO & 60.8 & 45.9 & 4.8 & 5.4 & 3.1 & 2.8 \\ \hline \end{tabular}
\end{table} 
Table 5: The value of THC and CO\({}_{2}\)/CO. The type of transformer fault is judged by the Duval triangle [33]. It needs ethylene and methane dissolved in the oil samples to assist. The analysis results of the Duval triangle are shown in Figure 16.  
According to the definition of Duval triangle, the formula for the proportion of C\({}_{2}\)H\({}_{2}\), C\({}_{2}\)H\({}_{4}\), and CH\({}_{4}\) is as follows:  
\[\%C_{2}H_{2}=\frac{100X}{X+Y+Z};\ \%C_{2}H_{4}=\frac{100Y}{X+Y+Z};\ \%CH_{4}= \frac{100Z}{X+Y+Z} \tag{9}\]  
\(X\)_; \(Y\); \(Z\) are the concentrations of acetylene, ethylene, and methane in transformer insulating oil.