## 3 Results and Discussion
### Analysis of Overall Data  
According to the previous analysis, we first determined the insulation resistance data that were lower than \(10^{7}\)\(\Omega\) in each case, counted the cable failure time for each case, calculated the multiple cable failure time, and counted the surface temperature of a power cable at 20 min and the cable failure time, as shown in Table 4.  
Figure 7: Temperature and logarithmic value for insulation resistance-time curve: (**a**) curves of case 1; (**b**) curves of case 2; (**c**) curves of case 3; (**d**) curves of case 7; (**e**) curves of case 8; (**f**) curves of case 11.  
We could see from the table that compared with the control group, the failure time of the cable could be delayed by 1.57 to 14.86 times. According to the above table, the failure time of each case, the surface temperature of the power cable at 20 min, and the failure time were plotted as a dot plot, as shown in Figure 8, in order to compare the effects of each case more intuitively.  
There are 5 cases above the qualified line in the figure, which are case 3, case 8, case 9, case 10, and case 11. Among these cases, one case of IFC was qualified, three cases of NFC were qualified, and one case of FC was qualified.  
We used the time of the failure to characterize the fire protection effect. The later the failure time was, the better the fire protection effect was. Therefore, according to the statistical results, the fire protection effects of the 12 cases were ranked from good to bad as follows: case 8 > case 9 > case 11 > case 10 > case 3 > case 12 > case 4 > case 5 > case 7  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Case** & **Tibness of Material** & **Tibness of Material (mm)** & **Failure Time** & **Surface TEMP of Power Cable (\({}^{\circ}\)C)** & **Multiple** \\ \hline
1 & None (blank & & & & \\ control) & 0 & 00:04:40 & 725.269 & 77.664 & / \\
2 & Brand A IFC (W) & 4.4 & 00:09:30 & 433.878 & 133.977 & 2.04 \\
3 & Brand B IFC (W) & 4.4 & 00:23:20 & 78.872 & 91.943 & 5.00 \\
4 & Brand B IFC (W) & 3.5 & 00:14:00 & 168.631 & 117.251 & 3.00 \\
5 & Brand B IFC (W) & 2.5 & 00:11:50 & 198.060 & 130.034 & 2.54 \\
6 & Brand B IFC (W) & 1.5 & 00:07:20 & 246.353 & 85.932 & 1.57 \\
7 & Brand B IFC (O) & 4.5 & 00:11:40 & 146.576 & 86.925 & 2.50 \\
8 & Brand C NFC & 40 & 01:09:20 & 42.509 & 143.814 & 14.86 \\
9 & Brand C NFC & 30 & 00:04:00 & 48.243 & 82.223 & 8.57 \\
10 & Brand C NFC & 20 & 00:25:50 & 87.128 & 123.299 & 5.54 \\
11 & Brand D FC & 50 & 00:27:40 & 58.756 & 132.145 & 5.93 \\
12 & Brand D FC & 30 & 00:15:10 & 176.164 & 93.356 & 3.25 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Result statistics for 12 cases.  
Figure 8: Dot plot of surface temperature of power cable and failure time for 12 cases.  
> case 2 > case 6 > case 1. The high and low trends of the blue five-pointed star and the green dot were roughly symmetrical, as shown in Figure 8. That is, the order of the fire protection effects of the 12 cases from good to bad was roughly the same as the order of the surface temperature of the power cable at 20 min from low to high, which indicated that the temperature rise rate had a certain relationship with the failure time of the cable. The red triangle in the figure indicates the surface temperature of the power cable when it failed, which generally fluctuated around 100 \({}^{\circ}\)C.  
The comparison of the power cable's surface temperature curves for the 12 cases is shown in Figure 9. The temperature of each case increased in accordance with the trend of S-type or anti-S-type. Obviously, the temperature rise of the blank control group was the fastest. Among the other cases, the temperature rise of case 2 was the fastest, and that of case 8 was the slowest.  
The insulation resistance data that were lower than