## 4 Simulation Results and Discussion
#### 4.1.2 Outage Time of System with Fault  
When a fault occurs on the line, the fault signal is detected by the fault measuring module of the fault indicator and is also detected by the protection device on the feeder. After a certain time delay, the feeder where the fault occurs will be cut off by the protection device. As a result, the feeder loses power at this time. Then, according to the fault section information located by the fault indicator, the staff can quickly locate the fault point by patrolling the line from upstream to downstream, cut off the fault point, and close the circuit breaker. Consequently, the feeder resumes power supply at this time. The time from the feeder loses power to the feeder resumes power supply is called outage time. In this paper, the fault indicator is optimized according to the outage time of system with fault is less than 2 h, but in actual operation, the less the outage time of system with fault is, the earlier the fault point is accurately located, the higher the reliability of the system. Therefore, the change of configuration scheme of fault indicator can be observed by setting different outage time of distribution system with fault as shown in Table 3. When the outage time is assumed as less than 1.5 h, the average time for fault location is 0.234 h, which is less than the average time for fault location when the outage time is assumed as less than 2 h. However, the total number of fault indicators is 17 (when the outage time is 1.5 h), which is more than 15 (when outage time is 2 h), and the total cost is 262.29 USD (when the outage time is 1.5 h), which is more expensive than that of 2 h.  
Moreover, the time required for any fault point to be accurately located under different outage time of the system with fault is shown in Figure 10. For example, when the fault occurs at point 1, after locating the corresponding fault section through the fault indicator and patrolling the line at a certain speed, the locating time is about 1.5 h when outage time is assumed as less than 2 h, while the locating time is about 0.7 h when outage time is assumed as less than 1.5 h, which is much less.  
It can be seen from Table 3 and Figure 10 that if the outage time of the system with fault is shorter, the total installation number of acquisition unit and collection unit will be more, and the total cost will be higher. However, the shorter the outage time of the system with fault is allowed, the earlier the fault point is located accurately, and the higher the security of the system is. Therefore, in the case of sufficient capital budget, increasing the number of installations of fault indicators on the line reasonably is conducive to the rapid removal of fault points and power-supply recovery.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Outage** \\ **Time (h)** \\ \end{tabular} } & **Installation** & **Installation** & **Installation** & **Average** & \\  & **Number of** & **Position of** & **Number of** & **Position of** & **Time for** & **Total Cost** \\  & **Acquisition** & **Acquisition** & **Collection** & **Unit** & **Unit** & **Location (h)** & \\ \hline \multirow{3}{*}{2} & \multirow{3}{*}{14} & 3, 5, 6, 8, 9, 10, & & & & & \\  & & 11, 12, 13, 15, 18, & 19, 22, 23 & & & & \\ \hline \multirow{3}{*}{1.5} & \multirow{3}{*}{15} & 2, 3, 5, 6, 8, 9, 10, & & & & & \\  & & 11, 12, 13, 15, 18, & 2 & 7,12 & 0.234 & 262.29 \\ \cline{1-1}  & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Optional placement of fault indicators under different outage time of the system with fault.  
Influence on Fault Indicator Configuration Scheme by Changing Some Parameter Values Related to the Different Power Lines  
The situation will be different for different power lines configurations. In order to analyze the results related to the cost savings for different power lines, we can observe the impact on the configuration scheme of a fault indicator by changing some parameter values related to different power lines.