## 2 Distribution Network Reliability Evaluation Method
### Fault Impact Analysis
(4) Considering the reliability analysis process of sense-control terminal fault  
Based on the above reliability analysis of the fault of the sense-control terminal, this paper establishes the fault influence table of the sense-control terminal Table 1. The specific values of \(t_{2}\), \(t_{3}\) and \(t_{4}\) in the table depend on the type of sense-control terminal configured by the sectional switch and the contact switch. Although the outage time of the fault upstream area and the fault area is the same in both cases, the range of the fault area will expand and the range of the fault upstream area will decrease in the case of a fault location error. At the same time, due to the fault location error, two fault isolation and load transfer operations are required to isolate the fault area. Therefore, the outage time of the fault downstream area is the sum of the fault location time, the two fault isolation times, and the two load transfer times (\(t_{1}+2t_{2}+2t_{3}\)). Reliability Collaborative Evaluation Method of Multi-Voltage Levels Distribution Network Considering the Fault of Sense-Control Terminal  
Necessity Analysis of Reliability Collaborative Evaluation of Multi-Voltage Levels Distribution Network  
The traditional way to evaluate the influence of distribution system faults on the reliability of low-voltage users is to use the sequential evaluation method, that is, to evaluate the reliability of the medium-voltage distribution network first and then the reliability of the low-voltage distribution network. The specific idea is to first evaluate the network system from the 10 kV bus of the step-down substation through the medium-voltage distribution line to the low-voltage distribution transformer. Considering the failure rate and repair time of the main components of the medium-voltage distribution network, such as feeders (overhead lines, cables), circuit breakers, fuses, disconnectors, distribution transformers, etc., the failure rate, annual average outage time, and repair time of the entire medium-voltage distribution network are calculated. Then, the calculated system reliability parameters are taken as the basic information of the low-voltage distribution network structure, that is, the reliability parameters of the 10 kV low-voltage public distribution \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Upstream Fault Zone** & **Fault Domain** & **Fault Downstream Area** \\ \hline The fault location is correct & \(t_{1}+t_{2}\) & \(t_{1}+t_{2}+t_{4}\) & \(t_{1}+t_{2}+t_{3}\) \\ Fault location error & \(t_{1}+t_{2}\) & \(t_{1}+t_{2}+t_{4}\) & \(t_{1}+2t_{2}+2t_{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Fault impact table of the sense-control terminal. Figure 4: Fault isolation area under fault location error. Figure 5: Power restoration area under fault location error. transformer in the low-voltage distribution network, and then combined with the reliability parameters of the low-voltage bus in the low-voltage distribution network, the reliability index of each low-voltage user and the reliability index of the low-voltage distribution network are calculated. The reliability index of low-voltage distribution networks obtained by the above-mentioned sequential evaluation method of multi-voltage levels distribution networks cannot fully reflect the influence of medium-voltage distribution network faults on the reliability of low-voltage distribution networks. Because the reliability parameters input from the medium-voltage distribution network to the low-voltage distribution network are the average reliability parameters of all 10 kV low-voltage public distribution transformers, the reliability parameters of the distribution transformers at the weak links in the medium-voltage distribution network are weakened, which cannot reflect their impact on the reliability of low-voltage users, which is not conducive to the power grid company's formulation of effective improvement measures.