## 1 Introduction  
The power supply reliability of the distribution network runs through the whole process of power grid planning, involvement, and operation. The power supply reliability evaluation result is an important basis for formulating the system construction and operation scheme [1]. The multi-voltage levels distribution network covers two voltage levels: medium voltage and low voltage. It is an important component of power distribution and supply to end users and has the most direct impact on users' electricity consumption. However, due to the great difference between medium and low-voltage distribution networks in the power supply range and the grid structure, the traditional sequential evaluation method is inconvenient for analyzing the weak links of the low-voltage distribution system. Therefore, it is urgent to propose a multi-voltage levels distribution system reliability evaluation method that can accurately evaluate the power supply capacity of the low-voltage distribution system and then guide the reliability management of the distribution system. At the same time, with improvement of informatization and automation, smart grid has become the development direction of the current distribution network step by step [2; 3], and provides a new path to improve the reliability of the distribution network. By configuring sense-control terminal equipment on switch equipment, the information communication is involved in the fault processing process, which can effectively reduce the outage time of the load. However, faults of the sense-control terminal will lead to the failure of the sensing and control ability of the distribution network [4]. If the sense-control terminal malfunctions and cannot perform the normal automation functions of fault location, isolation, and load transfer in the event of primary equipment malfunction, the efficiency of fault handling will be reduced and the power outage time will be extended. Therefore, the reliability evaluation method, considering the influence of the fault of the sense-control terminal, can reflect the real situation of the reliability of the distribution network. At present, there are few studies on the reliability evaluation of multi-voltage levels distribution networks. The existing work mainly focuses on the exploration of reliability evaluation methods for a low-voltage distribution system and the construction of an index system. Based on the load characteristics and the operation mode of the low-voltage distribution network, the reliability evaluation indices are established at the three levels of equipment, users, and system in Reference [5], so as to realize a comprehensive evaluation of the reliability. In Reference [6], the reliability index of low-voltage power users in the area to be evaluated is calculated by establishing the sub-region model of the distribution network and using probability and statistics theory to extract the power outage information of some power users. In Reference [7], a new statistical index system is established, and the statistical index formula and statistical boundary conditions are defined so as to realize the reliability analysis of low-voltage distribution networks. The literature in [8] set up an evaluation index system based on the user's power consumption characteristics and demand. The proposed multi-voltage comparison index can reflect the difference in the reliability level of the line between medium- and low-voltage users and highlight the reason why low-voltage distribution networks affect the reliability of electricity. The above literature expands the scope of reliability statistics and statistical indicators and supplements the evaluation methods of reliability. However, few studies have proposed reliability evaluation methods that take into account multi-voltage levels. The wireless sensor is one of the necessary pieces of equipment for building a smart grid system. Its reliability is directly related to the reliability and safety of the system.