# Monitoring System of Transmission Line in Mountainous Area Based on LPWAN
## 1 Introduction  
The reliability of power grid transmission largely depends on the reliability of the transmission line working state [1]. Compared with the populated urban areas, transmission lines in remote mountainous areas are difficult to monitor and maintain due to their special geographical location. Traditional methods of transmission line monitoring generally adopt manual inspection, which is time-consuming and laborious. In [2; 3; 4; 5], robots and unmanned aerial vehicles (UAVs) were proposed for automatic line inspection, showing the advantages of low cost and high efficiency compared with manual inspection. However, these methods are still not real time and are difficult to operate in mountainous area. The online monitoring systems of transmission line can be usually divided into wired systems and wireless systems. Although the cable communication technology exhibits the merits of large capacity and fast speed [6; 7], its application in mountainous areas is limited by the expensive installation and maintenance cost. For a wireless monitoring system based on a mobile cellular network [8; 9], it can achieve a high wireless transmission speed, large communication bandwidth and wide communication coverage. However, the cost of a mobile cellular network is expensive and its communication coverage is hard to reach in some remote mountainous areas. Due to the merits of simple deployment, low cost, no on-site maintenance, etc., wireless sensor networks (WSNs) are rapidly applied in variousmonitoring fields since its emergence [10]. There are already many reports on transmission line monitoring systems based on WSN such as wire galloping [11; 12], icing warning [13; 14; 15; 16], and tower tilt [17; 18; 19; 20]. However, the communication distance of WSN is relatively short and its work life is limited, which is not suitable for long-term monitoring of transmission lines in mountainous areas. Low power wide area network (LPWAN) is a new emerging internet of things (IoT) communication technology, which complements between mobile cellular technology and WSN. Compared to the WSN, LPWAN technology shows a longer work life (up to 10 years) and larger communication distance (up to 10 km) [21], hence it is regarded as the mainstream communication technology in the era of 5G IoT [22; 23]. Narrow band Internet of Things (NB-IoT) and long range radio (LoRa) are two typical technologies of LPWAN. NB-IoT is built on the cellular network and works in the authorized spectrum [24; 25; 26; 27], LoRa works in unauthorized spectrum and can self-organize a communication network like WSN [28; 29]. In [30], a monitoring system based on LoRa was proposed and achieved a maximum transmission distance of 8.33 km. Although NB-IoT can provide higher quality of service (QoS), LoRa is more suitable for application in mountainous areas due to the communication blind area of the cellular mobile network. [PERSON] [31] proposed an information monitoring method combining NB-IoT and LoRa, which not only improved the transmission distance, but reduced the operation cost of the monitoring system. However, the low communication speed of LoRa makes it hard to satisfy the demand of the transmission line monitoring system. The hybrid monitoring networks in [32; 33] provided us with an excellent choice in achieving the balance between the network performances and network cost. Compared with ordinary schemes, the monitoring schemes in mountainous areas exhibit great differences in monitoring scheme selection, measurement accuracy, daily monitoring operation maintenance, and implementation [34]. Single working mode is difficult in terms of satisfying the requirements of the online monitoring of transmission lines in mountainous areas [35]. This paper proposes a long-term online monitoring scheme based on LPWAN. Considering the different failure rates, three monitoring periods of transmission lines in mountainous areas were proposed.