Evaluation of Wireless Communication for Maintenance of Underground Power Transmission Lines

In the smart grid environment, power sources using unstable renewable energy, such as wind and solar power, connected to the transmission and distribution lines may make the power facilities severe status. Properly grasp of the state of power facilities using ICT is required in order to realize efficient maintenance work, and beside to detect abnormal signs of them automatically. In this paper, applicability of wireless communication system to the maintenance work of underground power transmission lines, that is usually carried out inside of a manhole, is discussed. In order to realize data transmission from inside to outside of a manhole without any additional construction work around a manhole, the use of a wireless communication technology is essential. Since a radio signal may not propagate sufficiently due to a metallic lid laid on the top of a manhole, radio propagation characteristics of 920 MHz band using LoRa were evaluated through the experimental study using a real manhole equipment. Furthermore, for a simple design of a wireless communication system between inside and outside of a manhole, applicability of a computer simulation method of the radio propagation, that is finite difference time domain (FDTD), is shown through a comparison between measured and simulated results.