Time-Aware Monitoring of Overhead Transmission Line Sag and Temperature with LoRa Communication

Abstract

The techniques of Dynamic Line Rating (DLR) for Overhead Transmission Line (OTL)’s are currently dynamically developed. DLR systems typically rely on weather, temperature, inclination, and current measurements to calculate tension and sag, where sensors need to be installed directly on wires. Such systems are very reliable and ensure high accuracy in determining maximum allowable current. However, their installation may require switching off the transmission line from the operation. In order to receive precise values regarding the actual operating conditions of the whole transmission line, DLR sensors measuring wire temperature or tension should be installed at many points of OTL. The minimum number of installation points should cover at least each tension section and critical spans, thereby increasing installation costs. The alternative method that allows for the monitoring of OTL is the use of the vision system based on cameras. Installed on the OTLs’ poles, cameras can take photos which, appropriately processed, can provide data about the sag and temperature of wires, without the necessity of switching OTL from the operation for installation or further maintenance. Such a vision system facilitates also data transmission, because it does not require measurement data to be transmitted from the sensor station installed on the wire to the base station located on the pole (for instance, via radio). This article aims to present the concept of a vision system that monitors sag and temperature of Overhead Transmission Lines (OTLs)’ using Long Range (LoRa) wireless communication and data transmission. The developed system consists of a camera and a microcomputer equipped with LoRa communication module. The whole system monitors OTLs’ spans by taking photos, processing images for wire sag-temperature estimation, and sending results to the operator’s Supervisory Control And Data Acquisition (SCADA). The system communication architecture is also proposed and investigated for data transmission time when monitoring the whole OTL.

Keywords

• overhead transmission line
• sag
• temperature
• estimation
• dynamic line rating
• vision system
• image processing
• wireless sensor networks
• LoRa
• transmission time