Data Acquisition System for Thermal Monitoring in High-Voltage Step Down Substation using Raspberry Pi and IoT Sensors

Transformer substations are critical nodes in power transmission and distribution networks. Transformers are subject to internal and external thermal stresses, which can compromise their operational lifespan and the reliability of the power system. This study presents a cost-effective, low-power data acquisition system designed based on publishing/subscribe architecture for real-time thermal monitoring and modelling of machine rooms in primary substations. The system integrates four IoT-based Raspberry Pi Pico Enviro Weather Aboard sensors, a Raspberry Pi 5, and a GSM router for data transmission. Environmental data, including air temperature, humidity, and pressure, is directly sent to InfluxDB via HTTP API and visualized through Grafana, while OpenVPN ensures secure remote access. This scalable and efficient solution enables data-driven analysis of seasonal and operational thermal behaviour, contributing to enhanced transformer safety and substation thermal management.