Humidity control and data collection of Transformer Low Tension cable Box using IoT

Power Transformers are most vital and costly equipment of EHV grid substation. At Tata Power Mumbai, Transmission we faced transformer failures due to failure of support insulators of newly commissioned transformers within one or two years after commissioning. These failures occurred irrespective of transformer manufacturers i.e., ABB, Siemens, TBEA and Schneider etc. It was observed that this typical type of failure occurred early morning hours after first spell of monsoon shower.

Suspected cause of failure is high humidity level condition arises due to rains. But it was difficult to ascertain the cause as it is not possible to open the transformer LT cable compartment while it is service due to safety concerns. Also, repetitive outages of Power Transformers cannot be availed as it has negative impact on company's revenue stream.

To address the challenge, we at Tata Power decided to explore the new technology and latest sensors available in market. With help of Information Technology group, we partnered with Tata Communication team to assess the internal condition of transformer LT cable box and develop the solution to address the cause. With help of Tata Communication, our team explored IoT based temperature and humidity sensor which work on LoRa (Long Range Technology) and can be installed inside transformer LT cable box. As a pilot project, Power Transformer located at Tata Power Parel division was identified for conducting experiments. Temperature and humidity data were fetched from cloud-based server and same was analysed with different environmental conditions like outside temperature and humidity level to achieve the correlation between outside temperature and humidity level with temperature and humidity level present inside transformer LT cable box. Also, data was analysed with different design conditions of transformer LT cable box i.e., without louvers, with louvers-without heaters and with louvers -with heaters. This paper illustrates in detail the different scenarios with data and photographs to ascertain the cause of failure of transformer. It explains the use IoT based technology for condition monitoring to minimize the requirement of outages to access the condition.

After establishing the correlation between external weather condition, design aspects of equipment and humidity level, next challenge was to eliminate the root cause of problem. For the same we designed inhouse solution i.e., Battery RF (Radio Frequency) sensor and remote humidity controller to control the humidity level inside transformer LT cable box.

The pilot project was found effective to achieve mobility and connectivity as data generated by IoT sensors can be accessed through mobile handset and humidity level can be controlled by sending SMS to controller through mobile headset. This pilot was also effective for automating process to control humidity level of transformer LT cable box and switchgear. Paper discusses the same in details.