A comprehensive evaluation and advancements in dissolved gas analysis for biodegradable oil in photovoltaic solar plants

Abstract

Over the past three decades, the energy industry has embraced the adoption of a new type of biodegradable oil. Presently, the prevailing international standard for its evaluation is IEEE C57.155–2014. Various working groups, including those within CIGRE A2.68, IEC, and industry manufacturers, have embarked on endeavors to explore new evidence and methodologies for assessing the accuracy and alternatives in detecting failures. These failures are often indicated by elevated levels of seven gases: Hydrogen, Ethane, Acetylene, Methane, Ethylene, Carbon Monoxide, and Carbon Dioxide. Consequently, instances of high oil temperatures have been observed during the optimization of dimensions near hot-spot limits, particularly in renewable energy applications. This research article presents an in-depth analysis of a substantial database comprising 2834 units, aimed at establishing new thresholds for dissolved gas analysis applied to biodegradable oil in photovoltaic solar plants. The developed methodology successfully identified 844 oil samples in poor condition, 332 samples exhibiting one or more failure modes without fault or disconnection, and 1658 units in good condition. Validation of the instrumentation was conducted on 87 transformers through internal inspection, verifying the classification according to the new methodology for evaluating relevant variables and limits of gases through Gaussian distribution and seven algorithms. This validation aimed to enable early detection of failures and establish a health index, achieving an accuracy rate of 90.8 % with support vector machine, 97.6 % with random forest, and 98.3 % with XGBoost. Future research directions should consider evaluating viscosity as a factor in assessing the quality and degradation of transformers utilizing biodegradable oil.