Understanding the Relationship Between Insulation Aging and Gassing Tendency of Some Biodegradable Dielectric Fluids

This study investigates the degradation mechanisms and gas generation behaviors of three biodegradable dielectric fluids, bio-based mineral oils (Bio-MO), natural esters (NE), and synthetic esters (SE), under electrical stress, focusing on their application in power transformers. The research adopts an extended experimental protocol that includes multiple aging durations (250–2000 hours) and repeated breakdown voltage (BDV) tests to simulate arc fault conditions and ensure reproducible trend analysis. Key characterizations such as Dissipation Factor (DDF), Interfacial Tension (IFT), and Total Acid Number (TAN) were combined with Dissolved Gas Analysis (DGA) to monitor fluid degradation. A novel contribution of this work is the statistical correlation framework introduced to quantify the relationships between increases in gases (%C<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, %TDCG) and aging markers using correlation coefficients (r, p-value). Furthermore, Duval’s diagnostic tools (Triangle 1/Pentagon 1 for Bio-MO, Triangle 3/Pentagon 3 for esters) revealed that fault types evolve with aging. Specifically, Bio-MO transitioned from high-energy (D2) to low-energy (D1) discharges, strongly correlated with rising %DDF and %TAN. In contrast, NE and SE maintained stable D1 diagnostics. These findings offer a predictive approach to fault identification and transformer health assessment, paving the way for broader implementation with larger sample sets and field validation.