Intelligent Thermal Protection of Power Transformers Using ANN–FLC Framework for Smart Grid Applications

Transformer lifetime is greatly impacted by thermal stress under overload conditions, while traditional threshold-based protection and delayed cooling may react only after the hottest-spot temperature has already progressed to a critical stage. This study presents an adaptive framework to that combines ANN–FLC control with nanofluid cooling and Lyapunov-guided gain adaptation, while quantifying insulation loss of life based on the IEEE C57.91-2011 loading guide. The approach is evaluated on a 400 kVA, 33/0.38 kV, ONAN transformer under challenging conditions (40°C ambient, up to 140% overload, 5.2% THD, and a 15°C thermal step) each experiment was repeated five times (N = 1200 samples, 30 ms sampling). In comparison with ON–OFF, PID, and conventional ANN–FLC controllers. The proposed approach yields a faster transient response (28 s settling, 2.3°C overshoot), maintains operation within the 120°C limit, and decreasing aging-related indices. Long-period trajectories further present improved correlation aging and a projected insulation life of 32.4 years, enabling proactive operation/management, stability-aware transformer protection for intelligent-grid asset lifecycle management.