This research article investigates the performance and fault detection capabilities of 35 zig-zag transformers connected to solar power plants in the medium voltage busbar, focusing on “dissolved gas analysis” (DGA) and fault diagnostics. Despite the absence of sudden disconnections, the transformers exhibited evolving failure modes. The study details the protection mechanisms employed, including overcurrent, overvoltage, and me chanical protections, integrated with a master trip system. Revealing significant deviations from normal levels before faults. Elevated hydrogen and methane levels, along with increased acetylene concentrations, indicated severe arcing and overheating, while treated oil samples showed a notable reduction in gas concentrations, underscoring the effectiveness of oil treatment in managing thermal and electrical stresses. This paper highlights the evolution of fa...