You need special tools to test transformers. These tools are vital for commissioning, checking, and fixing power and distribution transformers. The equipment makes sure these critical parts of the electric grid stay reliable, efficient, and last long. Testers check three main parts: windings, insulation, and oil. Key tools include Resistance Meters, TTRs, Meggers, and Power Factor units. They check if the transformer is safe electrically. For deeper checks, SFRA finds mechanical issues. DGA also looks for internal heat or electric faults by testing the oil. Always use certified testing gear. This is key to meeting standards (like IEEE/IEC) and stopping huge failures.