Which method of determining turn ratio of transformer is more accurate and why?

The most accurate method for determining the turn ratio of a transformer is the impedance method, which involves measuring the primary and secondary impedances under load conditions. This approach accounts for the effects of winding resistances and leakage reactances, providing a more realistic representation of the transformer's performance. Unlike the open-circuit or short-circuit methods, the impedance method reflects actual operating conditions, leading to a more precise turn ratio assessment.