Why are oil immersed transformers dominant in transmission networks?

Oil immersed transformers dominate transmission networks because they support very high voltages and power ratings efficiently. Oil provides superior dielectric strength and cooling, enabling compact insulation systems and reliable long-term operation. Transmission transformers experience heavy thermal and electrical stress, which oil insulation manages effectively. Dry-type alternatives are not practical at transmission voltage levels due to size, insulation limits, and cooling constraints.