220/330/500kV transformers are high voltage oil-immersed transformers with a heart structure. According to the number of phases can be divided into single-phase transformers, three-phase transformers; according to the regulating method can be divided into on-load regulating, non-excitation regulating; according to the winding coupling method can be divided into power transformers, autotransformers; according to the number of windings can be divided into double-winding, three-winding, three-winding + balance winding. Also included are split transformers, combined transformers and other special types of 220/330/500kV transformers. The products are designed according to IEC international standards, IEEE standards and current national standards.