Classification of Power Transformers

Power transformers are classified according to their usage: step-up (6.3kV/10.5kV or 10.5kV/110kV in power plants, etc.), interconnection (220kV/110kV or 110kV/10.5kV between substations), and step-down (35kV/0.4kV or 10.5kV/0.4kV for distribution).
Power transformers are classified by phase number: single-phase and three-phase.
Power transformers are classified by winding: dual winding (each phase is installed on the same iron core, and the primary and secondary windings are separately wound and insulated from each other), triple winding (each phase has three windings, and the primary and secondary windings are separately wound and insulated from each other), and autotransformer (the middle tap of a set of windings is used as the primary or secondary output). A three winding transformer requires the capacity of the primary winding to be greater than or equal to the capacity of the secondary and tertiary windings. The percentage of the capacity of the three windings is in the order of high voltage, medium voltage, and low voltage: 100/100/100, 100/50/100, and 100/100/50. It is required that both the secondary and tertiary windings cannot operate at full load. Generally, the voltage of the tertiary winding is relatively low, and it is mostly used for nearby power supply or compensation equipment to connect three voltage levels. Autotransformer: There are two types of transformers: step-up or step-down. Due to its low loss, light weight, and economical use, it is widely used in ultra-high voltage power grids. The commonly used model of small autotransformers is 400V/36V (24V), used for power supply of safety lighting and other equipment.
Power transformers are classified according to insulation media: oil immersed transformers (flame retardant, non flame retardant), dry type transformers, and 110kVSF6 gas insulated transformers.
The iron cores of power transformers are all of core structure.
The three-phase power transformer configured in general communication engineering is a dual winding transformer.