The difference in voltage grading between the step-down transformer and the step-up transformer:
According to the guidelines for the selection of power transformers (GB/T17468-1998), the selection of transformers:
Transformer rated voltage: refers to the specified voltage induced between the single-phase or three-phase transformer line terminals, when specified or applied.
The rated voltage of the step-down transformer (input) is usually: 3, 6, 10, 15, 35, 66, 110, 220, 330, 500 kV.
The rated voltage of the booster transformer is usually:
The generator transformer (input) voltages are 3.15, 6.3, 11 (10.5), 13.8, 15.75, 18, 20, 24 kV.
(output) voltage: 38.5, 72.5, 121, 242, 363, 550kV.
The difference on the tap-changer:
1. The step-up transformer is generally a transformer with no load regulating tap changer. The generator is a variable non-functional source with excellent regulation performance. Under normal circumstances, the step-up transformer of the generator does not need to be adjusted with load taps, and even a transformer without a voltage tap can be used.
2. The network transformer is the same as the step-up transformer. For network transformers with 220kV and above connected to the highest voltage level power grid, it is generally not suitable to use load voltage regulation for the transformer including the step-up transformer and the two transformers with the highest voltage level.
3. Step-down transformers are generally transformers with on-load tap-changers. The voltage regulation requirements for transformers that supply power directly to the load are quite different from those of the above two types of transformers. It is necessary to widely use voltage-adjustable voltage taps.
The voltage at the output of the booster transformer and the step-down transformer is different. The voltage at the output of the transformer needs to be 10% higher than the voltage on the load side (such as the bus voltage).
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