What are the voltage levels of transmission and transformation lines in China? How can we distinguish between step-up and step-down transformers?

In China, the voltage levels of transmission and transformation lines include the following values (kV): 0.38, 3, 6, 10, 15 (20), 35, 60, 110, 220, 330, 500. The voltage at the beginning (power source end) of the line is higher relative to these values. In voltage levels of 10kV and below, the starting voltage is 5% higher; for voltage levels above 10kV, the starting voltage is 10% higher. Therefore, the rated voltage of transformers also increases accordingly. The rated voltage (kV) of the starting transformers for the line is: 0.4, 3.15, 6.3, 10.5 (11), 15.75, 38.5, 66, 121, 242, 363, 550.

Hence, if the high-voltage rated voltage of the transformer is higher than the voltage level of the line, the transformer is a step-up transformer; conversely, if the high-voltage rated voltage is lower than the starting rated voltage of the line, it is a step-down transformer.

In addition, the rated voltage (kV) of generators is usually higher than the line voltage levels, with common values such as 6.3, 10.5, 13.8, 15.75, and 18. Therefore, based on the comparison of rated voltages, only when the low-voltage rated voltage is higher than the line voltage level, it is a step-down transformer; in other cases, it is a step-up transformer. For example:

Example 1: Rated voltage ratio of 121kV/10kV indicates a step-up transformer (low-voltage rated voltage is not high).

Example 2: Rated voltage ratio of 110kV/10.5kV indicates a step-down transformer (only the low-voltage rated voltage is high).

Example 3: Rated voltage ratio of 121kV/10.5kV indicates a step-up transformer (both low and high-voltage rated voltages are high, essentially a generator transformer).

Example 4: Rated voltage ratio of 242kV/121kV/13.8kV indicates a step-up transformer.

Example 5: Rated voltage ratio of 110kV/38.5kV/11kV indicates a step-down transformer.

LuShan, est. 1975,  is a Chinese professional manufacturer specializing in power transformers and reactors for 48 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

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