Why are the parameters of Northwest Power Grid different from other power grids?

Under the condition that the technology is not in place, Northwest Power Grid takes the lead in using the voltage level of 330 kV. Display query power grid display. At that time, the technology of 500 kV equipment could not be reached in China, so 330 kV equipment was chosen to be laid in the northwest first. After the technology was realized, 500 kV equipment was used in other parts of China. Therefore, the parameters of Northwest Power Grid are different from those of other power grids because when the technology is not in place, Northwest Power Grid takes the lead in using the voltage level of 330 kV.