The compare of different 750 kV transmission lines from Manping to Lanzhou

In this paper, an analysis of the simplified equivalent circuit and an EMTP simulation study are presented, based on the programming of the 750 kV power transmission system in Northwest of China in 2005. With different types of transmission lines, surface gradients and power frequency overvoltages are studied and the preferred one is given. The surface gradient is one of the important parameters to evaluate the corona discharge performance. When its level exceeds certain value, it may initiate corona that results in corona loss, audible noise, radio interference etc., so a new method is used to get its value. The complicated trend of power frequency over-voltage is explained also.