Selection of Impedance Parameter for 500kV Large Capacity Transformers in Guangdong Power Grid

Combining actual demand for large capacity transformers in 500 kV load-center substations of Guangdong power grid,relationship among short-circuit impedance,short-circuit current level,reactive power compensation capacity,transformer structure and loss are analyzed.It is believed that raise of medium and high impedance voltage can reduce breaking current,but it also increases construction price of transformers,energy losses,reactive power loss and operating expenses of power system and so on.Accordingly,it is suggested that the medium and high impedance voltage of 1500 MVA large capacity voltage in 500 kV load-center substations of Guangdong power grid can be selected between 22% and 24%,taking manufacturing technology,energy loss of transformers and reactive power loss and other facors into account.