In power transmission systems of330~500kV(domestic)and750kV(abroad)
MOA has several different protection levels.This paper studies the switching surges in a750kV power transmission system with MOA of different pro-tective levels.The lower the rated voltage of MOA
the lower the switching surge
and the more the energy absorbed by MOA.The measures to limit switching surges are presented under the situation of the elimination of closing resistor.