The MFU3-B, C and D series of flow modular surge protectors are suitable for the power supply systems such as the gate AC 50/60Hz, the rated voltage 380V and the following TT, IT, TN-S, TN-C, TN-C-S and other power supply systems, and protect the power grid because of lightning or surge overvoltage. The design is based on C61643-1, GB18802-2002 and it can vent the 100KA lightning current. The shell is designed and installed on the 35mm electric guide. The detaching device can automatically remove it from the power grid, and the state indicator window is turned from green to red.