In the switching process of microgrid from the state of being intergrated in external grid to the state of island operation, many devices such as energy storage devices, after sudden disturbance changes its running state, in some extreme cases, this change will overcome the device's affordability, requires the using of relay protection device to avoid further damage. The platform of the microgrid laboratory of xi 'an jiaotong university is used to verified the phenomenon of the microgrid mode switching in extreme circumstances, and points out the importance of reasonable in microgrid relay protection setting, providing a reference direction for the further theory research of control strategy in mode switching.