MDD3000S switchgear can be online monitoring system can monitor the operating status of the switchgear, by the online monitoring and fault diagnosis of the two major components. The fault monitoring part includes the fault judgment module, the fault diagnosis module, the fault severity and the development trend analysis module, the fault hazard assessment module and the maintenance strategy module. The fault diagnosis module includes the fault diagnosis module, the fault diagnosis module, the fault severity and the development trend analysis module, the fault hazard assessment module and the maintenance strategy module The