The JN900A series decentralized microcomputer protection and monitoring device is a protection and monitoring device developed based on the fully decentralized design mode of "one device (one bay), one device" on the switchgear. The device chassis is designed with a compact structure, good sealing, strong anti-interference and vibration resistance, and can meet the protection and monitoring needs of equipment such as 10KV and below voltage level feeders. The device can be flexibly configured according to user requirements to achieve the best performance price ratio. Mainly including J900A-XL microcomputer line protection and monitoring device, JN900A-DR microcomputer capacitor protection and monitoring device, N900A-DJ microcomputer motor protection and monitoring device, JN900A-PTB voltage parallel device, and JN900A-FBT backup power automatic switching device. Through different settings, it can be applied to line protection (including incoming and outgoing lines), segmented protection, and line transformer group protection (including station and substation).