The detection of partial discharge is crucial for the safe operation of the power grid. Current live detection technologies are ineffective at detecting intermittent partial discharge signals, and online monitoring systems are not widely adopted due to high costs. This paper presents the development of a flexible deployment long-term partial discharge monitoring device that enables rapid deployment, full-station coverage, continuous data collection, and remote control capabilities. The device consists of digital sensors, a digital frequency synchronization unit, a power supply and communication unit, and an analysis and diagnostic backend. It receives, analyzes, and diagnoses partial discharge signals, and uses an integrated 4G communication module to display monitoring data and diagnostic results via the cloud.