To reduce misinterpretations of long intermittent and latent partial discharges that occur inside electrical equipment during live detection and online monitoring, avoid equipment failure and power failure due to insulation breakdown. This paper first studies the discharge characteristics of long intermittent partial discharges, and then designs a portable long intermittent partial discharge monitoring system based on existing live detection and online monitoring. This system can not only complete the collection of partial discharge signals in different frequency bands inside the device and the initial positioning of discharge defects, but also can dynamically track the development status of partial discharge defects in the cloud platform. The test and field application results prove that the designed long-interval sparse partial discharge monitoring system can complete the long-term tracking of partial discharge defects in electrical equipment, and evaluate the abnormal equipment insulation status through online data analysis.