On-line PD detection is an effective way to understand the insulation status of the equipment in MV and HV power system. It can be carried out with the equipment being in normal services. This is a new technology developed in recent years and there are still a lot of researches and development works to be done to solve the problem it is currently with. The system introduced here in this paper is a new approach to the online PD detections for MV plants. It is simple but effective. It utilizes the normal HFCT and TEV as the sensors for PD detections as most of the other technologies do. It can be used for the long term PD activities monitoring, diagnoses and prediction of the equipment such as switchgear panels, cables and cable accessories.