This paper discuss on developing particle detection system for High Voltage (HV) Gas Insulated Switchgear (GIS) using image processing in order to prevent flashover phenomena. The borescope is inserted to newly assembled switchgear to detect any existing particles inside the GIS enclosure. The system was designed to detect various sizes and shapes of the particles. The in-lab tests were conducted on simulated GIS to detect samples particles placed inside the unit. As a result, the detected particle will be shown on-screen live-view mode and enable user to view inside the GIS and count how many particles ware inside the set. Removing the particles can be done before the set were installed with the insulated gas. This method is highly suggested for every first installation of the GIS on site as it could reduce the chances for flashover occurred on HV GIS. © 2012 Praise Worthy Prize S.r.l. - All rights reserved.