The purpose of this study is to design a predictive monitoring system for an effective maintenance and replacement program for gas insulated switching-gear (GIS). This paper presents a new acoustic monitoring technique using partial discharge (PD) noise in GIS bus sections to detect the time-accumulated damage of insulation performance. This is accomplished using effective computer memory management techniques. The proper selection of equipment and a well-organized system configuration enhanced the analysis methods. Pattern recognition and Fast Fourier Transform has been applied for conditioning monitoring. This study showed warning patterns and recent conditions on all phases for long period. Prioritizes for maintenance and part replacement for effective management of the substations were established by this study.