Electrical insulation materials play a key role in stable and uninterrupted operation of electrical power system. Researchers working in the field of electrical insulation have turned their focus to nano composite insulation materials for better performance and reliability. A typical nano composite insulation material is a combination of nano particles and base materials. Since last 25 years silicon rubber and epoxy are two widely used electrical insulation materials for outdoor and indoor applications respectively. To further enhance the electrical insulation performance of these materials addition of nano particles has proven to be of practical value. This study presents an investigation on zepoxy (a military grade epoxy) incorporated with three different nano particles at varying percentages. The main aim was to find the nature of relationship between leakage current (LC) and partial discharge (PD). In addition to that optimum composition which results in lowest values of PD and LC was also investigated for each of three nano composites. The results of this study help to understand the interdependence between LC and PD for indoor electrical insulation based on zepoxy. LC and PD play a vital role in condition assessment of any insulation material.