Partial Discharge (PD) occurs when insulation containing voids is subjected to high voltage (HV). If left untreated PD can degrade insulation until, eventually, catastrophic insulation failure occurs. The detection of PD current pulses, however, can allow incipient insulation faults to be identified, located and repaired prior to plant failure. Traditionally PD is detected using galvanic contact methods or capacitive/inductive coupling sensors. This article discusses the use of Software Defined Radio (SDR) for PD detection and localization, and presents proof of principle experimental results that suggest SDR can provide a simple and reliable solution for PD-based monitoring of HV insulation integrity. Introduction to Partial Discharge Insulation of HV equipment is vital for its efficient operation. However, in most HV power systems, degradation and breakdown of insulation is a major challenge, [1]. Partial discharge in electrical systems indicates the deterioration of insulating materials. Sometimes this is just an air or gas-filled void in a solid or liquid dielectric insulator. When insulators are subjected to intense electrical stresses in the presence of impurities, PD is likely to occur. If two insulating materials with different dielectric permittivity are subjected to a voltage, the resultant electric field is greater in the region of smaller permittivity (e.g. in a void). Electrical breakdown can occur in this region without occurring elsewhere. Figure 1 shows an equivalent circuit for the partial discharge phenomenon where a capacitive voltage divider is formed between the two regions. Repeated partial discharge further damages the insulation by causing treeing and may eventually result in complete catastrophic discharge, i.e. flashover. Thus PD is defined as a localized electrical discharge that only partially bridges the insulation between conductors.