The Center for Advanced Power Systems (CAPS) is developing novel cryogenic dielectric materials and designs for High Temperature Superconducting (HTS) power applications. It is envisioned that HTS power cables would replace conventional cables in applications where efficiency, space, and weight are limiting design factors. Research and development efforts at CAPS and elsewhere have demonstrated the technical feasibility and benefits of gaseous helium (GHe) cooled HTS power cables for shipboard applications. HTS cables offer significant benefits and are more efficient than conventional copper cables for high-capacity applications. One of the obstacles currently faced by HTS cable developments is a lack of choice in electrical insulation materials with high dielectric strength suitable for operation at cryogenic temperatures. The image above shows the results of testing the breakdown strength of a material at cryogenic temperatures. The electrical treeing seen in the image shows that partial discharge occurred in the sample before electrical breakdown was achieved. Partial discharge and electrical breakdown are two of the important parameters that characterize electrical insulation systems. This research is funded by the Office of Naval Research.