This document provides an overview of high voltage insulation diagnostics and testing. It discusses the application areas of HV insulation testing, factors that influence insulation resistance, common symptoms of bad insulation, and various testing methods. It then goes into more detail on insulation testing with DC voltage, describing insulation characteristics, test parameters like polarization index and dielectric absorption ratio. Limit values for insulation resistance of different equipment are also presented. The document concludes by discussing general requirements for HV insulation testers, features of Metrel HV insulation testers, and Metrel's services including product training, technical support, and custom solution development.