With the development of distributed power generation using solar power and renewable energy, smart grid-type DC power distribution is gradually spreading. However, DC distribution has a disadvantage in that the electric corrosion phenomenon of the ground electrode is prominent compared to the AC distribution system. The destruction of the stability of the ground electrode due to the electrostatic phenomenon deteriorates the reliability of the distribution system by causing electric shock accidents to human life, failure and malfunction of equipment. Therefore, the main issues of DC distribution are the electric corrosion of the ground electrode and the need to increase the reliability of the distribution system for smooth power supply. In this paper, the insulation resistance measurement device (IMD: Insulation Monitoring Device) is to be researched and developed to measure the insulation resistance in the live state and monitor the insulation state of the power line in order to secure the insulation resistance of the line and to secure electrical safety through monitoring. Based on this study, we intend to analyze the reliability of equipment safety according to IT (non-grounding) ground fault and power line insulation resistance degradation.