A Study on Estimation of Insulation Resistance in Low-Voltage Direct Current Systems Using Open-Type Midpoint Grounding System

In low-voltage DC systems, the grounding system is mainly a two-wire or three-wire IT system. Among them, the IT high-resistance midpoint grounding system has advantages in detecting 1-wire ground fault, but has disadvantages in continuous loss and insulation resistance measurement. This paper proposes a method to estimate the insulation resistance of the + and - lines using the measured voltage when the switch of the high-resistance midpoint is closed/opened in the open-type midpoint grounding system. Through the proposed method, it prevents continuous losses due to high-resistance midpoint grounding and allows the insulation resistance to be estimated through switch control when the measured voltage exceeds a certain value. The proposed method was verified by simulation using MATALB/SIMULINK and experiment.