Insulation Monitoring Devices (IMDs) are essential electrical safety components used to continuously monitor the insulation resistance between active conductors and earth in electrical systems. These devices are primarily used in ungrounded or IT (Isolated Terra) power systems where the power supply is not directly connected to earth. Their main function is to detect insulation faults before they become dangerous, helping to prevent electric shocks, equipment damage, and system downtime. Insulation failure can occur due to aging cables, moisture, dust, mechanical stress, or environmental conditions. By constantly measuring insulation resistance, IMDs provide early warnings when insulation begins to deteriorate, allowing maintenance teams to address problems before a complete system failure occurs.