IMD (Insulation Monitoring Device) is a device that monitors the insulation resistance between the line and the ground (ground) in real time in an ungrounded (IT) system.

IMD's operating principle and functions

• IMD measures the insulation resistance between the line and ground in real time in ungrounded AC/DC systems. This allows immediate detection of insulation degradation or leakage current (i.e. ground fault).

• IMD injects a signal (voltage/current) between the power line and the ground point, analyzes the response, and calculates the insulation resistance value. If this value falls below the set threshold, an alarm is generated so that the user can immediately recognize the problem .

• IMD can monitor insulation resistance in real time even when the line is live (electricity is flowing), so it can check the grounding status (whether insulation resistance is reduced) even while the system is operating.

Meaning of 'grounding' as verifiable by IMD

• IMD checks whether the insulation resistance between the line and the ground (earth) is sufficiently high (i.e., whether the insulation is well maintained) when the power system is in the 'ungrounded (IT)' state.

• If the insulation resistance drops sharply, this means that a current leakage (ground fault) has occurred between the line and the ground (ground) or that the insulation has been damaged. In other words, the 'grounding status (whether the insulation resistance has decreased)' of the ungrounded system can be checked in real time through IMD.

• However, IMD is not a device that directly checks whether 'the ground wire is well connected', but rather a device that monitors whether 'the insulation between the line and the ground (ground) in an ungrounded system is well maintained'.

summation

• Through IMD, you can check the grounding status (=insulation resistance reduction, current leakage) of the ungrounded (IT) system in real time.

• IMD immediately detects ground faults by alarming when insulation resistance falls below a critical value.

• Therefore, IMD is an essential device for ensuring safety and maintaining ungrounded systems.