Insulation Monitoring Devices
An insulation monitoring device (IMD) is a device that continuously measures the insulation resistance between the mains conductors and earth in ungrounded IT systems and raises an alarm when the resistance falls below the set threshold. It is used in industrial, marine and generator-fed installations where the supply must not be interrupted at the first earth fault, to report an insulation fault without stopping operation. This category includes Schneider Electric's IM9 (on-line), which monitors the energized AC network, and IM9-OL (off-line), which monitors the insulation of standby motors that are not energized; both operate with an auxiliary supply between 110 and 415 V AC. Choose the device according to whether monitoring is done on an energized network or on a motor that is out of service, the mains voltage, the setting range of the alarm threshold and the auxiliary supply voltage. Insulation monitoring devices for IT systems are defined in the IEC 61557-8 standard. An insulation monitoring device is not a residual current device: the relay detects differential current in a grounded network and trips the circuit, while the insulation monitoring device measures insulation resistance and raises an alarm.
Products
- Schneider Electric IMD-IM9 Insulation monitoring device (ON-line) 110 / 415 Vac — Schneider Electric · SKU: IMD-IM9 · TRY 21,294.69 · Made to order
- Schneider Electric IMD-IM9-OL Insulation monitoring device for motors (OFF-Line) 110 / 415 Vac — Schneider Electric · SKU: IMD-IM9-OL · TRY 23,518.67 · Made to order
How to choose Insulation Monitoring Devices
An insulation monitoring device (IMD) is a device that continuously measures the insulation resistance between the mains conductors and earth in ungrounded IT systems and raises an alarm when the resistance falls below the set threshold. It is used in industrial, marine and generator-fed installations where the supply must not be interrupted at the first earth fault, to report an insulation fault without stopping operation.
- Separate overcurrent/leakage protection, motor starting and local isolation requirements.
- Select rated current, pole count and breaking capacity (kA) from the installation calculation.
- Match coil voltage, auxiliary contacts and tripping curve to the control circuit and load type.
Frequently asked questions
What is Insulation Monitoring Devices and where is it used?
An insulation monitoring device (IMD) is a device that continuously measures the insulation resistance between the mains conductors and earth in ungrounded IT systems and raises an alarm when the resistance falls below the set threshold. It is used in industrial, marine and generator-fed installations where the supply must not be interrupted at the first earth fault, to report an insulation fault without stopping operation.
What should I compare when choosing Insulation Monitoring Devices?
Choose the device according to whether monitoring is done on an energized network or on a motor that is out of service, the mains voltage, the setting range of the alarm threshold and the auxiliary supply voltage.
Where can I find technical details for Insulation Monitoring Devices products?
It is used in industrial, marine and generator-fed installations where the supply must not be interrupted at the first earth fault, to report an insulation fault without stopping operation.