Insulation monitoring device

An insulation monitoring device monitors the ungrounded system between an active phase conductor and earth. It is intended to give an alert(light and sound) or disconect the power supply when the impedance between the two conductors drops below a set value, usually 50 kΩ.

It works by injecting low level ac or dc on the line and detecting.

External links

• Ungrounded Power Supply Systems in Medical Sites

Additional Reading

• Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 8: Insulation monitoring devices for IT systems