This discussion is locked.

You cannot post a reply to this discussion. If you have a question start a new discussion

Coordination of insulation monitoring devices

Hi all,

I occaisionally come up againt a requirement to provide an IMD where there already is one elsewhere on the same network (for example, on an IT system where the downstream equipment contains its own IMD out of the box, but has been installed in such a way that it might be disconnected with the distribution circuits still energised, leaving the latter unprotected)

In the past I've been advised by manufacturers that you can't have two separate IMDs monitoring the same network as they'll see each other as faults, so we've ended up with convoluted arrangements to priorise devices such that only one is in use at any time, or simply removed downstream devices.

But this doesn't feel satisfactory to me, and I suspect I'm missing something... Is there a better way to coordinate IMDs?

Parents

0 Former Community Member over 4 years ago

The only time I've coordinated IMD's is where downstream devices are connected to loads that are "dead" - eg a large motor, where you monitor insulation resistance whilst the motor is off, but when it's on, you revert to the source IMD.

You can have IMD's on each source (where you have a series of IT Islands) - but not usually multiple IMD's cascades on a single source

Where the source feeds a number of feeders you usually have a single IMD and then a series of fault locators that manage each circuit - all usually operating from the same low frequency AC or DC injection by the IMD

I think your initial assumptions are correct - if you are familiar with Schneider gear, then something like an IM 400 at source and an XD 312 for the feeders. Larger systems might use something like a central supervisor with a IMD per feeder connected to a transformer switchboard (with or without circuit monitoring)

For Andy, there are some very large IT systems to be found where downtime or safety or both are paramount - I could point you towards IT distribution that covers some pretty large industrial facilities - dockyards are one example, large chemical plants another.

Regards

OMS
Cancel
Vote Up 0 Vote Down

Cancel

Reply

0 Former Community Member over 4 years ago

The only time I've coordinated IMD's is where downstream devices are connected to loads that are "dead" - eg a large motor, where you monitor insulation resistance whilst the motor is off, but when it's on, you revert to the source IMD.

You can have IMD's on each source (where you have a series of IT Islands) - but not usually multiple IMD's cascades on a single source

Where the source feeds a number of feeders you usually have a single IMD and then a series of fault locators that manage each circuit - all usually operating from the same low frequency AC or DC injection by the IMD

I think your initial assumptions are correct - if you are familiar with Schneider gear, then something like an IM 400 at source and an XD 312 for the feeders. Larger systems might use something like a central supervisor with a IMD per feeder connected to a transformer switchboard (with or without circuit monitoring)

For Andy, there are some very large IT systems to be found where downtime or safety or both are paramount - I could point you towards IT distribution that covers some pretty large industrial facilities - dockyards are one example, large chemical plants another.

Regards

OMS
Cancel
Vote Up 0 Vote Down

Cancel

Children

No Data

Coordination of insulation monitoring devices

Community Rules & Guidelines