Dip control 400 V MCC 2

[simisteven]

We have a dip control panel in our 400v MCCs which I have never come across before. It consists quite basically of two Rhomberg slimline voltages relays set to detect a percentage over or under voltage. Occasionally they react and we have a system shut down. It is never clear whether there was any real problem or not and I am not convinced that this dip control has any positive advantage at all.
I have attached a line diagram.
Perhaps somebody can offer any comment for or against this so called protection.

 

[rbulsara]

Sounds like an appendix....

You can play with settings and time delays if any. Unless this MCC is controlling something special that requires shutdown on OV/UV, I would get rid of it or at least disable it for a while and see what happens. Or wire it alarm only.

If at all important have OV/UV and single phasing protection at individual motor controllers/starters and not at MCC main.

By the way what is "dip control"? Something that protects against voltage "dips"? or a name of a process?


Rafiq Bulsara

http://www.srengineersct.com

 

[jraef]

No AutoCAD on this machine, but from your description this is not at all uncommon. But "control"? I would call that "protection" because control implies you would do something to rectify it, not just shut down.

Most UV/OV protection schemes entail a time delay of some sort to avoid nuisance tripping. A more modern Digital Protection Relay would also provide you with some additional threshold levels at which you could send an alarm to a SCADA system rather and maybe execute an orderly shutdown or a load shed rather than suffer a complete shutdown. It may be time to upgrade...


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[simisteven]

many thanks chaps, I am inclined to agree with you