Circuit Breaker Micrologic Accuracy

[edward_lim_uon_]

Hello,

I understand that Micrologic accuracy is impacted at low load conditions. Due to our customer querying the difference between master meter and submeters (Micrologic) kWh, we discovered that one of the circuit breaker kWh had a difference of up to 40% because of low load for the the rated breaker size.

Can anyone explain why the kW per phase calculated shows 0 kW during low load conditions when there is current measurement. Is this a limitation in the Compact NS Micrologic E algorithm?

It is a 1250A breaker.

We have both ION6200 and Micrologic on the same feeder:

Best regards
Edward

[Grant_IPACS]

Edward,

I believe the micrologic metering is essentially leveraging protection CT's to derive these energies for display, and may not be accurate at low load (it takes about 30% load for them to be 'excited' enough) to be within accuracy.  Whereas the 6200's and a good set of CT's would be much more accurate at low load.

HTH

Grant

[edward_lim_uon_ · Accepted solution]

Grant,

Thanks for your reply.

The Micrologic accuracy is only guaranteed when current is greater than 10% of nominal current.

Meter and CT is definitely better than Micrologic and from my experience iEM3xxx KWh meter readiings are better than the IOn6200 at very low load.

For NS breakers kW reading only accurate greater than 30kW.

NSX breakers: