False operation of Breakers' Digitrips

[MYAMYAMYA]

Hi all

I am looking for a help in what could be a root cause analysis of repeated false operations of Solid State LV Breakers Digitrips. The digitrips were tested and found OK. However it creates false operation from time to time. Does the aging be a reason of the same? Those devices are about 13 years old in operation.

Thanks

 

[RRaghunath]

False operation is a possibility considering the age.
You only can confirm by testing the Digitrip protection releases and confirming the calibration still holds and drift if any is within permissible limits. The Digitrip instruction manuals and if necessary, the manufacturer technical support can help you in this.
Other thing is about the change in load magnitude over the period and whether the protection release settings are still valid or need to be revised!

 

[MYAMYAMYA]

Thanks Raghunath

The digitrip was tested by the manufacturer and found OK for all operations. It is about ten incidents for different digitips. In one case, the digitrip was replaced by a new one but still operated incorrectly after few weeks which make the possibility of aging doubtful.

 

[RRaghunath]

Then, the ball is in your court and you have to verify the actual load and update the Digitrip settings.
See my post second part - "Other thing is about the change in load magnitude over the period and whether the protection release settings are still valid or need to be revised!"

 

[mparenteau]

Some electronic trip units false trip under harmonic conditions. Something to check...

Mike

 

[unclebob]

What kind of false indication? Unwanted tripping? Any indications on the type of fault (Overload, short circuit, ground fault)?

 

[MYAMYAMYA]

Thanks Mike

 

[MYAMYAMYA]

Thanks unclebob

In fact it is mixed of unwanted events including tripping, single phase current reading, No digitrip recording, voltage unbalance, etc. All are in different timing with different digitrips.