Cutler Hammer DS II Breakers tripping

[pawdge]

Has anyone had any issues with Cutler Hammer DSII breakers with RMS overloads tripping for no apparent reason? We have had numerous trips on these breakers at very low loads with no indication as to why they are tripping. Cutler Hammer has suggested that it is a humidity issue.

 

[Zogzog]

That is a BS response from C-H. Have you tested these breakers? I assume they are Digitrip RMS trip units. What are the settings? What function are they tripping on? How much loading do you have? What is the rating plus size?

These trip units can failsafe to the lowest setting from failed compoents or dirt accumulation in the trip unit. We repair and replace these units every day.

http://www.cbsnuclear.com

 

[dpc]

Humidity?? What is C-H problem these days - their engineering support has really gone downhill. I agree with Zog- the trip units may have defaulted to minimum settings due to some internal problems.

I'd have the trip units tested ASAP - ALL of them.

 

[pawdge]

We did perform secondary injection testing and got screwy results. Replaced with new unit and worked for some time. The problem is, we have approx. 200 ea. of these type of breakers and it seems as though the problem is spreading. We currently are having problems with 3 total. The main issue is that when they do trip, we never get an indication of why it tripped. On one particular breaker, we installed a dranetz recorder on the feeders and could see no issue with the current. Thanks for the input.

 

[Zogzog]

Can you define "Screwy results"? Could also be a CT problem, you wouldnt see that with seconday injection.

We can probally repair your failed units and do a more in depth analysis on what is causing the failures.

 

[dpc]

Are you sure the trip unit is initiating the trip? Any other tripping devices - shunt trip, UV release, etc.

 

[alehman]

If you have zone interlocks, it could be caused by problems with the wiring or auxiliary switches (cell position, etc). Also, I have seen problems with the zone interlock secondary connector support brackets being bent if they get out of alignment. That usually results in a broken connector.

 

[pawdge]

No zone interlocks. The default setting is the most probable so far. Since we are at a NASA facility, the SPE has indicated to C-H that we may blacklist these breakers and overloads from the center. C-H has now indicated that it is most likely the Kinney switchgear enclosures (source of the moisture problem) that the breakers are installed in. I'm just not buying it.

 

[rbulsara]

pawdge:
Something does not sound right. Firstly, as requested eariler by others, you need to provide more details as to what those "screwy" results mean?. Who tests your breakers and when were they last tested? What type of loads are served? What are the ambient conditions etc. Provide set points.

It may be true that real harsh conditions may be damaging the electronics in the trip unit.

What I have understood from many experienced people is DSII breakers are some of the better made breakers in the united states. . You may want to speak to some different people at CH.

 

[dpc]

Has someone from C-H been out to look at the installation, or are they just shotgunning from their office?

I'm not really buying the moisture explanation.

 

[pawdge]

Screwy Results: When performing secondary injection tests by qualified technicians who have tested hundreds of these overloads for the past 8 years (they are on a two year cycle), they could not even arrive at the correct test amperage before the breaker would trip with no indication of why.This is only on the overloads giving the intermittent trips. It is happening only with outdoor unit substation breakers where the breakers are housed in non-CH switchgear. Of course, these breakers supply loads that are sometimes not even 15% of the rating of the overload.
We also have GE micro versa trip plus, Siemens static trip, and ABB overloads. These overloads have never caused problems and are outdoors with non-manuf. switchgear.
CH salesman made a site visit as well as CH field service technician.
We are at the end of our rope. Of course, other than replacing these overloads with new ones.

 

[pawdge]

As far as the moisture issue goes. CH claims it may be caused by condensation and that the heaters are installed differently than the way CH would do it. So, in addition to exhaust fans, we have installed a 16,000 BTU A/C unit in the switchgear as well a a de-humidifier. This has been an ongoing issue for about 18 months now. We have installed unit heaters in other switchgear that did not provide success.

 

[Zogzog]

"Screwy Results: When performing secondary injection tests by qualified technicians who have tested hundreds of these overloads for the past 8 years (they are on a two year cycle), they could not even arrive at the correct test amperage before the breaker would trip with no indication of why.This is only on the overloads giving the intermittent trips. It is happening only with outdoor unit substation breakers where the breakers are housed in non-CH switchgear. Of course, these breakers supply loads that are sometimes not even 15% of the rating of the overload."

When you have less than 20-50% (Depending on type of trip unit) the CT's dont have enough output to power the trip unit so it runs on battery power, running at 15% load will cause the battery to go dead, if the battery is dead the trip unit will not display the cause of trip.

My guess is that the dirt/moisture has caused the trip units to fail to default settings, which would explain the trip before the expected trip value and dead batteries causing the lack of the unit displaying the cause of trip. However I am guessing my guess is wrong because I would expect a C-H tech to know this and have explained this to you already.

 

[pawdge]

Yeah, I already knew about the percentage of current. That's why I mentioned it. And also, the batteries are good. The batteries do not power the trip unit. It's only function is to maintain the LED indication of fault. That was my first assumption when there was no indication of fault.

 

[Zogzog]

Lithium batteries can have a good volatge when simply checked with a meter, need a load to be sure they are good but it sounds like you are on top of the battery problem. At this point I am out of ideas on why they wont indicate the trip cause, must be a board problem, no way of knowing with out more in depth testing.

You got me curious on this one, I would be willing to have our lab evaluate one for you if you like.

 

[rbulsara]

pawdge:

Nothing in your posts suggest that any more attempt than just the secondary injection test by others have been investigated. Why not primary injection test? It does appear that the trip units are damaged. They key is to find out exact cause.

I would try to arrange sending one or two bad breakers to CH factory and have them diagnose the exact cause. With their reputation on line they will be happy to do that.

 

[pawdge]

You're right. Secondary injection is the only test that has been done. I just assumed that with the type of trips we were getting with very little load was an overload problem. But, you know what they say about ASS-U-ME.

 

[Zogzog]

pawdge, Any updates on this?

 

[pawdge]

Update! Cutler Hammer has assumed that the overloads are damaged due to moisture and it seems as though the only breakers we are having issues with are those that are installed in Kinney switchgear cabinets. We are in the middle of performing on inventory as to how many breakers are installed in these switchgear and how many are not and comparing the trouble calls we have received over the past 10 years dealing with CH breaker trips. Will update again

 

[Zogzog]

I still dont buy that "Assumption", I would hope that C-H is covering the cost of the replacements.