Mysterious Breaker Operations

[PWR]

A three year old commercial facility recently began experiencing a problem with molded case breakers opening for no apparent reason. In almost all cases, the breakers open they do not trip! The breakers are all Square D "homeline" (a residential grade) or type QO (a commercial grade) and range in size from 225A two pole to 20A single pole. The problem began happening at random about 10 weeks ago. All breakers are fed from a common 120/240 single phase transformer.

There is considerable evidence that the most likely cause; deliberate human actions, does not explain what is happening. Extensive efforts are underway to find an explanation and I'm not looking for suggestions on how to proceed in that regard. I am asking if anyone has experience with a similar situation.

 

[dpc]

What does Square D say? These small molded case breakers are a commodity and not built with the same level of quality as larger breakers. This is true regardless of manufacturer. A surprising number of these small breakers fail acceptance testing right out of the box.

What percentage of the breakers are doing this? I'd try replacing a few of the bad actors. If the replacements seem to work OK, I would lean on Square D for an explanation.

I don't think it is a power quality issue. Sounds more like a manufacturing or design issue. Are the breakers subject to temperature extremes, vibration or particulate contamination?

I'd still be suspicious of a human cause.

 

[PWR]

The most troublesome panel had all the breakers replaced. When that didn't work, the panel itself was replaced with different style breakers along with the service conductors, the utility drop, the utility service transformer, and anything else they could think of. Enough ground rods have been driven to make it the lowest reading service within miles. At least 10 "eyewitnesses" to the openings have been identified. When I was called in by the utility, they said there was an internal debate as to whether they needed yet another so-called expert or an exorcist.

 

[dpc]

That's very strange. It sounds like all of the obvious things have been tried.

So when you say the breakesrs are opening, not tripping, do you mean the breakers are found in the full OPEN position, not in the intermediate TRIPPED position? If this is the case, I don't see how it can be a power quality issue.

 

[PWR]

Correct, the breaker handle goes to the off position. There is no need to reset it before reclosing.

With regard to the exorcist, the jury is still out.

 

[Barry1961]

Amazing problem. I may have to dig up a spare breaker and take it apart to see what would have to happen for it to do that.

Make sure you post the answer when you find it.

Barry1961

 

[BJC]

/Check your loads. Is your system generating harmonics. Usually it's just odd harmonics heating the neutral but it could be spikes or a harmonic componet. Lot of black magic and voodoo with harmonics. They best thing is to use a recording current meter on selected circuits and watch watch what happens.

Did you add any equipment or have it worked on about the time this started? Are the trips coincidential with any operations, such as starting process equipment, computers, coffee pots etc?
Do you have any office funiture systems that you feeding.
Are you voltage levels ok?

 

[cdhorne]

This is not the first time I have heard of this problem. In my experience with moulded case circuit breakers, the only thing that will turn them "off" is a deliberate switching action.

We provided this advice to an industrial client and after they took action to prevent human intervention the problem went away.


You say that "There is considerable evidence that the most likely cause; deliberate human actions, does not explain what is happening." What evidence do you have to suggest that deliberate human action is not involved?

 

[dpc]

I can't think of a possible cause other than someone opening the breaker manually. It just doesn't have the necessary stored energy to move the handle to the OPEN position by itself, no matter what scenario I can think of.

You might try a hidden video camera, if that hasn't been tried already. Something smells fishy.

 

[busbar]

Very long shot — It may be possible to trip small circuit breakers with mechanical shock, like striking the enclosure or its supports with a mallet.

 

[PWR]

I'm going to be out of town for a few days and won't be able to followup until next week. Will definitely post if a believable solution comes about.

I would add the comment that in most situations like this one, the true solution has to "overcome" all the bad "facts" that are presented. I remain highly skeptical of the "off" versus "tripped" issue as well.

Human beings can often be lousy eyewitnesses!

 

[BJC]

PWR
Doh! I missed the part about them being in the off position.
Try putting something on the breaker handles. Maby a small amount of silicon grease brushed on with vertical brush strokes. You don't want them to see or notice the stuff but a purposeful operation of the breaker will show up.
You could also put something on the door or the door operating handle. Jame Bond used a strand of his hair in one movie.
They use to sell flourscent powder to put on things to see was stealing them. I think they stopped selling the powder because it gave people diahera.


“When you eliminate the impossible, whatever you have left, no matter how improbable, must be the truth."
Sherlock Holmes

 

[jraef]

I'm going to vote for the human intervention factor. All the harmonics, thermal, vibration, surge or other explainations would or could cause a Trip, but the way the mechanisms are aligned inside, the breaker handle cannot go into the Off pposition easily unless physically moved it there. The mechanism that is used to Reset after a trip is engaged even if it is a "normal" Off move, and that requires considerable physical force to overcome, probably even more than a poltergiest can muster. The only other explaination might be that they are remote controlled breakers and you did not know that, but these would be rather obvious because they have a small motor attached to each one.

Tug-tug... someone is pulling your leg...

"Venditori de oleum-vipera non vigere excordis populi"

 

[Alwaysexciter]

I have personally experienced a similar situation. The end conclusion was that when a near by co-gen plant was experiencing some vibration problems with thier mechanical equipment it would create a resonant vibration in the breaker panels. We determined this by installing a vibration monitor on the effected panels. The trips occurred during periods of high vibration.

Another facility had a problem that once a month on the same day (the third Thursday)several breakers in this one particular panel would trip. Investigation revealed that when the UPS service man opened the ups cover for an inspection, the cooling fans would cavitate causing the breakers to trip. The breakers were on a different circuit in a different room from the UPS.

Bottom Line______ Check for vibration

 

[jraef]

Now THAT is interesting, although I have had circuit breakers in panels mounted directly to the sides of portable rock crushers and have never seen that problem. The resonant frequency issue raises the possibility however. Rock Crushers operate on fairly low frequency vibrations, albeit high amplitude.

"Venditori de oleum-vipera non vigere excordis populi"

 

[ruggedscot]

Talk about wierd...

Read about an incident in a hospital where the cleaner unplugged a lead to plug in her floor burnisher, only trouble was that the room had run out of points and the nurse had plugged in an IV pump to a point fed from this extension. Patients IV was unaffected as it had battery back up inside but when the nurse saw the unplugged lead there was a huge investigation...

sometimes its the simplist things that fox us, and human error is soemthing that has to be understood. If it can be done some time it will be done, and you must prepare for that eventuality.

Rugged

 

[dpc]

I can believe that a molded case breaker could **trip** due to vibration. I do not see how it could move to the OPEN position due to vibration

In the original problem, it was reported that the breakers were found in the OPEN, not the TRIPPED position.

The simplest explanation is the most likely - manual operation.

 

[durf208]

If you want to rule out human intervention try installing a lock to the breaker box.

 

[ruggedscot]

The lock on the box is easily messed about with, if the MCB is feeding a final circuit with sockets good old Joe Public sometimes puts in an 'accidental' short to trip it out. Seen this done to kill the lights in an area. Then guy mugged anyone going through in the safety of the darkness.

Rugged

 

[jraef]

I'm with you dpc, I still think it can't move all the way to the Off position, it would be in the Trip position. It takes extra force to finish the job.

"Venditori de oleum-vipera non vigere excordis populi"