thelatinist
Member
Seems as though we might have determined the cause of our issue this afternoon when our transformer blew up. CL&P is on their way out to replace it sometime tonight. With any luck this will solve our problem...
... suspect that it is a transformer issue and are recommending a recording line monitor between our transformer and the rack...but that will take time to arrange. ...
It's a shame you didn't get that BMI/Power Quality Analyzer installed in time to prevent a catastrophic failure. Although it's possible/probable the local poco would not have done anything about it until there was an actual power interruption (and the associated loss of revenue). (No offense intended toward CL&P.)Seems as though we might have determined the cause of our issue this afternoon when our transformer blew up. CL&P is on their way out to replace it sometime tonight. With any luck this will solve our problem...
Glad to hear (for once) it wasn't an issue with the dimmer rack. (No offense intended toward Strand Lighting.)
More at View attachment Hidden_Harmonic_Filter.pdf (PDF warning!)The failure was quite simple in its description: when large numbers of
dimmers were set to levels below full, the entire system flickered
and flashed, and horrible noises came from the dimmer rack and
feeders.
So much for the 0.56% that Murphy says will bite you every time.
Hey epimetheus, could the problem be upstream of the local mains transformer?
Did CL&P offer any explanation of how/why the old one failed? Was it spectacular?
I guess thelatinist still needs to put a BMI / Power Quality Analyzer on his service for a week or so to see what, if anything, it shows.
More at(PDF warning!)
Note the author.
Be sure to operate the troublesome circuits for at least a few minutes during the measurement period.
So I'm coming to this party just a little bit late, and I'm so impressed with the thoroughness with which thelatinist has undertaken his troubleshooting that I almost hesitate to ask these questions.
Are there any other electrical systems in your facility that draw power from the same tap as your dimmer rack? If you have three-phase power in the building (I remember you said your dimmer rack has a single-phase supply, but does the building have 3-phase supply?), what is running on the other two phases?
KbNot at all. Please, ask away.
We do not have three-phase power in the building as it is not available in our rural area. We have two three-hundred amp legs with two load conductors for each leg, both legs in the same phase, entering the building from our transformer. These legs pass through a safety switch and into a cabinet where they are fed into two 400-amp 80:1 step-down transformers which feed the meter outside the building. The ground and neutral are bonded in this cabinet, which is sealed by CL&P. There are three conductors leading from each of these step-down transformers; two conductors from each leg feed into a two-leg 400-amp circuit breaker which feeds our dimmer rack; the remaining conductor from each leg feeds a total of five sub-panels that power the rest of the building.
And, yes, there is lots of junk on those other panels: gym lights, heating and ventilation blowers, fluorescent lights, sump pump, sewer pumps, etc. We have considered the possibility that one of these systems is causing the problem, but we have not noticed any difference in the flickering whether gym lights, heat, etc. are on or based on time of day, occupancy, or whether any other systems are turned on or off; and nothing has changed in the building since the lights were working in the fall. But this has been a nagging doubt in my mind. I have wanted to turn off everything else in the building and see if I can replicate the problem, but that would mean disabling the alarm, etc. I might go in tomorrow and give it a try.
We did investigate this on the advice of the folks from Strand. Our electrician checked and all the grounds are bonded to the neutral at the main panel (as described above). He also checked across grounds on different circuits throughout the building, including outlets fed by the sub-panels I mentioned above and our dimmer rack; as far as we could tell, everything appears to be in the same ground plane.
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