Jeff said:
I had the problem while trying to trim hybrid resistors with a sand
blaster and later a laser. Besides the earthquake simulating
vibration from the passing trains, there was the slight tilt in the
concrete slab foundation when the train was parked near the building.
The weight of the train would cause the foundation to tilt, ruining
the laser alignment. I found the problem by setting up an optical
(non-laser) tilt measuring contraption using a distant mountain top
reference point. Actually, that was a marginal idea because I found
myself measuring tides and freeway traffic. When the number of cars
on a nearby freeway increased during rush hour, the ground would sink
sufficiently to deflect the inclinometer. However, it did demonstrate
that train induced foundation tilt was the primary culprit.
Speculation was that the building was floating on the water table, but
that was never proven. Until the system was rebuilt to be less
sensitive to building movement, we posted the train schedule on the
wall, and production arranged to have breaks when the trains were
scheduled to pass.
My sense of smell tells me that the problem has something to do with
the utility power, but exactly what and how, I can't deduce. Are you
doing any monitoring of the DC component of the utility power? Perhaps
even order harmonic distortion, which would show up as a change in
waveform symmetry?
No I have not done that but like I said, the feeds come in a long ways
from that location plus we have our own transformers. If memory serves
we have 12kv lines coming in to our transformer stations. We have 2 out
side and 5 transformer vaults in the basement of the main building. But
like I said, they are far way, if there was that sort of issue I think
we'd see problems in other equipment.
I'll tell you what happen one day though, non related to this thread
here, was a general inspection was being done of the 12kV feeds coming
in out side from the electric company, something that is done by one of
the E1's there. He was out side looking up at a commercial feed coming
in and noticed a connecting link to our building was dangling? how could
this be? That would mean we're single phasing however, the plant was
fully loaded as normal.
It was strange, we started to doubt how our place was wired, because
we have another feed coming in. After remembering conversation a I over
heard about the third shift electrician making a comment about one area
having a voltage issue and he couldn't figure out, it all clicked in and
we all seem to agree with that. What was happening was, with all the
induction motors we have operating, they were generating the third leg
for us..
Jamie