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In a message dated 6/2/00 9:21:59 AM Central Daylight Time,
spallen@rolemail.ccis.edu writes:
<< If tow conductors are connected in one
place, aren't they effectively connected "everywhere"?
>>
Yes, normal people would think that, but the authors of the National Electric
Code don't seem to agree with that premiss. We are all stumbling over the
defination of the "grounded" conductor and the "grounding" conductor. The
grounded conductor is the neutral on power distribution systems in the US.
This is the same for all voltages, no matter how high. It has to do with the
way the transformers are connected together at the distribution pole.
It is my understanding of the NEC that the neutral (grounded) conductor can
only be connected to the ground (grounding) conductor in the main power
panel. It is further my understanding that this is suppose to be related to
the unbalanced load that may be on the neutral. If the neutral is carrying
an unbalanced load, and it is connected to a ground other than at the main
power panel, then the ground wire can become a current carrying conductor,
which is NOT a good thing. An unbalanced load condition is when one 100 watt
lamp is connected between leg A and the neutral while two 100 watt lamps are
connected between leg B and the neutral. This will give an unbalanced load
of 100 watts on the neutral. Once the electricity flows through the lamp it
is still electricity and has energy; it is not consumed by the light. In a
perfect system the load on each leg would be exactly the same and there would
be no unbalanced load, but a perfectly balanced electrical system is about as
hard to obtain as a perfectly balanced combat wheel on a MB/GPW (mv content).
So if you've got an unbalanced load on one leg of you system far away from
the panel, say in the garage, and the neutral is connected to the ground in
the garage, then the entire ground system will have this unbalanced load on
it for it's return path to the main power panel.
At least that's the most reasonable explanation that I've come up with for
this situation.
Tom Campbell
This archive was generated by hypermail 2b29 : Sun Jul 02 2000 - 23:51:27 PDT