[TowerTalk] CQ article error(?)
garyschafer at comcast.net
Fri Oct 7 21:15:10 EDT 2005
Jim Lux wrote:
> At 11:58 AM 10/7/2005, Gary Schafer wrote:
>> You seem to be saying two different things here?
>> The neutral wire IS to be grounded to earth along with the safety ground
>> at the service panel. Both are tied together and connected to earth
>> ground at the main service panel. The power company also grounds the
>> neutral connection at the transformer to earth ground.
> Not necessarily.. for the same reason as you have a single interconnect
> between neutral and ground. You don't want neutral return currents
> flowing back to the transformer via the ground path.
> Also, if the neutral opens between your house and the transformer (which
> does happen, particularly on an overhead service), you don't want the
> entire neutral return current flowing through ground. You'd rather have
> the voltages on the two sides become unbalanced. Radical voltage
> fluctations may destroy equipment, but at least it doesn't create a
> shock safety hazard.
> I suspect, however, that there is some variation in local practice
> here. It probably depends on things like how many loads are serviced
> from the transformer, how far the transformer is from the load, and so
> I seem to recall reading some fairly complex story about a swimming
> pool, a multiunit apartment complex, and how the NEC required grounding
> strategy resulted in the pool being electrified.
Yes it would seem that the neutral should not be grounded at the power
pole for the reasons you stated.
However it is in all places I have seen. Further there are more grounds
connected to the power pole end of your neutral line via your neighbors
houses that are fed from the same transformer. Each house has its own
ground to earth at each neighbors entrance panel.
If the neutral opens between your house and the power pole that
effectively lets neutral currents flow from your ground connection to
your neighbors house ground connection through the earth!
Not only that but it can also flow through the cable tv lines that feed
each house where the cable tv drops are connected to each utility ground
at the houses.
City water lines come into play in this scenario also as current carriers.
The power company grounds their neutral at the transformer poles and
along the way at various poles to help alleviate this stray current
situation should it occur. They also ground their neutral for lightning
It is not a perfect system by any means. A safer system would be a full
floating neutral system right back to the power company generators and
appliances designed accordingly. But then there other hazards that can
creep into that system too.
>> The neutral should never be grounded anywhere else.
>> Gary K4FMX
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