[Boatanchors] Storm Damage to Electronics

[J. Forster]

I said "flat two-phase", not just two-phase", which is correct.

There IS a difference.

-John

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>
>
> The 240V is NOT a two phase!
>
> The rest of your comment is correct.
>
> This can also stem from a very poor ground.  Look at the distribution
> system.  In a heavily populated area.  You'll see three pole mounted
> transformers.  EACH is ONE of the three phase distribution.  For that
> matter, a less densely populated area will have a single pole mounted
> transformer every pole.  Look carefully, and you'll see that each one is
> fed from a different phase.
>
> This is to keep the entire Three Phase system fairly balanced.
>
> Each single phase transformer transforms ONE phase down from the
> 4160/2400VAC, (Note the sqrt of three figured in.) down to a SINGLE
> phase 240VAC with a center tap of the winding that becomes the neutral.
>
> Yes, when the neutral is broken, things get wild.  This also occurs when
> the ground is broken.  The poles in areas of VERY good soil conductivity
> can run ground by pole butt grounding.  However, places like coral
> islands with changing tides, REQUIRE a continuous ground from pole to
> pole.
>
> Otherwise, the same effect is seen when the tide changes.
>
> Been there, done that.  Eniwetok Atoll 1977.  The engineers designed the
> system solely on butt grounds.  Bad news!  We spent one day stringing a
> fourth overhead ground over a 40 acre rock of coral.
>
> The issue went away.  The neutrals were ALWAYS connected.
>
> The neutral on a single phase transformer is NOT connected to ground.
> The transformer "can" is grounded.  That way if the insulation and oil
> breakdown, the fused disconnect on the pole blows, NOT a surge to the
> residence.
>
> Bob - N0DGN
>
> On 11/4/2011 7:22 PM, J. Forster wrote:
>> When the neutral failed, the sides of the flat two-phase were
>> unbalanced.
>>
>> Instead of it being 120-0-120; the voltages were divided unequally, such
>> as 210-0-30.
>>
>> The line-to-line stayed the same, but the line-to-neutral went way up on
>> one side, way down on the other.
>>
>> The overvoltage blew stuff.
>>
>> -John
>>
>> ===================
>>
>
>