Lightning Revisited [RE-wrenches]

Allan Sindelar allan at positiveenergysolar.com
Sat Apr 13 19:01:15 PDT 2002


Bill, what you describe is what I would do, and fits as a common-sense
approach. We do relatively little wind, as our solar resource is so
reliable, so my opinion isn't based on extensive experience. I'll forward
this to J. Wiles (J. Wi.?) and post his response.
Allan

----- Original Message -----
From: "Bill Brooks" <billbrooks7 at earthlink.net>

> In the three-phase AC windturbine example there is no grounded conductor.
> All three current-carrying conductors need surge arrestors (probably best
to
> mount the surge arrestors both at the tower, grounded to the tower ground,
> and again at the inverter/controller, grounded to the service entrance
> ground). I would discuss this with the inspector, but it seems like having
a
> separate tower ground would be okay as long as it sufficient distance
> (including guy wires) from the building it is serving. Would you agree
with
> that approach?
>
> Bill.
>
>
> -----Original Message-----
> From: Allan Sindelar [mailto:allan at positiveenergysolar.com]
> Bill,
> I see a possible problem with your recommended solution. The separate
> structures provision also requires a separate single-point bond in each
> "structure" between grounding conductor and a grounded conductor. On the
> three-phase wild AC of many wind generators, what would be the grounded
> conductor (the equivalent of AC neutral or DC negative)? Have I missed
> something here?
> Allan at Positive NRG
>
> ----- Original Message -----
> From: "Bill Brooks" <billbrooks7 at earthlink.net>
>
> > What about employing the grounding of separate structures provision in
NEC
> > 250-32 (2002 code)? If there is a grounded conductor, then that
conductor
> > should be grounded at the tower (or PV Array for PV) and at the service
> > entrance with no ground wire between them and no metalic conduit. All
> > ungrounded conductors must have surge protection (Phasor, Delta,
voodoo).
> > The main issue is that you cannot touch the tower or module frames while
> > touch something connected to the house. The inverter, however, is
working
> > with conductors that are all referenced to the same grounding system.

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