Lightning Revisited [RE-wrenches]

[Bill Brooks]

Allan,

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]
Sent: Thursday, April 11, 2002 6:53 PM
To: RE-wrenches at topica.com
Subject: Re: Lightning Revisited [RE-wrenches]


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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