[Antennas] Ground rod questions (Ground currents)

[rbethman]

Milt, N5IA wrote:
> That is a Delta system you are describing, Eric.  Delta is used primarily in 
> transmission systems, but many Munis and IOUs still utilize Delta 
> distribution systems.  California is famous for it's Delta distribution 
> systems.
>
> Chris' explanation was for Wye systems.
>
> There are advantages and disadvantages associated with both types of 
> systems.  Each of you have for the most part identified correctly how each 
> system is "wired".
>
> As in most things, it is COST that determines the solution, given all other 
> parameters are equal or nearly so.
>
> Typically Delta systems are used where most of the load is in concentrated 
> areas or the load requirements are for full three phase power.  The 
> advantage is no 4th conductor (neutral) has to be installed (cost saving) 
> with 3-phase distribution systems.  Load balance is achieved quite easily on 
> a full three phase Delta distribution system.
>
>   
This NEXT segment is NOT true in most areas!  "Perhaps", that is what 
LONG HAUL transmission is using.  However my experience is that the 
transmission systems and distribution systems DO use WYE!  We generated 
it as WYE, we stepped it up from 4160/2400 to 13.8KV WYE for 
transmission.  This included the entire Panama Canal Zone.  We produced 
at least a third of the entire power grid.

> That is why transmission is always Delta if it is operating AC.  Perfect 
> load balance with no need for a neutral.  Today most all HV and EHV 
> transmission lines are constructed with one or two static wires above the 
> power carrying phase conductors.  The static wires are for that very 
> purpose; to keep lightning off the phase conductors and NOT for carrying 
> load current.
>
> So the Delta system is a cost saver installation wise under these 
> conditions.
>
> Typically Wye systems are used where the majority of the load is NOT 
> concentrated, or there is a large quantity of lightly loaded, long distance, 
> rural single phase lines.  Load balancing is more difficult on Wye systems.
>
> With a Wye system, single phase is run as a single "hot" wire and the common 
> grounded neutral wire.  This can be done with one pole top insulator of 
> proper rating and the neutral installed lower on the pole with little or no 
> insulation.  To deliver single phase power a Delta system, TWO properly 
> insulated phase conductors have to be run, most of the time with a Xarm and 
> two insulators of proper rating.  This costs a LOT more on long runs to a 
> single ranch home out in the boonies.
>
> If the distribution is underground, then only one HV conductor with a 
> concentric neutral has to be run. 
The area here in Virginia is NOT built with a concentric neutral!  The 
system is 12470/7200.  Single phase is run for feeders with a separate 
ground

>  With a Delta system, TWO phase conductors 
> with appropriate insulation values have to be installed to deliver single 
> phase service.  In high concentration areas, no problem.  But for long runs 
> to single, small load services, it costs TWICE as much to do Delta vs Wye in 
> conductor alone.
>
> In single phase Wye systems, the common grounded neutral conductor IS an 
> integral part of the circuit.  It carrys ALL the return connection to the 
> substation transformer with exception of what might incidentally conduct 
> through good ground.
>
> So the Wye system is a cost saver installation wise under these conditions.
>
> It would be best if a utility could use both types of systems together; that 
> is Delta in the high density areas and Wye in the rural areas.  But the two 
> systems are not compatible without transformer interconnection and there 
> would be the safety factor of trying to remember which system you were 
> working on.
>
> So, typically you will not see Delta and Wye systems integrated in a 
> utility's service area.
>
> However, on the actual service side of distribution transformers you can and 
> will find a mix of both Wye and Delta in a single distribution system. 
> Again, the cost factor comes into play.
>
> For example, even if a distribution system is Wye, for full, balanced 3 
> phase loads (industrial pumping and irrigation pumps are two types of this 
> use) a cluster of the single phase transformers will be connected in Delta 
> across the primary and also connected Delta for the secondary.  This again 
> is related to cost savings, both in the quantity and type of transformer 
> that has to be kept in stock, and the amount of conductors that have to be 
> installed to connect to the metering and the load.
>
> Now back to the subject of the "loose" of "broken" neutral is a typical USA 
> electric power homw service.  Since the neutral is derived from a center 
> tapped winding on the distribution transformer secondary, and that neutral 
> connection is required to provide the 120 VAC of the normal 120/240 VAC 
> service, the loss of that connection produces the potentially damaging 
> conditions some of you have explained.
>
>
>   
We are NOT discussing foreign systems.  So it doesn't fit in to the 
discussion.
> I trust this short explanation will shed a bit more light on some of the 
> things that have been talked about.  It of course has nothing to do with the 
> "Subject" of the thread.  Continue on with the GROUND ROD discussion.
>   
It has NOT shed light, it casts more doubt as to the validity of claims 
and KNOWN methods some "say" that they are doing.

I know WYE systems, I know Delta systems.  When I've brought in multiple 
1MW trailer mounted gas turbines, backed them up to poles and ties in 
hot, it was 4160/2400 WYE.

Bob - N0DGN

> Milt, N5IA 
>   

-- 
Bob - NØDGN