[RE-wrenches] Utility transformer limitations

[Darryl Thayer]

It is common practice for the utility to overload the transformer a lot for
the potential load.  They expect no one will use their service at maximum,
furthermore, they expect non coincidence of loads.  Look at the transformer
most have a label as to the kW or the unit, and the utility should give you
that number along with the impedance.  Note I have had area engineers not
understand that solar reduces the load on the transformer.  They have two
concerns, you will overload and you will raise the voltage
to other customers.  Overload is ridiculous; the transformer must be at
least 20 kW if a 15 kW concern is valid.  However, raising the voltage is
not.  If all the customers shut off their power, the voltage would rise to
the inverter limit,and/or feed current back on the distribution line
raising up/downstream customers voltage.  I have had this problem, on three
occasions discussions with the utility upper engineering, not local
engineer, i prevailed, one case I did not.   In one cast utility allowed
connection and put a voltage monitor on secondary voltage, then later
allowed permanent connection..   Good luck

On Sun, Dec 25, 2022 at 1:16 PM William Miller via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Wrenched:
>
>
>
> Merry Christmas to those of you that observe such traditions, or
> substitute the winter festivity of your choice.
>
>
>
> I helped a previous employee install an Enphase IQ8 system on his home.
> He applied for the utility approval concurrently with his building permit
> The day he got his final inspection the utility contacted him and claimed
> "The aggregate generation exceeds the identified transformer rating" and
> refused him a Permission to Operate letter.
>
>
>
> Adding up the service ratings of the homes on his secondary we get about
> 336 kW of potential consumption.  Adding the grid-tied systems on his
> secondary we get about 16.5 kW.  How is it that the back-feed exceeds the
> transformer rating?
>
>
>
> I would appreciate any insight on how to consider this situation and how
> to fight it.
>
>
>
> Sincerely,
>
>
>
> William Miller
>
>
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com
>
> CA Lic. 773985
>
>
>
>
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