[RE-wrenches] Utility transformer limitations

Darryl Thayer darylsolar1 at gmail.com
Mon Dec 26 08:31:24 PST 2022 

Hello, my first thought is the BMS board, on the battery reaching near full
charge the BMS does a top balance where the board diverts the current
around fully charged cells and continues to charge cells not fully
charged.  this diversion current generates heat.  that the board must
dissipate.   When all cells are charged the heat depends upon charging
voltage.  Is the radian set at too high a charging voltage?  Also, if a
cell fails that cell will overheat and the board will overheat.  .

On Mon, Dec 26, 2022 at 8:40 AM Peter Giroux via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Morning all. Just got a call from a customer with a radian and fortress
> battery that caught fire. Has anyone had any issues with either unit?? We
> have numerous systems with combos of both and no issues. System has been in
> place for well over a year, climate controlled garage and system has worked
> well. Did a BMS board replacement earlier this year.
>
>
>
>   Any and all help appreciated.
>
>
>
> Thank you
>
> Peter Giroux
>
> ASAE
>
>
>
> *From:* RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> *On
> Behalf Of *Christopher Warfel via RE-wrenches
> *Sent:* Monday, December 26, 2022 8:17 AM
> *To:* re-wrenches at lists.re-wrenches.org
> *Cc:* Christopher Warfel <cwarfel at entech-engineering.com>
> *Subject:* Re: [RE-wrenches] Utility transformer limitations
>
>
>
> Wouldn't the microinverters shut down if the voltage rose?  They wouldn't
> be able to raise voltage about PUC/DPU limits I would think. They would
> shut down on high voltage. I am saying this because of an experience this
> fall where our infamous Block Island Power Company raised the taps on a
> local xfmr due to their "secret heat pump program" that was dragging down
> local voltage. They claimed solar was a burden, but were quiet on the load
> building program they embarked upon without any disclosure.   When the
> cooling loads disappeared, the voltage went above our grid tied systems set
> points and they shut down.  We told the utility they had a high voltage
> problem and they adjusted the taps.  Of course they did not acknowledge or
> thank us.  It seems our little coop which is now head from a guy from the
> Vermont Electric Coop is taking an old utility approach instead of
> cooperation, integration and maximization of performance and economics.
>
> I'd think you be able to ask how the supply can raise the voltage when
> there is so much diversified load on the same device.   Electricians have
> to do a diversity calculation, and I know a utility has to conduct them as
> part of these studies. Worse case of no load and all generation is such a
> low probability that to design for it, when/if it occurred, is not a danger
> and of no material consequence makes little sense. But, we've been dealing
> with that ever since this person arrived in our neck of the woods.
>
>
>
> Chris Warfel
>
>
>
>
>
> On 12/25/2022 5:21 PM, Garrison via RE-wrenches wrote:
>
> Hi William,
>
>
>
> One possible path forward would be to ask the utility co what AC inverter
> capacity would be allowed. Maybe the solution would be to unplug a micro or
> two if you are just over the limit. Even better, maybe they would allow you
> set an export limit on the micros you have installed.
>
>
>
> I had a recent situation where a 40kW DC system had exceeded a utility
> transformer by only 2kW AC, so a simple redesign avoided an $8k invoice
> from the utility. The utility was not transparent about this option at
> first and only made it clear after some persistence.
>
>
>
> Good luck,
>
>
>
> Garrison Riegel
>
> Celestar Solar
>
>
>
> On Dec 25, 2022, at 3:14 PM, Darryl Thayer via RE-wrenches
> <re-wrenches at lists.re-wrenches.org> <re-wrenches at lists.re-wrenches.org>
> wrote:
>
> 
>
> 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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> --
>
>                                          Christopher Warfel
>                      ENTECH Engineering, Inc.
> PO Box 871, Block Island, RI 02807
>                                                             401-466-8978
> <http://entech-engineering.com/>
>
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