Series Parallel PV in Battery systems [RE-wrenches]

[Bob-O Schultze, Electron Connection]

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William,
Don't see your drawing, but unless you are using shunt regulation,  
those strings are protected from battery current feedback two ways.  
1) by the controller itself and 2) by the battery/controller OC  
device, these days most often a DC rated CB.
Granted that CB will be likely be too oversized to protect the PV  
interconnect wires in a partial fault, but that event plus a shorted  
controller is extremely unlikely. In a full-on short AND in the very  
unlikely event the controller is somehow shorted as well, it should  
break the circuit. There are no absolutes in electricity. Anything  
"could" happen. We protect against the likely probabilities.
Bob-O

On Nov 20, 2006, at 6:11 PM, William Miller wrote:

>
>
>
>
>
> Friends:
>
> We have all learned that in grid-tie systems, string quantities of  
> two or less do not require series fusing (and in some cases, string  
> quantities of 3).
>
> I am wondering if that holds true for battery based systems.   
> Specifically,  if I have two series strings of modules, can I  
> connect them together without fuses?
>
> How about if I have multiple pairs of strings?  Can two series  
> string groups be connected with fuses only between the groups of  
> two strings?
>
> I have drawn a block diagram and, in this scenario, the two strings  
> hard wired together are all protected from external fault current  
> by the properly sized string fuse.
>
>
> Comments?
>
> William Miller
>
>
>
>
> __________________________________________________________________
> William Miller
> Miller Power and Communications
> Voice :805-438-5600     Fax: 805-438-4607
> email: wrmiller at mpandc.com
> http://mpandc.com
> License No. C-10-773985
> _____________________


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