[Milsurplus] Brouhaha over Navy ROTHR radar

[Peter Gottlieb]

I did a lot with lithium ion and now I work with vanadium redox flow batteries.  
Depending on the system the voltage range will most commonly be in the 400 to 
1100 volt DC range.  4 kV strings are being discussed for larger systems but not 
much so far.  Short circuit on a string is at least 3 kA and on a system can 
easily be over 100 kA.  When testing we sometimes related a 1 MW fault to a 
stick of dynamite.  You remember being nearby when it happens.  Most big DC 
fuses have a max interrupting current of 100 kA and they can explode violently 
if you exceed that, so yes, the big systems have some challenging protection 
problems (then there's arc flash).  Oh yes there's design calculations you have 
to do on busbars because the mutual magnetic field on a fault could break them 
from their supports.  There are load break contactors to react to less severe 
problems and the overload "relay" function is programmed into a controller and 
the current is monitored with current transformers. Also voltage taps so any 
number of current and voltage vs time parameters can operate that circuit 
breaker.  So yes a lot of thought goes into over-current and short circuit 
protection.



On 3/30/2017 8:15 PM, Richard wrote:
> Large battery systems are interesting.  What kind of batteries are you using, 
> how many and what voltage?  I see interesting problems with over-current and 
> short-circuit protection.
>
> Richard, AA1P
>
>
> On 03/30/2017 06:31 PM, Peter Gottlieb wrote:
>> I work in that industry. Wind and solar are both economically wins even 
>> without any subsidies. Some companies actually don't even file for the 
>> subsidies as the paperwork is quite onerous. I make large battery systems 
>> which solve the intermittency problem and yes those are now economically 
>> feasible as well.  My batteries are made in 1 MW chunks and run 4-10 hours 
>> depending on how much electrolyte is used. Typical real systems are 4 to 35 
>> MW.  Investors buy the battery systems and sell the services to utilities and 
>> there is no subsidy from anyone. Ratepayers save money and both utilities and 
>> investors make their desired returns.
>>
>> As with all things electrical and electronic the price keeps decreasing and 
>> asymptotically approaches material costs.
>>
>>
>
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