Author Topic: From wisecrack to reality...  (Read 4069 times)

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Offline rossw

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Re: From wisecrack to reality...
« Reply #15 on: November 10, 2018, 07:43:49 pm »
What string voltage do they use on such large arrays.

I believe Steve said in IRC that they're running 1050V in operation, about 1450VoC

Quote
I have seen panels that caught fire on grid connect systems here in Australia. They were running something crazy like 600+ volts string voltage.

600V is far from "crazy", it seems to be pretty much standard today.
My "grid tie" inverter actually wants 1400V but I'm running it at only 450V because it makes the installation and compliance much easier (and the switchgear, conduit, cable, connectors etc much cheaper)


Offline Wolvenar

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Re: From wisecrack to reality...
« Reply #16 on: November 10, 2018, 08:57:18 pm »
600v would likely been used in such scenarios so they can use wire with the cheaper insulation.

Cheap being a relative term.
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline Pete

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Re: From wisecrack to reality...
« Reply #17 on: November 11, 2018, 02:54:58 pm »
Hi Ross thanks for your answer. I am still concerned about such high voltages on panels. I used to repair valve amplifiers ( fortunately not too many) and managed to destroy a few multimeters because the high voltages would jump across the tracks in the switches.
I don't know if the panels I saw were faulty or not, one power company man said that they had a few panels catch fire. He said that they had no way of turning the rest off to stop the fire. I did suggest that he carries a dark coloured tarpaulin and just threw it over the other panels. He looked a bit surprised that I had offered such a simple solution.
I run my panels in 60 volt strings. That means that as I am no longer a licenced electrician in Tasmania, I can still do all the work myself. Anything under 100 volts DC is considered Extra low voltage and anyone can work on it and do the wiring. Fortunately we have very small power requirements, we have 2.2 kilowatts of panels and a 600 amp hour battery bank that does us fine.
Thanks again for your answer
Pete

Offline MadScientist267

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Re: From wisecrack to reality...
« Reply #18 on: November 12, 2018, 04:29:09 pm »
Ross is correct, ~1kV Vmp, 1.4kV Voc... around 9A Imp as I recall per string. So yeah if something breaks loose, even assuming the string fuse opens and isolates it from the rest in the combiner, there's still a lot of angry electrons wanting to go somewhere depending on how what went wrong lol

The currents at that voltage are what stand out at me... not so much a single string but when you "see the math done" on things like labels and there's obviously no mistake by the size of the cables, it's... ahem... enlightening... to say the least. Not that anyone can't or otherwise wouldn't do some subconscious math... it doesn't really hit home just how much power flows thru what you're seeing until you put the labels next to the wiring... lol it "changes everything"

I had a moment the other day where I just happened to gaze down at a single cell in a panel and the printed collection conductors got my attention... they're tiny as anyone that's seen them knows... but then I started to run away with the idea of how many bazillions of these little dinky "wires" does it take to collectively pump well over 3000A [not a typo] into an inverter (at the 1kV mind you lol)...  :o

I stopped right there before my head exploded  ;D

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