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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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fonant
Joined: 01 Feb 2005
Posts: 24
Location: West Sussex
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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 Posted: Mon Jul 04, 05 3:42 pm Post subject: |
 
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| fonant wrote: |
| dougal wrote: |
Generators simply cannot "plug in" because they'd have unsafe exposed live plug 'pins' if ever unplugged...  (and yes, Windsave's publicity does talk about "plugging in"  ) |
Yes, they can. Any grid-connected power generation system _must_ switch itself off if the grid fails. This is so that anyone working on the disconnected part of the grid is safe. |
 I already stand corrected on this!
| nathanbriggs wrote: |
{22 June 2005}... there is nothing in BS7671 which precludes the use of a 13Amp plug as a source of power as long as it safe to touch... Removal of the plug and touching the pins has to be safe, the energy must be below 50V within 2 cycles and less capacity than will stop a human heart, btw its still possible to get a little tingle if you are quick.
The windsave device is fitted with a plug, having said that most people will get it installed by a competent electrician who will promptly hard wire it.
Lastly the plug is standard but the socket requires a metal cover plate |
One point that hasn't been brought out is the necessary implication that such systems therefore *cannot* provide independence of the mains. During a powercut, your own generator *must* shut down too.
I'm not saying its physically impossible, just that it is the inevitable consequence of a "plug-in" system's mode of operation. (But would a power outlet on the generator side of the isolater be possible..?)
However there are a couple of points that might be taken in mitigation of my error.
1/ Isolating from the mains to protect maintenance/repair workers, does not require an *instant* disconnect. Personal safety on accidental unplugging demands a much more rapid response.
2/ While you can safely *just* isolate a solar pv panel, my understanding is that a wind turbine generator can't just be left to freewheel 'off-load' in the same fashion as one might isolate the pv panel. My understanding is that such freewheeling could destroy the turbine and/or the generator - please correct me if I've got that wrong! A mechanical brake can substitute for the braking effect of the electrical load, but I don't think such things are part of the design of these small domestic turbines. (Note that this is independent of the "self-furling" self-protection from increasing windspeed.) And dumping a kilowatt from the braking load is not exactly inconsiderable.
3/ And, Milud, I was mislead!
| nathanbriggs wrote: |
| {23 March 2005}...this means you can directly connect the Windsave power into the mains (although not by just plugging it in it must be hardwired). |
{My emphasis - Dougal}
As above, I think solar pv isolation can be just switching off, but that its more involved with turbines. And I note that those units are handling just 1/10th of the claimed maximum output of a Windsave.
| fonant wrote: |
| I love electronics - these things work so fast it makes the 50Hz mains frequency look slow! |
I remember learning Assember programming on a 1Mhz 6502 Microprocessor system, 25 years ago. The response and stability of stepper motor control is an experience that lives with me! Shortly thereafter I was faced with the problem of measuring the quiescent current of CMOS custom chips (nanoamps) in a rather noisy RF environment. Having rather fancy test equipment, I didn't bother with shielding at all. I simply made 1k measurements (!) and averaged them by adding and shifting the "decimal" point (1k rather than 1000 so it was simply a matter of a "binary shift"). The results were brilliantly reproduceable for particular chips - it worked!
I suspect that the programming problem for the solar inverter isolater would have been in reliably and quickly recognising the difference between noise and a powercut.
I am well aware just how quickly microelectronics can respond, and how difficult this can make interfacing to the real, slow, physical world..! |
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