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kingull Regular Member Joined: 08/04/2010 Location: AustraliaPosts: 44
Posted: 08:21am 16 Apr 2010
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Rather than run the output 120 metres to the house, I can run the house power to the Hydro Generator location.
Then the load dumper and the Grid Tied inverter can be adjacent to the generator.
The feed back AC curent will then be around two amps and with 2.5 mm cable, the losses will be minimal.
The DC cables will be around two metres long at maximum thus minimising DC losses.
The AVO with its add ons will be used to test output from the HG.
The house already has a latronic 1600 watt GTI solar array and the special meter will arrive shortly.
So I envisage getting lots of 60 cents\ kilowatt paybacks with a bit of luck.
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 10:19am 16 Apr 2010
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For the 120m run of mains AC, i think i would be considering 4mm-6mm cable, as the cost is not that much more when the trench is open compared to a up grade later.
I think the benifits would be well worth it in the long run.
Pete.Sometimes it just works
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 12:34pm 16 Apr 2010
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GTI inverters expect a quite low line impedance. Expecting them to work on a 120m extension cord will likely result in anti islanding doing its bit. 6mm underground would be a minimum. I hope you don't have much rock, as 600mm deep is required, or a lot of concrete for a 120m run. Could end up being expensive.
The potential 500W, 24/7/365, will make up for some overheads.
Gordon.become more energy aware
kingull Regular Member Joined: 08/04/2010 Location: AustraliaPosts: 44
Posted: 08:59pm 16 Apr 2010
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Great advice again but last time I read SAA it was 300 mm deep but 600 accross vehicle ways. I am retired (75)so it is some time back since I read wiring rules.
If the tests show high DC volts out, I will go DC to the house and locate the GTI there. Sunny Boy seems best GTI?
I would not use extension leads. Probably the cheaper TPS as building wire is often more costly.
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 02:37am 17 Apr 2010
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It has been 600mm depth required for some time now unless you have concreet over the top of it.
If you run DC then you will need to ensure it is in condute and sealed from any water entering or you will get a break down of insulation and bad electrolis between the cables.
Once water gets into condute you can not get it out and failure will result with time.
Pete.Sometimes it just works
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 05:57am 17 Apr 2010
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Hi Frank,
I did not mean you would actually have an extension cord as such, but using thin wiring with a GTI has a similar effect.
How many months of the year can you expect flow?
You can go up to 10kW per phase, and a good hydro site has excellent potential.
Sounds like you have some rock to contend with as well.
Gordon.
become more energy aware
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 10:04am 17 Apr 2010
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I'm inclined to throw away the GTI, and buy a 415v star/240v delta 3 phase 5kw induction motor with/without electric brake..... and drive the mains direct.
Wire the motor as delta (for 240v), and a simple lock out. Drive your mains direct. No electronics other than the turbine drop out protection (overspeed on mains loss). Islanding is auto anyway.... so no problems there.
If you monitor the rpm, you can use this as the mains connect/disconnect system.
It's cheap and simple..... and I am wondering why you have not been advised to do this type of setup sooner..... am I missing something here?
..............oztules
Edit: This type of 3 ph motor is ideal for single or three phase operation.Edited by oztules 2010-04-18Village idiot...or... just another hack out of his depth
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 10:20am 17 Apr 2010
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Hi Oz
I did suggest that a few posts back but in the form of a 3 phase alternator but a three phase motor works quite well with some caps across a phase or two to give it some excitement so it powers up a bit rather than dropping it DOL
I have an old 50 kva alternator 750 rpm that we used for helping sagging mains many years ago.
All the best
BobFoolin Around
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 10:37am 17 Apr 2010
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No Bob,
No... none... nix capacitors.... we use the mains for excitement, so when the mains drops out, it ceases to make power.
If we used caps for excitement, we would need to have a separate anti islanding system.
When we use the mains for excitement, it is automatic and error proof islanding. This also means if we need to use any PF correction, it must be small enough that it does not self excite when the grid drops out, and the revs increase to maybe double.....so no caps are the best way to go for small units of this size.
One of the mills over here is big enough to require PF correction, so the freq and volts are monitored to make sure it drops out when the grid dies. (80kw is more than a handfull to a linesman I suspect).
Thats the beauty of asynchronous induction mains connected generators, auto synchronising, and auto islanding.... heavenly simple.
..............oztulesEdited by oztules 2010-04-18Village idiot...or... just another hack out of his depth
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 10:50am 17 Apr 2010
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Hi Oz
Yes I see your point I was used to working with bigger units that if you didn't have some output the help synchronize them they caused problems when dropped on line
A small unit wouldn't be noticed it would just shake its tail and synchronize if it was slightly above synchronous speed.
All the best
BobFoolin Around
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 11:45am 17 Apr 2010
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Yes,
On the bigger units here we just use chokes/big inductors that get switched out after a second or so..... limits the damage considerably
............oztules
Edit: Actually, they stay in circuit, but a relay shorts them out.... same effect, just easier to achieve...Edited by oztules 2010-04-18Village idiot...or... just another hack out of his depth
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 12:16pm 17 Apr 2010
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Hi Oz
I haven't seen the relay system, the ones I was working with where 500 and 250 kva units so they where big small ones, noisy greasy and fun while it all worked.
All the best
BobFoolin Around
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 01:20pm 17 Apr 2010
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Hi Oz,
You comment [quote]and I am wondering why you have not been advised to do this type of setup sooner..... am I missing something here?
[/quote]
We is more of a matter "you" have been missing here, for some time and we have not had the input of your wisdom.
This goes to show how valid you points of view and knowledge is to thing many do here.
As always it is educational to read your take on situations.
Good to have your input back.
Pete.Edited by Downwind 2010-04-18Sometimes it just works
kingull Regular Member Joined: 08/04/2010 Location: AustraliaPosts: 44
Posted: 10:56pm 17 Apr 2010
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Hey Oztules,
I worked for Crompton Parkinson for 16 years and have a nice well built metric series 5 HP 3 phase motor sitting on a concrete pad right on the spot where the hydro would be situated. It is a six terminal job so I shall look at your great idea.
Hey GWATE. WE can get flow all year with current conditions. I targeted for 500 watts continuous as a mean average flow rate. When it rains, this place sounds like a tornado. Water rushes from top of Mount Nullum down gullies that you cant climb. I would guess potential would be in the thousands of kilowatts.
If anyone can find Mount Nullum Altitude then the Hydro Generator site would be around 15 metres above sea level.
The tweed river and its tributaries are very close to our place.
SSW_squall Senior Member Joined: 20/03/2010 Location: AustraliaPosts: 111
Posted: 12:36am 18 Apr 2010
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Hi Oz,
Actually i suggested the induction motor(generator) setup towards the start of this thread.
Even refered to your induction motor grid tie experiment with your chain saw blade mill'
ABEinstein: Everything should be made as simple as possible, but not one bit simpler
kingull Regular Member Joined: 08/04/2010 Location: AustraliaPosts: 44
Posted: 11:58pm 18 Apr 2010
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It is apparently illegal to backfeed with a motor according to Ecoinnovation.
kingull Regular Member Joined: 08/04/2010 Location: AustraliaPosts: 44
Posted: 12:00am 19 Apr 2010
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It is apparently illegal to do it with a motor.Edited by kingull 2010-04-20
kingull Regular Member Joined: 08/04/2010 Location: AustraliaPosts: 44
Posted: 12:02am 19 Apr 2010
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Kingull says that a 3 phase gives out at best, 33 percent of its rating when connected at 240 volts.Edited by kingull 2010-04-20
SSW_squall Senior Member Joined: 20/03/2010 Location: AustraliaPosts: 111
Posted: 02:44am 19 Apr 2010
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I would agree with Micheal from ecoinv.
It would definitely be illegal to do it unless the generator was registered, certified and had proper safety interlocks and controls.
Because it is possible in exceptional circumstances, for a grid connected asynchronous machine to remain excited when the (wider) grid fails.
Also there's the matter of fault protection, overcurrent, overvoltage, under/overfreq ect
All this stuff would just ensure that there is a 0% chance that any problem doesn't cause a dangerous or destructive situation to occur.
And as an engineer my self i am always interested in ensuring that 0% chances, don't materialize into anything other than 0%
Not designing for the worst case can lead to nasty things like law suits and prosecution!! And there's no shortage of lawyers out there (who have never designed anything) ready to poke holes in your hard work...
Don't be put off by this, if you think it's the way to go, it may just mean you mean to involve some (of the right) professional people to help comply with the regulations and stuff.
ABEinstein: Everything should be made as simple as possible, but not one bit simpler
SSW_squall Senior Member Joined: 20/03/2010 Location: AustraliaPosts: 111
Posted: 03:14am 19 Apr 2010
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You might want to check out the paronella park web site:
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