Your 5kw grid connect

[Roger Willott]

Ivan,

You will remember I bought a 5kw wind turbine from you which I want grid connect. A friend produces BioFuels at Rotherwas and uses the surplus to power generators which produce 240w ac and therefore need no inverter, which you know better than I costs several arms and legs.

Your spec says that the 5kw produces 240w ac. If that is the case, with the right switching etc and the right control box, surely no costly inverter is needed?

This was part of the reason I have been stalling as I can't afford a WindyBoy.

Best wishes,

Roger Willott
PS I bought 200m 7mm stainless cable on ebay for 60 quid. 

[chaso]

Roger,

Firstly I can't imagine your friend is connected to the grid without an inverter unless he has some clever equipment which makes sure it is connected at the right voltage and cycles as the grid and that the most important part; it disconnects from the grid if there is a power cut (this is so it does not kill anyone working on the power lines).

He probably is not grid connected and is only using his power generators for his own electricity in his house.

Secondly a wind turbine can produce good amounts of power but it is governed by the variable wind so is not constant. You either use batteries to stabilise the power or you use a grid tie inverter which uses the grid as a battery.
The only problem with the grid connection is that because it is not yours and workers on the line need to be guarenteed that they are safe to do their job. Which means the grid connection needs to have a fail safe which not many companies make so is a lot of money.

I hope this helps in your quest to get your 5kw wind turbine working

[Roger Willott]

The generators are grid connected and on an industrial estate in Rotherwas, close to Hereford. They use fuel which has been processed from restaurants etc but solidifies and thus cannot be sold for road fuel use. It is heated and then used in the generators. They have their own sub station which connects to the national grid. The generators do not have an inverter as they produce 240 volts alternating current. I realise that a wind turbine varies enormously in its speed and a diesel generator has a relatively constant speed.

As I understand it the inverter does what it says, that is it inverts direct current to alternating current. The smaller Navitron wind turbines produce 12/24/36 volts direct current and therefore require an inverter. You can buy them to use with batteries. Equally, it seems that the 5kw produces 240 volts alternating current and therefore is compatible with the grid and thus requires no inverter.

I realise there may have to be other equipment, which was my question.

Thank you for your help.

Roger Willott

[Alan]

Hello Roger

The frequency of the electrical system in the United Kingdom is 50 H.Z. or 50 cycles per second. To connect any alternator to the electrical system an alternator needs to produce a nominal alternating voltage which is the same as the voltage available in your house, to export energy to the grid system your alternator needs to produce a slightly higher voltage than the voltage available at your house.

The frequency of the alternator you want to connect must be exactly the same as the grid system at 50 H.Z. or 50 cycles per second.

The frequency from your alternator (  wind generator  ) will vary from  0  cycles per second with no wind to hundreds of  cycles per second in very high winds running unloaded. The voltage from your alternator will range from 0 volts at no wind to a voltage considerably greater than your house electrical supply in low winds when run unloaded.

The diesel generators you refer to will have the necessary electrical and mechanical safety inter locks and controls to keep the diesel alternator running at precisely the speed required to allow it to connect the grid system.  They will also have over and under frequency protection. Under and over voltage protection and Anti island protection to shut the diesel generators down if the grid supply fails.

Because your wind Alternator (  Wind turbine  )  varies in frequency depending on the wind speed it cannot be connected directly to the grid system.

It cannot be directly connected to the Windy Boy range of inverters because the design of these inverters is very poor. Other protective features need to be installed.

Regards

Alan

[AndySV1K]

Your friends generator sounds like small scale power plant generation, this is very much larger than your average domestic wind turbine, it has to comply with similar regs though to be able to grid tie, i think its g59 for larger inverters?

i think G83 covers inverters up to 5 or 6Kw, your inverter (that you must have) must comply with G83 to be able to grid tie, i beleive you will be breaking the law if you connect with a non-approved model.

Andy.

[mike85]

G83 covers anything below 16amps per phase, anything over this has to be G59.

[Ted]

Actually the UK grid is 50Hz +- 0.5Hz. It dips down towards 49.5 Hz when demand is high and can go above 50 Hz when demand is low. Currently my mains is 49.8 Hz.

A grid-tie inverter has to track these changes and output accordingly.

[Alan]

Hello Ted

Correct. Was trying to keep it simple. Been shot down in flames for getting carried away before

regards

Alan

[Alan]

For people that cant sleep

www.energynetworks.org/spring/engineering/pdfs/FES_00318_v040211.pdf

I must be one of them cause Ive read It

Regards

Alan

[Roger Willott]

Alan,

Many thanks, it was explained to me when I went to look at the generators yesterday that they keep at a constant speed and that's why they don't need an inverter. You confirmed it. Ted mentioned the locking effect and the fact that they speed up or slow down. It seems they slow down so much that they stop.

Apart from a control box which has been supplied, but is for battery application (I presume as one of the connections says to batteries) which Ivan is going to change what else do I need? Do you reckon I could use this control box for grid connect?

I have the DTI good practice pdf file which shows the switches etc, but there seems to be more needed in this case.

Many thanks

Roger.