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Topic Title: Wind Turbine Cable Selection
Topic Summary: Selection of cable connecting a 500kW wind turbine to the grid.
Created On: 07 August 2010 08:05 AM
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 07 August 2010 08:05 AM
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GMAC

Posts: 64
Joined: 12 September 2006

Can anyone advise what needs to be considered when sizing/selecting a cable between a Wind Turbine and the grid.
The Wind Turbine in question has a nominal output of 500kW at 400V 3ph 50Hz (after its control and protection gear).
The cable length is 1.5km and has to be buried underground.

The main question is on how to size the cable taking into consideration volt-drop, etc. I am assuming at this stage that the grid connection will be at 11kV, therefore a transformer at the Turbine end will be required to transform up to 11kV.

Can an 11kV cable be buried safely underground for that distance?
Any regulations to be considered with regards to burying an 11kV cable?
Will short circuit/overload protection be needed at both ends of the cable?
Any examples of an existing installation?

Any examples of a suitable cable type?

How does the cable get connected at the Grid end?

Any help is much appreciated.
 07 August 2010 08:54 AM
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ArthurHall

Posts: 737
Joined: 25 July 2008

You are talking here of a fairly serious job and I would advise you to get expert advise.
What you are proposing is feasable but will be expensive.
I would think you could connect the turbine to the transformer throught the turbine LV breaker. A HV cable could be run from the transformer to switchgear that will connect to the local network. The HV switchgers would have to be a circuit breaker with protection so a battery supply will be required as well as a building of some sort.
The HV cable can be buried for that length with no problem, however your biggest problem could be wayleaves, especialy if it runs in public ground.
I would imagine cost of the HV connection would be in the same order as the turbine its self.
You will also have to consider, earthing (HV & LV) protection design and commissioning, fault levels, LV supply to HV switchroom and many other subjects.
 07 August 2010 10:25 AM
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JonathanHill

Posts: 225
Joined: 09 September 2002

You really need to first discuss your proposals with your Distribution Network Operator (DNO) to ensure that their network can accommodate the generation. They'll advise of the works they would have to undertake to provide the connection and also the protection that needs to be in place on your side of the interface (reference document "G59" available from the Energy Networks Association http://www.ena-eng.org/ENA-Docs/). For a WTG of this size, it's highly likely that the Under & Over Voltage and Under & Over Frequency protection may be provided within the WTG's own protection. Sometimes the "Loss of Mains" protection is also part of the WTG package. The DNO will advise if they require Neutral Voltage Displacement protection on the HV side of the connection.

For this rating, you'll have a choice as to whether your connection with the DNO is at HV (eg 11kV) or LV - ie the DNO install and owns the 11kV to LV transformer and all the HV cable & switchgear. The simplest, in my view will be for the latter arrangement as this avoids your having to provide an "Authorised Person" for the operation of your HV network.

The key regulations impacting on this type of installation are the Electricity, Safety, Quality & Continuity Regs 2002 as amended, and the Electricity @ Work Regs (get the "Memorandum of Guidance" to these Regs). The former is a free download, the latter is available from the HSE (Google). However, I agree with Arthur in recommending you get specialist assistance from a consultant or specialist contractor.

You may also find the Technical Guide to the Connection of Generation (free pdf download see page http://2010.energynetworks.org/distributed-generation/) useful, even though this is now 6 years old.

Jonno

-------------------------
Jonno
 07 August 2010 03:58 PM
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alancapon

Posts: 5832
Joined: 27 December 2005

Assuming that this is a real scenario and not an exam question, I would like to think that you have approached the DNO before you have got very far with this project, to discuss the connection arrangements. You should receive a quote from them for the connection, which is likely to include any upgrades needed to their network to make it suitable for connection, as well as the specification for the G.59 protection that you will have to provide. As Arthur and Jonathan have both alluded to, the cost of the grid connection for this size of generator may be significant.

Regards,

Alan.
 08 August 2010 06:51 AM
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GMAC

Posts: 64
Joined: 12 September 2006

Many thanks for all of your replies.
This is the initial stages of a proposed project.
I will take your advice and contact our DNO before going any further.
If the project goes ahead I will post updates to help others.
Thanks again for your time and input.
 08 August 2010 02:14 PM
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alancapon

Posts: 5832
Joined: 27 December 2005

Originally posted by: JonathanHill
You may also find the Technical Guide to the Connection of Generation (free pdf download see page http://2010.energynetworks.org/distributed-generation/) useful, even though this is now 6 years old.


The ENA have recently reorganised their website, and a lot of things have moved round. There is now a page for distributed generation topics here: http://2010.energynetworks.org/distributed-generation/. The guide Jonathan referred to is available from this new page: Technical Guide to the Connection of Generation to the Distribution Network

Regards,

Alan.
 08 August 2010 02:15 PM
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alancapon

Posts: 5832
Joined: 27 December 2005

Originally posted by: GMAC
. . . . This is the initial stages of a proposed project. I will take your advice and contact our DNO before going any further. . . .

That is a wise decision. What you don't want, is get your turbine constructed and ready for use, then find that because of your location you either cannot get a connection, or the cost of the connection outweighs the money that you can make from generating electricity over the lifetime of the turbine.


Regards,

Alan.
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