Wind Turbine Bonding With LP

[delbertson]

HI folks, I have a bit of a problem that it’d like some opinions on. I have a small wind turbine installed that the DNO will not allow on their system, this is because the metal tower and the main earth are connected together. The customers property is supplied by a TN-C-S system, so I guess I can see their point as they don’t want a lightening strike to be channelled down the PME. My belief is that we need to bond the Generator (exposed conductive part)and the tower (extraneous conductive part) together as an engineer will almost certainly come into contact with both the tower and the generator at the same time.

My proposed solution would be to not use the property earth(PME) and put the Turbine on it’s own TT system. So, sink a dedicated earthing rod at the tower and connect the tower metal work and electrical system main earth to the earth rod and put in a 4 pole RCD (the turbine is three phase and neutral).

Does this seem like a reasonable solution? Is there something here I haven’t considered? If a TT system is the correct solution them I have a question about the implementation.

My feeling is that it would be best to connect the turbine SWA cable’s armour to the property earth and ensure its insulated at the turbine so no-one can come into contact with it and the TT earth simultaneously, then have the RCD protection at the supply end of the SWA that’s supplying the turbine.

I have practically no TT system experience so any comments or feedback will be gratefully received.

Thanks in advance.

Del

 

[DurhamSparky]

TT sounds ok as your removing the Link and thus earthing the tower and also the switch gear via the SWA

 

[gaffer]

Terminate your SWA into a plastic box at the turbine end and thats your form of separation.And dont forget to label it at both ends.HTH.

 

[delbertson]

Big thanks to both of you for your responses.

The box that the supply cable goes to is plastic, but if I use a standard gland on the turbine end of the SWA then I'll bring the property earth into the same box as my seperated earth bar. Would I not be better to bring the SWA through a stuffing gland and heatshrinking the end of the armour?

Also I still can't quite get my head round wether I should have the RCD in the property or at the turbine end. I'm sure someone once said to me the RCD should go at the turbine (actually it was a garage in their TT example) but I think it would be better in the property, that way it's protecting the turbine and the cable and is also more easily accessed for testing.

Any thoughts anyone?

Thanks

Del

 

[Markc]

The one we done in Norfolk had to be a TT as the property was on TNCS however the turbine installer and manufacture required the stake to be no higher that 10ohms. We had to get trenches dug and laid copper band until we got the reading down. You may find the manufacture has a maximum value and it will not be very high.