[spadlet]

Possible not exactly to the point but it seeemed relevant:

One of the things that needs to be considered when connecting a wind turbine to the National Grid is the capacity of the Local Distribution Network. In the UK the National Grid has historicaly developed to take large electricity loads from a few sources throughout the country and distribute them to the rest of the country. Thus there are networks with different electrical load carrying capacities. I am fairly sure (Besoeker or someone similar might know better) that the transformers used to convert electricity between the networks were designed primarily to transfer current from the higher voltage networks (the one that can take the most electricity) to the lower voltage networks.

If the maximum ammount of electricity that can be generated exceedes the minimum electricity demand on the local distribution network, there may be serious problems. It is not very easy to acurately predict the output of a wind farm half an hour in advance. This means that it may not be possible to reduce the output of other generators on the local distribution network, or increase the ammount of electricity that is being stored within the local distribution network, if the wind farm generates an excess of electricity.

An excess of electricity within a local distribution network may lead to serious equipment problems.

It is possible to upgrade the local distribution network but it costs money which has to come from somewhere. The capacity of the local distribution network can thus impose it's own limits on the ammount of wind farm generating capacity which may be installed.