Wind station operators in the region have become increasingly impatient with E.ON Netz's frequent demands for them to curtail output because of alleged shortage of transmission capacity. Under voluntary pacts with E.ON Netz, operators agree to curtail output on demand in return for a grid connection permit (Windpower Monthly, September 2006). But the curtailments have stretched the patience of owners to breaking point. A group is now preparing damage claims against E.ON Netz over lost income due to "generation management."
The current norm for setting the maximum transmission capacity of a cable in Germany assumes an ambient temperature of 35 degrees Centigrade and no breath of wind to cool the wires down, says E.ON Netz. But ambient temperature in Germany is rarely so high and the wind blows almost constantly in northern Germany where the worst bottlenecks occur.
Climate monitoring points installed at regular intervals along the transmission cable route now continuously deliver data to the network control system which computes the real transmission capacity available. Data processing for the network is highly complex and also has to account for available capacity on connecting cables, says E.ON Netz.