Substation Question for Electrical Engineers

Socymonster

I'm doing a college project which is based on the substation and integration of a wind farm.
I have come across a Directional Overcurrent Relay and cant explain exactly what it does. The turbines are spread across 3 feeder circuits before entering a main incomer. I have decided it's either to protect against reverse current which would cause the turbines to act as motors instead of generators, or it's to prevent disruption of other 2 feeders if one goes down.
Anybody have any experience with this?

Sparky_Larks

Is the directional relay on each turbine or on the connection to the grid.

The directional over current is often used to stop a fault inside the substation being fed from the grid. It is to protect the grid from a fault in the substation.

A fault in the substation may have a much lower current that the maximum export current.

Socymonster

Thanks for the reply. I got the line diagram for the station. It turns out there's directional relays on the 20kV side, on each feeder. More than likely for earth fault currents and descrimination purposes. It turns out there's one on the 38kV side too to prevent against anti-motoring. Thanks for the help on this anyway...