The wind turbine is connected to the over-voltage trip first, and then to the other loads.  If the other loads become disconnected, then the voltage will rise, and the over-voltage trip will operate.


The over-volt trip contains a dump load that can dissipate the turbine’s output and that will tend to stall it when the wind reduces in speed.  This dump load is connected by default.  Active intervention is needed to disconnect this dump load.  The circuit is fail-safe.


A power source such as a battery or the mains is needed to power the circuit (a watt or two of power).  This power source energises a relay that turns the dump load off.  The dump load is connected to a ‘normally closed’ (N.C.) contact.  When the relay is energised then the load is off.


The relay itself has a second set of contacts.  When it is on it holds itself on, but if it is off then it can only be re-energised by bypassing the second contacts with a rest button that latches it back on, disconnecting the dump load and allowing the wind turbine to run and produce full power.


Finally you need a second relay driven by the wind turbine.  It is fed via a potentiometer (variable resistor) so that you can adjust the voltage at which it clicks over.  When it does so it disconnects the first relay’s power source so that the dump load comes on and the wind turbine is ‘tripped’.  After that it will not run fast without a manual reset.