Futaleufú hydropower plant has 4 Francis turbines rated 118 MW and it is connected to the power system by 2x330 kV lines. Studies carried out in the past did not predict the instable operation of Futaleufú after a 330 kV line fault, when some Futaleufú turbines are automatically disconnected as a consequence of the faulted line tripping. Load rejection caused by disconnected turbines generate large transients in the remaining turbines due to hydraulic coupling through the common conduits. Then, to improve related models and, therefore, to improve studies results of such a line fault it was necessary to make several tests in Futaleufú power plant. Finally, these models were used to conduct studies to design a new automatism, like the gate partial closing of the remaining turbines, to obtain a dynamically stable operation of Futaleufú after the disconnection by fault of a line of 330 kilovolts.

The ECS is UNITROL F from ABB and, the VJC is implemented in a programmable logic controller (PLC).The AVR, RPC, and VJC models are presented. These models were predefined with information furnished by the manufacturer.Then, these models were validated by tests. Test records and their simulations with the proposed model are also presented.Described models have been incorporated to the database of dynamic models used for stability studies in the SADI.

Abstract-TwoBoth oscillatory episodes produced great variation of active and reactive power in several 330 kV and 500 kV power system nodes.At first sight, these oscillations seemed inter-area electromechanical oscillations, but carried out studies suggest that this oscillatory behavior could be a consequence of interaction between Reactive Power Control of generators and the ac-dc Converter Control of high power loads.