This work studies the possible effects of a simultaneous single grid fault and a significant reduction of wind power production on the Finnish 400 kV main grid in some future scenarios. The N-1 fault and the significant reduction of wind power were expected to happen in 15 minutes. The work was accomplished by simulating the Nordic power system with PSS/E software. One future scenario for 2000 MW and four scenarios for 4000 MW installed wind power were made. For the 4000 MW scenarios, two different wind power siting options were used and, additionally, two different grid extension plans (extensive and minimum) were used. For these scenarios, two power flow cases were made, the winter and the autumn. In all cases studied, Finland was importing power from Sweden through northern 400 kV AC lines. Two different market models, Wilmar [1] and EMPS [2], were used for creating realistic production and power flow scenarios for the simulated future cases. Wind power was decreased 15, 30 or 50 percent from the instantaneous wind power generation values in the simulated power flow cases mentioned above and also a systematic N-1 contingency analysis was made. Simulation results of the study indicate that a simultaneous grid fault and at the most 25 percent wind power reduction from nominal power don't cause a great risk to the (operational) security of the Finnish power system as long as the system is under assumptions used in the simulations. Nevertheless, the results show undervoltages in eastern Finland during some power flow cases, when there was a generator trip and wind power was decreased over 25 percent from the installed capacity. During low import, simulation shows no undervoltages in the system.
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