Basic design considerations for a mechanically switched capacitor with damping network (MSCDN) within a high-voltage-grid

Because of the ambitious plans of the German government to have 80 % renewable electric energy production by 2050, the German transmission system operators (TSOs) are facing difficult decisions when it comes to supplying sufficient amounts of reactive power to provide voltage stability and sufficient transmission capacities without building a large numbers of new transmission lines. One possible solution is the installation of capacitive compensation units to provide reactive power. A special form of capacitive compensation is the mechanically switched capacitor with damping network (MSCDN). This paper gives a brief insight into the basic design considerations for an exemplary MSCDN including the dimensioning of the basic components and the calculation of operation voltages and currents using a simple equivalent circuit diagram. It is also discussed how capacitor and reactor losses could be included into the modeling of the MSCDN. An approach for dimensioning the damping resistor is shown. Furthermore, basic switching phenomena have been simulated using a MATLAB
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SimPowerSystems™ model.