Mechanically Switched Capacitor with Damping Network (MSCDN) - Engineering aspects of application, design and protection

The application of harmonics filters in transmission systems has experienced a fast increase in the last decade or more, as a result of the installation of new SVC and HVDC schemes. In addition, an innovative and cost-effective solution has been introduced some years ago and is already being used in several countries: the Mechanically Switched Capacitor with Damping Network (MSCDN). It consists in large shunt capacitor banks, arranged as a C-type harmonic filter, connected to the high voltage system to provide reactive compensation and harmonic control, but with reduced losses in the resistor at fundamental frequency by means of a resonance between the reactor and auxiliary capacitor. This paper discusses engineering aspects of the application, design and protection of the MSCDN, providing relevant information and some recommendations regarding the specification of the filter components.