The future integration of multi-terminal HVDC (MTDC) networks in the European power grids lead to novel challenges for transmission grid operators, grid planners, and manufacturers. A major hindrance towards building HVDC networks is the limited experience regarding their operation and in particular regarding their protection.Within the EU Horizon 2020 project PROMOTioN, a laboratory-scaled MTDC demonstrator – the MMC Test Bench – has been built at RWTH Aachen University and now serves to address these issues. At the core of this test bench are eight laboratory-scaled Modular Multilevel Converters (MMCs). The DC transmission lines are represented by frequency-dependent cascaded PI-sections. On the AC-side, the MMCs are embedded in a real-time simulation of the surrounding AC systems by the usage of four-quadrant linear power amplifiers.To increase the confidence in DC grid protection and test the MMC controls during fault operation, a protection scheme including laboratory-scaled DC circuit breakers and protection IEDs has been integrated into the Test Bench. This presentation gives an overview of the DC grid protection demonstrator, addresses the corresponding research objectives and provides a comparison between results obtained with the demonstrator and its full-scale HVDC grid digital twin.