Cyber-Physical Systems (CPS) rely on advanced communication and control technologies to efficiently manage devices and the flow of information in the system. However, a wide variety of potential security challenges has emerged due to the evolution of critical infrastructures (CI) from siloed sub-systems into connected and integrated networks. This is also the case for CI such as a smart grid. Smart grid security studies are carried out on physical test-beds to provide its users a platform to train and test cyber attacks, in a safe and controlled environment. However, it has limitations w.r.t modifying physical configuration and difficulty to scale. To overcome these shortcomings, we built a digital power twin for a physical test-bed that is used for cyber security studies on smart grids. On the developed twin, the users can deploy real world attacks and countermeasures, to test and study its effectiveness. The difference from the physical test-bed is that its users may easily modify their power system components and configurations. Further, reproducing the twin for using and advancing the research is significantly cheaper. The developed twin has advanced features compared to any equivalent system in the literature. To illustrate a typical use case, we present a case study where a cyber attack is launched and discuss its implications.