The main goals of this work were to expand the initial dynamic model of CE (IDMCE) with the Nordic power system model (NPSM) and an HVDC interconnection, and then to deploy the expanded model in the OPAL-RT simulation platform for potential transient stability studies considering HIL methods. In light of this, three different implementation schemes were developed, including: 1) the assembling of the IDMCE, the HVDC link, and the NPSM altogether into one system and in PSS/E format, and then supplemented with an FMU based HVDC representation for compatibility reasons in ePHASORsim, 2) a co-simulation scheme with only the IDMCE and the NPSM incorporated into one *.raw/*.dyr file and the dynamics of an HVDC interconnection integrated through a Simulink model, and 3) a geographically distributed co-simulation scheme with the IDMCE running on one OP5600 simulation system (ZHAW side) and the NPSM and HVDC model running on another OP5600 hardware (SINTEF side). Using the base case scenarios portrayed by the considered power system models, offline and real-time simulations were carried out to qualitatively assess the dynamic performance of the expanded grid. For this purpose, no fault conditions and step changes on the reference active power of the converter controlling the power flow through the HVDC link were assumed, and the frequency dynamics at representative buses in the involved networks were monitored and analysed. Real-time simulation results from the predefined set point changes in the real power injected to the IDMCE showed expected system performance in terms of transient frequency deviations and new steady state operating points. Moreover, the geographically distributed co-simulation configuration provided a viable alternative for the realtime simulation of very large power systems, since limitations such as the size of the system that can be run in a particular target environment or the unavailability to share grid models due to non-disclosure agreements may be overcome in this way. The extended power system model (obtained through the three proposed implementation schemes) can now be utilized for multiple applications, including the development and evaluation of advanced and innovative control mechanisms for large and practical power grids under real-time HIL simulation setups. Achievements of the work reported here will be disseminated through technical conference papers and exploited with industrial partners in future collaboration projects.