High- Voltage DC has gained popularity due to its advantages, such as transferring bulk power over long distances with low transmission losses and improved stability. As a result, choosing the appropriate HVDC system model is of paramount importance. In this contribution, the authors used DIgSILENT power-factory simulation software to model the Ethiopia-Kenya line commutated converter HVDC. The Newton-Raphson algorithm was applied for numerical analysis and calculation. To validate the model, transient simulation studies are performed for various fault conditions and comparisons are made with the case where HVDC is installed and without HVDC interconnection. Critical clearing time has been given special consideration in this comparison. According to the overall simulation results, installing HVDC between Ethiopia and Kenya improves the Ethiopian power grid's transient stability by increasing the critical clearing time in comparison to the case without HVDC links.