Power systems across the globe are undergoing a transition away from fossil-fuelled, synchronous generators (SGs) in favor of emission-free, inverter-based renewable generation. To maintain reliable operation of the power system, it is vital to achieve an understanding of the effects that are induced due to the displacement of SGs. In this paper, a representative model of the New South Wales (NSW) transmission network is developed to investigate how oscillation modes are affected by the displacement of a SG. The damping of oscillatory modes is examined following the removal of main fossil-fuelled SGs, both individually and in series. Both increases and decreases in damping are observed for each of the cases examined. Following the removal of a single SG, the impacts observed on inter-area modes are more significant than those observed for local modes. As the number of displaced SGs increases, local modes appear to generally decrease in damping.