The objective of the studies presented in this paper is to demonstrate that the deployment and operational control of Synchronous Condensers (SynCons) combined with Static Compensators (STATCOM) in the GB transmission system can mitigate a part of the challenges associated with the high penetration of renewable energy sources. The case studies include scenarios such as transmission-level faults, fault level calculation and dynamic reactive power provision. For these scenarios, SynCons and STATCOMs of different capacity and design are installed at different regions of the GB transmission system. For these studies, verified models of SynCons and STATCOMs are deployed which are integrated to a representative GB network model. All the studies have been implemented in RMS simulation environment using Power Factory-DIgSILENT package software.