In the future a growing amount of power electronics will lead to a transition of the power system to a structure with very low synchronous generation. Due to large transit power flows and uncertainties, transmission systems are being operated under increasingly stressed conditions and are close to their stability limits. Together with the integration of large amounts of renewable generation with power electronic interfaces and the addition of high-voltage direct current (HVdc) links into the power system, these challenges will necessitate a review of the operation and control of transmission networks. This article will demonstrate the need for R&D performed by network operators and explain a set of challenges, focusing on three main areas: transmission grid operation in a new power system environment, the need to increase overhead line (OHL) utilization, and the impact of reduced inertia on power system frequency.