There are many limits in power system operation however transient stability poses some of the most stringent limitations. Typical measures to assess transient stability, such as critical fault clearing time, provide some indication of whether or not a power system will remain stable after a large disturbance. However, these measures do not give any further insight into how system parameters should be regulated to ensure adequate system security. This paper explores the sensitivity of (a) power transferlimits and (b) transient stability margins to variations in a number of system parameters for a single machine infinite bus system. Several alternative stability margins are considered.