Conventionally, transient stability constraints for power systems are defined in terms of active power. However, there is some weakness in the conventional approach due to the fact that the real limit is more directly related to angle difference and its accuracy depends on the accuracy of dynamic models of the power system components. Thus, additional capacity can be released under normal conditions if transient constraints are applied in terms of angle difference instead of power flow. With the wider penetration of Wide Area Measurement Systems (WAMS), it is now possible to use angle measurements for transient stability limits. This paper investigates the effect of defining a transient stability limit in terms of angle rather than active power and presents the benefits that an angle constraint can offer.