A new approach to transient stability evaluation in power systems

A relay margin concept is proposed for transient stability evaluation in power systems. Attention is given to modeling issues, security monitoring through relay margins, and their sensitivities for a given contingency. In response to a given contingency the relay activity is monitored by doing a fast simulation. A relay margin is defined for all the relays in the system, including those which clear the fault and those which are affected by the fault. It is suggested that this information would be more useful to an operator than a single quantity such as critical clearing time as in direct methods