Relay misoperations play an important role in cascading blackouts. Power swing and out-of-step conditions caused by large disturbances in the system may result in relay misoperations. This effect is analyzed and simulated in this paper. Synchronized sampling based fault location (SSFL) algorithm was proposed as part of an advanced fault analysis tool to give precise fault information and verify relay judgments. This paper further analyzes the algorithm under power swing and out-of-step conditions and tests it by both static and dynamic scenarios generated in ATP. The test results indicate that SSFL algorithm performs better than distance relay under power swing and out-of-step conditions and can be used as a robust fault analysis tool for practical use.