In order to verify a substation automation system based on IEC 61850, Korea Electric Power Research Institute under the project related to SAS has constructed IED testing system, which consists of HMI, IED(Intelligent Electronic Device), network equipment, V/I generator, and performed a various of communication tests such as the interoperability test between two IEDs made by other vendors. The test was proceeded based on SCL(Substation Configuration Description Language). This paper presents ways and procedures to simulate those tests and solutions to clear up SCL based engineering problems and compatibility among the individual manufacture tools.