A processor-implemented method for determining an expected overall performance value of a substation automation system is disclosed. The method comprises causing a processor to provide a plurality of virtual Intelligent Electronic Device (IED) representations, each virtual IED representation being associated with a respective data structure defining a previously generated physical IED performance profile obtain a data structure defining an arrangement of the provided plurality of virtual IED representations, the arrangement relating to a substation automation system test configuration receive data defining arrangement stimulation test values and determine an expected overall performance value of the arrangement by combining performance metrics for each of the virtual IED representations in the arrangement in accordance with the arrangement, the performance metric for each of the virtual IED representations being retrieved from the respective data structure defining the previously generated physical IED performance profile by addressing the data structure using the arrangement stimulation test values.
