Abstract: This invention introduces the concept that on an interconnected electric power system, the area-caused components of memory parameters system time deviation and the total inadvertent interchange of each constitutent control area are separable and measurable. Methods and means are disclosed for separating each of the components and determining its magnitude, utilizing known or measurable parameters, thereby providing new long-desired area memory parameters which are precise measures of the control performance of each area. The portion of system time deviation and the portion, designated primary inadvertent, of total area inadvertent interchange caused by an area's own regulating deficiencies, and the portion, designated secondary inadvertent, of total area inadvertent interchange caused by regulating deficiencies of each remote area, are identified.