Symmetrical Nomenclature of Three-Phase Circuits

Two methods of identifying three-phase conductors, voltages, and currents are in general use today. One method, used extensively on power systems and based on 30° voltage relations, is called ``standard´´ nomenclature.<sup>1,2,3</sup> The other method, used frequently for analytical purposes and based on 90° voltage relations, is called ``symmetrical´´ nomenclature.4 The following advantages of the symmetrical plan are discussed: 1. It is easier to use. 2. It identifies single-phase currents. 3. It requires fewer angles. 4. It is universal. 5. It is symmetrical.