SPN correspond to the English term Single Phase Node. Equivalent to the Spanish term phase. The phase term in domestic premises or homes means you have a single phase alternating current. Usually contracted power in homes is up to 10kW. The difference with the phase installations is that these can be divided into three phases, namely three alternating currents. The instalaciones-phase may also be divided into parts. Facilities include single-phase 3-wire cable 1. phase (black or brown cable) that is providing electricity. 2. Neutral (blue wire) is responsible for the electricity back where it came from creating a circle. 3. Physical cable (two colors) protects the energy absorbing phase of their environment, in some cases this third cable is not used, but isrecommended it for security. 1. In the image-phase power system three-phase power system 2.