 Electric power distribution

Electric power distribution is the part of an electric power system that delivers electrical energy from supply points to connected electrical loads. It uses conductors, switching and protective equipment, and often electrical transformers to provide suitable local electric potential differences. Electric power transmission mainly transfers bulk power between supply regions and major receiving points; the distinction concerns network function rather than one universal voltage threshold.

A one-line diagram suppresses individual phase conductors to show the supply-to-load structure. The DOE handbook's apparatus example connects utility and standby supplies, buses, switching and protection to the consuming circuits.^[ref] Following the actual connection points is necessary before assigning losses or assuming that two loads share a return path.

For an original two-wire direct current example, a source holds $V_s=240\mathrm{V}$ and supplies a resistive electrical load $R_L=12\Omega$ through an outgoing-plus-return conductor electrical resistance $R_w=0.4\Omega$. Ohm's law givesThe conductor heating is $I^2{R}_w\approx 149.84\mathrm{W}$, while the load receives $I^2{R}_L\approx 4.4953\mathrm{kW}$. Their sum equals the source output $V_{s}I\approx 4.6452\mathrm{kW}$. Assigning the full source electric potential difference to the load would miss both its reduced terminal value and the location of the dissipated energy.

A proposed bench demonstration uses a current-limited low-voltage supply, a known series resistor representing the wires and a separate load resistor. Simultaneously measuring source and load electric potential differences and branch electric current tests the loss calculation. Real alternating current networks add electrical reactance, phase imbalance and protection constraints; the simple example isolates conductor heating rather than representing every distribution effect.