Engineering Methodology & Physical Equations

1. Conductor Resistance & Voltage Drop (NEC & IEC 60364)

At standard operating temperature ($75^\circ\text{C}$), the electrical resistivity of Electrolytic Tough Pitch Copper is $\rho_{\text{Cu}} = 0.0214\ \Omega\cdot\text{mm}^2/\text{m}$ and Aluminum is $\rho_{\text{Al}} = 0.0353\ \Omega\cdot\text{mm}^2/\text{m}$.

• Single-Phase / DC Voltage Drop: $\Delta V = \frac{2 \times L \times I \times \rho}{A}$
• Three-Phase AC Voltage Drop: $\Delta V = \frac{\sqrt{3} \times L \times I \times \rho}{A}$
• Maximum Recommended Drop: $\le 3\%$ for branch circuits and feeders, and $\le 5\%$ total combined drop.

2. Three-Phase Apparent & Active Power

For three-phase AC circuits with line-to-line voltage $V_{LL}$ and power factor $\cos\varphi$:

$$I = \frac{\text{kVA} \times 1000}{\sqrt{3} \times V_{LL}} = \frac{\text{kW} \times 1000}{\sqrt{3} \times V_{LL} \times \cos\varphi}$$

3. Solar PV & Battery Storage Modeling

Array capacity ($\text{kWp}$) is derived from daily consumption divided by regional Peak Sun Hours ($\text{PSH}$) and a conservative system performance ratio ($\text{PR} = 0.80$).