1. What is a Voltage Drop Calculator for Underground Wire?

Definition: This calculator estimates the voltage drop in underground electrical wiring based on wire material, length, current, and cross-sectional area.

Purpose: It helps electricians and engineers ensure proper voltage levels in underground electrical installations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( VD \) — Voltage drop (volts)
• \( \rho \) — Resistivity of conductor material (ohm-m)
• \( L \) — Length of wire (meters)
• \( I \) — Current flowing through wire (amps)
• \( A \) — Cross-sectional area of wire (m²)

Explanation: The factor of 2 accounts for the return path in DC or single-phase AC circuits. The formula calculates the voltage lost due to the wire's resistance.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop estimation ensures electrical devices receive adequate voltage, prevents overheating, and maintains system efficiency.

4. Using the Calculator

Tips: Enter the resistivity (default 1.68×10⁻⁸ ohm-m for copper), wire length in meters, current in amps, and cross-sectional area in m². All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is voltage drop important for underground wiring?
A: Underground wires typically can't be easily replaced, so proper sizing is crucial to avoid future problems with voltage levels.

Q2: What's a typical resistivity value for copper?
A: Copper has ρ ≈ 1.68×10⁻⁸ ohm-m at 20°C. For aluminum, use ρ ≈ 2.65×10⁻⁸ ohm-m.

Q3: How does temperature affect the calculation?
A: Higher temperatures increase resistivity. For precise calculations, use resistivity values at operating temperature.

Q4: What's an acceptable voltage drop?
A: Most standards recommend less than 3% drop for branch circuits and 5% for feeders.

Q5: Does this work for three-phase systems?
A: For three-phase systems, replace the 2 with √3 (approximately 1.732) in the formula.