1. What is Resistance Overhead DC?

Resistance Overhead DC is defined as the property of the wire or line that opposes the flow of current through it in a two-wire mid-point earthed DC system.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( R \) — Resistance Overhead DC (Ω)
• \( \rho \) — Resistivity of the material (Ω·m)
• \( L \) — Length of Wire DC (m)
• \( A \) — Area of Overhead DC Wire (m²)

Explanation: The resistance of a conductor is directly proportional to its resistivity and length, and inversely proportional to its cross-sectional area.

3. Importance of Resistance Calculation

Details: Accurate resistance calculation is crucial for determining power losses, voltage drop, and efficiency in DC transmission systems.

4. Using the Calculator

Tips: Enter resistivity in Ω·m, length in meters, and area in m². All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What factors affect wire resistance?
A: Resistance is affected by material type (resistivity), wire length, cross-sectional area, and temperature.

Q2: Why is mid-point earthing used in two-wire systems?
A: Mid-point earthing provides better voltage stability and reduces the risk of electric shock in case of faults.

Q3: How does temperature affect resistance?
A: For most conductors, resistance increases with temperature due to increased atomic vibrations.

Q4: What are typical resistivity values for common materials?
A: Copper: 1.68×10⁻⁸ Ω·m, Aluminum: 2.82×10⁻⁸ Ω·m, Silver: 1.59×10⁻⁸ Ω·m at 20°C.

Q5: How can resistance be reduced in transmission lines?
A: Resistance can be reduced by using materials with lower resistivity, shorter lengths, or larger cross-sectional areas.