1. What is Earth Fault Loop Impedance?

Earth Fault Loop Impedance (Zs) is the total impedance of the earth fault current loop starting and ending at the point of earth fault. It's a critical parameter in electrical safety calculations to ensure protective devices operate correctly under fault conditions.

2. How Does the Calculator Work?

The calculator uses the earth fault loop impedance formula:

Where:

• \( Zs \) — Total earth fault loop impedance (ohms)
• \( Ze \) — External earth fault loop impedance (ohms)
• \( R1 \) — Resistance of phase conductor (ohms)
• \( R2 \) — Resistance of earth conductor (ohms)

Explanation: The equation sums the external impedance (Ze) with the resistances of both the phase (R1) and earth (R2) conductors in the circuit.

3. Importance of Zs Calculation

Details: Accurate Zs calculation is essential for verifying that protective devices will operate within required times under earth fault conditions, preventing electric shock and fire hazards.

4. Using the Calculator

Tips: Enter Ze (external impedance), R1 (phase conductor resistance), and R2 (earth conductor resistance) in ohms. All values must be non-negative.

5. Frequently Asked Questions (FAQ)

Q1: Why is earth fault loop impedance important?
A: It determines if fault current will be sufficient to operate protective devices quickly enough to prevent danger.

Q2: What are typical Zs values?
A: Values vary by system type and protection method, but typically range from 0.1Ω to several ohms.

Q3: How is Ze measured?
A: Ze is measured at the origin of the installation with all parallel earth paths connected.

Q4: What affects R1 and R2 values?
A: Conductor material, size, length, and temperature all affect resistance values.

Q5: How does Zs relate to fault current?
A: Fault current (If) = Uo/Zs, where Uo is nominal voltage to earth (usually 230V).