1. What is Fault Current?

Fault current is the abnormal current that flows through a circuit during an electrical fault (short circuit). It's crucial for designing protective devices and ensuring electrical system safety.

2. How Does the Calculator Work?

The calculator uses Ohm's Law for fault current:

Where:

• \( I_{fault} \) — Fault current (amps)
• \( V \) — System voltage (volts)
• \( Z \) — Total impedance (ohms)

Explanation: The equation calculates the maximum current that would flow if a dead short occurs in the system.

3. Importance of Fault Current Calculation

Details: Knowing fault current helps in selecting properly rated circuit breakers, fuses, and other protective equipment to safely interrupt faults.

4. Using the Calculator

Tips: Enter system voltage in volts and total impedance in ohms. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between available fault current and bolted fault current?
A: Bolted fault current is the theoretical maximum, while available fault current accounts for real-world factors like arc resistance.

Q2: Why is fault current important for circuit breakers?
A: Circuit breakers must have an interrupting rating higher than the available fault current at their location.

Q3: How does impedance affect fault current?
A: Higher impedance results in lower fault current. Impedance includes both resistance and reactance components.

Q4: What are typical fault current levels?
A: Residential systems might have 5-10kA, while industrial systems can have 50kA or more at service equipment.

Q5: Should I add a safety factor to calculations?
A: Yes, it's common to add 10-20% margin to account for future system changes and calculation uncertainties.