What Is Fault Current?
Fault current is electrical current that flows along an unintended path because of a fault in a circuit. A damaged wire touching a metal enclosure is an example. The current may rise high enough to trip a breaker, which opens the circuit and stops the flow.
Quick Facts About Fault Current
- Category
- Electrical circuit condition
- Used for
- Selecting protective devices
- Common confusion
- Circuit overload
- Often discussed with
- Circuit Breaker Replacement
Key Takeaways About Fault Current
- Fault current differs from the current used by everyday appliances.
- A breaker's interrupting rating must suit the available fault current.
- A circuit overload and an electrical fault aren't the same condition.
How Fault Current Works
Fault current depends partly on how much resistance the unintended path offers. A path with little resistance can let a large current flow. The electrical supply and wiring also affect the amount that can flow at a given point.
Related glossary terms: Electrical Short, Ground Fault, Circuit Overload.
Electricians use the term available fault current for the current a fault could draw at a particular location. That amount may differ between the service equipment and an outlet farther along a circuit. Longer wiring runs generally add resistance to the path.
A breaker's interrupting rating describes the fault current it can safely interrupt. This rating is separate from the breaker's normal current rating. A replacement breaker needs an interrupting rating suited to the available fault current at its location.
From the Earth Electric team
When we replace a circuit breaker, we check that the replacement suits the panel and the available fault current. We also look at the breaker's interrupting rating, not just its normal current rating. The panel location and supply details help guide that check.
Fault Current in Practice: A Real-World Example
During a breaker replacement, an electrician checks the panel's available fault current. The electrician selects a compatible breaker with an interrupting rating suited to that current.
Related Services
Related Terms
Electrical Short
An electrical short is a fault that lets electric current take an unintended path with little resistance.
Ground Fault
A ground fault is an electrical fault that sends current along an unintended path toward ground.
Circuit Overload
A circuit overload is a condition that occurs when connected devices draw more electrical current than a circuit is designed to carry.
Breaker Panel
A breaker panel is an electrical enclosure that distributes power to circuits in a building.
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