Calculate your transformer’s secondary fault current
Available Fault Current Calculator
You need to understand your available fault current to ensure your protective devices can shield your system from a short circuit. Use this calculator to check your setup.
How to use the fault current calculator
Three phase formula
Single phase formula
When to use the Available Fault Current Calculator
Common applications for our Available Fault Current Calculator:
Need help with complex fault current scenarios? Our application engineers can assist with multi-source systems, high-fault applications, or custom transformer impedance specifications.
What to do with your fault current calculation
You’ll use your available fault current calculations in several key areas:
Working on a high-fault application? Giga's engineering team can help. Schedule a consultation to discuss your specific project requirements.
What else affects available fault current?
The Available Fault Calculator focuses on transformer-limited fault current, but real-world systems have additional variables:
Need a more advanced fault current study for your build? Our engineering team can recommend transformer specifications that work for your application. Get in touch for project-specific guidance.
Calculator variables & definitions
Below are the definitions for the different terms that this calculator uses
What is Voltage?
Electric potential, measured in volts (V), represents the amount of electrical potential energy per unit charge at a specific point in the circuit. Voltage is the driving force that causes electric charges to move within a circuit.
What is kVA?
kVA stands for kilovolt-ampere, which is a unit of apparent power in an electrical system. It measures the total power, both real and reactive, in an alternating current (AC) circuit. The symbol for kilovolt-ampere is "kVA."
What are Amps?
Amps, short for amperes, is a unit of electric current. It is a measure of the rate at which electric charges flow through a conductor in an electrical circuit.
What is a transformer?
A transformer is an electrical device that takes a given input voltage and changes it to a different output voltage. This change can either be an increase or a decrease in voltage.
Available fault current FAQs
What's the difference between available fault current and full-load current?
Available fault current is the maximum current during a short-circuit condition. Full-load current is your unit’s normal operating current.
Do I need to recalculate fault current after system changes?
Yes. Whenever you change transformer capacity, add parallel sources, or modify the system configuration, recalculate available fault current and update your labels.
Is this calculator suitable for utility-side fault current?
No. This calculator determines transformer secondary fault current only. For primary-side or utility contribution calculations, contact your utility provider.
Can I reduce fault current if it's too high for my equipment?
Yes. You can reduce fault current by specifying higher-impedance transformers, selecting switchgear and breakers with higher interrupting ratings, or taking a number of other steps. Our engineering team can help you evaluate trade-offs for your specific application.
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