Welcome to our transformer short circuit calculation! This page will allow you to undertake a transformer short circuit current calculation using the transformer rating in kVa, the voltage rating of the secondary winding and the per unit impedance of the transformer in percentage. Let's begin!


⬇️ Inputs

S (kVA)

V (LL)

Z %

⬆️ Outputs

I (3P)

I (PP)

I (PN)

I (PE)

🔄 Z% to find Zn




💬 We'd love your feedback on this template! It takes 1min


In a transformer, fault current refers to the amount of current that flows through the transformer when there is a fault or short circuit in the system. This current can be much higher than the normal operating current of the transformer. It can cause damage to the transformer and other electrical equipment if it is not properly protected.
Several types of fault conditions can occur in a transformer, such as a short circuit between the primary and secondary windings, a short circuit between the windings and the transformer's core, or an external short circuit on the secondary side of the transformer. Each of these fault conditions can result in a different fault current magnitude and waveform.

💡Understanding and analysing these fault currents is important to properly design and protect the transformer and the electrical system.


Zero, Positive and Negative Sequences (Zn)

👉 Important note!

Additional Resources

Have you tried our other calculators?
  1. 🔗 Power (DC circuits)
  1. 🔗 Ohm's Law
  1. 🔗 Capacitive Reactance