Simple Method for Basic Short Circuit Current Calculations

simple method for short circuit study calculations

In order to dig deep into the easy way to calculate the short circuit current calculations, we must first develop our knowledge base on the basics of short circuit analysis.

“A Short Circuit current analysis is used to determine the magnitude of the short circuit current which the system is capable of producing and compares the magnitude of the short circuit magnitude with the interrupting rating of the overcurrent protective devices (OCPD).”

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Short Circuit Study & its Importance in Power Systems

A basic electrical theorem say that the short circuit current actually depends upon the two most important parameters:

  1. The total impedance from the source to the point of the fault
  2. The nominal voltage of the system

With the help of the basic formula, we can easily calculate the short circuit current at the fault location and with the help of those values, we can analyze the system and install protective devices and protect the facility from any major harm or damage.


There are many methods to calculate the short circuit currents, however, we will give you the basic idea of how we can calculate the short circuit currents in a simple AC distribution system.

Read on to find out the easiest way to calculate a short circuit current.

arc fault occur in power systems

What does this mean? and why is it important to the simple calculation?

Suppose, if we have a 480 V/220 V step-down transformer which has an impedance of 5%, this means that 5% of 480 V i.e. 24 V, applied to its primary side will cause rated load current flow in its secondary.

If 5% of primary voltage will cause such current, then 100% of primary voltage will cause 20 times (100 divided by 5) full-load-rated secondary current to flow through a short circuit on its secondary terminals.

Now that we understand the basic variables that determine the short-circuit currents, let’s do a simple calculation for the same One Line diagram that has been mentioned earlier.

In order to prevent short circuit incidents within an industrial or commercial setting, get to know an easier method to determine short circuit current calculations in detail here.

Let us know if you have any queries regarding this topic and do provide us with your feedback in the comments.

About The Author

Abdur Rehman is a professional electrical engineer with more than eight years of experience working with equipment from 208V to 115kV in both the Utility and Industrial & Commercial space. He has a particular focus on Power Systems Protection & Engineering Studies.

Abdur Rehman is the CEO and co-founder of and creator of GeneralPAC by AllumiaX. He has been actively involved in various roles in the IEEE Seattle Section, IEEE PES Seattle, IEEE Region 6, and IEEE MGA.

Leaders in Industrial & Commercial Power Systems Engineering