Short Circuit Study
AS the name suggest Short Circuit study is done to find available fault currents at different busses in the system in case of a short circuit also referred as bolted fault. This is typically done through various software’s that are available in the market such as EasyPower, SKP ETAP etc. Once the available fault currents are determined then these faults are compared against equipment ratings to make sure all the equipment is appropriately rated in each System.

For example, based on the short Circuit study conducted in figure 1, the fault current available at main MDP is 16.02kA. which means in case of a dead short on this panel can see up to 16.02 kilo Amperes of current. So, the MDP has to be rated for the minimum of 16.02kA or higher. All the manufacturers have typical SC ratings for each of their breakers, so in above case the breakers that should be installed in the MDP has be rated for at least 16.02kA. In this case the closest higher will be 18kA or 22kA depending upon the manufacturer. As you move away from the main transformer the available short circuit tends to keep decreasing and so does the rating for that equipment at that point (unless you have big motor loads that are contributing to available Short circuit currents).
Circuit breakers and fuses are designed to protect people and equipment from this current, but they have their limits. Just like loading a structural member too far, you must make sure the circuit breakers and fuses can stop the damaging flow of excess current safely. Short circuit analysis is required to make sure equipment is not used outside of its effective range.