A Short Circuit Study is an analysis of the protective devices of one’s electrical system, such as fuses, circuit breakers, fused switches, or any other devices intended to protect the equipment or isolate short circuits.
An SCS is needed to ensure that during a fault or short circuit, that the protective devices are not subjected to mechanical or current levels that they are not designed to withstand. If this happens, they might not open, explode, or some other undesirable result. It helps ensure that you are operating within the manufacturer’s tolerance for the devices.
You will need some basic information before you can have an SCS done. You will need the manufacturers protective device data, as well as the max amount of current that the device may experience. Tools like SKM or E-Tap are available to help do the SC analysis. These tools have libraries with many of the popular devices from manufacturers already loaded to make the studies easier.
You can expect a report from the study that comes back and shows the difference between what the manufacturers ratings to the amount of fault current that you currently have in the system. It involves many factors including what loads are in your system as well as power from the incoming or utility source.
This report can help you identify any devices that are over-rated, or not able to protect your system from the amount of short circuit in the system. The report that is generated will usually be ranked with the top priorities of devices that need your immediate attention.
Generally, you will need a one-line for your system to be able to do an SCS, but if you don’t one will be generated when you run the SCS through a tool like E-Tap or SKM.
An SCS is recommended to be done every 5 years or as major changes are performed on your system. Most of the available fault current is generated by the incoming utility source. As new plants are built and utility demands change, it can change the fault current on the system. When changes happen inside the plant, especially more load is added it can result in the rating of fault current on your breaker in kA might now be over duty, or no longer acceptable to protect your system.
Usually, the plant engineer or sometimes the safety director is responsible for requesting an SCS as well as managing short circuit restraints, making sure the system isn’t over duty and performing any actions from the SCS report.
Don’t miss the opportunity to protect your equipment and more importantly your people by having an SCS study performed on your electrical distribution system.