Short circuit study for your electrical installation
We calculate the fault current at every point of your system to confirm that breakers, panels and cables withstand and interrupt a fault without damage. It is the basis for protection coordination and the Arc Flash study.
What is a short circuit study?
A short circuit is an accidental, very low-impedance connection between phases, or between a phase and ground. At that instant the current can be tens of times higher than normal operating current, and every breaker, fuse, busbar and cable it passes through must withstand it until the protective device interrupts it.
The short circuit study (also known as a fault current calculation) builds a model of your installation, from the CFE service entrance to the main panels, and calculates the value of that current at each point. With that result we check whether your equipment has enough interrupting capacity and obtain the starting data to set protections and assess arc flash risk.
When is it needed?
- You are going to connect new equipment or an expansion to the existing installation.
- The capacity of the transformer or the CFE service entrance changed or increased.
- A breaker was damaged, exploded or failed to open during a fault.
- The project will be reviewed by an Electrical Verification Unit (UVIE).
- You need the basis for protection coordination or the Arc Flash study.
- An audit, your insurer or your corporate office requires it.
What it includes
The final scope is defined with you, based on your installation and what you need to solve.
Site survey and model
Updated single-line diagram with nameplate data for transformers, feeders, motors and protections.
Fault calculation
Three-phase and phase-to-ground faults at each panel or bus, including the contribution of motors and on-site generation.
Equipment review
Comparison of fault current against the interrupting capacity of breakers, fuses and busbars.
Overdutied equipment
List of equipment that would not withstand a fault, with the priority for addressing it.
Recommendations
Correction options: breaker replacement, current limiters or configuration changes.
Technical report
Calculation report, results tables and an explanation of the findings with your team.
What we need to perform the study
The basics are enough to quote. If you are missing some data, don't stop: we gather it on site as part of the service.
To perform the study
Requested once the service is confirmed. We help you gather it.
- Short-circuit power or current available at the connection point (provided by CFE).
- Nameplate data for each transformer: kVA, voltages, impedance (%Z) and connection.
- Size, length and raceway type of the main feeders.
- Power and voltage of the largest motors and variable frequency drives.
- Brand, model and interrupting capacity of main breakers and fuses.
- Connected emergency generators, solar systems and capacitor banks.
- Access to the panels for the site survey, under your plant's safety rules.
Your information is treated as confidential and is used only for your project.
How the study is performed
Information review
We review the single-line diagram and the data you already have, and define the scope.
On-site survey
We verify nameplate data, feeders and protections in your panels.
Fault current calculation
Using your facility data, we determine the fault current at each point.
Delivery of results
We deliver the report and review with your team what to address first.
What people ask us most
What is the difference between a short circuit study and protection coordination?
The short circuit study calculates how much current flows during a fault and checks whether your equipment can withstand it. Protection coordination uses that result to set the protections so that only the device closest to the fault trips. They are usually done together.
Do I need data from CFE?
Yes. The starting point is the short-circuit current or power available at your connection point, which is requested from CFE. While it arrives, the calculation can proceed with a conservative value that is documented in the report.
How often should it be updated?
Every time the installation changes: a new transformer, a change in supply or a large load. As a reference, it is best reviewed together with the Arc Flash study, which NFPA 70E recommends reviewing at least every five years.
Does the plant need to shut down?
Usually not. The survey is done with the installation in operation; if any data requires opening a panel, it is scheduled with you and under your safety procedures.
Do you have a case at your plant?
Tell us what you need to solve and what information you have. A specialist will reply with the scope and next steps.