Short Circuit Study

There have been various instances in an industrial facility when a connection is established by accident between two current carrying conductors in an electrical circuit or conductors. This excessive fault current potentially causes equipment and circuit damage, overheating, magnetic stress, arcing, fire or may lead to explosion.

Short Circuit analysis is required to ensure that existing and new equipment ratings are adequate to withstand the available fault current at each point in an electrical power system. Equipment evaluation is performed based on the maximum available fault current for each crucial power system component. A “flag” or “exception” is considered when equipment’s calculated fault current is greater than the rated fault current. Then necessary measures are taken to appropriately rate the failing equipment.

Why perform Short Circuit Analysis?

The main objective of short circuit analysis is to provide necessary safety and code recommendations to the facility owners, EEORs and gear manufacturers on the equipment SCCR/withstand and interrupting ratings of protection devices in compliance with NEC, OSHA, IEEE, and UL standards. NEC 110.9 and 110.10 require installing equipment rated for the available Short Circuit Current (SCA). NEC 409.110, 440.4(B), 670.3 states that the equipment and machinery must be marked with its short circuit current rating (SCCR). NEC (409.22) also requires the equipment must not be installed where the available fault current exceeds its SCCR marking.

OSHA’s General Industry standard 1910.303 (b) (5) requires that a short circuit analysis is done to ensure that the design and installed equipment is correctly rated and coordinated. IEEE endorsed recommended practices for performing short circuit studies for industrial and commercial power systems.

The adequate ratings will prevent injury to personnel, minimize damage to system components, limit the severity and minimize the duration of service interruption during equipment failures, overload, or short circuit conditions. Consequently, ensure that all equipment such as Switchboards, Switchgears, Panelboards, Cables, MCCs, ATS/MTS, VFDs, UPSs, disconnects and other protective devices (circuit breaker and fuses) are safe and have adequate SCCR (Short Circuit Current Ratings).

Producing Short Circuit Results and Identifying Issues

The maximum available short-circuit current is a central parameter for all power distribution networks as it provides the necessary information to ensure equipment is being utilized within its rating and the system is running smoothly and reliably. A comprehensive modelling of the system is first done by using the data acquired from the existing facility documents. The next step is to calculate the continuous full load current rating for each electrical point in the system.

The short circuit currents can then be calculated based on the impedance represented by the “equivalent circuit”. This impedance may be calculated after separately summing the various resistances and reactance in the fault loop, from (and including) the power source to the fault location. After obtaining the impedance, it is used to divide the Full load Amperes at the specified electrical point to evaluate the short circuit current.

Results of fault current calculations are also used to determine the required short-circuit ratings of power distribution system components including bus transfer switches, variable speed drives, switchboards, load centers, and panelboards. In calculating the maximum fault current, it is necessary to determine the total contribution from all generators that may be paralleled and the load contribution from induction and synchronous motors.

Qualified and Certified Engineers:

Providing engineering recommendations about the causes of exceptions, the integrity of the system, or recommendations for corrective actions requires knowledge and skills beyond those of power systems engineering. Our team comprises certified professional engineers specialized in analyzing short circuit scenarios, particularly in critical areas related to life safety and essential components within facilities. We excel in determining optimal series rating combinations to enhance the AIC (Ampere Interrupting Capacity) and WCR (Withstand Current Ratings) of downstream equipment and protective devices that previously failed short circuit assessment. We help manufacturers, ECs and EEORs identify ATSs, panels and PDs combinations are adequately rated and are following the latest UL standards thereby maximizing design reliability. We work closely with our clients in gathering data, modeling the system, simulating faults and abnormalities, documenting fault magnitudes & recommending solutions in compliance with code requriements.

AllumiaX, LLC provides independent consulting and third-party engineering support by presenting comprehensive deliverable reports backed by the latest industry standards and best practices. Analysis is performed based on industry-leading software: SKM PowerTools, ETAP and Easy Power, they have proven results based on accurate modelling and calculations. The reports are expected to include the following deliverables:

1. A comprehensive electrical model of the facility
2. Evaluation of the equipment under short circuit conditions for normal and emergency scenarios
3. Interrupting ratings of protective devices and marking maximum short circuit on electrical equipment.
4. Comparisons between the existing protective device ratings and the available fault current
5. Design parameters of the protective devices that are required for optimal protection
6. Recommendations for the protection of equipment and personnel
7. Recommendations for the corrective action of the protective devices for protection against high fault currents
8. Available fault current (AFC) labels on service entrance equipment as well as electrical distribution equipment such as panelboards, switchboard, MCC, etc.

What is the customer/client responsible for?

At AllumiaX, we evaluate the power system and flag potential problems and high-risk situations while also recommending various options for resolutions and best-in-the-market practices to our customers for a safe, regulated, reliable, and well-designed power system. Clients who choose not to perform the study misses out on a huge value proposition.

Clients should help develop a list of equipment to be evaluated via onsite data collection for the existing facility or by providing updated one-line, BOMs and cutsheets for new equipment

What to Expect?

Short circuit studies will be 100% in compliance with the latest NEC, OSHA IEEE & NFPA standards. Study outcomes and recommendations are expected to improve your facility in the following areas:

1. Identification of critical areas in the power system.
2. Determining adequate SCCR/WCR current ratings for each equipment
3. Identifying acceptable interrupting ratings of the protective devices
4. Maximize protection for life safety, emergency, and essential equipment.
5. Minimize the risk of failing switchgears, switchboards, panelboards, ATS/MTS and MCCs.
6. Preparing contingency plans for emergency shutdowns
7. A significant reduction in power blackouts in case of severe faults
8. Adequate protection for the working personnel against high available fault currents