SHORT CIRCUIT STUDY

Short Circuit (Fault Current) studies are required to insure that existing and new equipment ratings are adequate to withstand the available short circuit energy available at each point in the electrical system. Fault currents that exceed equipment ratings are capable of extensive equipment damage and are a serious threat to human life.

On large systems, short circuit studies are required to determine both the switchgear ratings and the relay settings.

No substation equipment, motor control centers, breaker panels, etc. can be purchased without knowledge of the complete short circuit values for the entire power distribution system.

The short circuit calculations must be maintained and periodically updated to protect the equipment and the lives. It is not necessarily safe to assume that new equipment is properly rated.

BENEFITS OF SHORT CIRCUIT STUDY

• Reduce the risk a facility could face and help avoid catastrophic losses.
• Increase the safety and reliability of the power system and related equipment.
• Evaluate the application of protective devices and equipment.
• Identify problem areas in the system.
• Obtain recommended solutions.

DELIVERABLES OF SHORT CIRCUIT STUDY

A typcial short circuit study includes:

• Short circuit calculations, which highlights any equipment that is ascertained to be underrated as specified
• Suggested modifications to rectify the underrated equipment; (trip sizes within the same frame, the time curve characteristics of induction relays, CT ranges, etc.).

The Protective Device Setting and Coordination Study is the suggested follow on analysis to develop the coordination curves, highlighting areas lacking coordination. Presentation of a protecitve device study would includ a technical evaluation with a discussion of the logical compromises for best coordination.

FAQs about SHORT CIRCUIT STUDIES

What are Short Circuit Currents?

Short-Circuit Currents are currents that introduce large amounts of destructive energy in the forms of heat and magnetic force into a power system, as indicated by IEEE 242-1986, IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems.

Risks Associated With Short Circuit Currents?

The building/facility may not be properly protected against short-circuit currents. These currents can damage or deteriorate equipment. Improperly protected short-circuit currents can injure or kill maintenance personnel. Recently, new initiatives have been taken to require facilities to properly identify these dangerous points within the power distribution of the facility.