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 and limb. 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 of workers. See “Determining When Studies are Necessary”
Never assume that new equipment is properly rated. All equipment ratings should be compared with an up-to-date base-line short circuit study.
Fault Current studies provided by PAA are comprehensive and meet the specifications of NETA (International Electrical Testing Association), NFPA 70B, Recommended Practice for Electrical Equipment Maintenance (Chapter 23), and U.S. Army Corps of Engineers Specifications. PAA studies provide a rigorous network analysis of three-phase, single line-to-ground, line-to-line, and double line to ground fault currents. For each potential fault point the following parameters are applicable; RMS momentary fault currents, asymmetrical fault duties at three, five and eight cycles, and the positive, negative and zero impedance values. The current direction, X/R ratio and the magnitude of all fault currents are also supplied. Fault contributions from utilities, motors and generators are considered.
· The ANSI C37 Fault Analysis Study calculates three-phase and single line to ground fault duties in full compliance with the ANSI/IEEE recommended standards for low, medium and high voltage systems.
· The IEC 909 Fault Analysis Study calculates three-phase and unbalanced fault duties in full compliance with the IEC 909 recommended standards for low, medium and high voltage systems.
For all Short Circuit Analysis Studies each regional office of PAA uses the latest SKM A-Fault (ANSI C.37) and IEC-Fault (IEC 909) software package equipped for 2000 buses.SKM is an international leader in Electrical Systems Analysis software. All PAA Engineers are graduates of SKM training.