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Short Circuit Analysis Training
On Demand Class | 6 Hours | 23 Modules | By Jim Phillips, P.E.

Current limiting fuses. series ratings. fuse selection, short circuit analysis calculation, dc short-circuit analysis

National Electrical Code Section 110.9 Interrupting Ratings states: Equipment intended to interrupt current at fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that is available at the line terminals of the equipment.

Equipment intended to interrupt current at other than fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that must be interrupted.

How would one know whether this requirement has been met? By conducing a short circuit study to predict the available fault current at each piece of equipment.  This course takes you through the process of performing a short circuit study including the necessary data, study process and detailed short circuit calculations using Jim Phillips’ calculations worksheets which are part of this online course.

  • SHORT CIRCUIT ANALYSIS – INTRODUCTION
    Short Circuit Study Requirements, NEC® 110.9 and 110.10, Interrupting and Withstand Ratings, Data Requirements, Available Utility Short Circuit Current, Conductor Impedance, Source Impedance, X/R Ratio, Per Phase Calculations, Thevenin Equivalent, Impedance
  • CONDUCTOR IMPEDANCE AND SHORT CIRCUIT CALCULATIONS
    Determining the Source Impedance, Calculating the Conductor Impedance, Conductor Impedance Tables, Conductor Calculation Worksheets.  In Class Problems – Short Circuit Calculations with Conductor Impedance
  • TRANSFORMER IMPEDANCE AND SHORT CIRCUIT CALCULATIONS
    Transformer Testing and Percent Impedance, X/R Ratio,  Using Percent Impedance for Short Circuit Calculations,  Determining the Source Impedance in Percent, Infinite Bus Calculations, Transformer Calculation Worksheets.  In Class Problems – Short Circuit Calculations with Transformer Impedance
  • MOTOR CONTRIBUTION
    Theory of Motor Short Circuit Contribution, Sub-Transient Reactance, Xd”, Effect of Motor Contribution on Short Circuit Current, Multipliers for Motor Contribution.  In Class Problems – Consideration of Motor Contribution
  • DEVICE INTERRUPTING RATINGS
    Circuit Breaker and Fuse Interrupting Ratings, UL and ANSI Testing Methods, Symmetrical and Asymmetrical Short Circuit Current, Effect of X/R Ratio on Interrupting Ratings, Multiplying Factors when the X/R and Asymmetry are Too Large
  • SERIES RATINGS
    Development of Series Ratings, Proper Application of Series Ratings, Dynamic Impedance, Fully Rated vs. Series Rated, Current Limitation, Let Thru Current, U.L. Tests
  • CASE PROBLEM
    Short Circuit Study of Small Industrial System.  Calculations Include Source, Conductor and Transformer Impedance, Motor Contribution and Protective Device Adequacy Evaluation

Course Content

Download: Short Circuit Analysis Worksheets
Module 1: Introduction
Module 2: Types of Faults
Module 3: Per Phase Analysis
Module 4: Short Circuit Current Flow
Module 5: Impedances and X/R Ratio
Module 6: Conductor Impedance Data
Module 7: Problem 1 – Conductor Calculations
Module 8: Problem 1 – Solution
Module 9: Problem 2 – Conductor Calculation
Module 10: Problem 2 – Solution
Module 11: General Discussion about Inadequate Equipment
Module 12: Transformer Impedance
Module 13: Problems 3 and 4 – Infinite Bus Calculation Examples
Module 14: Transformer and Source Impedance Calculations
Module 15: Problem 5 – Transformer and Source Calculation
Module 16: Problem 6 – Transformer and Source Calculation
Module 17: Problem 6 – Solution
Module 18: Motor Contribution
Module 19: X/R Ratio and Asymmetry
Module 20: Interrupting Ratings and X/R
Module 21: Current Limitation and Series Ratings
Module 22: Introduction to Final Case Problem
Module 23: Final Case Problem – Solution
Final Quiz: Short Circuit Analysis