# Short Circuit Analysis

Learn how to perform short circuit analysis / calculations and equipment adequacy evaluations. Understand the importance of X/R ratios, symmetrical vs. asymmetrical faults and how series ratings work. Many calculation examples are used to illustrate how to perform an analysis. The methods are based on the IEEE Violet book and the course is loaded with many in class examples and problems for a hands on learning experience.

﻿Learn how to perform short circuit analysis / calculations and equipment adequacy evaluations. Understand the importance of X/R ratios, symmetrical vs. asymmetrical faults and how series ratings work. Many calculation examples are used to illustrate how to perform an analysis. The methods are based on the IEEE Violet book and is loaded with many in class examples and problems for a hands on learning experience.

Jim has developed this course based on almost four decades of extensive experience with industrial, commercial and utility power systems. Even instructors from other training companies have attended Jim’s classes to see how it’s done. You will learn how to conduct a short circuit study.

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.

• What questions do I ask the utility company?

• What is the X/R ratio?

• How does the X/R ratio effect a device’s interrupting rating?

• What is motor contribution?

• How do I calculate motor contribution on new systems with an undefined load?

• Is a short circuit study legally required?

• What kind of data is required for the short circuit studies?

• What if I can’t find all of the data, what assumptions can I make?

• Why is the L/E ratio so important?

• How do current limiting fuses operate?

• What is a symmetrical current vs. asymmetrical current?

• How do I properly apply series ratings?

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### Instructor #### Jim Phillips

Instructor

• Founder: Brainfiller.com Electrical Power, Safety and Arc Flash Training • Associate Director: Electrical Safety UK Ltd. - Rotherham, England • Contributing Editor: Electrical Contractor Magazine • Author: Complete Guide to Performing an Arc Flash Hazard Study • B.S. Electrical Engineering • Registered Professional Engineer • Four Decades of Industrial and Utility Experience • Vice Chair: IEEE 1584 - IEEE Guide for Performing Arc Flash Hazard Calculations • TC Member: NFPA 70E - Electrical Safety in the Workplace • International Chair: IEC TC 78 Live Working Standards • Steering Committee – IEEE/NFPA Arc Flash Collaborative Research Project. E-mail: jphillips@brainfiller.com

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CEU 0.6/PDH 6