Specifications Document
Project: ARC-FLASH INCIDENT ENERGY REDUCTION
Date(s): February 22, 2013
Prepared by: Don Newman, William Hecksher, Ivan Botello, Francisco Martinez
Document status: X_Draft __ Proposed __ Validated __ Approved
Introduction
When electric current flows between two or more separated energized conducting surfaces, an arc
occurs. Temperatures at the arc terminals can reach or exceed 10,000+ degrees Fahrenheit. The heat
energy and intense light at the point of the arc is termed ARC FLASH. Air surrounding the arc is instantly
heated and conductors are vaporized causing a pressure wave termed ARC BLAST. The blast
resembles an explosion. (NFPA)
Many facilities are performing arc-flash hazard analyses to better understand how to protect personnel
from the possibility of being injured in an arc-flash incident. In many cases, it is unsafe or not practical to
shut down electrical equipment to do work. This project design will reduce incident energy levels in the
existing low-voltage system where the arc-flash hazard analysis results in unacceptably high levels.
(Shipp)
Proposed Project
We will be analyzing an existing facility’s electrical distribution system and extending the distribution
system. We will coordinate the new added devices with the existing in order to determine and minimize
the level of arc-flash hazard. During the process we will design a selectively coordinated circuit breaker
system study to lower the hazard level of arc-flash.
The following is a SKM Power Tools sample similar to our design.
Project Design and Methodology
Our project design will be conducted as follows:
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1. Data Collection:
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Receive existing electrical distribution equipment information and diagrams (see attached)
from the site staff.
Analyze the data on the existing electrical distribution equipment drawings.
The one-line drawing will be used as the basis for the study and calculations.
Review the proposed short circuit, and coordination cases to be studied.
2. Short Circuit Study
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Contact local utility company to determine available fault current at the service point.
Run the SKM DAPPER program to evaluate the available fault current at each fault bus (each
change of impedance) including all three phase panels/loadcenters and all three phase
motors to verify calculations.
Evaluate the results of the SKM DAPPER program.
Produce a report (including computerized printouts) showing the results and any
recommendations.
3. Protection/Coordination Study:
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Design selective circuit breaker coordinated system to reduce AFIE.
Run the SKM CAPTOR program and develop time-current curves to verify calculations.
Evaluate the results of the SKM CAPTOR program.
Produce a report showing the results of the study (protective device vs ampacity,
recommended relay settings, motor protection settings, circuit breaker settings, etc.) and any
other recommendations. This information will be used in the Flash Protection Boundary
Distance Calculations.
The consultant will provide a list of recommendations to improve coordination and/or load
distribution as well as ground fault requirements.
4. Arc Flash Evaluation
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Calculate the arc-flash incident energy (AFIE) at all equipment locations.
The information will be entered into the SKM DAPPER program to verify calculations.
The Flash Protection Boundary Calculations and PPE Requirements will be determined using
the SKM Power Tools program.
Review the results and determine if design has improved the AFIE at electrical equipment.
Design Constrains
Engineering Standards:
1. Institute of Electrical and Electronics Engineers, Inc. (IEEE):
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IEEE 141 – Recommended Practice for Electric Power Distribution and Coordination of
Industrial and Commercial Power Systems
IEEE 242 – Recommended Practice for Protection and Coordination of Industrial and
Commercial Power Systems
IEEE 399 – Recommended Practice for Industrial and Commercial Power System Analysis
IEEE 241 – Recommended Practice for Electric Power Systems in Commercial Buildings
IEEE 1015 – Recommended Practice for Applying Low-Voltage Circuit Breakers Used in
Industrial and Commercial Power Systems.
IEEE 1584 -Guide for Performing Arc-Flash Hazard Calculations
2. American National Standards Institute (ANSI):
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ANSI C57.12.00 – Standard General Requirements for Liquid-Immersed Distribution, Power,
and Regulating Transformers
ANSI C37.13 – Standard for Low Voltage AC Power Circuit Breakers Used in Enclosures
ANSI C37.010 – Standard Application Guide for AC High Voltage Circuit Breakers Rated on a
Symmetrical Current Basis
ANSI C 37.41 – Standard Design Tests for High Voltage Fuses, Distribution Enclosed SinglePole Air Switches, Fuse Disconnecting Switches and Accessories.
3. The National Fire Protection Association (NFPA)
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NFPA 70 -National Electrical Code, latest edition
NFPA 70E – Standard for Electrical Safety in the Workplace
Qualifications:
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The short-circuit, protective device coordination and arc flash hazard analysis studies shall be
conducted under the supervision and approval of a Registered Professional Electrical Engineer
skilled in performing and interpreting the power system studies.
Computer Analysis Software:
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The studies shall be performed using the latest revision of the SKM Systems Analysis
Power*Tools for Windows (PTW) software program.
Design Flow Chart
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Figure 1
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