Arc flash edsa manual

Version 6.00.00 Arc Heat March 2005
AC & DC Arc Flash Evaluation
Manual
Based on NFPA® 70E
&
IEEE Standard 1584
EDSA Micro Corporation
16870 West Bernardo Drive, Suite 330
San Diego, California 92127
USA
©Copyright 2005
All Rights Reserved

AC & DC Arc Heat Exposure
Version 6.00.00 i Arc Heat 2005
Table of Contents
Arc Heat Program Overview ....................................................................................................................... 1
Heat Exposure Due to Arcing Faults........................................................................................................... 2
Program Capabilities....................................................................................................................................... 3
Arc Flash Study........................................................................................................................................... 4
Exposure Defined ....................................................................................................................................... 5
Personal Protective Equipment Defined ..................................................................................................... 6
Arc Resistance Defined .............................................................................................................................. 8
Key Concepts.............................................................................................................................................. 9
Open Arc................................................................................................................................................. 9
Directed Arc ............................................................................................................................................ 9
Radiant Energy ....................................................................................................................................... 9
Blast Energy............................................................................................................................................ 9
References................................................................................................................................................ 10
Program Verification & Validation ............................................................................................................. 11
1.0 Arc Heat Tutorial Introduction ........................................................................................................... 12
1.0.1 Key Concepts............................................................................................................................. 16
1.0.2 Network-Based Arc Heat Exposure on AC Systems / Single Branch Case ............................... 16
1.0.3 Network-Based Arc Heat Exposure on AC Systems / Multiple Branch Case............................. 31
PDC ArcHeat Methodology Summary....................................................................................................... 40
Special Features in Arc Heat .................................................................................................................... 48
1.1 Stand-Alone Arc Heat Exposure on AC Systems.............................................................................. 65
1.2 Network-Based Arc Heat Exposure on DC systems ......................................................................... 73
1.3 Stand-Alone Arc Heat Exposure on DC systems .............................................................................. 80
1.4 Verification and Validation Data ........................................................................................................ 87
1.4.1 V&V of AC Arc Heat Programs with Longhand using IEEE1584 Standard in Stand Alone Mode /
Prepared by Dr. Lifeng Liu, PhD 12/2/2004 .............................................................................................. 87
1.4.2 V&V of Stand Alone Results for DC Arc Heat Programs Comparing with Network Mode
Prepared by Dr. Lifeng Liu, PhD 12/2/2004 .............................................................................................. 89
1.4.3 V&V of ARC HEAT with PDC Interface by Conrad St. Pierre .................................................... 90
Using ArcHeat for Single Phase Circuits................................................................................................. 102
Putting Arc-Flash Calculations in Perspective............................................................................................. 103
Data Required......................................................................................................................................... 103
IEEE Equations and Test Results for Open Air Arc ................................................................................ 104
Enclosed Arcs......................................................................................................................................... 106
Personal Protective Equipment............................................................................................................... 107
Arc Blast Pressure .................................................................................................................................. 107
Limiting Arc Exposure ............................................................................................................................. 109
Calculation Means .................................................................................................................................. 111

ii
About Conrad St. Pierre.......................................................................................................................... 112
Conrad St. Pierre Bio .......................................................................................................................... 112
Publications by Mr. Conrad St. Pierre..................................................................................................... 113
List of Figures
Figure 1 –Circuit for Arc Model ....................................................................................................................... 1
Figure 2 - Arc Flash Zones.............................................................................................................................. 4
Figure 3 - Network under study, showing a ½ cycle fault analysis at BUS-05 .............................................. 17
Figure 4 - PDC Study for Motor on BUS-05 .................................................................................................. 18
Figure 5 - Network topology for job-file “IEEEPDE.axd” showing ½ cycle fault results for Bus4................... 31
Figure 6 - Simplified view of Bus4 and its fault contributing branches (1/2 cycle Sym. Currents) ................. 32
Figure 7 - PDC Study for Bus4 including all 6 converging branches. Currents are plotted at 13.8 kV. ......... 33
Figure 8......................................................................................................................................................... 42
Figure 9 - Portion of IEEEPDE.axd One-line with Bus 4 Fault Flows............................................................ 90
Figure 10 - Time Current Curve showing Protective Device operating times................................................ 91
Figure 11 - Time Current Curve showing Protective Device operating times................................................ 95
Figure 12 - Time Current Curve Showing Protective Device Operating Times ............................................. 97
Figure 13 - Bus 3 Protective Devices............................................................................................................ 99
Figure 14 - Bus 28 Protective Devices........................................................................................................ 100
List of Tables
Table 1 – Typical Thermal Performance of Various Fabrics in Cal/ cm2
......................................................... 6
Table 2 - NFPA-70E Flash Hazard Risk Categories ....................................................................................... 6
Table 3 – Glove Classes................................................................................................................................. 7
Table 4 - Fault Currents and Protective Device Operating Times................................................................. 90
Table 5 - Determining Controlling Branch ..................................................................................................... 92
Table 6 – Comparison of Results.................................................................................................................. 93
Table 7 - Fault Currents and Protective Device Operating Times................................................................. 94
Table 8- Determining Controlling Branch ...................................................................................................... 94
Table 9 - Comparison of Results................................................................................................................... 94
Table 10 - Fault Currents and Protective Device Operating Times............................................................... 96
Table 11 - Determining Controlling Branch ................................................................................................... 96
Table 12 - Comparison of Results................................................................................................................. 96
Note: You can view this manual on your CD as an Adobe Acrobat PDF file. The file name is:
AC & DC Arc Heat ACDCArcHeat.pdf
You will find the Test/Job files used in this tutorial in the following location:
C:EDSA2005SamplesArcHeat = AC & DC Arc Heat
Test Files: ACAHSTANDALONE, IEEEPDE, ARCHEAT_SB, DC_SC2
©Copyright 2005
All Rights Reserved

1
Arc Heat Program Overview
The EDSA Heat Exposure Program uses empirical equations based on test results given in IEEE-
1584 [12] to provide an estimate of the energy falling on a surface removed from a fault. As more
data become available, this test data will be used to refine the program empirical equations. As
an option, personal protective equipment (PPE) based on NFPA-70E [13] is provided.
The arcing current used in this program is greater than those often associated with the minimum
arcing currents used to set relays. In setting relays, the minimum arcing is used so that the relays
can be set to ensure that they operate. While for heat exposure, the maximum arcing current is
of concern. In the above references, it was found that there is a driving voltage needed to sustain
an arc. As an arc becomes longer, the arc voltage increases and becomes greater than the
voltage needed to maintain itself. This voltage is approximately 150-V to 180-V rms depending
on the fault X/R ratio [9,10].
The circuit use in Fig. 1 is a simplified model for arc current calculations. The power dissipated
in the arc radiates to the surrounding surfaces. The further away from the arc the surface is, the
less the energy is received per unit area. One use of the program is to identify the grade of
clothing required by the operator who is working with energized equipment. The program allows
either a manual input of the source voltage and short-circuit bolted fault current or entry via the
EDSA short-circuit program. Using the information in the reference papers, empirical equations
from IEEE 1584 are used to determine the arc voltage and the radiated heat.
There are several uses for this program. For example, it could be used to provide a protective sign
on a piece of electrical equipment stating the type of protective clothing required when working
around energized equipment. Warning of Arc Flash Hazard is a requirement given in 2005 National
Electrical Code (NEC)
®
, Article 110.16. Personal Protective Equipment (PPE) requirement are given
in NFPA 70E-2004, section 130. Alternatively, the converse, knowing the thermal capability of the
protective clothing being used, the program could indicate if it is satisfactory. In this regard, the
protective level of the clothing is entered into the program and the program gives a ‘pass’ or ‘fail’
result.
Figure 1 –Circuit for Arc Model

2
Since most equipment is an enclosed area and a workman would have to open a door or remove
a panel, the box will direct the arc radiant and blast energy in one direction. Therefore, the higher
energies from ’Switchgear box’ or ‘MCC box’ (if it applies) are recommended to be use
switchgear and switchboards.
Reference #10 test results are for two conditions: an open arc and an arc-in- box. The open-arc
has the arcing electrodes extending in air approximately 2 feet from a wall. The arc-in box has
the barrier on all sides except it is open in front. This would be similar to an open door in a
switchgear cubicle. The latter directs the energy so that it increased 2 to 3 times on a touched
surface. Arc Heat provides both the open-arc and switchgear and MCC arc (arc-in-box) energy to
a surface.
If all the heat in the arc is considered radiation, then the distance will reduce it from the arc
squared. Based on the measured data, more than just the radiated energy is reaching surface.
Therefore, some heat must be due to the hot gases touching the surface. The difference
between the calculated radiant energy and total measured energy must be due to convection of
heat produced by the explosive gases reaching the surface. From the test results, a different
exponent when being ‘in a box’ disperses the incident energy. The exponent is not squared, but
a lower factor. These factors are included in the EDSA program.
Heat Exposure Due to Arcing Faults
For the calculation of maximum short-circuit current magnitudes for equipment evaluation, the arcing
short-circuit impedance, or arc resistance is considered zero. When the fault does contain an arc,
the heat released can damage equipment and cause personal injury. It is the latter concern that
brought about the development of the heat exposure program. The heat exposure due to an arc can
harm, or burn, bare skin or protective clothing. ‘The Standard for Electrical Safety Requirements
for Employee Workplaces’, (NFPA 70E-2004), provides information on the protective performance
of various fabrics, which would limit heat exposure to second-degree burns.
In addition to burns, there are other exposure risks to arcing faults, such as:
a. Electrical shorts due to touching energized conductors.
b. Arc blasts, due to expanding gases, that can cause flying debris, knock a person off
balance, and cause ear damage.
c. Exposure to arc plasma can result in temporary or permanent blindness.
d. Arc plasma or heat can result in a fire.
e. Metal vaporization can condense on cooler materials.
The above list of points (a-e) does not express the amount of energy in an arc. However, if you
compare the arc blast to dynamite exploding, the heat produced can ignite clothing situated
farther than 10 feet away. Clearly, any exposure to an arcing fault can be hazardous.

3
Program Capabilities
Arc Flash Exposure based on IEEE 1584
Arc Flash Exposure based on NFPA 70E
Network-Based Arc Flash Exposure on AC Systems/Single Branch Case
Network-Based Arc Flash Exposre on AC Systems/Multiple Branch Cases
Stand-Alone (Non-Network) Arc Flash Exposure on AC Systems
Network Arc Flash Exposure on DC Networks
Stand-Alone Arc Flash Exposure on DC Systems
Exposure Simulation at Switchgear Box, MCC Box, Open Area and Cable Grounded and
Ungrounded
Calculate and Select Controlling Branch(s) for Simulation of Arc Flash
Test Selected Clothing
Calculate Clothing Required
Calculate Safe Zone with Regard to User Defined Clothing Category
Simulated Art Heat Exposure at User Selected Bus(s)
User Defined Fault Cycle for 3-Phase and Controlling Branches
User Defined Distance for Subject
100% and 85% Arcing Current
100% and 85% Protective Device Time
Protective Device Setting Impact on Arc Exposure Energy
User Defined Label Sizes
Attach Labels to One-Line Diagram for User Review
Plot Energy for Each Bus
Write Results into Excel
View and Print Graphic Label for User Selected Bus(s)
Work permit

4
Arc Flash Study
Figure 2 shows three arc-flash zones that can have different calculated arc-flash energy levels for
each fault location; although the Figure 2 bus fault current level is the same, the fault clearing
time can be different. Zone 1 extends from the secondary main breaker to the transformer
primary upstream protective device. A Zone 1 fault on the transformer secondary (to within the
secondary main breaker) has to be cleared by an upstream device with a backup fault clearing
time. Zone 1 also covers main breaker racking-in and racking-out conditions. In the EDSA
program, a dummy bus is usually furnished with the breaker symbol on the source side of the
breaker.
Zone 2 includes the load side terminals of the secondary main breaker, main bus, feeder breaker
load terminals, and tie breaker (not shown). The Zone 2 bus/breaker zone is protected by the
secondary main breaker and would also include feeder breaker racking-in and racking-out
conditions. When the secondary main breaker is not provided, Zone 1 would also include Zone 2.
Zone 3 includes the feeder breaker load terminals to the downstream device (load, sub-bus or
MCC or panel breaker). Typically, with selective protective systems, Zone 2 fault clearing time is
greater than the Zone 3 clearing time. In the EDSA program, a dummy bus is usually furnished
with the breaker symbol on the load side of the breaker.
Zone 1
Zone 3
Zone 2
Figure 2 - Arc Flash Zones

5
Exposure Defined
The amount of heat from an arc depends on the voltage across the arc, the current, single phase
or multi-phase arc, confinement of the arc, and the distance the subject is away from the arc
plasma. Most of the data collected for heat exposure have been staged, since the modeling of
the arc is very complex [5, 6, 7, 8, 12].
The power in the arc (VARC * IARC) is radiated out as incident energy falling onto a surface. Again,
test results are often used to compare the amount of energy produced in the arc and radiating to
a surface at some distance away. As expected, the radiated energy depends if the arc is
unrestricted in free air, or semi-confined, or directed as it would be in a switchgear cubicle with a
panel removed or the door open. The latter directs the radiating energy toward the open area,
greatly increasing the incident energy falling onto a surface. The arc produces quickly expanding
gases. These gases heat the surfaces they contact. Thus, the energy of an arc can burn
contacted surfaces due to both radiant and convection heat transfer.
Low voltage switchgear type of equipment can have bare buses and a line-to-ground or a line-to-line
fault and can quickly become a three-phase arcing fault with the corresponding increase in arcing
energy. Arcing faults beginning, as line-to-ground faults in cables and on insulating buses must burn
through the second insulating material before a multi-phase fault can result. This can be several
cycles to 10's of cycles depending on the energy in the fault.

6
Personal Protective Equipment Defined
Personal protective equipment includes many items, such as gloves, tools, face protection,
glasses as well as the clothing to be worn. The main arc flash consequences are burns to the
body that could cause death. Therefore, the head and chest areas are more critical. While burns
on the person’s limbs are serious, they are not likely to cause death. For example, when working
on electrical equipment, gloves are voltage rated to protect from electrical shock while fire
retardant overalls have only a thermal rating. When gloves are worn, some thermal protection is
also provided.
Table 1 and 2 provide guidance to the thermal capabilities of some clothing articles. Table 2 is
from NFPA 70E. NFPA 70E-2004 has divided the personal protective clothing (PPE) requirements
into four (4) risk categories, Table 2. These hazard risk categories are listed below. Table 3 gives
the voltage capabilities of gloves up to 40-kV.
Table 1 – Typical Thermal Performance of Various Fabrics in Cal/ cm
2
Rating
Material Total Weight (Cal/cm 2)
Bare skin (clean) - 0.5
Bare skin (dirty) - 1.0
Untreated cotton 4.0 oz/yd
2
2.0
Single layer FR cotton 7.5 oz/yd
2
6.0
Single layer FR cotton 12.5 oz/yd2
13.8
PBI fiber blend 4.5 oz/yd2
6.1
Nomex III® 4.5 oz/yd2
9.1
Nomex III® 6.0 oz/yd2
13.7
Nomex III A® 4.5 oz/yd2
9.2
Nomex III A® 6.0 oz/yd2
13.1
Cotton (4 oz) under FR cotton (8 oz) 12.0 oz/yd2
12.5
Nomex (2 layers) 12.2 oz/yd2
22.6
Nomex (8oz) over FR cotton (8 oz) 16.0 oz/yd2
31.1
Switching suit of FR coverall 24-30 oz/yd2
40.0+
Table 2 - NFPA-70E Flash Hazard Risk Categories
Flash Hazard Risk
Category
Range of Calculated
Incident Energy
Min. PPE Rating Clothing Required
0 0-1.2 cal/cm
2
N/A 4.5-14.0 oz/yd
2
untreated cotton
1 1.2+ to 4 cal/cm2
4 cal/cm2
FR shirt and pants
2 4+ to 8 cal/cm2
8 cal/cm2
Cotton underclothing plus FR shirt and pants
3 8+ to 25 cal/cm
2
25 cal/cm
2
Cotton underclothing plus
FR shirt, pants, overalls or equivalent
4 25+ to 40 cal/cm2
40 cal/cm2
Cotton underclothing plus FR shirt, pants, plus double layer
switching coat and pants or equiv.
FR = Fire resistance fabric

7
Table 3 – Glove Classes
Glove Class Use Voltage
(kV)
Max. Test Voltage
(kV)
00 0.5 2.5
0 1.0 5.0
1 7.5 10
2 17.5 20
3 26.5 30
4 36.0 40

8
Arc Resistance Defined
Short-circuit arc resistance is a highly variable quantity that changes non-linearly with the arc
current during a cycle and on a cycle-by-cycle basis. As the current increases, so does the
ionized area, and, consequently, the resistance becomes lower. The voltage across the arc varies
non-linearly with the length and current flowing in it. Arcing short-circuit current magnitudes on
low-voltage systems (<1000 V) are more affected by arc resistance than they are on higher
voltage systems. Arc resistance results in the short-circuit currents smaller than in the bolted
short-circuit current.
On high voltage networks, the short-circuit arc resistance and resulting arc voltage are often low
compared to the circuit voltage; the arcing fault and bolted fault current can be approximately the
same. Arcing ground short-circuits have been known to have short-circuit currents that range
between zero and 100% of the bolted short-circuit current depending on the system voltage and
the type of arcing short circuit involved. [1] The environment in which the arcing short circuit takes
place affects the arc resistance and its continuity.
An arcing short circuit in a confined area is easily perpetuated due to the concentration of ionized
gases allowing easy current flow. An arc occurring on open conductors is elongated due to heat
convection, thereby lengthening the arc allowing cooling of ionized gas, so the arc may extinguish
itself.
The results of tests show that arcing short-circuit currents are very erratic in nature and do not
provide a constant resistance during any one cycle. Over several cycles the arc re-ignites, due to
un-cooled ionized gases, almost extinguishes, and then fully re-ignites again. There is not an exact
equation available to determine arc resistance. The bibliographies’ references by Alm, Brown and
Strom [2, 3, 4] provide approximations to the arc resistance.

9
Key Concepts
Open Arc
This term is used to describe a non-enclosed Arc in which the energy is radiated equally in all
directions. An arcing fault on an overhead line would be an example of an open arc topology.
Directed Arc
This term, also known as “arc in a box”, describes an Arc that occurs in a partially enclosed area
such as a MCC or a Switchgear cubicle. In this case the energy radiated includes the energy
reflected from the enclosure walls. A fault in a switchgear cubicle with the door open would be an
example of a directed arc.
Radiant Energy
This term refers to the energy as the light, which is released by an Arc during a fault.
Blast Energy
This term describes the energy released by an Arc, in the form of convection. When the Arc
occurs, the gaseous mass surrounding the area is violently displaced and heated. The energy
contained in this rapid moving mass, as it collides with surrounding objects, is called the Blast
Energy of the Arc.

10
References
1. Kaufmann, R. H. and J.C. Page, "Arcing Fault Protection for Low Voltage Power
Distribution Systems - The Nature of the Problem", AIEE Transaction, PAS vol 79, June
1960, pp 160-165. (Note: the value in Table 1 should be multiplied by 2 due to the
correction with CT probe ratio.)
2 Alm, Emil, " Physical Properties of Arcs in Circuit Breakers", Transactions of the Royal
Institute of Technology, Stockholm, Sweden, No. 25, 1949.
3. Brown, T. E., "Extinction of A-C Arcs in Turbulent Gases", AIEE Transaction Vol 51,
March 1932, pp 185-191.
4. Strom, A. P., "Long 60-Cycle Arcs in Air", AIEE Transaction, March 1946, Vol 65, pp
113-118, (See discussion PP 504-506 by J. H. Hagenguth).
5. Wagner C. F., and Fountain, L.L., "Arcing Fault Currents in Low-Voltage A-C Circuits."
AIEE Transactions. 1948, vol 67, pp 166-174.
6. R. Lee, “The Other Electrical Hazard: Electrical Arc Blast Burns.” IEEE Trans. Ind. Appl.
Vol. 18-1A, May/June 1982, pp 246-251.
7. R.A. Jones et al, “Staged Tests Increases Awareness of Arc-flash Hazards in Electrical
Equipment. Conf. Rec. IEEE PCIC Sept 1996, pp 298-281
8. J.R. Dunki-Jacobs, “The Impact of Arcing Ground Faults on Low-voltage Power System
Design”, GE publication GET-6098
9. Lawrence Fisher, “Resistance of Low-Voltage AC Arcs”, IEEE Trans. Ind. Appl. Vol. IGA-
6, Nov./Dec 1970, pp 607-616.
10. Richard Doughty et al, “Predicting Incident Energy to Better Manage the Electric Arc
Hazard on 600-V Power Distribution Systems.” IEEE Trans. Ind. Appl. Vol. 36-1, Jan/Feb
2000, pp 257-269.
11. O.R. Schurig, “Voltage Drop and Impedance at Short-Circuit in Low Voltage Circuits”,
AIEE trans, Vol 60, 1941, pp 479-486.
12. IEEE Std 1584-2002, “IEEE Guide for Performing Arc-Flash Hazard Calculations”
13. Standard for Electrical Safety in the Workplace, NFPA 70E, 2004

11
Program Verification & Validation
The AC Arcing Faults for the Arc Heat program were verified against the empirical equations in
IEEE-1584 and NFPA 70E. The results of the incident energy and flash boundaries calculated in
Arc Heat produce nearly identical results as the equations in the IEEE-1584 Standard.
Any differences were generally less than 1.0% and are likely due to rounding of the numbers
used and the results printed. All equipment configurations were checked from 480V to 34.5kV.
These configurations included the grounding options and switchgear options given in Step 2 of
the Arc Heat program.
If you would like a copy of the Verification & Validation calculations for this program, they are
available. Please contact us for details.

12
1.0 Arc Heat Tutorial Introduction
This tutorial, will illustrate how to conduct ARC HEAT EXPOSURE analyses on both AC & DC
distribution systems. The exercise will be presented in sections 1.1 through 1.5 as explained
below.
Section 1.1 Network-Based Arc Heat Exposure on AC Systems.
This application allows the user to evaluate the heat exposure caused by arcing faults, based on
an existing AC network file. Once a complete short-circuit analysis is performed on the subject
file, the relevant results are automatically passed on to the AC ARC HEAT program for analysis.
In addition to short circuit analysis data, the program is also capable of automatically reading the
tripping times of the protective devices assigned to any coordination study performed on the
network. The program offers two output options: single bus analysis and/or complete network
analysis (all busses). Both output reports can be directly exported into MS Excel. In terms of the
analytical standards that can be used, the user can choose between ANSI IEEE 1584, NFPA 70E
or both. Graphical outputs include Energy vs. Distance output, and printable warning labels. The
program also incorporates the ability to analyze arcing faults on busses that are fed from multiple
power supplies and/or sources of short circuit currents. In such cases, the arc-heat algorithm will
scan all the protective devices that control the current contributions into the fault. Once the scan
has been completed, the program selects the “Controlling” branch (slowest significant tripping
branch). Significant branches are those branches that contribute with a fault current equal or
greater than [IF/(n+1)]. In this case “IF” is the total bus bolted fault current and “n” is the total
number of branches feeding the fault. At that point, the branch arcing current is computed by
using the total bus arcing fault current “IF” and the ratio of contributing branch to the total bolted
fault current. The slowest tripping time significant branch with either 85 or 100% branch arcing
current (program checks both) is used in the arc heat program unless the tripping time is changed
by the user in Step 5 window. In other words, out of all the branches whose fault-current
contribution is equal or greater than [IF/(n+1)], the program chooses the slowest tripping branch
(longest time). This is by definition the “Controlling” branch. This is not necessarily the branch
with the greatest contribution into the fault. The slowest tripping time is, of course, dictated by the
protective device assigned to that branch. This multiple branch processing technique helps
ensure a conservative approach and complies with all the required standards. However, there
may be cases with several strong fault current sources where the power system engineer may
want to use a time of a branch that is not in the [IF/(n+1) list or the branch selected by the
program. The “Refresh Duration from PDC” will show the branch selected by the program.
Changing the time in Step 5 window can also be used to replace the time overcurrent trip time
with bus or transformer differential relay trip times.
This section is in turn subdivided into two exercises described as follows:
1.1.1 Network-Based Arc Heat Exposure on AC Systems / Single Branch Case
This exercise consists of an arcing fault that occurs on a bus fed from a single branch.
The purpose is to illustrate how to build the file, run the analysis and correlate the data
input to the calculation mechanism. The file used in this example is
“ARCHEAT_SB.axd”.
1.1.2 Network-Based Arc Heat Exposure on AC Systems / Multiple Branch Case
Once the mechanics of building a file has been understood from following the exercise
illustrated in 1.1.1, this next example will show a more complex network in which an
arcing fault is fed from 6 different sources of short circuit current, each equipped with its

13
own Protective Devices. The file that will be used in this example is “IEEEPDE.axd”.
This file has protective devices placed on BUS3, BUS4, and 28.
Section 1.2 Stand-Alone Arc Heat Exposure on AC systems.
In this option, a single line diagram/network file is not required. The AC ARC HEAT program will
rely on short circuit and tripping-time information being provided by the user. The job file used in
this exercise is “ACAHSTANDALONE.mas”.
Section 1.3 Network-Based Arc Heat Exposure on DC systems.
This application allows the user to evaluate the heat exposure caused by arcing faults, based on
an existing DC network file. Once a complete short-circuit analysis is performed on the subject
file, the relevant results are automatically passed on to the DC ARC HEAT program for analysis.
The program also offers two output options: single bus analysis and/or complete network analysis
(all busses). Both output reports can be exported directly into MS Excel. Graphical outputs
include Energy vs. Distance output, and printable warning labels. The job file used in this exercise
is “DC_sc2.axd”.
Section 1.4 Stand-Alone Arc Heat Exposure on DC systems.
Consistent with the explanation given above (Section 1.2) this option does not require a network
file. It relies on DC Short Circuit information being provided by the user. The job file used in this
exercise is “DCAHSTANDALONE.axd”.
Section 1.5 Verification and Validation Data
This section contains various documents used in the testing validation and verification of the ARC
Heat program.
_____________________________________________________________________________
As mentioned earlier, the program is capable of producing two types of reports; one based on the
IEEE 1584 standard and one based on the NFPA 70E standard. The results of both reports can
also be viewed simultaneously if so required. The reporting formats are Microsoft Excel based,
and can be generated in “Summary” or “Detailed” formats. The difference between the two
formats lies on the number of parameters that are included. The table shown in the next page
lists the parameters included in each report. The parameters marked with (1) are listed only in
the NFPA 70E reports or if the “Both” option is selected and those marked with (2) are listed only
in the IEEE 1584 or if the “Both” option is selected. The rest of the parameters are common to
both standards reports.

14
Bus Name
Protective Device Name
LL Voltage (kV)
3P Bolted Fault (Amp)
Protective Device Rating (Amp)
3P Arcing Current (kA) at 100%
Trip Delay Time (sec)
Breaker Opening Time (sec)
3P Fault Duration (sec)
Configuration
Gap (mm)
3P Arc Flash Boundary (inch) at 100%
NFPA 70E Arc Flash Boundary (inch) (1)
Working Distance (inch)
3P Energy (cal/cm^2) at 100%
Required IEEE 1584 PPE Class (2)
PPE Description
Required NFPA 70-E PPE Class (1)
PPE Description
Unit System
IEEE Calculation Factor (2)
IEEE 1584 Distance Factor (x) (2)
3P Arcing Current (kA) at 85% (2)
3P Fault Duration at 85% (sec) (2)
3P Energy (cal/cm^2) at 85% (2)
3P Arc Flash Boundary (inch) at 85% (2)
Restricted Shock Distance (inch)
“Summary Reports”.
“Detailed Reports”.

15
IMPORTANT NOTICE
In order for the program to produce a report on all of the nodes of the system, the user MUST
specify the ARC Heat Category under which every one of these busses has been classified.
These categories are:
- No Arc Heat (not classified by the user / no result will be produced by the program)
- Open – Grounded
- Open – Ungrounded
- Cable – Grounded
- Cable – Ungrounded
- Box – Grounded
- Box – Ungrounded
Categories can be assigned from either the job file editor as the file is being constructed
(recommended), or entered one by one from the program’s interface. The screen capture shown
below, illustrates how to classify a bus directly from the editor during the construction of the file.
ARC Heat Categories

16
1.0.1 Key Concepts
a. Open Arc
This term is used to describe a none-enclosed Arc, in which the energy is radiated equally in all
directions. An arcing fault on an overhead line would be an example of an open arc topology.
b. Directed Arc
This term, also known as “arc in a box”, describes an Arc that occurs in a partially enclosed area.
In this case the energy radiated includes that which is reflected from the enclosure walls. A fault
in a switchgear cubicle with the door open would an example of a directed arc.
c. Radiant Energy
This term refers to the energy in the form of light, which is released by an Arc during a fault.
d. Blast Energy
This term describes the energy released by an Arc, in the form of convection. When the Arc
occurs, the gaseous mass surrounding the area is violently displaced and heated. The energy
contained in this rapid moving mass, as it collides with surrounding objects, is called the Blast
Energy of the Arc.
1.0.2 Network-Based Arc Heat Exposure on AC Systems / Single Branch Case
This section of the tutorial is based on the network-file “ARCHEAT_SB.axd”. The topology of the
network is shown in Figure 2 below in conjunction with back-annotated ½ cycle short-circuit
results. The tripping times of the breaker protecting the motor are defined in a coordination study
that has been previously carried out on the network (Study 0: Motor PDC Study). The TCC graph
on the next page, shows the phase coordination settings of the realy, along with bus and branch
fault currents.
When using “All Buses” output in Step 6 window, the user does not have the option to change
items such as relay trip time on individual buses. If a bus does not have any protective devices,
IEEE 1584 default times will be used. In cases where a bus has multiple contributing branches
where not all major contributing branches have protective devices, the highest contributing
branch is used as the controlling branch. If there happens to be a protective device on that
controlling branch, the protective device trip time will be passed back to Step 5 window. The
program output should be checked to make sure the maximum tripping time agrees with the
device controlling device on the time-current curve.

17
Figure 3 - Network under study, showing a ½ cycle fault analysis at BUS-05
½ Cycle 3-P Symmetrical
Branch Fault Current:
9426.62 Amps.
½ Cycle 3-P Symmetrical
Bus Fault Current:
11200.53 Amps.

18
Figure 4 - PDC Study for Motor on BUS-05
Bus Fault Current
at BUS-05 (11,201 A)
Branch Fault Current
through BKR-02 (9,427 A)

19
Step 1.
Proceed to open the file
“ARCHEAT_SB.axd”.
Step 2.
Double click on each of the nodes/busses
and make sure that a proper arc heat
classification has been given to each one of
them. For example double click on Bus-02 to
verify the arc heat setting as shown here.
Step 3.
The arc-heat designation for each node of
this network is shown here. The designations
chosen are not to be considered typical; they
are only intended to serve as examples.

20
Step 4.
Proceed to enter/verify that all the protective devices (in this case
circuit breakers) have been properly characterized from the short
circuit point of view. In this exercise, emphasis will be made on
breaker BKR-02 since it is the one protecting the motor on BUS-05.
BUS-05 will be the objective of the arc heat analysis that will follow.
Also remember that the relay associated with this breaker is shown
in figure 2.
Step 5.
Double click on BKR-02 to
invoke its respective editor,
and select the Short Circuit
tab.
Step 6.
Complete all the required ANSI
settings, paying special attention to the
“Interrupting Time” in cycles. This
number is very important since it plays
a role in the total time in which an
arcing fault can be cleared. In this case
notice that this is a 5 cycle breaker.
Step 7.
Finally if there is an intentionally added
Trip Relay Delay (for example, aux.
Tripping Relays), enter it here in
cycles.
For this example enter “0”.
Step 8.
Next proceed to create a PDC study for the branch
under analysis. For this example, a PDC study has
already been created and it is shown in figure 2.

21
Step 9.
Select the “AC Arc Heat” command.
Step 10.
Carefully read and make sure that you
understand the program’s usage
guidelines before proceeding.
Step 11.
Select “Yes” to run and produce the most
recent short circuit answer file for the project.
Step 12.
Enter the required fault cycle to be analyzed.
For this example, type “0.5” cycle and press
“Next” to continue. The user may want to
select 0.5 cycle for devices that clear in the
first cycle and a longer time for time delayed
trips.
Step 14.
Select the units to be used in the
analysis. Selected “US”.
Step 13.
From the pick-list, select an individual
Bus to be analyzed. For this example,
select “Bus-05”.

22
Step 15.
Verify the values for the Bus
Fault Current and Controlling
Branch Current.

23
Step 16.
Select the “1584 Table” button
to review the IEEE 1584
control parameter settings.
Step 17.
Select “Back” to
return.
Step 18.
Select “View Library” to view and/or edit
the NFPA 70E Fabric Material Library.
Step 19.
The user can double click on any
of the entries to edit as needed.
Select “OK” to return.
Step 20.
Select “Next” to
continue.

24
Step 21.
Select/verify that the Arc Heat Equipment
Category for the bus under study has
been properly assigned. In this case the
program has automatically assigned the
category that was entered into the model by
the user as it was being built.
Step 22.
Select/verify that the ARC Heat
Grounding Category for the bus under
study has been properly assigned. In this
case the program has automatically
assigned the category that was entered into
the model by the user as it was being built.
Step 23.
Enter the working distance over which the Arc
Heat yield is to be calculated. The user can
enter actual known values or use the IEEE 1584
defaults if deemed safe for the application.
Step 24.
Select the “Calculation” option. In this
example we will ask the program to
calculate the minimal protective
clothing required for the application.
Select “Calculate Clothing Required”.
Step 25.
Select “Next” to continue.

25
Controlling Branch
100% Arcing Current.
Controlling Branch
85% Arcing Current.
1.89 sec.
Relay Tripping Time
1.89 sec.
0.08 sec.
5 cycles
Breaker Opening Time
5 cycles = 0.08 sec.
Step 26.
Enter/Verify the “Phase Gap” and “Cf” factor as
required, and then press “Refresh Duration from
PDC”. All the pertinent tripping times that correspond to
the arcing currents and controlling branch, are calculated
and entered into the respective fields. The user in the
single bus mode can change the trip time to represent
differential relay trip time.
Step 27.

26
1.89 sec.
Relay Tripping Time
1.89 sec.
0.08 sec.
5 cycles
Breaker Opening Time
5 cycles = 0.08 sec.

27
Step 28.
The clothing required for the application
is shown here as “Category 3”.
Step 29.
The Warning Label Options are shown
here.
Step 31.
Select “Graphic Label” to generate
the equipment warning label.
Step 30.
Select the Calculation standard and the
select “Plot” to generate the respective
Energy vs. Distance plot of the results.

28
Step 32.
From the “Calculation Standards”
section, switch over to NFPA 70E.
Step 34.
The recalculated rating for the NFPA
70E selection instead of IEEE 1584 is
shown here. In this case NFPA 70E
shows a more conservative (Category 4)
rating.
Step 33.
Press the “Calculate” button to
refresh the analysis results.

29
Step 35.
To produce a text-based output report, proceed as follows:
- Select Single or All Busses to be reported.
- Select a Summary or Detailed report.
- Select the Calculation Standard to be used.
- Select “Results to Microsoft Excel”
This will create a report and save it into a Microsoft Excel
Spreadsheet. Use the settings shown here for this
example.
Step 36.
Specify the name and a folder in
which to save the report. Press
“Save”.
Step 37.
The complete report is shown here.
Arc Heat Analysis results
Key Definitions page.

30
The following table shows the results of the analysis using both IEEE 5184 and NFPA 70E
Standards.
Bus Name BUS-05
Protective Device Name Motor Relay
LL Voltage (kV) 2.4
3P Bolted Fault (Amp) 11200.5
Protective Device Rating (Amp) 800
3P Arcing Current (kA) at 100% 10.85
Trip Delay Time (sec) 1.89
Breaker Opening Time (sec) 0.08
3P Fault Duration (sec) 1.97
Configuration Box - Grounded
Gap (mm) 102
3P Arc Flash Boundary (inch) at 100% 796.3
NFPA 70E Arc Flash Boundary (inch)
Boundary equation not valid for voltage > 600V; IEEE
1584 3 Phase boundary = 796.3
Working Distance (inch) 35.8
3P Energy (cal/cm^2) at 100% 24.4
Required IEEE 1584 PPE Class 3
PPE Description
Cotton underclothing plus FR shirt, pants, overalls or
equivalent
Required NFPA 70-E PPE Class 4
PPE Description
Cotton underclothing plus FR shirt, pants, plus double
layer switching coat and pants or equiv.
Unit System US
IEEE Calculation Factor 1
IEEE 1584 Distance Factor (x) 0.973
3P Fault Duration at 85% (sec) 1.97
Restricted Shock Distance (inch) 26

31
1.0.3 Network-Based Arc Heat Exposure on AC Systems / Multiple Branch Case
This section of the tutorial is based on the network-file “IEEEPDE.axd”. The complete topology of
the network is shown in Figure 4 below. The Arc Heat analysis described in this section is based
on Bus4 of this network. Figure 5, shows a simplified view of Bus4 along with the 6 fault-current
contributing branches.
The tripping times of the protective devices involved in the 6 branches are derived from a
coordination study that has been previously carried out on the network (Study 0: BUS 4). The
TCC graph shown in Figure 6, shows the phase coordination settings of all the protective devices.
Figure 5 - Network topology for job-file “IEEEPDE.axd” showing ½ cycle fault results for
Bus4

32
Figure 6 - Simplified view of Bus4 and its fault contributing branches (1/2 cycle Sym.
Currents)
ML 269
0.50kA
Bus 11 Bus 8Bus 10
Bus 4
200/5
IAC53
CO-8
0.81kA
5.45kA
8.71kA
Bus 3
0.45kA
200/5 400/5
1000/5
ML 750
1200/5
IAC53
Bus 12
600/5
BE1-50/51B
*
24.2kA
8.39A
Bus 2
5447.3 A
445.4 A 501.6 A 809.6 A 8393.0 A
8705.3 A
24225.1 A
Util-Transformer2
As will be shown in the Arc Heat Analysis
calculation that follows, this will turn out to
be the “Controlling” branch for an arcing
fault at Bus4.

33
Figure 7 - PDC Study for Bus4 including all 6 converging branches. Currents are plotted at
13.8 kV.

34
Step 1.
Proceed to create your file and prepare it as explained in section
1.1.1, steps 1 to 8. In this example, we will be using the file called
“IEEEPDE.axd”, which has already been prepared for the study.
Proceed to open the file “IEEEPDE.axd”.

35
Step 2.
Select the “AC Arc Heat” command.
Step 3.
understand the program’s usage
Step 4.
Step 5.
Enter the required fault cycle to be analyzed. For this
example, type “0.5” cycle and press “Next” to continue.
The user may want to select 0.5 cycle for devices that clear
in the first cycle and a longer time for time-delayed trips.
Step 7.
Select the units to be used in the
analysis. Selected “US”.
Step 6.
select “Bus4”.
This is the current in the controlling
branch. Refer to figure 4.

36
There are a total of 6 branches contributing fault current at Bus4. The Arc Heat program interface, only
considers branches contributing at least 14.3% {[1/(6+1)] * 100%} of the total “Bus4” fault current to
establish which branch is the Arc Heat “controlling branch”. It was determined that the greatest
contribution into the fault originates from the Tie breaker branch (contribution from Bus3). However,
since the relay labeled “Trans f2” (contribution from Bus 2 through the Util-Transformer2) takes longer
to open, it is the “Trans f2” branch that is used as the Arc Heat “controlling branch”.
Highest contribution > 17%.
Contribution > 17% and slowest responding protective device.
Therefore this is used as the “Controlling” branch.

37
Step 8.
Step 9.
return.
Step 10.
Select “View Library” to view and/or edit
the NFPA 70E Fabric Material Library.
Step 11.
Step 12.
continue.

38
Step 13.
Category for the bus under study has
been properly assigned. In this case the
program has automatically assigned the
category that was entered into the model by
the user as it was being built.
Step 14.
Select/verify that the ARC Heat
Grounding Category for the bus under
study has been properly assigned. In this
case the program has automatically
assigned the category that was entered into
the model by the user as it was being built.
Step 15.
defaults if deemed safe for the application. In
this case a distance of 35.8 inches has been
entered purely from an academic exercise point
of view.
Step 16.
Step 17.

39
Step 18.
Enter/Verify the “Phase Gap” and “Cf” factor as
required, and then press “Refresh Duration from
PDC”. All the pertinent tripping times that corresponds to
the arcing currents and controlling branch, are calculated
and entered into the respective fields. The user in the
single bus mode can change the trip time to represent
differential relay trip time.
Step 19.
Fault data information and critical tripping times.
Calculated controlling branch
and tripping times.
Arcing currents calculated by the program.

40
PDC ArcHeat Methodology Summary
This summary provides a high-level overview of the methodology used by PDC ArcHeat.
Determining the Controlling Branch
1) The bolted fault currents for each adjacent branch to the bus are analyzed to determine
a minimum contributor threshold percentage. Since the program cannot visually see the one-
line and its protective devices, the following Major Contributor rule is used. The logic holds most
of time in selecting the correct branch, but it is realized that there may be some conditions where
the program may not select the correct controlling branch. The method used assumed that once
the controlling branch opens the arc-flash energy that exists after is small compared to the initial
and can be neglected. The program also assumes that the system is properly coordinated.
This percentage is calculated using the formula below:
Major Contributing Threshold Percent = 1 / ((# of connections to bus contributing at least 2% of
BoltedFaultCurrent) + 1)
The branches meeting the above criteria are further checked as indicated in step 3
below.
2) Arcing current is calculated from the bolted fault current using the criteria given in
IEEE 1584-2002, section 5.2.
3) PDC ArcHeat checks along each path connected to the bus that contributes at least
Major Contributing Threshold Percent calculated in Step 1.
The arcing current in each branch is calculated based on the ratio of bolted fault current in branch
to total bolted fault current times the arcing current calculated in step 2.
Branch arcing current = (Bus arcing current)* (branch bolted fault current)
(total bolted fault current)
From the TCC made by PDC, for each of the major contributing branches the arcing current is
used to determine the fault clearing time. The device with the shortest clearing time on each path
is recorded, then (using the shortest clearing times of each path) the path with the longest
clearing time is used in the archeat calculation.
It is realized that the opening of the other major contributing branches before the controlling
branch would reduce the arcing current, but holding the initial arcing constant for a longer time
helps provide conservative cal/cm2
.
Deleted: document

41
4) The path with the (slowest is okay) tripping time is used as the controlling branch and
the cal/cm2
is from total arcing and the its device trip time
Exceptions to this rule are as follows:
• If a path is encountered that either has no protective device, or has multiple source
branch connections, the path with the maximum contribution to the bus is used as the
controlling branch, and ArcHeat reports this condition.
• If the Arcing current exceeds the protective device short circuit value along a particular
path, that path is used as the controlling branch, and ArcHeat reports this condition.
Note: If multiple adjacent branches that are greater than Major Contributing Threshold Percent
are present, the ArcHeat interface allows you to manually choose a different branch path as the
controlling branch.

42
Known Limitations
There is currently a limitation in that PDC ArcHeat cannot search beyond upstream buses
connected to 2 or more source branches. Source branches are defined as branches sharing the
same downstream "To-Node" bus. The message "Multiple Sources Present" will indicate this
condition. Another limitation is that PDC ArcHeat cannot search beyond downstream buses
connected to 2 or more child branches. These limitations are illustrated in Figure 1 below.
Figure 8
Let’s assume the ArcHeat is being calculated for Bus “A” and that all the adjacent branches for
Bus “A” are contributing at least “MajorContrubutingThresholdPercent” at Bus “A”. PDC ArcHeat
would travel each of the paths in the direction of the arrows, looking for protective devices.
Traveling upstream along path “AB”, PDC ArcHeat would stop at Bus “B”. Likewise, traveling
downstream along path “AD”, PDC ArcHeat stops at Bus “D”. In the example above, it is
expected that the arcing current contributions from C and D are small, less than 25% [from
equation 1, 1/(3 + 1)] and would take a long time to open their protective devices. It is expected
in the above example, that breaker on the secondary of the transformer would be the controlling
device. It the breaker does not exist, the program should select the fuse on the primary.

43
*Enabling PDC ArcHeat Activity Trace
Detailed PDC ArcHeat navigation of the one-line along with calculated values can be viewed by
enabling the PDC ArcHeat Activity Trace. The Activity Trace is typically used for troubleshooting
as well as V&V purposes, and can be enabled by opening C:EDSA2005ConfigPDCOORD.INI
using NOTEPAD (or other text editor) and changing the value “Enabled” to “1” under the section
“[DebugMode]”. Each bus analyzed by PDC ArcHeat will generate a trace log that pops up in a
notepad window so it is important to only turn on the Activity Trace when analyzing one bus at a
time.
ArcHeat Trace Sample
******************** ArcHeat PDC session at bus
'Bus4'for 85% Arcing Current
Using bolted fault current 24225 at 85% = 20591 A
Arcing ratio is 0.959
Only adjacent branches contributing at least 14% (or 2942
amps) will be tested.
** Heading upstream along branch defined as '0040' to 'Bus4'
** Fault contribution for this branch is 4630 amps
** Arcing fault current to test PDC devices is 4439 amps
@@ Found PDC device branch record of type: Relay
@@ Using FaultVoltage=13800,
ArcingFaultCurrent=4439.0
@@ Device Relay labeled 'Trans f2' trips at 3.270s max
@@ Applying breaker opening time of 5 cycles.
@@ Dev Trip Time: 3.354
@@ Dev Opening Time: 0.083
@@ Found PDC device node record of type: Load
## Next upstream branch is 'BUS2' to '0040'
## Next upstream branch is '5' to 'BUS2'
@@ Device Relay labeled 'CB2_UTILITY' trips at 5.664s
max
## Next upstream branch is 'UTILITY' to '5'
## Stopped traveling this path
** Heading upstream along branch defined as 'Bus3' to 'Bus4'
** Can't test this location because fault current is 0.
## Number of upstream connections at bus 'Bus3' is 2
** Heading downstream along branch defined as 'Bus4' to
'11'
'12'
@@ Device Relay labeled 'Bus 12' trips at 0.010s max
## Next downstream branch is '12' to 'BUS24'
## Number of connections at bus 'BUS24' is 5
** Heading downstream along branch defined as 'Bus4' to '8'
** Heading downstream along branch defined as 'Bus4' to '9'
'Bus3'
@@ Device Relay labeled 'Tie' trips at 1.341s max
## Number of connections at bus 'Bus3' is 6
&&& Max contributing branch is 'Bus4' to 'Bus3' with
branch current 7400 Amps
&&& Controlling branch set to Slowest device branch is
'0040' to 'Bus4' with branch current 4630 Amps and Arcing
current 888 Amps

44
The following diagram places in perspective the figures obtained in the previous screen.
2.77 sec.
3.35 sec.
100% of Controlling Branch Arcing Current.
5208 Amp.
85% of Controlling Branch Arcing Current.
4427 Amp.
0.08 sec.
0.08 sec.
100% Bus Arcing Fault
Current: 23161 Amp.
Breaker opening time: 0.08 sec.

45
Step 20.
This application exceeds the NFPA maximum hazard
risk category of 4 and therefore is listed as N/A.
Step 21.
here.
Step 22.
Step 23.

46
Step 24.
From the “Calculation Standards”
section, switch over to NFPA 70E.
Step 26.
The recalculated rating for the NFPA
70E selection instead of the IEEE 1584
is shown here. In this case NFPA 70E
shows a less conservative (Category 4)
rating. NFPA values are based on
typical substation with faster fault
clearing times than that given in the Step
5 window for this example.
Step 25.
Press the “Calculate” button to
refresh the analysis results.

47
Standards.
Bus Name Bus4
Protective Device Name Trans f2
LL Voltage (kV) 13.8
3P Bolted Fault (Amp) 24225.1
Configuration Box - Grounded
Gap (mm) 153
NFPA 70E Arc Flash Boundary (inch)
Boundary equation not valid for voltage > 600V;
IEEE 1584 3 Phase boundary = 3086.5
Required IEEE 1584 PPE Class N/A
PPE Description Level exceeds NFPA-70-E - Never work on or near energized system.
PPE Description
Cotton underclothing plus FR shirt, pants,
plus double layer switching coat and pants or equiv.
Unit System US
IEEE Calculation Factor 1

48
Special Features in Arc Heat
The new Arc Heat program:
Calculates categories for each bus
Assigns size for labels
Assigns color for “Safe Zone”
Calculates and shows Safe Zone area
Outputs to Excel for all the selected buses
Prints labels for one or all the selected buses
Enables user to assign Work Permit
First, load your job file, then run EDSA AC Arc Heat.

49
The Arc Heat program is linked to the Short Circuit program. You may choose to run the Short
Circuit program or not.

50
From “Bus Name” you can select
the busses that you desire to
perform Arc Heat Estimation.

51
For every bus you select, complete Step 2 – “Environment” and Step 3 – “Distance”, as shown
above.

52
Use “Refresh Duration from PDC” and make sure that before running Arc Heat Estimation you
have already performed Protective Device Coordination (PDC) for each bus; the opening time of
device is related to the amount of Arc Heat Exposure and energy available at the bus.

53
Select “Calculate” for
clothing category.
Based on the category you define, it will
give you the “Safe Zone”.
Make sure you set:
Output report at “All Buses” and “Detailed”.

55
When you plot, you have a list of the bus(es) you performed Arc Heat Estimation. You can select
any bus listed and the plot will display.
For each label, go back and repeat the steps for each bus.
When you click graphic
label, you can select, one
or more, or all buses to
print for labels.
When finished,
select Display
Labels…the labels
will display.

56
This icon allows you to choose
the “Label Style Options”. See
the following screen capture.
This icon allows you to “Print
the Current Label”.
This icon allows you to “Print
All the Labels”.
Once you are done you can
“Close the Current Label”.
Use the drop down menu to
choose which label to display
or use the “Show Previous” or
“Next Label” arrows.
The label appears. You can then choose the options above.
When you select “Label Style Options”, the following screen will display:

57
Go back and click “Safe Zone”. Then below click “Display Safe Zones”.
Select “Pass Color” to choose your color. Proceed to enter the PPE category. Click “Done” or
select “Display Safe Zones”.

58
The “Safe Zone” is color-coded above.
You can Press Plot and view plot for each Bus Arc Heat Exposure

59
You can also see which areas have had labels generated. The buses (above) are highlighted to
show that Labels are generated.
Select the highlighted buses, then click to display the labels for buses you select.

60
The label is displayed.

61
Also users now have the option to assign a work permit. See the following screen captures.
Click on “Work Permit” and then
proceed to select the task as shown
in the following screen captures.

62
User can select “Add” to
create a new task.
Use can give the added
task a unique name.
Once the user clicks
“OK”, the new task has
been added. Click “OK”
once the task is selected
and the Work Permit will
display as shown on the
next page.
The user may also
choose a task using the
drop-down menu. Once
the user has made a
selection, click “OK”. The
Work Permit is shown on
the next page.

63
The work permit appears as a word document, which the user can edit.
Once the user has entered the necessary information on the document, it can be printed and
saved. A complete sample of the work permit is shown on the next page.

64
ENERGIZED ELECTRICAL WORK PERMIT
Job/Work Order Number:
PART 1: TO BE COMPLETED BY THE REQUESTER
(1) Description of circuit / equipment / job location / bus name:
1A
(2) Description of work to be done:
Remove/install CBs or fused
switches
(3) Reasons why the circuit / equipment cannot be de-energized or the work deferred until the next scheduled outage:
_________________________________________________ ______________________________________
Requester / Title Date
PART II: TO BE COMPLETED BY THE ELECTRICALLY QUALIFIED PERSONS DOING THE WORK:
Check
When
Complete
(1) Detailed job description procedure to be used in performing the above detailed work: ____
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
(2) Description of the Safe Work Practices to be employed: ____
___________________________________________________________________________________________________________
___________________________________________________________________________________________________________
Flash Boundary 11.8 in Flash Hazard 0.5 cal/cm^2 Working Distance 17.9 in
Shock Hazard 4.8 kV Restricted Approach 26.0 in Glove Class 1
Required PPE 0 4.5 - 14.0 oz/yd^2 untreated cotton
(3) Means employed to restrict the access of unqualified persons from the work area: ____
___________________________________________________________________________________________________________
(4) Evidence of completion of a Job Briefing including discussion of any job-related hazards: ____
___________________________________________________________________________________________________________
(5) Do you agree the above described work can be done safely? Yes No (if no, return to requestor)
_________________________________________________ ______________________________________
Electrically Qualified Person(s) Date
_________________________________________________ ______________________________________
Electrically Qualified Person(s) Date
PART III: APPROVAL(S) TO PERFROM THE WORK WHILE ELECTRICALLY ENERGIZED
_________________________________________________ ______________________________________
Maintenance / Engineering Manager Manufacturing Manager
_________________________________________________ ______________________________________
Safety Manager Electrically Knowledgeable Person
_________________________________________________ ______________________________________
General Manager Date

65
1.1 Stand-Alone Arc Heat Exposure on AC Systems
Step 1.
Start the EDSA program, and without
opening any job files, select the “AC
Arc Heat” command.
Step 2.
Create a new standalone file,
by selecting “File/New”.
Step 3.
Assign a name to the new file.
And press “Save”.

66
Step 4.
understand the program’s usage guidelines
before proceeding. Select “Next”.
Step 6.
Select the units to be used
in the analysis. Selected
“US”.
Step 5.
Type a name for the bus to
be studied.
Step 7.
Select “User Defined
Voltage”.
Step 8.
Enter the bus voltage
(480 V) and press “OK”.
Step 9.
Select “User Defined Short Circuit”
Step 10.
Enter the 3P Bus and Branch
fault currents & press “OK”.
Step 11.

67
Step 12.
Step 13.
return.
Step 14.
Select “View Library” to view and edit the NFPA
70E Fabric Material Library.
Step 15.
Step 16.
continue.

68
Step 18.
Select the proper ARC Heat Grounding
Category for the bus under study. For this
example, select “Ungrounded.
Step 19.
Step 20.
Step 21.
Step 17.
Select the proper Arc Heat Equipment
category for the bus under study. For this
example, select “Switchgear Box”.

69
Step 22.
Manually enter the tripping times for the protective
devices that correspond to 85% and 100% of the
arcing current. Also enter the “Breaker Opening Time”
in seconds. For this example, use the numbers shown
here. Also specify the “Phase Gap in mm” and the
“IEEE 1584 Calc. Factor”. Press “Next” to continue.

70
Step 23.
Step 24.
here.
Step 25.
Step 26.

71
Step 27.
- Select a Detailed report.
- Select the Calculation Standard to be used (BOTH).
Spreadsheet.
Step 28.
“Save”.
Step 29.

72
Standards.
Bus Name Bus1
Protective Device Name
3P Bolted Fault (Amp) 50000
Configuration Box - Swgr - Ungrounded
Gap (mm) 32
NFPA 70E Arc Flash Boundary (inch) 79.7
Working Distance (inch) 24
PPE Description
Cotton underclothing plus FR shirt, pants, plus double layer
switching coat and pants or equiv.
PPE Description
Cotton underclothing plus FR shirt, pants, overalls or
equivalent
Unit System US
IEEE Calculation Factor 1.5

73
1.2 Network-Based Arc Heat Exposure on DC systems
Step 1.
Proceed to open the file “C:EDSA2004SamplesDCSCDc_sc2.axd”.
Step 2.
Double click on each of the nodes/busses and make
sure that a proper Arc Heat classification has been
given to each one of them. For example double click on
BATT-1A to verify the arc heat setting as shown here.
Step 3.
The Arc Heat designation for each bus is shown right
next to it. The designations chosen are not to be
considered typical; they are only intended to serve as
examples.

74
Step 4.
Select the “DC Arc Heat” command.
Step 5.
Carefully read and make sure that
you understand the program’s usage
Step 6.
Step 7.
Step 8.
Select “US units for the study.
Step 9.
select BATT-1A.
Step 10.
Press “Next” to continue.

75
Step 11.
Category for the bus under study has been
properly assigned. In this case the program
has automatically assigned the category
entered into the model as it was being built.
Refer to steps 1, 2 & 3 of this section.
Step 12.
Step 13.
Step 14.

76
Step 15.
Enter the tripping time that
corresponds to the protective device
present in the network.
Step 16.
Enter/verify the “Phase Gap” and
the “Cf” factor. Select “Next” to
continue.

77
`
Step 17.
Step 18.
here.
Step 20.
Step 19.
Select “Plot” to generate the Energy
vs. Distance plot of the results.

78
Step 21.
- Select “All Busses” to be reported.
- Select “Detailed” report.
Spreadsheet.
Step 22.
“Save”.
Step 23.

79
Standards, for Bus BATT-1A.
Bus Name BATT-1A
DC Bolted Fault (Amp) 47734.8
DC Arcing Current (kA) at 100% 11.765
DC Fault Duration (sec) 0.2
Configuration Open
Gap (mm) 32
DC Arc Flash Boundary (inch) at 100% 30.2
Energy (cal/cm^2) at 100% 3.4
PPE Description FR shirt and pants
Unit System US
IEEE 1584 Distance Factor (x) 2
DC Arcing Current (kA) at 85% 10
DC Fault Duration at 85% (sec) 0.2
DC Energy (cal/cm^2) at 85% 2.8

80
1.3 Stand-Alone Arc Heat Exposure on DC systems
Step 2.
Create a new standalone file,
by selecting “File/New”.
Step 3.
Assign a name to the new file.
And press “Save”.
Step 1.
Start the EDSA program, and without
opening any job files, select the “DC
Arc Heat” command.

81
Step 4.
understand the program’s usage guidelines
before proceeding. Select “Next”.
Step 6.
Select “US units for
the study.
Step 5.
Type a name and a description
for the bus to be studied.
Step 7.
Select “User Defined Voltage” and
enter the voltage for the analysis
(250 VDC). Select “OK”.

82
Step 9.
Select the Arc Heat Equipment Category for
the bus under study.
Step 10.
Step 11.
Step 12.

83
Step 13.
Enter the tripping time that
corresponds to the protective device
present in the network.
Step 14.
Enter/verify the “Phase Gap” and
the “Cf” factor. Select “Next” to
continue.

84
`
Step 15.
Step 16.
here.
Step 18.
Step 17.
Select “Plot” to generate the Energy
vs. Distance plot of the results.

85
Step 19.
- Select “Detailed” report.
Spreadsheet.
Step 20.
“Save”.
Step 21.

86
Standards, for Bus BATT-1A.
Bus Name BATT-1A
DC Bolted Fault (Amp) 47734.8
DC Arcing Current (kA) at 100% 11.765
DC Fault Duration (sec) 0.2
Configuration Open
Gap (mm) 32
Energy (cal/cm^2) at 100% 3.4
PPE Description FR shirt and pants
Unit System US
IEEE 1584 Distance Factor (x) 2
DC Arcing Current (kA) at 85% 10
DC Fault Duration at 85% (sec) 0.2
DC Energy (cal/cm^2) at 85% 2.8

87
1.4 Verification and Validation Data
1.4.1 V&V of AC Arc Heat Programs with Longhand using IEEE1584 Standard in Stand
Alone Mode / Prepared by Dr. Lifeng Liu, PhD 12/2/2004
Project name: ACAHStandAlone.mas
Longhand calculation in IEEE1584 Standard
Refer to AH-standalone(3).doc prepared by Conrad.
Program Version results
Table for Variance of Program Results and IEEE1548 longhand
Items EDSA Results IEEE1584 Calc. % Difference
Bus Name Bus1 Bus1
LL Voltage (kV) 0.48 0.48
3P Bolted Fault (Amp) 50000 50000
Trip Delay Time (sec) 0.35 0.35
Breaker Opening Time (sec) 0.05 0.05
Configuration Box - Swgr - Ungrounded
Gap (mm) 32 32
Working Distance (inch) 24 24
Input
Data
IEEE Calculation Factor 1.5 1.5
3P Fault Duration (sec) 0.4 0.4 0.00
3P Arcing Current (kA) at 100% 24.063 24.06 0.01
3P Arc Flash Boundary (inch) at
100% 205.5 204.88 0.30
3P Energy (cal/cm^2) at 100% 28.2 28.22 0.07
Output
Data
Required IEEE 1584 PPE Class 4 4 0.00
Program Arc Heat Exposure Max. % Diff. 0.30
Conclusion:
The maximum difference between the program results and IEEE1584 longhand
is 0.3%.

88
In previous V&V the AH program was verified against the IEEE 1584 spreadsheet. To make sure
the program is using the correct arcing current and times. The table below shows that the
program is using the correct current and time (total bus current and longest time)
Voltage = 0.48
Working distance = 24 inch
Ungrounded
Gap = 32 mm
EDSA IEEE Spreadsheet
Bolted Fault 50000 50000
Arc Current 24063 24060
Clearing time 0.4 0.4
Cal/cm^2 28.2 28.22
Risk Class 4 4
Boundary distance 205.5 204.88

89
1.4.2 V&V of Stand Alone Results for DC Arc Heat Programs Comparing with Network
Mode Prepared by Dr. Lifeng Liu, PhD 12/2/2004
Project name: DCAHStandAlone.mas
The Network results
Project name : DC_sc2.AXD
Results Table: DCARCHEAT50.CSV
The network results have been verified.
Please see V-V_DCNetwork.doc.
Stand Alone results
See DCAHStandAlone.csv
The results are got by using the input data of DC_sc2.mas in network mode.
V&V table
Table for Variance of the Results between Stand Alone and network mode
Items Stand Alone Network Mode % Difference
Bus Name BATT-1A BATT-1A
LL Voltage (kV) 0.25 0.25
DC Bolted Fault (Amp) 47734.8 47734.8
DC Fault Duration (sec) 0.2 0.2
Configuration Open Open
Working Distance (inch) 17.9 17.9
Gap (mm) 32 32
Input
Data
DC Fault Duration (sec) 0.4 0.4
DC Arcing Current (kA) at 100% 11.765 11.765 0.00
DC Arc Flash Boundary (inch) at 100% 30.2 30.2 0.00
Energy (cal/cm^2) at 100% 3.4 3.4 0.00
Output
Data
Required IEEE 1584 PPE Class 1 1 0.00
Program Arc Heat Exposure Max. % Diff. 0.00
Conclusion:
Program in Stand Alone mode produces the same results as those in Network mode.

90
1.4.3 V&V of ARC HEAT with PDC Interface by Conrad St. Pierre
The one line used for the V&V was IEEEPDE.axd. A portion of the diagram is shown in Figure 7
below. Using the relays and their settings the bolted fault operating times for each device shown
in Table 3. These values were taken from Figure 8 and based on the currents in the relay for the
Bus 4 fault. Protective devices were also placed on the 69-kV primary of the transformer, 13.8-kV
Bus 3, and 480V Bus 28.
Figure 9 - Portion of IEEEPDE.axd One-line with Bus 4 Fault Flows
Condition 1 – Controlling Branch: Transf. Source.
Relay Loc. Type Pickup
Amp
Time
Dial
Inst Fault
Amp
Operating
Time
Breaker
Time
Bolted fault
Total Time
To Transf IAC53 960 10 - 5450 2.45 0.083 2.56
To Bus 3 IAC53 800 8 - 8710 1.2 0.083 1.18
To Bus 10 ML 750 200 7 1600 450 7.2 0.083 9.4
To Bus 11 CO-8 320 4 2400 810 5.40 0.083 5.04
To Bus 8 ML 269 159 2 1600 500 15.5 0.083 17.72
To Bus 12 BE1-50/51B 720 5 3600 8390 0.0 0.083 0.08
Table 4 - Fault Currents and Protective Device Operating Times
ML 269
0.50kA
Bus 11 Bus 8Bus 10
Bus 4
200/5
IAC53
CO-8
0.81kA
5.45kA
8.71kA
Bus 3
0.45kA
200/5 400/5
1000/5
ML 750
1200/5
IAC53
Bus 12
600/5
BE1-50/51B
*
24.2kA
8.39A
Bus 2

91
Figure 10 - Time Current Curve showing Protective Device operating times
13800 Volt Phase and Ground Time-Current Characteristic Curves
BUS 4
12/10/2004
07:26:09
C:EDSA2004SAMPLESARCHEATIEEEPDE.PDC
.01.11101001000TimeinSeconds
.5 1 10 100 1000 10000
Current in Amperes X 10
CB2_UTILITY
GE SR750/760 N.INV.
10.000 TD 0.800 Tap
300/5CT
8.0 InstTap
Trans f2
GE IAC-53
10.000 TD 4.000 Tap
1200/5CT
Bus 10
GE SR750/760 N.INV.
7.000 TD 1.000 Tap
200/5CT
8.0 InstTap
Bus 8 Motor
GE EJO-1 9F62 DD 150E
Bus 8 Motor
GE 269/269+ S.OL
1.000 TD 1.000 Tap
200/5CT
8.0 InstTap
Bus 11
west_ch CO-8
4.000 TD 4.000 Tap
400/5CT
30.0 InstTap
Bus 12
BASLER BE1-50/51B V
5.000 TD 6.000 Tap
600/5CT
30.0 InstTap
Tie
GE IAC-53
8.000 TD 4.000 Tap
1000/5CT

92
Using data transferred between the short-circuit program, PDC, and arc heat program, the EDSA
package has to determine which major contributing branch current will result in the greatest arc
heat energy. Using a major branch with the longest relay time approximates this. In a real
system some of other contributing branches may have their protective relay operate first and
therefore reducing the fault current and energy. The program is based on having all of these
contributing branches opening at the same time as the controlling branch.
Noting the total number of contribution branches to a bus and taking the longest protective device
operating time of branches determines the controlling branch. The branches that are carrying
more than 100/(branches +1) percent of the total fault current are checked. Branches with less
than this current are likely to be back feed current from motor feeders.
In Figure 7 the major controlling branches are likely to be the incoming transformer, the tie to Bus
3, and the connection to Bus 12. Bus 12 does go to a generator that is several nodes away with
low impedance branches.
Using the equation for the controlling branch currents 100/(6+1)= 14% of Bolted Fault, the
branches with more than 0.14*24,225 = 3392A are in the possible list of controlling branches.
Table 4 has higher major contributing buses noted. After calculating the corresponding arcing
current in each branch, the longest operating time protective device is determined from Figure 8.
The results are shown in Table 4. The branch with the transformer has the longest operating
time.
The arcing current for a 13.8-kV fault in grounded switchgear with 35.8 inch working distance and
153 mm arc gap is the same for both the EDSA arc heat program and the IEEE-1584
spreadsheet reference.
Relay Loc Bolted Fault IEEE 1584
100% Arc fault
Controlling
Branches
100% Fault
time (sec)
IEEE 1584
85% Arc fault
85% Fault
time(sec)
Total 24,225 23,161# 19,689#
To Transf 5450 5211(5208)* X 2.67 $ 4429(4427)* 3.33 $
To Bus 3 8710 8328 X 1.21 $ 7079 1.31 $
To Bus 10 450 430 366
To Bus 11 810 775 659
To Bus 8 500 478 406
To Bus 12 8390 7994 X 0.0 $ 6794 0.0 $
# The values from IEEE-1584 spreadsheet are 23.14kA and 19.67kA
Highlighted branch has highest time of branches >14% total fault current and longest clearing
time.
$ Does not include breaker time. Taken from Figure 8
* First value manual calc., (EDSA) value
Table 5 - Determining Controlling Branch

93
Using the IEEE spreadsheet for this bus.
Voltage = 13.8kV
Type switchgear (box)
Arc gap = 153 mm
Working distance = 35.8 in
Bolted fault = 24.225
IEEE-spreadsheet calculation arcing current at 100% is 23.15kA, arcing current at 85% is
19.67kA.
Arc Heat program is in agreement.
100% Relay time = 2.67 sec
85% relay time = 3.33 sec
Breaker time = 0.083
IEEE Spreadsheet Results:
100% arcing = 89.68 cal/cm2
100% boundary 3018 in
85% arcing = 91.6 cal/cm2
85% boundary 3085 in
85% arcing current controlling.
Item EDSA AH program Reference
Controlling branch Transformer incoming Transf. incoming
100% Arcing Current 23,161 23,150
85% Arcing Current 19,689 19,670
100% Arcing time 2.77 + 0.083 2.67 + 0.083
85% Arcing Time 3.35 + 0.083 3.33 + 0.083
100% Cal/cm2
- 88.1
85% Cal/cm2
91.3 91.6
100% Boundary distance (in) - 2963
85% Boundary distance (in) 3086.6 3085
Table 6 – Comparison of Results
EDSA results are in agreement. Program gives the higher of the 100% and 85% energies.

94
Condition 2 – Controlling Branch: Tie .
The relay settings were changed to check the ability of the program to select the proper
controlling branch. The highlighted values in Table 6 shows the changes made from Condition.
Since the one-line was not changed the fault currents are the same as condition 1.
Amp
Time
Dial
Inst Fault
Amp
Operating
Time
Breaker
Time
Bolted fault
Total Time
To Transf IAC53 960 5 - 5450 1.17 0.083 1.25
To Bus 3 IAC53 800 10 - 8710 1.55 0.083 1.63
To Bus 10 ML 750 200 7 1600 450 7.2 0.083 9.4
To Bus 11 CO-8 320 4 2400 810 5.40 0.083 5.04
To Bus 8 ML 269 159 2 1600 500 15.5 0.083 17.72
To Bus 12 BE1-50/51B 720 5 3600 8390 0.0 0.083 0.08
Relay Loc Bolted Fault IEEE 1584
100% Arc fault
Controlling
Branches
100% Fault
time (sec)
IEEE 1584
85% Arc fault
85% Fault
time(sec)
Total 24,225 23,161# 19,689#
To Transf 5450 5211 X 1.23 $ 4429 1.49 $
To Bus 3 8710 8328(8323)* X 1.59 $ 7079(7074)* 1.75 $
To Bus 10 450 430 366
To Bus 11 810 775 659
To Bus 8 500 478 406
To Bus 12 8390 7994 X 0 $ 6794 0 $
Highlighted branch has highest time of branches >14% total fault current and longest clearing
time.
$ Does not include breaker time. Taken from Figure 9.
• First value manual calc., (EDSA) value
Table 8- Determining Controlling Branch
100% Arcing Current 23,161 23,150
100% Arcing time 1.68+ 0.083 1.59 + 0.083
85% Arcing Time 1.82+ 0.083 1.75 + 0.083
100% Cal/cm2
56.4 53.5
85% Cal/cm
2
- 49.2
Table 9 - Comparison of Results
Scaling of time from curve is different than EDSA program by 6%

95
Figure 11 - Time Current Curve showing Protective Device operating times
BUS 4
12/10/2004
04:42:06
C:EDSA2004SAMPLESARCHEATIEEEPDE2.PDC
.5 1 10 100 1000 10000
Trans f2
GE IAC-53
5.000 TD 4.000 Tap
1200/5CT
Bus 10
GE SR750/760 N.INV.
7.000 TD 1.000 Tap
200/5CT
8.0 InstTap
Bus 8 Motor
Bus 8 Motor
GE 269/269+ S.OL
1.000 TD 1.000 Tap
200/5CT
8.0 InstTap
Bus 11
west_ch CO-8
4.000 TD 4.000 Tap
400/5CT
30.0 InstTap
Bus 12
BASLER BE1-50/51B V
5.000 TD 6.000 Tap
600/5CT
30.0 InstTap
Tie
GE IAC-53
10.000 TD 4.000 Tap
1000/5CT

96
Amp
Time
Dial
Inst Fault
Amp
Operating
Time
Breaker
Time
Bolted fault
Total Time
To Transf IAC53 960 5 - 5450 1.16 0.083 1.24
To Bus 3 IAC53 800 4 - 8710 0.57 0.083 0.65
To Bus 10 ML 750 200 7 1600 450 7.2 0.083 9.4
To Bus 11 CO-8 320 4 2400 810 5.40 0.083 5.04
To Bus 8 ML 269 159 2 1600 500 15.5 0.083 17.72
To Bus 12 BE1-50/51B 720 9.9 9600 8390 1.50 0.083 1.58
Relay Loc Bolted
Fault
IEEE 1584
100% Arc fault
Controllin
g
Branches
100% Fault
time (sec)
IEEE 1584
85% Arc fault
85% Fault
time(sec)
Total 24,225 23,161# 19,689#
To Transf 5450 5211 X 1.23 $ 4429 1.51 $
To Bus 3 8710 8328 X 0.58 $ 7079 0.64 $
To Bus 10 450 430 366
To Bus 11 810 775 659
To Bus 8 500 478 406
To Bus 12 8390 7994(8024)* X 1.55 $ 6794(6821)* 1.70 $
Highlighted branch has highest time of branches >14% total fault current.
$ Does not include breaker time. Taken from Figure 10
* First value manual calc., (EDSA) value
Table 11 - Determining Controlling Branch
100% Arcing Current 23,161 23,150
100% Arcing time 1.62 + 0.083 1.55 + 0.083
85% Arcing Time 1.77 + 0.083 1.70 + 0.083
100% Cal/cm
2
56.4 52.2
85% Cal/cm
2
- 47.9
Table 12 - Comparison of Results
Scaling of time from curve is different than EDSA program by 5%

97
Figure 12 - Time Current Curve Showing Protective Device Operating Times
BUS 4
12/10/2004
05:01:20
C:EDSA2004SAMPLESARCHEATIEEEPDE3.PDC
.5 1 10 100 1000 10000
Trans f2
GE IAC-53
5.000 TD 4.000 Tap
1200/5CT
Bus 10
GE SR750/760 N.INV.
7.000 TD 1.000 Tap
200/5CT
8.0 InstTap
Bus 8 Motor
Bus 8 Motor
GE 269/269+ S.OL
1.000 TD 1.000 Tap
200/5CT
8.0 InstTap
Bus 11
west_ch CO-8
3.000 TD 4.000 Tap
400/5CT
30.0 InstTap
Bus 12
BASLER BE1-50/51B V
9.900 TD 6.000 Tap
600/5CT
80.0 InstTap
Tie
GE IAC-53
4.000 TD 4.000 Tap
1000/5CT

98
Bus 40 Fault
For a fault at Bus 40 (Between Transf #2 secondary and transformer breaker), program picked
the 13.8-kV breaker. Based on rules used for the program this is correct. The utility relay is
shown on Figure 7.
Bus 40 has 2 contributing branches for a total of 24.2kA (18.8kA and 5.5 kA). Program checks for
breakers over 1/(2 +1) = 33%. 0.33*24.2 = 8kA. While 69-kV breaker has a longer operating
time, most of the arc energy comes from the 18.8-kA flowing in the 13.8-kV breaker. When it
opens the remaining arc energy from the 69-kV current via the transf. is small due to the fault
current dropping from 24.4kA to 5.5kA. The energy is 45.7 cal/cm
2
. The amount of added
energy to the opening 69-kV breaker is 23.1 cal/cm
2
(from IEEE spreadsheet). The energy that
would have been calculated if the primary relay was selected is 165 cal/cm
2
. Using the rules in
program is a good compromise. Having the program calculate the two step relay operating will
be very difficult.
Bus 3 fault
Program picked Transf. #1 secondary breaker. See Figure 11. This is correct.
Bus 28 fault
Program picked Transf. main secondary breaker. See Figure 12. This is correct.
This V&V is supported by File IEEEPDE.axd and file IEEEPDE.csv file output shown on last
page.
C. St. Pierre

99
Figure 13 - Bus 3 Protective Devices
BUS3
12/10/2004
08:02:39
.5 1 10 100 1000 10000
CB2_UTILITY
GE SR750/760 N.INV.
10.000 TD 0.800 Tap
300/5CT
8.0 InstTap
0038
GE IAC-53
10.000 TD 4.000 Tap
1200/5CT
CB2_BUS3
west_ch CO-8
5.000 TD 5.000 Tap
400/5CT
60.0 InstTap
FU_BUS3
S&C SM-5-STD 200E
CB1_BUS3
west_ch CO-8
3.000 TD 4.000 Tap
150/5CT
50.0 InstTap
0037
west_ch CO-8
3.000 TD 4.000 Tap
200/5CT
60.0 InstTap

100
Figure 14 - Bus 28 Protective Devices
BUS 28
12/10/2004
08:09:25
.5 1 10 100 1000 10000
CB_BUS28
GE AKR MIC VT +/PM
AKR-75 2400 Amp
CB_BUS28
GE AKR MIC VT +/PM
AKR-75 2400 Amp
0042
GE AKR ENH MIC VT +/PM
AKR-30 800A 300 Amp
0043
GE AKR ENH MIC VT +/PM
AKR-30 800A 300 Amp

102
Using ArcHeat for Single Phase Circuits
Using ArcHeat energy levels for arcing faults on single-phase circuits and line-to-ground faults or
Line-to-line on three-phase circuits is not covered by the program. None of the tests that were
done for the IEEE 1584 equation development were for a single phase circuit or for a line to
ground faults. Therefore empirical equations are not available. From over 350 tests that made, 4
tests were for a line-line fault at 2.4-kV. The furnished data did not state if the arc stayed a
single-phase arc or went to a three-phase arc. On the tests that were made for three-phase
faults the "in a box" the initial three-phase arcs also jumped between the conductors to the box
sides. This occurred whether the box was grounded or ungrounded. Therefore for the initial line-
to-line it would be expected that the arcing became three phase before the test ended resulting in
higher energy level than if the fault stayed single-phase. In these line-to-line tests the energy was
approximately 65 to 80% of the similar 3-phase tests.
Drawing a conclusion from the data would be just an estimate. By logic a single-phase or line-to-
ground would have less energy than a 3-phase arc, one could be conservative and use the 3-
phase ArcHeat results for the single-phase and line-to-ground faults. One could also deduce that
a single-phase or line-to-ground condition would be approximately 33% of the three-phase
condition and use a factor greater than 33% for an estimate. Using 40% to 50% of the three-
phase could an option.

103
Putting Arc-Flash Calculations in Perspective
Conrad St. Pierre, Electric Power Consultants, Schenectady, NY
The 2002 National Electrical Code (NEC)®
, Article 110.16 added wording to improve electrical
safety and to inform electrical technicians of the burn hazards of electrical arcs. A summary of
the wording is similar to the following: ‘Flash protection is required when examining, adjusting,
servicing, or maintaining energized equipment. The equipment shall be field marked to warn
qualified persons of potential electric arc flash hazards’.
In conjunction with the requirements in NEC, Proposed NFPA 70E - May 2003 Electrical Safety
Requirements for Employee Workplaces states “Flash hazard analysis shall be done before a
person approaches any exposed electrical conductor or circuit part that has not been placed in an
electrically safe working condition. The flash hazard analysis shall determine the flash protection
boundary and the personal protective equipment that people within the arc flash boundary must
use.” IEEE Std. 1584TM
-2002 - IEEE Guide for Performing Arc-Flash Hazard Calculations
provides details of the calculation methods. The three documents should be viewed as a working
package. While, NFPA 70E gives some of the same equations as given in IEEE Std. 1584
TM
-
2002, more detail is given in the latter. The focus of NFPA-70E and IEEE Std. 1584 is the
radiated heat or incident energy falling on a surface that is produced by an arcing fault. 1.2
calorie/cm
2
(1.2 calorie/cm
2
= 5.02 Joules/cm
2
= 5.02 Watt-sec/cm
2
) for 0.1 second is the incident
energy generally used as a guide to restrict the flash hazard to a second-degree or curable burn.
For 1.0 second, the energy level would be approximately 0.12 calorie/cm
2
. A bolted fault does
not produce any radiated flash energy.
Data Required
To properly estimate the exposure hazard, the maximum bolted short-circuit current, the arcing
fault current, and the operating time of the interrupting device at the arcing fault current are
needed. The incident energy should be calculated at maximum and at 85% of maximum arcing
fault currents. Due to the inverse nature of protective devices, such as fuses and relays, a longer
operating time at lower arcing currents can result in a higher energy exposure.

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