arc flash
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There are six (6) worksheets in this document each serves different purposes.
There are sufficient calculation methods in this document for an experienced or thoughtful person to determine if an in-depth Arc Flash Study is actually required for their system.
Associated Training offers courses designed to assist organizations in developing their own Arc Flash Mitigation Programs. Outlines of two of these courses are included on the tab labeled "Course Out;ines".
Thorough engineers and others will be tempted to compare values between the various methods. You will not get the same numbers. Nor will the numbers calculated herein match numbers from ArcPro another calculating method from Kinetrics of Canada. Comparison is recommended. However comparisons with ArcPro and Aspen at 240 volts are shown on the tab labeled "Comparisons"
Using the same parameters in this document's IEEE 1584 calculations for voltages less than 1000 volts will usually yield a different answer than the spread sheet provided by IEEE because IEEE 1584 selects or assigns the "Gap" arc length for the user. Different arc length different answer. In at least some cases this results in a more conservative answer. Which is correct, better or best is left to the discretion of the user.
Contact us by E Mail if you have questions or comments concerning the correct use or benefit of this document. Thanks
Today is 4/8/2023 0:20 4/2/2024 0:20
ArcPro Calculations
ASPEN Calculations
[email protected] 1584 Calculations
ATC Consulting Services 972-889-9075
04/08/2023 © All Rights ReservedATC Consulting Services
Grounded, Un Grounded and High Resistance Systems
Condition Case # 1 Case # 2 Case # 3 Case # 4 Case # 5
Open Air 0 0 0 0 0
Box Arc 1 1 1 1 1
Grounded Systems yes yes yes yes yes
Ungrounded & HRG No No No No No
Arc Gap in inches 1/2 - 6" 2.5 2.5 2.5 2.5 2.5
Voltage in kV for 208<V<15kV 0.48 0.48 0.48 0.48 0.48
Current in kA for 0.7kA<If<106kA 0.8455 0.7922 0.8186 0.8061 1.9237
Worker Distance in inches 18 18 18 18 18
Clearing time in cycles for 100% Ia 15 57 215.4 669.6 30
Clearing time in cycles for 85% Ia 31.8 79.2 366 918 94.8
Distance Exponent (x Factor) 1.641 1.641 1.641 1.641 1.641Energy Normal 100% Ia Expired Expired Expired Expired Expired
Energy Normal 85% Ia Expired Expired Expired Expired Expired
Calculate Factor 1.5 1.5 1.5 1.5 1.5
Case # 1 Case # 2 Case # 3 Case # 4 Case # 5
#VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
#VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
Joules/Cm2 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
Cal/Cm2 #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!
Case Descriptions
Case # 1 For 3 phase fault in T4 Coolers pa
Case # 2 For 3 phase fault in HVAC heating coils
Case # 3 3 Phase fault in AC distribution Panel "A" serving HVAC circuits
Case # 4 3 phase fault HVAC condenser unit
Case # 5 3 ohase fault in 480V Station Service #345 kV - 1B disconnect
Notes
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75
EIncident Energy for 100% Ia
Joules/Cm2
Cal/Cm2
EIncident Energy for 85% Ia
Lee's Calculation Method Expire Date 9/14/2015
V - is system voltage (kV)
t - is arcing time (cycles)
D - is distance from possible arc point to person (inches)
Inches & Cycles Millimeters & Seconds
Case # Case #
Case # 10.5 kV 24.0 6 18
expired Case # 10.48
2000 kVA PadMount 2000 kVA Padmounted Xfmr
Case # 2 expired Case # 2
Case # 3 expired Case # 3
Case # 4 expired Case # 4
Case # 5 expired Case # 5
Case # 6 expired Case # 6
Case # 7 expired Case # 7
Case # 8 expired Case # 8
Case # 9 expired Case # 9
Case # 10 expired Case # 10
Case # 11 expired Case # 11
Case # 12 expired Case # 12
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E = (2.14x106VIbf(t/D
E - is incident energy (Cal/cm2)
Ibf - is bolted fault current
System Volts kV
Bolted Ifault kA
Time Cycles
Work Distance Inches E cal/cm2 System
Volts kV
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E - is incident energy (J/cm2)
V - is system voltage (kV)
t - is arcing time (seconds)
D - is distance from possible arc point to person (mm)
Millimeters & Seconds
E cal/cm2
24 0.1 457.2Expired
2000 kVA Padmounted Xfmr
Expired
Expired
Expired
Expired
Expired
Expired
Expired
Expired
Expired
Expired
Expired
E = (2.14x106VIbf(t/D2)
Ibf - is bolted fault current
Bolted Ifault in kA
Time Seconds
Work Distance
mm
Ask for a free copy of ATC's Fault Current Calculator
Fault Current & Flash Calculations
If Transformer is 3 phase enter "Yes" in Cell B4
Enter Transformer size in kVA (example 300)
Enter Secondary Phase to Phase Voltage in Decimal Form (Example 2400 volt or 12,470v) (Do not use kV)
Enter Transformer Percent Impedance in Decimal Form (Example 2.65)
Ground Fault Current Calculations
Single Phase to Ground Fault Current
Three Phase to Ground Fault Current
Enter Breaker or Fuse Clearing Time in Cycles
Ralph Lee Flash Calculations for "Just Curable Burn"
Considered Valid for: ALL Conditions & ALL Values
Fault Energy in MegaWatts
For Additional Information E-Mail
0
Maximum Arc Energy in a Cubic Box (20 Inches on sides with one end open)
IEEE Standard 1584 - Incident Energy in cal/cm2
USE the IEEE 1584 Excel Spreadsheets
Distance in Feet for Curable Burn (DC) B-2-3.2 Pg 70E-69
Distance in Feet for Curable Burn (DC) B-2-3.3 Pg 70E-69 - Ralph Lee Alternate Method
NFPA 70 E 2004 - Incident Energy in cal/cm2
Valid for: 3 Phase Fault Currents are 16kA < Isc < 50kA, 1" ≤ Arc Gap ≤ 6", Distance to electrodes ≥ 18 Inches and voltage < 600 Volts
Enter Distance From Arc in Inches (DA)
Maximum Open Arc Energy For Arc in Open Air (B-5.1, pg. 70E-71, NFPA 70E, 2000 Edition)
Valid for: Three (3) Phase Voltages 208 ≤ V ≤ 15kV, 50≤ Hz ≤ 60, 700≤ Ibf ≤ 106kA, 1/2" ≤ Arc Gap ≤ 6"
Ask for a free copy of ATC's Fault Current Calculator
Data Fieldsyes
2500.0 kVA
480 Volts
5.30% Impedance
6.00 Cycles
Ralph Lee Flash Calculations for "Just Curable Burn"
Considered Valid for: ALL Conditions & ALL Values
#VALUE!#VALUE!
#VALUE!0.00 Feet or
0.00 Inches
18.00 Inches
IEEE Standard 1584 - Incident Energy in cal/cm2
USE the IEEE 1584 Excel Spreadsheets
Sorry your subscription has
expiredSorry your subscription has
expired
NFPA 70 E 2004 - Incident Energy in cal/cm2
Valid for: 3 Phase Fault Currents are 16kA < Isc < 50kA, 1" ≤ Arc Gap ≤ 6", Distance to electrodes ≥ 18 Inches and voltage < 600 Volts
Calculation not valid for data used
Calculation not valid for data used
Valid for: Three (3) Phase Voltages 208 ≤ V ≤ 15kV, 50≤ Hz ≤ 60, 700≤ Ibf ≤ 106kA, 1/2" ≤ Arc Gap ≤ 6"
