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Enclosure Size Equations and Calculator for Arcing Current per IEEE 1584-2018

Electrical and Electronics Design and Engineering

Enclosure Size Equations and Calculator for Arcing Current per IEEE 1584-2018

Once the enclosure type has been classified, the equivalent height and width need to be determined by comparing their values against specific ranges for each of the three electrode configuration.

Related:

Arc Flash Hazard Calculations Procedure and Considerations For Medium Voltage System 

For certain ranges, the equivalent height and width are determined using the following equations and calculator:

Preview (Calculator coming soon): Enclosure Size Equations and Calculator for Arcing Current per IEEE 1584-2018

Equivalent enclosure width
Equation 1
See Table 1
for
Alternate
Eq.
Equivalent enclosure height equation
Equation 2
See Table 1
for
Alternate
Eq.
Equation 3
CF Typical Enclosure
Equation 4
Correction Factor
for
"Typical Enclosure"
Shallow Enclosure
Equation 5
Correction Factor
for
"Shallow Enclosure"

Where:

Height1 = Equivalent enclosure height
Width1 = Equivalent enclosure width
Width = Actual enclosure width (mm)
Height = Actual enclosure height (mm)
Voc = Open-circuit voltage (system voltage) (kV)
A = Constant, equal to 4 for VCB and 10 for VCBB and HCB
B = Constant, equal to 20 for VCB, 24 for VCBB, and 22 for HCB
EES = Equivalent enclosure size used to find the correction factor, typical enclosures the minimum value of EES is 20.
CF = Enclosure size correction factor
b1, b2 and b3= Coefficients from Table 2

Determination of enclosure type—Typical or shallow
The enclosure is “Shallow” when the following conditions are met:

a) The system voltage is less than 600 V ac.
b) Both the height and width are less than 508 mm (20 in).
c) The enclosure depth is less than or equal to 203.2 mm (8 in).

If any of these conditions are not met, the enclosure is considered “Typical.”

The table below provides the guidelines to determine the equivalent enclosure height and width (Height1 and Width1) for different ranges of enclosure dimensions and electrode configurations.

Table1

E.C.
Range
< 508
(mm)
≥ 508 and ≤ 660.4 (mm)
> 660.4 and ≤ 1244.6 (mm)
> 1244.6 (mm)
VCB
Width1
= 20 (if Typical)
= 0.03937 × Width
(if Shallowa)
= 0.03937 × Width
obtained from Equation (1)
and actual Width
obtained from Equation (1)
with Width = 1244.6 mm
Height1
= 20 (if Typical) or
= 0.03937 × Height
(if Shallowa)
= 0.03937 × Height
= 0.03937 × Height
= 49
VCBB
Width1
= 20 (if Typical) or
= 0.03937 × Width
(if Shallowa)
= 0.03937 × Width
obtained from Equation (1)
and actual Width
obtained from Equation (1)
with Width = 1244.6 mm
Height1
= 20 (if Typical) or
= 0.03937 × Height
(if Shallowa)
= 0.03937 × Height
obtained from Equation (2)
and actual Height
obtained from Equation (2)
with Height = 1244.6 mm
HCB
Width1
= 20 (if Typical) or
= 0.03937 × Width
(if Shallow a)
= 0.03937 × Width
Equation (1)
and actual Width
obtained from >Equation (1)
with Width = 1244.6 mm
Height1
= 20 (if Typical) or
= 0.03937 × Height
(if Shallowa)
= 0.03937 × Height
obtained from Equation (2)
and actual Height

obtained from Equation (2)

with Height = 1244.6 mm

Coefficients for Equations 4 and 5
Table 2

Box Type
E.C.
b1
b2
b3
Typical Enclosure
VCB
-0.000302
0.03441
0.4325
VCBB
-0.0002976
0.032
0.479
HCB
-0.0001923
0.01935
0.6899
Shallow Enclosure
VCB
0.002222
-0.02556
0.6222
VCBB
-0.002778
0.1194
-0.2778
HCB
-0.0005556
0.03722
0.4778

VCB: Vertical conductors/electrodes inside a metal box/enclosure
VCBB: Vertical conductors/electrodes terminated in an insulating barrier inside a metal box/enclosure
HCB: Horizontal conductors/electrodes inside a metal box/enclosure
VOA: Vertical conductors/electrodes in open air
HOA: Horizontal conductors/electrodes in open air

Reference:

IEEE 1584-2018

Verify results and send feedback if a discrepancy is found.

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