SOUTH INLAND RAW WATER PS
BOSSIER CITY PROJECT P14-02
SUBMITTAL FOR
Short Circuit, Coordination, and Arc Flash Study
D-16020-001-A
Submittal Number
9/17/14
Date
Bill Hussey
Max Foote Construction
Certification Statement: By this submittal, I hereby represent that I have determined and
verified all field measurements, field construction criteria, materials, dimensions, catalog
numbers and similar data and I have reviewed and approved this submittal and checked and
coordinated each item with other applicable approved shop drawings and all contract
requirements.
City of Bossier Project #P14-02
South Inland Raw Water Pump Station
Electrical
16020 Short Circuit, Coordination
And Arc Flash Studies
Submittals
By
Feazel Electrical Contracting - Electrical Contractor
For
Max Foote Construction - General Contractor
Manchac Consulting Group - Engineers
Electrical Power System Short-Circuit,
Coordination and Arc-Flash Studies
For
The City of Bossier City
South Inland Raw Water Pump Station
Bossier City, Louisiana
Distributor: Rexel
Contractor: Feazel Electrical
September, 2014
GE Engineering Services
Plano, Texas
Job #30034550
Note:
Equipment Arc-Flash labels
can be provided once the
arc-flash study in Section
7 and the specific label
content contained in the
11” x 17” sheets at the
rear of that section are
approved.
Electrical Power System Short-Circuit, Coordination &
Arc-Flash Studies
for the
The City of Bossier City
South Inland Raw Water Pump Station
Bossier City, Louisiana
Report by:
Jason Korn
September, 2014
GE Engineering Services
Plano, Texas
Job #30034550
SECTION INDEX AND TABLE OF CONTENTS
Section
Contents
1
Study Purpose & Summary of Conclusions and Recommendations
2
Discussion of Short Circuit Results
3
Short Circuit Calculation Computer Output
4
Discussion of Coordination Study Results
5
Protective Device Setting Sheets
6
Time Current Coordination Plots
7
Arc-Flash Study Results
Page 1 - Rev 0 - 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
GE Energy
Disclaimers:
1.
The recommendations and analysis set forth in this report are wholly dependent upon the
quality of data and other information supplied to Seller by Buyer, Buyer’s agents,
employees, contractors, utilities, or affiliates, and Seller shall not be responsible for the
accuracy or completeness of this report in the event that faulty or incomplete information
is provided to Seller. Buyer alone bears the risk of any damage or injury resulting from
the provision of inaccurate or incomplete information.
2.
The recommendations and analysis set forth in this report are valid only for the
configuration(s) studied. In the event of system changes such as but not limited to
equipment or line additions or removals, any results or recommendations prepared for
Buyer by Seller shall be null, invalid and accordingly withdrawn.
3.
Seller makes no representation, express or implied, that implementation or use of or
adherence to the recommendations or analyses in this report will guarantee or constitute
compliance with any standards, regulations or other applicable legal requirements.
Personal Protective Equipment (PPE) recommended by any calculation method will NOT
provide complete protection for all arc-flash hazards. Injury can be expected when
wearing recommended PPE.
4.
Buyer assumes all responsibilities and bears all the risk of correctly affixing the arc-flash
hazard labels, prepared by Seller in or onto the corresponding equipment.
Page 2 - Rev 0 - 9/9/2014
SECTION
1
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 1 - Purpose of Study & Summary of Conclusions and Recommendations
Contents
1.0
1.1
Purpose of Study
Summary of Conclusions and Recommendations
1.0
Purpose of Study
When an electrical power distribution system is installed in a new facility like the City of Bossier
City South Inland Raw Water Pump Station, a confirming short-circuit study should be
performed. This study can confirm that all new circuit breakers, panelboards, fuses and other
protective devices within the scope of the study are properly rated for the maximum imposed
system fault current. The short-circuit study documented in Sections 2 and 3 of this report
fulfills this need.
A protective device coordination study is necessary in order to provide device settings for the
adjustable circuit breaker trip devices. The coordination study seeks to balance several
objectives, which in some cases can be competing. This coordination study and the
recommended trip device settings are an attempt to address and balance these objectives.
This study is documented in Sections 4, 5 and 6 of this report.
Finally, an arc-flash study is contained in Section 7 of this report. The results of the short-circuit
and coordination study are utilized to determine the arc-flash boundaries and incident energies
for the equipment locations within the scope of this study.
A set of equipment arc-flash labels for placement by the job electrical contractor will be provided
separately from this report for all new electrical equipment in the scope of the study, once the
arc-flash study has been reviewed and approved.
1.1
Summary of Conclusions and Recommendations
The following summary of conclusion and recommendations are in no particular order. Refer to
the other sections of this report for more details.
1) The short-circuit study shows that all evaluated electrical equipment is applied well within
the applicable short-circuit ratings.
2) It has been possible to selectively coordinate the power system devices to a high degree.
However, as discussed in detail in Section 4, there are some compromises in selectivity due
primarily to the inherent characteristics of the circuit breakers and the inherent design and
device sizing within the power system – the emergency system in particular.
3) For almost all the 480 Volt panelboards and ATS equipment, arc-flash energies are 12
cal/cm2. The arc flash energy at the emergency generator is 24.5 cal/cm2.
Page 1-1 - Rev 0 - 9/12/2014
SECTION
2
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 2 – Short-Circuit Study
Contents:
2.0
2.1
2.2
2.3
2.4
2.5
2.6
Introduction
Summary of Results
Short Circuit Study Procedures
System Impedance Data and Data Reduction
Short-Circuit Calculation Procedures
Switchgear Ratings
Series Rating Applications
Appendixes:
•
2.0
Summary of Case 1 Fault Duties, (1 sheet).
Introduction
This section of the report summarizes the findings of the short-circuit study and discusses
general short-circuit calculation procedures in light of the relevant industry standards. This study
was performed using the AFAULT™ module of PTW for Windows™ by SKM Systems Analysis,
Inc.
The computer output has been reproduced in Section 3 of this report. However, the goal of
this section of the report is to summarize the information in a manner that enables the reader
to gain an understanding of the results of the study without having to refer to the actual
computer output.
2.1
Summary of Results
The results of the fault calculations are summarized in the spreadsheet contained at the rear of
this section of the report. The detailed computer output is contained in Section 3 of this report.
Calculations were performed for two different case configurations at:
Case 1 – Normal system configuration with ATS device switched to the normal system.
Case 2 – Emergency system configuration with ATS device switched to the emergency
generator.
The tables at the rear of this section of the report verifies that all evaluated equipment is
applied well within the equipment fault ratings for both cases.
Page 2-1 - Rev 0 - 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 2 – Short-Circuit Study
2.2
Short Circuit Study Procedures
A power system short-circuit study is used to calculate system fault current levels which can
be compared with the short-circuit current ratings of circuit-interrupting devices, such as circuit
breakers and fuses. Fault duties are also calculated as a guide in the selection and rating or
setting of protective devices such as direct acting trips, fuses, and relays.
The short circuit study begins with the representation of the electric power distribution system
in matrix form in a digital computer. Each of the power system components, utility sources,
inplant generators, motors, transformers, cables, etc., is represented by an impedance value;
resistance and reactance or reactance alone. The computer program places an assumed
three-phase fault at each bus location in the system, and a set of short-circuit currents is
calculated which can be compared with the published ratings of the power system equipment
including interrupting devices.
Interrupting devices must be able to withstand and interrupt the most severe short-circuit
currents realizable in the actual system. Three-phase bolted faults at maximum load,
maximum utility short-circuit MVA availability, and maximum inplant generation are usually
considered most severe. Under some conditions tie circuit breakers in the distribution system
are assumed to be closed to produce the highest possible short-circuit currents.
The calculation techniques used are in accordance with American National Standards C37.13
for low-voltage circuit breakers.
2.3
System Impedance Data and Data Reduction
The one-line diagrams furnished with this report represents the electrical power distribution
system under study. The impedance values used are listed in the study data after conversion
to per-unit on the appropriate study bases.
A utility system is represented by a per-unit impedance which is equivalent to the maximum
short-circuit MVA level available from the utility at the incoming service.
The system cable and busway impedances are typical impedance values for such equipment
as shown in standard references, such as the IEEE "Red Book".
The transformer impedances, usually given on the nameplate in percent on the self-cooled
transformer kVA rating, are converted to per-unit impedances on the study bases.
Motor fault contributions in the electrical systems of small to medium size commercial, medical
or educational facilities are normally not significant. However, any motors which have been
identified on customer drawings have been represented in the study per the appropriate
standards.
2.4
Short-Circuit Calculation Procedures
Four types of faults can occur in a three-phase system:
1. Three-phase fault - the three phase conductors are shorted together.
2. Phase-to-phase fault - any two phase conductors are shorted together.
3. Phase-to-phase-to-ground fault - any two phase conductors are shorted together and
Page 2-2 - Rev 0 - 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 2 – Short-Circuit Study
simultaneously to ground.
4. Phase-to-ground fault - one phase conductor is shorted to ground.
For a particular location in a power system, the initial magnitude of fault current is generally the
greatest for three-phase faults and least for phase-to-ground faults. However, phase-to-ground
fault current magnitudes can exceed the three-phase fault current magnitudes under certain
conditions. This can occur near a solidly grounded synchronous machine or near the solidly
grounded wye connection of; a delta-wye transformer of the three-phase core (three leg) design,
a grounded wye-delta "tertiary" auto-transformer or a grounded wye-grounded wye-delta tertiary
three-winding transformer.
Additional complexity is introduced in the calculation of phase-to-ground fault currents;
therefore, normally only three-phase fault currents are calculated. Phase-to-ground fault
currents are calculated only when the nature of the particular system, the operating conditions
or study requirements dictate.
2.5
Switchgear Ratings
Low-voltage power circuit breakers are tested and applied in accordance with ANSI C37.13.
Low-voltage circuit breakers of recent manufacture have symmetrical-current interrupting
ratings. For low-voltage breakers, calculated first-cycle symmetrical short-circuit currents are
compared with the manufacturer's symmetrical ratings, since these breakers may operate
rapidly enough to part their contacts during the first cycle of short-circuit current.
2.6
Series Rating Applications
The Underwriters Laboratory permits assigning a short circuit rating to a combination of molded
case circuit breakers, or fuses and molded case circuit breakers connected in series, that is
higher than the lowest rated protective device of the combination. This is defined as series
connected ratings. The combination rating cannot exceed the rating of the protective device
furthest upstream, although it will exceed the rating of the downstream protector(s).
The upstream protector can be a molded case breaker or fuse. Device combinations are not
limited to those in the same equipment. They can be in different equipments such as a
switchboard feeder or a panelboard main versus panelboard branches. There are no distance
restrictions between devices located in different equipment. Total fault current magnitude must
flow through both protectors. Thus, fault current contributions from any motors, as well as
power source fault current, must flow through upstream and downstream protectors. (It appears
the position of NEMA is that motor full load currents not exceeding 1% of the downstream
device interrupting rating can be ignored.)
Molded case circuit breakers may be applied as fully rated or series rated. In a fully rated
system, the short-circuit rating of all protective devices are equal to, or exceed, the available
short-circuit current. If mounted in equipment, the bus short-circuit withstand rating and
equipment short-circuit rating must equal or exceed the available short-circuit current. In a
series connected system, the short-circuit rating of the upstream protector is fully rated but the
downstream protector is not fully rated.
Full selectivity between devices requires the upstream protector to wait for the downstream
device to operate for all values of fault current on the load side of the downstream protector.
Page 2-3 - Rev 0 - 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 2 – Short-Circuit Study
This is only available when using low voltage power circuit breakers without instantaneous
devices as the line side device. Systems using molded case circuit breakers or fuses as the
line side device lose selectivity for fault magnitudes above their instantaneous setting. Systems
employing molded case circuit breakers or fuses as mains should not be used where full
selectivity between devices is required. For series rated or fully rated systems, both protectors
will open on short circuits. The fault current magnitude where selectivity is lost is determined by
the instantaneous pickup of the main. For panelboards, fully rated systems exhibit the same
lack of selectivity as series rated systems.
Page 2-4 - Rev 0 - 9/9/2014
CASE 1
Page 1 of 2
Summary of Equipment Short-Circuit Ratings versus Duties
Bossier City South Inland Pump Station, Bossier City, Louisiana
Case 1 - Normal System Configuration.
Bus
Manufacturer
Status
Type
Bus
Calc
Dev
Series
Isc
Calc
Dev
Mom
Voltage
Isc kA
Isc kA
Rating kA
Rating%
Mom kA
Mom kA
Rating%
RWP-PNL-030
GE
Pass
LV Panelboard
480
23.17
35.00
66.20
RWP-PNL-040
GE
Pass
LV Panelboard
208
1.92 (*N1)
10.00
19.23
RWP-SWB-010
GE
Pass
Switchboard
480 26.34 (*N1)
65.00
40.52
(*N1) System X/R higher than Test X/R, Calc INT kA modified based on low voltage factor.
(*Calc Isc kA) Device did not pass. Device is either Marginal (95%) or Failed (100%) of the device library Isc rating.
30034550 SC Tabulations Rev 0.xls!1_BUS
CASE 2
Page 2 of 2
Summary of Equipment Short-Circuit Ratings versus Duties
Bossier City South Inland Pump Station, Bossier City, Louisiana
Case 2 - Emergency System Configuration.
Bus
Manufacturer
Status
Type
Bus
Calc
Dev
Series
Isc
Calc
Dev
Mom
Voltage
Isc kA
Isc kA
Rating kA
Rating%
Mom kA
Mom kA
Rating%
RWP-PNL-030
GE
Pass
LV Panelboard
480
RWP-PNL-040
GE
Pass
LV Panelboard
208
RWP-SWB-010
GE
Pass
Switchboard
480
6.71 (*N1)
35.00
19.17
1.82 (*N1)
10.00
18.20
7.34 (*N1)
65.00
11.29
(*N1) System X/R higher than Test X/R, Calc INT kA modified based on low voltage factor.
(*Calc Isc kA) Device did not pass. Device is either Marginal (95%) or Failed (100%) of the device library Isc rating.
30034550 SC Tabulations Rev 0.xls!2_BUS
SECTION
3
Bossier City South Inland Pump Station
Bossier City, Louisiana
Distributor: Rexel
Contractor: Feazel Electrical
Section 3
Short-Circuit Computer Output
CASE 1
South Inland Raw Water Pump Station
Bossier City, LA
Proposed
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
Sep 09, 2014
19:14:14
Page 1
-----------------------------------------------------------------------------ALL INFORMATION PRESENTED IS FOR REVIEW, APPROVAL
INTERPRETATION AND APPLICATION BY A REGISTERED ENGINEER ONLY
SKM DISCLAIMS ANY RESPONSIBILITY AND LIABILITY RESULTING
FROM THE USE AND INTERPRETATION OF THIS SOFTWARE.
-----------------------------------------------------------------------------SKM POWER*TOOLS FOR WINDOWS
INPUT DATA REPORT
COPYRIGHT SKM SYSTEMS ANALYSIS, INC. 1995-2013
-----------------------------------------------------------------------------ALL PU VALUES ARE EXPRESSED ON A 100 MVA BASE.
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
Page 2
FEEDER INPUT DATA
===============================================================================================================
CABLE
FEEDER FROM
FEEDER TO
QTY VOLTS
LENGTH
FEEDER
NAME
NAME
NAME
/PH L-L
SIZE
TYPE
===============================================================================================================
CBL-0002
BUS-0004
ATS NORM
6
480
90.0 FEET
500
Copper
Duct Material: Non-Magnetic
Insulation Type:
Insulation Class:
THHN
+/- Impedance: 0.0276 + J 0.0373 Ohms/1000 ft
0.1797 + J 0.2428 PU
Z0
Impedance: 0.0438 + J 0.0999 Ohms/1000 ft
0.2852 + J 0.6504 PU
CBL-0004
RWP-SWB-010
BUS-0009
2
480
25.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0541 + J 0.0396 Ohms/1000 ft
Z0
Impedance: 0.0860 + J 0.1007 Ohms/1000 ft
FEET
CBL-0005
RWP-SWB-010
BUS-0014
2
480
25.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0541 + J 0.0396 Ohms/1000 ft
Z0
Impedance: 0.0860 + J 0.1007 Ohms/1000 ft
FEET
CBL-0006
RWP-SWB-010
BUS-0017
2
480
25.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0541 + J 0.0396 Ohms/1000 ft
Z0
Impedance: 0.0860 + J 0.1007 Ohms/1000 ft
FEET
CBL-0007
BUS-0010
BUS-0011
1
480 100.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0633 + J 0.0398 Ohms/1000 ft
Z0
Impedance: 0.1006 + J 0.1012 Ohms/1000 ft
FEET
CBL-0008
BUS-0012
BUS-0013
1
480 105.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0633 + J 0.0398 Ohms/1000 ft
Z0
Impedance: 0.1006 + J 0.1012 Ohms/1000 ft
FEET
CBL-0009
BUS-0015
BUS-0016
1
480 110.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0633 + J 0.0398 Ohms/1000 ft
Z0
Impedance: 0.1006 + J 0.1012 Ohms/1000 ft
FEET
CBL-0010
RWP-SWB-010
BUS-0019
1
480
40.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.2020 + J 0.0467 Ohms/1000 ft
Z0
Impedance: 0.3211 + J 0.1188 Ohms/1000 ft
FEET
CBL-0011
RWP-SWB-010
RWP-PNL-030
1
480
25.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0633 + J 0.0398 Ohms/1000 ft
Z0
Impedance: 0.1006 + J 0.1012 Ohms/1000 ft
FEET
250
Copper
Insulation Class:
0.2935 + J 0.2148 PU
0.4666 + J 0.5463 PU
250
Copper
Insulation Class:
0.2935 + J 0.2148 PU
0.4666 + J 0.5463 PU
250
Copper
Insulation Class:
0.2935 + J 0.2148 PU
0.4666 + J 0.5463 PU
4/0
Copper
Insulation Class:
2.75 + J
1.73 PU
4.37 + J
4.39 PU
4/0
Copper
Insulation Class:
2.88 + J
1.81 PU
4.58 + J
4.61 PU
4/0
Copper
Insulation Class:
3.02 + J
1.90 PU
4.80 + J
4.83 PU
2
Copper
Insulation Class:
3.51 + J 0.8108 PU
5.57 + J
2.06 PU
4/0
Copper
Insulation Class:
0.6868 + J 0.4319 PU
1.09 + J
1.10 PU
THHN
THHN
THHN
THHN
THHN
THHN
THHN
THHN
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
Page 3
TRANSFORMER INPUT DATA
=============================================================================================
TRANSFORMER
PRIMARY RECORD
VOLTS
* SECONDARY RECORD
VOLTS
FULL-LOAD
NOMINAL
NAME
NO NAME
L-L
NO NAME
L-L
KVA
KVA
=============================================================================================
RWP-XF-040
RWP-PNL-030
D
480.00
RWP-PNL-040
YG
208.00
30.00
30.00
Pos. Seq. Z%:
1.65 + J
4.51
(Zpu 55.12 + j 150.2 )
Shell Type
Zero Seq. Z%:
1.65 + J
4.51
(Sec 55.12 + j 150.2 Pri Open)
Taps Pri. 0.000 % Sec. 0.000 % Phase Shift (Pri. Leading Sec.): 30.00 Deg.
Utility XFMR
BUS-0001
YG 12470.0
BUS-0004
YG
480.00 1500.00
1500.00
Pos. Seq. Z%:
0.869 + J
5.68
(Zpu 0.579 + j
3.79 )
Shell Type
Zero Seq. Z%:
0.869 + J
5.68
(
Pri - Sec: 0.579 + j
3.79 )
Taps Pri. 0.000 % Sec. 0.000 % Phase Shift (Pri. Leading Sec.): 0.000 Deg.
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
Page 4
VFD INPUT DATA
=============================================================================================================================
VFD
VFD FROM
VFD TO
VOLTS
RATING
--CONTRIBUTION% OF RATING------BYPASS IMPEDANCE-----NAME
NAME
NAME
THREE PHASE
LINE-G
X/R
Z1%
X1/R1
Z0%
X0/R0
=============================================================================================================================
RWP-VFD-401
BUS-0009
BUS-0010
480
300 LineSide:
0
0
8
0
8
0
8
HP
LoadSide:
0
0
8
Bypass Z Not Applicable
Power Factor:
0.8 Efficiency:
0.9 Line Reactor:
0%
Sevice Factor:
1
NOT in Bypass Mode
***************************************************************************************************************
RWP-VFD-402
BUS-0014
BUS-0012
480
300 LineSide:
0
0
8
0
8
0
8
HP
LoadSide:
0
0
8
Bypass Z Not Applicable
Power Factor:
0.8 Efficiency:
0.9 Line Reactor:
0%
Sevice Factor:
1
NOT in Bypass Mode
***************************************************************************************************************
RWP-VFD-403
BUS-0017
BUS-0015
480
300 LineSide:
0
0
8
0
8
0
8
HP
LoadSide:
0
0
8
Bypass Z Not Applicable
Power Factor:
0.8 Efficiency:
0.9 Line Reactor:
0%
Sevice Factor:
1
NOT in Bypass Mode
***************************************************************************************************************
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
Page 5
GENERATION CONTRIBUTION DATA
=====================================================================================
BUS
CONTRIBUTION
VOLTAGE
NAME
NAME
L-L
MVA
X"d
X/R
=====================================================================================
BUS-0001
Utility
12470.0 186.14
Three Phase
Contribution:
8618.00 AMPS
3.57
Single Line to Ground Contribution:
5706.00 AMPS
3.01
Pos Sequence Impedance (100 MVA Base) 0.1449 + J
0.5173 PU
Zero Sequence Impedance (100 MVA Base) 0.4777 + J
1.28 PU
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
Page 6
MOTOR CONTRIBUTION DATA
=====================================================================================
BUS
CONTRIBUTION
VOLTAGE
BASE
Motor
NAME
NAME
L-L
kVA
X"d
X/R
Number
=====================================================================================
BUS-0011
RWP-P-401
480 250.67
0.1692
10.0 1.00
Pos Sequence Impedance (100 MVA Base)
6.75 + j
67.48 PU
BUS-0013
RWP-P-402
480 250.67
0.1692
10.0
Pos Sequence Impedance (100 MVA Base)
6.75 + j
1.00
67.48 PU
BUS-0016
RWP-P-403
480 250.67
0.1692
10.0
Pos Sequence Impedance (100 MVA Base)
6.75 + j
1.00
67.48 PU
BUS-0019
RWP-AC-421
480
30.08
0.1692
10.0
Pos Sequence Impedance (100 MVA Base)
56.23 + j
1.00
562.34 PU
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
Sep 09, 2014
19:14:14
-----------------------------------------------------------------------------ALL INFORMATION PRESENTED IS FOR REVIEW, APPROVAL
INTERPRETATION AND APPLICATION BY A REGISTERED ENGINEER ONLY
SKM DISCLAIMS ANY RESPONSIBILITY AND LIABILITY RESULTING
FROM THE USE AND INTERPRETATION OF THIS SOFTWARE.
-----------------------------------------------------------------------------SKM POWER*TOOLS FOR WINDOWS
A_FAULT SHORT CIRCUIT ANALYSIS REPORT
COPYRIGHT SKM SYSTEMS ANALYSIS, INC. 1996-2013
------------------------------------------------------------------------------
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
THREE PHASE LOW VOLTAGE DUTY PAGE
1
T H R E E
P H A S E
F A U L T
R E P O R T
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
ATS NORM
3P Duty: 26.143 KA AT -78.80 DEG ( 21.74 MVA) X/R:
5.07
VOLTAGE:
480.
EQUIV. IMPEDANCE= 0.0021 + J 0.0104 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
26.143 KA
MOLDED CASE CIRCUIT BREAKER > 20KA 26.338 KA
CBL-0002
BUS-0004
25.932 KA
ANG:
-78.76
AUTO-0003
RWP-SWB-010
0.212 KA
ANG:
-83.94
RWP-PNL-030
3P Duty: 23.169 KA AT -72.28 DEG ( 19.26 MVA) X/R:
3.13
VOLTAGE:
480.
EQUIV. IMPEDANCE= 0.0036 + J 0.0114 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
23.169 KA
MOLDED CASE CIRCUIT BREAKER > 20KA 23.169 KA
CBL-0011
RWP-SWB-010
23.169 KA
ANG:
-72.28
RWP-PNL-040
3P Duty: 1.680 KA AT -69.93 DEG (
0.61 MVA) X/R:
2.74
VOLTAGE:
208.
EQUIV. IMPEDANCE= 0.0245 + J 0.0671 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
1.680 KA
MOLDED CASE CIRCUIT BREAKER < 10KA
1.903 KA
MOLDED CASE CIRCUIT BREAKER < 20KA
1.680 KA
MOLDED CASE CIRCUIT BREAKER > 20KA
1.680 KA
RWP-XF-040
RWP-PNL-030
1.680 KA
ANG:
110.07
RWP-SWB-010
3P Duty: 26.143 KA AT -78.80 DEG ( 21.74 MVA) X/R:
5.07
VOLTAGE:
480.
EQUIV. IMPEDANCE= 0.0021 + J 0.0104 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
26.143 KA
MOLDED CASE CIRCUIT BREAKER > 20KA 26.338 KA
CBL-0010
BUS-0019
0.212 KA
ANG:
96.06
AUTO-0003
ATS NORM
25.932 KA
ANG: -258.76
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
UNBALANCED LOW VOLTAGE DUTY PAGE
1
U N B A L A N C E D
F A U L T
R E P O R T
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
LOCATION
FAULT
KA
X/R EQUIVALENT (PU) ASYM. KA AT 0.5 CYCLES
VOLTAGE
DUTIES
(RMS)
FAULT IMPEDANCE * MAX. RMS AVG. RMS *
==============================================================================
ATS NORM
3P Duty: 26.143
5. Z1=
SLG DUTY: 23.944
5. Z2=
480. VOLTS
LN/LN: 22.641
Z0=
LN/LN/GND: 25.440 ( 22.084 GND
4.6008
4.6008
5.8706
RETURN KA)
32.850
29.601
29.597
RWP-PNL-030
5.1915
5.1915
7.2348
RETURN KA)
26.105
22.851
24.660
3. Z1= 165.1878
3. Z2= 165.1878
Z0= 160.0008
1.716 GND RETURN KA)
1.842
1.861
1.762
32.850
29.601
29.597
3P Duty: 23.169
3. Z1=
SLG DUTY: 20.485
3. Z2=
480. VOLTS
LN/LN: 20.065
Z0=
LN/LN/GND: 22.271 ( 18.355 GND
RWP-PNL-040
3P Duty:
SLG DUTY:
208. VOLTS
LN/LN:
LN/LN/GND:
RWP-SWB-010
1.680
1.698
1.455
1.690 (
3P Duty: 26.143
5. Z1=
SLG DUTY: 23.944
5. Z2=
480. VOLTS
LN/LN: 22.641
Z0=
LN/LN/GND: 25.440 ( 22.083 GND
4.6009
4.6009
5.8706
RETURN KA)
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
UNBALANCED LOW VOLTAGE DUTY PAGE
2
F A U L T
S T U D Y
S U M M A R Y
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
BUS RECORD
VOLTAGE A V A I L A B L E
F A U L T
D U T I E S (KA)
NO NAME
L-L
3 PHASE
X/R
LINE/GRND
X/R
==============================================================================
ATS NORM
RWP-PNL-030
RWP-PNL-040
RWP-SWB-010
480.
480.
208.
480.
26.143
23.169
1.680
26.143
10 FAULTED BUSES,
20 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5.07
3.13
2.74
5.07
23.944
20.485
1.698
23.944
5 CONTRIBUTIONS
4.72
2.99
2.73
4.72
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
THREE PHASE MOMENTARY DUTY PAGE
T H R E E
1
P H A S E
M O M E N T A R Y
D U T Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
ATS NORM
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
RWP-PNL-030
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
RWP-PNL-040
VOLTAGE:
208.
( SEE LOW VOLTAGE REPORT )
RWP-SWB-010
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
UNBALANCED MOMENTARY DUTY PAGE
1
M O M E N T A R Y
D U T Y
S U M M A R Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
SOLUTION METHOD
: E/Z
==============================================================================
BUS RECORD
VOLTAGE
* 3 P H A S E *
* * * SLG * * *
NO NAME
L-L
KA
X/R
KA
X/R
==============================================================================
1 FAULTED BUSES,
20 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
THREE PHASE INTERRUPTING DUTY PAGE
T H R E E
1
P H A S E
I N T E R R U P U T I N G
D U T Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
ATS NORM
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
RWP-PNL-030
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
RWP-PNL-040
VOLTAGE:
208.
( SEE LOW VOLTAGE REPORT )
RWP-SWB-010
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
UNBALANCED INTERRUPTING DUTY PAGE
1
I N T E R R U P T I N G
D U T Y
S U M M A R Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
NACD OPTION: INTERPOLATED
==============================================================================
BUS RECORD
VOLTAGE NACD
* 3 P H A S E *
* * * S L G * * *
NO NAME
L-L
RATIO
E/Z KA
X/R
E/Z KA
X/R
==============================================================================
1 FAULTED BUSES,
20 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
Sep 09, 2014
19:14:14
-----------------------------------------------------------------------------ALL INFORMATION PRESENTED IS FOR REVIEW, APPROVAL
INTERPRETATION AND APPLICATION BY A REGISTERED ENGINEER ONLY
SKM DISCLAIMS ANY RESPONSIBILITY AND LIABILITY RESULTING
FROM THE USE AND INTERPRETATION OF THIS SOFTWARE.
-----------------------------------------------------------------------------SKM POWER*TOOLS FOR WINDOWS
A_FAULT SHORT CIRCUIT ANALYSIS REPORT
COPYRIGHT SKM SYSTEMS ANALYSIS, INC. 1996-2013
------------------------------------------------------------------------------
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
THREE PHASE LOW VOLTAGE DUTY PAGE
1
T H R E E
P H A S E
F A U L T
R E P O R T
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
UNBALANCED LOW VOLTAGE DUTY PAGE
1
F A U L T
S T U D Y
S U M M A R Y
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
BUS RECORD
VOLTAGE A V A I L A B L E
F A U L T
D U T I E S (KA)
NO NAME
L-L
3 PHASE
X/R
LINE/GRND
X/R
==============================================================================
6 FAULTED BUSES,
20 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
T H R E E
THREE PHASE MOMENTARY DUTY PAGE
1
P H A S E
M O M E N T A R Y
D U T Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
UNBALANCED MOMENTARY DUTY PAGE
1
M O M E N T A R Y
D U T Y
S U M M A R Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
SOLUTION METHOD
: E/Z
==============================================================================
BUS RECORD
VOLTAGE
* 3 P H A S E *
* * * SLG * * *
NO NAME
L-L
KA
X/R
KA
X/R
==============================================================================
0 FAULTED BUSES,
20 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
T H R E E
THREE PHASE INTERRUPTING DUTY PAGE
1
P H A S E
I N T E R R U P U T I N G
D U T Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
Sep 09, 2014
19:14:14
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Normal Operation
UNBALANCED INTERRUPTING DUTY PAGE
1
I N T E R R U P T I N G
D U T Y
S U M M A R Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
NACD OPTION: INTERPOLATED
==============================================================================
BUS RECORD
VOLTAGE NACD
* 3 P H A S E *
* * * S L G * * *
NO NAME
L-L
RATIO
E/Z KA
X/R
E/Z KA
X/R
==============================================================================
0 FAULTED BUSES,
20 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
CASE 2
South Inland Raw Water Pump Station
Bossier City, LA
Proposed
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
Sep 09, 2014
19:17:23
Page 1
-----------------------------------------------------------------------------ALL INFORMATION PRESENTED IS FOR REVIEW, APPROVAL
INTERPRETATION AND APPLICATION BY A REGISTERED ENGINEER ONLY
SKM DISCLAIMS ANY RESPONSIBILITY AND LIABILITY RESULTING
FROM THE USE AND INTERPRETATION OF THIS SOFTWARE.
-----------------------------------------------------------------------------SKM POWER*TOOLS FOR WINDOWS
INPUT DATA REPORT
COPYRIGHT SKM SYSTEMS ANALYSIS, INC. 1995-2013
-----------------------------------------------------------------------------ALL PU VALUES ARE EXPRESSED ON A 100 MVA BASE.
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
Page 2
FEEDER INPUT DATA
===============================================================================================================
CABLE
FEEDER FROM
FEEDER TO
QTY VOLTS
LENGTH
FEEDER
NAME
NAME
NAME
/PH L-L
SIZE
TYPE
===============================================================================================================
CBL-0003
GENERATOR BUS
ATS EMER
3
480
70.0 FEET
500
Copper
Duct Material: Non-Magnetic
Insulation Type:
Insulation Class:
THHN
+/- Impedance: 0.0276 + J 0.0373 Ohms/1000 ft
0.2795 + J 0.3777 PU
Z0
Impedance: 0.0438 + J 0.0999 Ohms/1000 ft
0.4436 + J
1.01 PU
CBL-0004
RWP-SWB-010
BUS-0009
2
480
25.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0541 + J 0.0396 Ohms/1000 ft
Z0
Impedance: 0.0860 + J 0.1007 Ohms/1000 ft
FEET
CBL-0005
RWP-SWB-010
BUS-0014
2
480
25.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0541 + J 0.0396 Ohms/1000 ft
Z0
Impedance: 0.0860 + J 0.1007 Ohms/1000 ft
FEET
CBL-0006
RWP-SWB-010
BUS-0017
2
480
25.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0541 + J 0.0396 Ohms/1000 ft
Z0
Impedance: 0.0860 + J 0.1007 Ohms/1000 ft
FEET
CBL-0007
BUS-0010
BUS-0011
1
480 100.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0633 + J 0.0398 Ohms/1000 ft
Z0
Impedance: 0.1006 + J 0.1012 Ohms/1000 ft
FEET
CBL-0008
BUS-0012
BUS-0013
1
480 105.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0633 + J 0.0398 Ohms/1000 ft
Z0
Impedance: 0.1006 + J 0.1012 Ohms/1000 ft
FEET
CBL-0009
BUS-0015
BUS-0016
1
480 110.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0633 + J 0.0398 Ohms/1000 ft
Z0
Impedance: 0.1006 + J 0.1012 Ohms/1000 ft
FEET
CBL-0010
RWP-SWB-010
BUS-0019
1
480
40.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.2020 + J 0.0467 Ohms/1000 ft
Z0
Impedance: 0.3211 + J 0.1188 Ohms/1000 ft
FEET
CBL-0011
RWP-SWB-010
RWP-PNL-030
1
480
25.0
Duct Material: Non-Magnetic
Insulation Type:
+/- Impedance: 0.0633 + J 0.0398 Ohms/1000 ft
Z0
Impedance: 0.1006 + J 0.1012 Ohms/1000 ft
FEET
250
Copper
Insulation Class:
0.2935 + J 0.2148 PU
0.4666 + J 0.5463 PU
250
Copper
Insulation Class:
0.2935 + J 0.2148 PU
0.4666 + J 0.5463 PU
250
Copper
Insulation Class:
0.2935 + J 0.2148 PU
0.4666 + J 0.5463 PU
4/0
Copper
Insulation Class:
2.75 + J
1.73 PU
4.37 + J
4.39 PU
4/0
Copper
Insulation Class:
2.88 + J
1.81 PU
4.58 + J
4.61 PU
4/0
Copper
Insulation Class:
3.02 + J
1.90 PU
4.80 + J
4.83 PU
2
Copper
Insulation Class:
3.51 + J 0.8108 PU
5.57 + J
2.06 PU
4/0
Copper
Insulation Class:
0.6868 + J 0.4319 PU
1.09 + J
1.10 PU
THHN
THHN
THHN
THHN
THHN
THHN
THHN
THHN
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
Page 3
TRANSFORMER INPUT DATA
=============================================================================================
TRANSFORMER
PRIMARY RECORD
VOLTS
* SECONDARY RECORD
VOLTS
FULL-LOAD
NOMINAL
NAME
NO NAME
L-L
NO NAME
L-L
KVA
KVA
=============================================================================================
RWP-XF-040
RWP-PNL-030
D
480.00
RWP-PNL-040
YG
208.00
30.00
30.00
Pos. Seq. Z%:
1.65 + J
4.51
(Zpu 55.12 + j 150.2 )
Shell Type
Zero Seq. Z%:
1.65 + J
4.51
(Sec 55.12 + j 150.2 Pri Open)
Taps Pri. 0.000 % Sec. 0.000 % Phase Shift (Pri. Leading Sec.): 30.00 Deg.
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
Page 4
VFD INPUT DATA
=============================================================================================================================
VFD
VFD FROM
VFD TO
VOLTS
RATING
--CONTRIBUTION% OF RATING------BYPASS IMPEDANCE-----NAME
NAME
NAME
THREE PHASE
LINE-G
X/R
Z1%
X1/R1
Z0%
X0/R0
=============================================================================================================================
RWP-VFD-401
BUS-0009
BUS-0010
480
300 LineSide:
0
0
8
0
8
0
8
HP
LoadSide:
0
0
8
Bypass Z Not Applicable
Power Factor:
0.8 Efficiency:
0.9 Line Reactor:
0%
Sevice Factor:
1
NOT in Bypass Mode
***************************************************************************************************************
RWP-VFD-402
BUS-0014
BUS-0012
480
300 LineSide:
0
0
8
0
8
0
8
HP
LoadSide:
0
0
8
Bypass Z Not Applicable
Power Factor:
0.8 Efficiency:
0.9 Line Reactor:
0%
Sevice Factor:
1
NOT in Bypass Mode
***************************************************************************************************************
RWP-VFD-403
BUS-0017
BUS-0015
480
300 LineSide:
0
0
8
0
8
0
8
HP
LoadSide:
0
0
8
Bypass Z Not Applicable
Power Factor:
0.8 Efficiency:
0.9 Line Reactor:
0%
Sevice Factor:
1
NOT in Bypass Mode
***************************************************************************************************************
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
Page 5
GENERATION CONTRIBUTION DATA
=====================================================================================
BUS
CONTRIBUTION
VOLTAGE
NAME
NAME
L-L
MVA
X"d
X/R
=====================================================================================
GENERATOR BUS GEN-0001
480.00 0.750
0.1620
23.15
KG: 0.9114 xdsat: 1.0000 Excitation Limit:
1.30 Ik ON
Pos Sequence Impedance (100 MVA Base) 0.9330 + J
21.60 PU
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
Page 6
MOTOR CONTRIBUTION DATA
=====================================================================================
BUS
CONTRIBUTION
VOLTAGE
BASE
Motor
NAME
NAME
L-L
kVA
X"d
X/R
Number
=====================================================================================
BUS-0011
RWP-P-401
480 250.67
0.1692
10.0 1.00
Pos Sequence Impedance (100 MVA Base)
6.75 + j
67.48 PU
BUS-0013
RWP-P-402
480 250.67
0.1692
10.0
Pos Sequence Impedance (100 MVA Base)
6.75 + j
1.00
67.48 PU
BUS-0016
RWP-P-403
480 250.67
0.1692
10.0
Pos Sequence Impedance (100 MVA Base)
6.75 + j
1.00
67.48 PU
BUS-0019
RWP-AC-421
480
30.08
0.1692
10.0
Pos Sequence Impedance (100 MVA Base)
56.23 + j
1.00
562.34 PU
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
Sep 09, 2014
19:17:23
-----------------------------------------------------------------------------ALL INFORMATION PRESENTED IS FOR REVIEW, APPROVAL
INTERPRETATION AND APPLICATION BY A REGISTERED ENGINEER ONLY
SKM DISCLAIMS ANY RESPONSIBILITY AND LIABILITY RESULTING
FROM THE USE AND INTERPRETATION OF THIS SOFTWARE.
-----------------------------------------------------------------------------SKM POWER*TOOLS FOR WINDOWS
A_FAULT SHORT CIRCUIT ANALYSIS REPORT
COPYRIGHT SKM SYSTEMS ANALYSIS, INC. 1996-2013
------------------------------------------------------------------------------
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
THREE PHASE LOW VOLTAGE DUTY PAGE
1
T H R E E
P H A S E
F A U L T
R E P O R T
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
ATS EMER
3P Duty: 5.677 KA AT -86.73 DEG (
4.72 MVA) X/R:
17.80
VOLTAGE:
480.
EQUIV. IMPEDANCE= 0.0028 + J 0.0487 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
6.438 KA
MOLDED CASE CIRCUIT BREAKER < 10KA
8.972 KA
MOLDED CASE CIRCUIT BREAKER < 20KA
7.604 KA
MOLDED CASE CIRCUIT BREAKER > 20KA
6.835 KA
CBL-0003
GENERATOR BUS
5.465 KA
ANG:
-86.84
AUTO-0003
RWP-SWB-010
0.212 KA
ANG:
-83.94
GENERATOR BUS
3P Duty: 5.775 KA AT -87.39 DEG (
4.80 MVA) X/R:
22.64
VOLTAGE:
480.
EQUIV. IMPEDANCE= 0.0022 + J 0.0479 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
6.664 KA
MOLDED CASE CIRCUIT BREAKER < 10KA
9.288 KA
MOLDED CASE CIRCUIT BREAKER < 20KA
7.872 KA
MOLDED CASE CIRCUIT BREAKER > 20KA
7.076 KA
CONTRIBUTIONS: GEN-0001
5.563 KA
ANG:
-87.53
CBL-0003
ATS EMER
0.212 KA
ANG: -263.92
RWP-PNL-030
3P Duty: 5.551 KA AT -84.99 DEG (
4.61 MVA) X/R:
11.51
VOLTAGE:
480.
EQUIV. IMPEDANCE= 0.0044 + J 0.0497 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
6.031 KA
MOLDED CASE CIRCUIT BREAKER < 10KA
8.405 KA
MOLDED CASE CIRCUIT BREAKER < 20KA
7.124 KA
MOLDED CASE CIRCUIT BREAKER > 20KA
6.404 KA
CBL-0011
RWP-SWB-010
5.551 KA
ANG:
-84.99
RWP-PNL-040
3P Duty: 1.533 KA AT -71.64 DEG (
0.55 MVA) X/R:
3.01
VOLTAGE:
208.
EQUIV. IMPEDANCE= 0.0247 + J 0.0743 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
1.533 KA
MOLDED CASE CIRCUIT BREAKER < 10KA
1.784 KA
MOLDED CASE CIRCUIT BREAKER < 20KA
1.533 KA
MOLDED CASE CIRCUIT BREAKER > 20KA
1.533 KA
RWP-XF-040
RWP-PNL-030
1.533 KA
ANG:
108.36
RWP-SWB-010
3P Duty: 5.677 KA AT -86.73 DEG (
4.72 MVA) X/R:
17.80
VOLTAGE:
480.
EQUIV. IMPEDANCE= 0.0028 + J 0.0487 OHMS
LOW VOLTAGE POWER CIRCUIT BREAKER
6.438 KA
MOLDED CASE CIRCUIT BREAKER < 10KA
8.972 KA
MOLDED CASE CIRCUIT BREAKER < 20KA
7.604 KA
MOLDED CASE CIRCUIT BREAKER > 20KA
6.835 KA
CBL-0010
BUS-0019
0.212 KA
ANG: -263.94
AUTO-0003
ATS EMER
5.465 KA
ANG:
93.16
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
UNBALANCED LOW VOLTAGE DUTY PAGE
1
U N B A L A N C E D
F A U L T
R E P O R T
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
LOCATION
FAULT
KA
X/R EQUIVALENT (PU) ASYM. KA AT 0.5 CYCLES
VOLTAGE
DUTIES
(RMS)
FAULT IMPEDANCE * MAX. RMS AVG. RMS *
==============================================================================
ATS EMER
3P Duty:
SLG DUTY:
480. VOLTS
LN/LN:
LN/LN/GND:
5.677
6.122
4.142
6.831 (
18. Z1= 21.1886
17. Z2= 29.1103
Z0=
8.6462
9.989 GND RETURN KA)
8.804
9.435
7.334
GENERATOR BUS
5.775
23. Z1= 20.8271
6.309
23. Z2= 28.7603
4.201
Z0=
7.6071
7.086 ( 10.631 GND RETURN KA)
9.159
10.005
7.574
RWP-PNL-030
5.551
5.906
4.065
6.605 (
12. Z1= 21.6690
10. Z2= 29.5864
Z0=
9.8870
9.314 GND RETURN KA)
8.155
8.516
6.921
RWP-PNL-040
1.533
1.572
1.301
1.577 (
3. Z1= 181.0065
3. Z2= 188.6479
Z0= 160.0008
1.684 GND RETURN KA)
1.714
1.751
1.625
RWP-SWB-010
5.677
6.122
4.142
6.831 (
18. Z1= 21.1886
17. Z2= 29.1103
Z0=
8.6463
9.989 GND RETURN KA)
8.804
9.435
7.334
3P Duty:
SLG DUTY:
480. VOLTS
LN/LN:
LN/LN/GND:
3P Duty:
SLG DUTY:
480. VOLTS
LN/LN:
LN/LN/GND:
3P Duty:
SLG DUTY:
208. VOLTS
LN/LN:
LN/LN/GND:
3P Duty:
SLG DUTY:
480. VOLTS
LN/LN:
LN/LN/GND:
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
UNBALANCED LOW VOLTAGE DUTY PAGE
2
F A U L T
S T U D Y
S U M M A R Y
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
BUS RECORD
VOLTAGE A V A I L A B L E
F A U L T
D U T I E S (KA)
NO NAME
L-L
3 PHASE
X/R
LINE/GRND
X/R
==============================================================================
ATS EMER
GENERATOR BUS
RWP-PNL-030
RWP-PNL-040
RWP-SWB-010
480.
480.
480.
208.
480.
5.677
5.775
5.551
1.533
5.677
9 FAULTED BUSES,
19 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
17.80
22.64
11.51
3.01
17.80
6.122
6.309
5.906
1.572
6.122
5 CONTRIBUTIONS
16.78
22.61
10.18
2.96
16.78
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
THREE PHASE MOMENTARY DUTY PAGE
T H R E E
1
P H A S E
M O M E N T A R Y
D U T Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
ATS EMER
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
GENERATOR BUS
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
RWP-PNL-030
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
RWP-PNL-040
VOLTAGE:
208.
( SEE LOW VOLTAGE REPORT )
RWP-SWB-010
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
UNBALANCED MOMENTARY DUTY PAGE
1
M O M E N T A R Y
D U T Y
S U M M A R Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
SOLUTION METHOD
: E/Z
==============================================================================
BUS RECORD
VOLTAGE
* 3 P H A S E *
* * * SLG * * *
NO NAME
L-L
KA
X/R
KA
X/R
==============================================================================
0 FAULTED BUSES,
19 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
THREE PHASE INTERRUPTING DUTY PAGE
T H R E E
1
P H A S E
I N T E R R U P U T I N G
D U T Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
ATS EMER
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
GENERATOR BUS
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
RWP-PNL-030
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
RWP-PNL-040
VOLTAGE:
208.
( SEE LOW VOLTAGE REPORT )
RWP-SWB-010
VOLTAGE:
480.
( SEE LOW VOLTAGE REPORT )
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
UNBALANCED INTERRUPTING DUTY PAGE
1
I N T E R R U P T I N G
D U T Y
S U M M A R Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
NACD OPTION: INTERPOLATED
==============================================================================
BUS RECORD
VOLTAGE NACD
* 3 P H A S E *
* * * S L G * * *
NO NAME
L-L
RATIO
E/Z KA
X/R
E/Z KA
X/R
==============================================================================
0 FAULTED BUSES,
19 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
Sep 09, 2014
19:17:23
-----------------------------------------------------------------------------ALL INFORMATION PRESENTED IS FOR REVIEW, APPROVAL
INTERPRETATION AND APPLICATION BY A REGISTERED ENGINEER ONLY
SKM DISCLAIMS ANY RESPONSIBILITY AND LIABILITY RESULTING
FROM THE USE AND INTERPRETATION OF THIS SOFTWARE.
-----------------------------------------------------------------------------SKM POWER*TOOLS FOR WINDOWS
A_FAULT SHORT CIRCUIT ANALYSIS REPORT
COPYRIGHT SKM SYSTEMS ANALYSIS, INC. 1996-2013
------------------------------------------------------------------------------
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
THREE PHASE LOW VOLTAGE DUTY PAGE
1
T H R E E
P H A S E
F A U L T
R E P O R T
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
UNBALANCED LOW VOLTAGE DUTY PAGE
1
F A U L T
S T U D Y
S U M M A R Y
(FOR APPLICATION OF LOW VOLTAGE BREAKERS)
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
BUS RECORD
VOLTAGE A V A I L A B L E
F A U L T
D U T I E S (KA)
NO NAME
L-L
3 PHASE
X/R
LINE/GRND
X/R
==============================================================================
6 FAULTED BUSES,
19 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
T H R E E
THREE PHASE MOMENTARY DUTY PAGE
1
P H A S E
M O M E N T A R Y
D U T Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
UNBALANCED MOMENTARY DUTY PAGE
1
M O M E N T A R Y
D U T Y
S U M M A R Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
SOLUTION METHOD
: E/Z
==============================================================================
BUS RECORD
VOLTAGE
* 3 P H A S E *
* * * SLG * * *
NO NAME
L-L
KA
X/R
KA
X/R
==============================================================================
0 FAULTED BUSES,
19 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
T H R E E
THREE PHASE INTERRUPTING DUTY PAGE
1
P H A S E
I N T E R R U P U T I N G
D U T Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
==============================================================================
Sep 09, 2014
19:17:23
South Inland Raw Water Pump Station
Bossier City, LA
Proposed - Emergency Operation
UNBALANCED INTERRUPTING DUTY PAGE
1
I N T E R R U P T I N G
D U T Y
S U M M A R Y
R E P O R T
PRE FAULT VOLTAGE: 1.0000
MODEL TRANSFORMER TAPS: NO
NACD OPTION: INTERPOLATED
==============================================================================
BUS RECORD
VOLTAGE NACD
* 3 P H A S E *
* * * S L G * * *
NO NAME
L-L
RATIO
E/Z KA
X/R
E/Z KA
X/R
==============================================================================
0 FAULTED BUSES,
19 BRANCHES,
UNBALANCED FAULTS REQUESTED
*** SHORT CIRCUIT STUDY COMPLETE ***
5 CONTRIBUTIONS
SECTION
4
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
Contents:
4.0
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
Introduction.
Recommendations & Discussion of Results
Discussion of Time Current Coordination Curves
Protective Device Coordination Philosophy.
Calibration and Testing of Protective Devices.
Coordination Procedures.
NEC Requirements.
Table P-1 - Maximum Continuous Ratings of Fuses and Circuit Breakers Permitted
for Various Transformer Voltage Levels and Impedances.
American National Standard for Transformers.
Table P-2 - ANSI Definition of Transformer Thermal and Mechanical Withstand
Curve.
Other Considerations for Protective Device Coordination.
General Discussion of Protective Devices.
Appendixes:
•
•
4.0
Utility Service Information, (1 sheet).
Cable circuit Information, (1 sheet).
Introduction
This section of the report summarizes and discusses the results of a protective device
coordination study. This study was performed using the CAPTOR™ module of PTW for
Windows™ by SKM Systems Analysis, Inc.
4.1
Summary of Recommendations
The power system protective devices contained within the study scope should be set
according to the setting recommendations provided in Section 5 of this report. To the extent
possible, the circuit breaker settings will provide selective operation of the overall protection
scheme. The discussion below cites situations where selectivity is unavoidably compromised.
Refer to the time-current curves provided at the rear of this section of the report upon which
the following discussions are based.
Page 4-1 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
4.2
Discussion of Time Current Coordination Curves
208 Volt Circuits
TCC RWP-PNL-030
The ‘RWP-PNL-030’ TCC shows that the 208V system fed by their respective transformer are
selectively coordinated down to 0.1 seconds. The overlap for the 480V feeder and the 208V
secondary main breaker can occur since they are series devices. Overlap was unavoidable from
the panelboard main breaker and downstream feeder. The panelboard main breaker and
switchboard breaker can overlap since they are series devices. The main switchboard breaker
and downstream breaker are coordinated. The cut off fuse overlaps the main breaker, which is
unavoidable.
TCC RWP-P-401
TCC RWP-P-401 EMER
TCC RWP-SWB-010 GF
TCC RWP-PNL-030 EMER
The time current curves ‘RWP-P-401’, ‘RWP-P-401 EMER’ and ‘RWP-PNL-030 EMER’ shows
complete selectivity from the downstream feeders to the panelboard main breaker and to the
main breaker. As discussed earlier, the cut off fuse overlaps the main breaker, which is
unavoidable. The generator breaker is coordinated with the decrement curve and the overlap
from the generator breaker and the emergency switchboard breaker can occur since they are
series devices.
TCC ‘RWP-SWB-010 GF’ shows that the main breaker ground fault device, because of it’s
inherent sensitivity, will overlap most of the downstream switchboard and panelboard feeder
breakers since they are not equipped with ground fault trip functions with which the main can be
coordinated. However, for higher magnitude ground faults, the main ground fault trip device
time delay will provide selectivity with the downstream breakers.
4.3
Protective Device Coordination Philosophy
The primary function of protective devices in a power system is to detect system disturbances
and isolate the disturbance by activating the appropriate circuit interrupting devices. A
Protective Device Coordination Study is required to properly select the protective devices and,
in the case of adjustable devices, specify the necessary settings so that the intended goals will
be achieved.
By industry standard definition (ANSI C37.100-1972) there is general agreement on the
meaning of the term selectivity:
Selectivity - for a protective system, a general term describing the interrelated
performance of relays and other protective devices, whereby a minimum amount of
equipment is removed from service for isolation of a fault or other abnormality."
Obviously, selectivity is a desirable characteristic in any protection scheme. However, it is not
always possible to obtain the desired degree of system and equipment protection in a
selective fashion. The term COORDINATION is sometimes used to describe a reasonable
Page 4-2 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
compromise, based on an engineering evaluation, between the mutually desirable but
competing objectives of maximum system protection and maximum circuit availability. The
protective device ratings and settings recommended in this study result from an exercise of
judgment as to the best balance between these factors.
The following is a tested, generally accepted philosophy for selecting and setting protective
devices:
1. A "first-zone" or "primary" protective device will remove a faulty circuit as quickly as
possible.
2. If the primary protection fails, a "back-up" protective device will remove the fault.
The protective device settings are individually chosen to accommodate circuit parameters.
The criteria used in determining the recommended settings for the protective devices are as
follows:
1. System or feeder circuit full-load current.
2. Allowance for coordination with downstream devices.
3. Transformer protection in compliance with American National Standards Institute
(ANSI) and National Electrical Code (NEC) requirements.
4. Avoidance of nuisance tripping due to transformer magnetizing inrush currents or
motor inrush currents.
5. Short-circuit currents for faults occurring in the protected zone of the system.
4.4
Calibration and Testing of Protective Devices
The time-current relationships between protective devices as established in this report
requires that the individual device operating characteristics do not depart appreciably from
those shown on the published time-current curves from the manufacturer. The specified
settings will provide operation of the devices essentially as shown. However, device
tolerances and the difficulty in obtaining exact field settings may result in deviations from the
specified operating times. Therefore, it is recommended that the device settings be calibrated
by field tests to insure the desired response.
Satisfactory device coordination depends on operation of the protective devices when
required, even though they may be inactive for long periods of time. To assure continued
proper device action, it is essential that the devices be calibrated and checked at regular
intervals.
4.5
Coordination Procedures
The most convenient way of determining the proper ratings and settings of protective devices
such as low-voltage power circuit breakers, insulated case circuit breakers, fuses and relays is
by plotting time-current curves. These curves are drawn on standard log-log paper and
illustrate the time-current characteristics of each of the protective devices as well as the
Page 4-3 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
protective criteria to be met.
coordination between devices.
Thus, such curves graphically illustrate the time-current
Time-current curves are generally drawn up to the maximum available fault current level for
the system being illustrated. As time goes by systems change and the maximum available
fault will increase. Thus, it is important that the results of this coordination study be reviewed
and updated at periodic intervals.
4.6
NEC Requirements
Enactment of the Federal Occupational Safety and Health Act of 1970 (OSHA) has made strict
compliance with the National Electrical Code (NFPA No. 70, ANSI No. C1) a legal requirement
on all new construction after 15 March 1972. Prior to the enactment of OSHA, industrial plants
were generally exempt from NEC requirements; today the code has the effect of Federal law
although its provisions are generally not retroactively enforceable on equipment installed
before 15 March 1972.
The NEC describes itself as containing "provisions considered necessary for safety." The
NEC was prepared by a team of recognized authorities and is based on firm engineering
principles. Thus, while the NEC may not be strictly enforceable in some of the older portions
of a system, it is a standard by which an entire system can be judged.
Article 240-3 of the NEC Code states that for circuits of voltages up to 600 volts,
"Conductors... shall be protected against overcurrent in accordance with their ampacity".
Page 4-4 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
Table P-1
Maximum Rating or Setting of Overcurrent Protection for Transformers Over 600 Volts as a
Percentage of Transformer Rated Current
From NEC Table 450-3(a)
Primary Side (>600V)
NEC Location
Secondary Side (2)
> 600 V
Definition (3)
Impedance
<=6%
Any
Any
<= 600V
Breaker (4)
Fuse
Breaker (4)
Fuse
CB or Fuse
<=600% (1) <=300% (1) <=300% (1) <=250% (1) <=125% (1)
>6% and <10% <=400% (1) <=300% (1) <=250% (1) <=225% (1) <=125% (1)
Supervised
Any
<=300% (1) <=250% (1) None Reqd None Reqd
Supervised
<=6%
<=600%
<=300%
<=300%
<=250%
<=250%
Supervised
>6% and <10%
<=400%
<=300%
<=250%
<=225%
<=250%
Supervised CTOP (5)
<=6%
<=600%
<=300%
None
None
None
Supervised CTOP (5)
>6% and <10%
<=400%
<=300%
None Reqd None Reqd
None Reqd
None Reqd
Notes: (Also see notes in NEC below Table 450-3(a))
1.
2.
3.
4.
5.
Where rating does not correspond to standard setting or rating next available setting or rating permissible.
Up to six secondary disconnects may be used in lieu of single secondary main. See NEC note for details and
conditions.
A supervised location where conditions of maintenance and supervision ensure that only qualified persons will monitor
and service the transformer installation.
Electronically actuated fuses that may be set to open at a specific current shall be set in accordance with settings for
circuit breakers.
CTOP = “Coordinated Thermal Overload Protection” provided by the transformer manufacturer and arranged to
interrupt the primary circuit.
Table P-2
Maximum Rating or Setting of Overcurrent Protection for Transformers 600 Volts and Less as a
Percentage of Transformer Rated Current
From NEC Table 450-3(b)
Primary Side (<=600V)
Currents
Impedance
Any
1.
2.
3.
Currents
>= 9 amps < 9 amps
<= 125% (1) <= 167%
Secondary Side (2)
Currents
Currents
Currents
< 2 amps >= 9 amps
<= 300%
None
< 9 amps
None
<= 167%
Any
<= 250%
<= 250%
<= 250% <= 125% (1)
<=6% with CTOP (3)
<= 600%
<= 600%
<= 600%
None
None
>6% and <10% with CTOP (3)
<= 400%
<= 400%
<= 400%
None
None
Where rating does not correspond to standard setting or rating next available setting or rating permissible.
Up to six secondary disconnects may be used in lieu of single secondary main. See NEC note for details and
conditions.
CTOP = “Coordinated Thermal Overload Protection” provided by the transformer manufacturer and arranged to
interrupt the primary circuit.
Page 4-5 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
Consequently on 480 volt circuits, the circuit breaker or fuse must be sized to protect the
ampacity of the circuit, (or the next available tap or size if the rating does not exceed 800
amps.)
Paragraph 240-101(a) of the Electrical Code states that, for overcurrent protection of feeders
above a nominal 600 volts, "The continuous ampere rating of a fuse shall not exceed three
times the ampacity of the conductors. The long-time trip element setting of a breaker or the
minimum trip setting of an electronically actuated fuse shall not exceed six times the ampacity
of the conductors."
The code contains tables of ampacity ratings published by the Insulated Power Cable
Engineers Association (IPCEA).
Article 450-3 of the NEC prescribes detailed requirements for transformer protection. These
requirements for protective device ratings or settings in multiples of full-load current are
summarized in Tables P-1 and P-2.
It should be noted that the Code permits a primary feeder protective device to provide the
defined transformer primary protection. Thus, in some cases one circuit breaker and its
associated relays can be used to protect several transformers.
In addition to cable and transformer requirements, the Code also includes extensive
requirements for overload and short-circuit protection of motors. The manufacturers of motor
starters and motor protective relays have recognized these requirements and have
incorporated them in their protection application tables, so that a detailed consideration of the
Code provisions is needed only in special cases.
4.7
American National Standard for Transformers
The ANSI curve, which may be shown on time-current curves, represents the amount of
mechanical and thermal stresses a distribution or power transformer is required to withstand
without injury as specified by ANSI-C57.12-1973.
ANSI Standard C57.109-1985 entitled “Transformer Through-Fault Current Protection Guide”
defines short-circuit through-fault withstand current and time limits for four categories of
transformers. The benchmarks for constructing this curve for the various transformer
categories are shown in Table P-3.
A line-to-ground fault in a system supplied from a delta-solidly grounded wye transformer
produces currents of only 58% of maximum line currents in certain windings and lines.
Similarly, a line-to-line fault on an ungrounded system supplied from a delta-delta transformer
produces currents of only 87% of maximum line currents in certain windings and lines. These
considerations dictate a lower rating or setting of primary protection devices based on either
58% or 87% of the maximum through-fault transformer withstand capability. Refer to Figure T1 which illustrates these relationships.
Page 4-6 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
Figure T-1
To account for this, the withstand curve is shifted to lower current values prior to the selection
Diagrams illustrating why phase fault devices must have added sensitivity for certain types of secondary faults.
All currents are in per unit of a secondary three-phase bolted fault.
DELTA-DELTA TRANSFORMER
THREE
PHASEFAULT
1.0
0.58
0.58
1.0
0.87
0.58
0.58
1.0
PHASEPHASE
FAULT
0.58
0.58
0.29
0.58
0.87
0.29
0.58
1.0
0.0
1.0
0.87
0.29
0.0
0.29
0.87
1.0
Three-phase secondary short-circuit. Maximum
winding currents approach ANSI Standard
withstand with equal per unit fault currents on the
secondary and primary lines.
Phase-to-phase secondary short-circuit. The same
winding current as for a three-phase fault, but 0.87
rather than 1.0 primary line current.
DELTA-WYE TRANSFORMER WITH SECONDARY NEUTRAL SOLIDLY GROUNDED
THREE
PHASEFAULT
1.0
1.0
0.58
LINE-TOGROUND
FAULT
1.0
0.58
1.0
0.0
1.0
1.0
1.0
0.58
0.58
1.0
1.0
0.58
1.0
0.0
1.0
1.0
1.0
Three-phase secondary short-circuit. Maximum
winding currents approach ANSI Standard
withstand with equal per unit fault currents on the
secondary and primary lines.
0.58
0.0
Phase-to-ground secondary short-circuit. For a 1.0
per unit fault current in the secondary, only a 0.58
pu fault is seen in two of the three delta line
connections.
of a protective device, unless the transformer is resistance grounded. Because resistance
grounding limits the fault current to values generally much less than the transformer withstand
capability, only the 100% withstand curve is plotted in these cases.
Page 4-7 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
Table P-3
ANSI Definition of Transformer Thermal and Mechanical Withstand Curve
KVA
Category
Single-Phase
I
5 to 25
15 to 75
40 or 1/Zt*
1250/X
37.5 to 100
112.5 to 300
35 or 1/Zt*
1250/X
167 to 500
500
25 or 1/Zt*
1250/X
II
501 to 1667
501 to 5,000
1/Zt
2t
III
1,668 to 10,000
5,001 to 30,000
1/(Zt+Zs)
2t
IV
Above 10,000
Above 30,000
1/(Zt+Zs)
2t
*
Zt
Zs
X
t
4.8
Withstand Capability
=
=
=
=
=
Three-Phase
Per-Unit Base Current Seconds
Use lowest value of current
Transformer per unit impedance (self-cooled rating).
System per unit impedance on transformer base.
(Chosen per unit base current)2
These points define an I2t curve in the short-time region. This region is from 70% to
100% of maximum through-fault current for Category II and 50% to 100% for
Category III and Category IV.
Other Considerations for Protective Device Coordination
Primary current sensitive instantaneous protective devices for transformers must be set high
enough to prevent false tripping on magnetizing inrush currents when transformers are
energized. If the protective device is set above eight times rated load current for transformers
rated 3 MVA or less and twelve times rated load current for those above 3 MVA (at 0.1
second), this criterion will usually be met for industrial type distribution transformers. For utility
type distribution transformers, twelve times rated load current (at 0.1 second) will usually meet
this criterion.
The time separation or "coordination margin" between time-current characteristics of induction
disk overcurrent relays is determined by the sum of three items; (1) relay overtravel, (2)
breaker fault clearing time, and (3) an arbitrary safety margin. The coordination margin must
exist between the curves at; (1) the highest pickup of the two devices, (2) at the instantaneous
setting of the downstream (i.e., load-side) feeder breaker relay, and (3) at the maximum shortcircuit current which can flow through both devices simultaneously.
A 0.1 second interval is judged to be a conservative overtravel estimate for electromechanical
relays. Breaker fault clearing times typically vary from three to eight cycles on a 60 Hz
system. The safety margin is an arbitrary value assigned by the engineer, usually 0.1 to 0.2
seconds. Thus, the coordination margin is typically 0.3 to 0.4 second for five and eight cycle
breakers. In general 0.35 seconds has been maintained as the minimum margin between
Page 4-8 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
curves although in just a few cases tighter margins may have been allowed based on overall
judgement of the situation.
Tolerance bands are provided for fuses and 480 volt trip devices which include applicable
breaker operating times so that no additional margin is required between these bands. A
margin of 0.2 seconds is typically used as the separation criteria between a downstream 480
volt breaker trip device characteristic and an upstream induction disk relay. A margin of 0.2
seconds is also used in coordination of an upstream relay with a downstream fuse.
Because the use of microprocessor relays eliminates induction disk overtravel, coordination
margins can be reduced. Typically, 0.2 seconds is used between relays and 0.1 seconds
between a relay and a downstream 480 volt trip device or fuse.
4.9
General Discussion of Protective Devices
The elements which make up an overall protective system include relays, low voltage circuit
breaker trip devices, and fuses. Low-voltage power circuit breakers and insulated-case circuit
breakers can be adjusted within certain limits to meet protection and coordination
requirements. In medium and high-voltage systems, relays are used almost exclusively in the
design of a flexible and coordinated protective system.
A brief discussion of typical low voltage trip devices follows.
Low Voltage Breaker Static Trip Devices
Modern air and insulated case circuit breakers and some molded case breakers are equipped
with static trip devices. The device package includes not only a solid state programmer but
current sensors and a means for tripping the breaker with all these components integrally
mounted in the breaker. The current sensors may be single ratio or may have taps for various
current rating selections. The programmer will be equipped with some or all of the following
trip functions. The current pickup adjustments and time ranges cited below are only typical.
There are many variations between various devices and manufacturers.
Long-time trip - An I2t sloped plot (a straight line on a log-log plot) typically adjustable from
50% to 110% of the sensor rating and time band adjustment in several discrete bands from 3
to 25 seconds at six times sensor rating.
Short-time trip - A vertical tolerance band which meets the long time characteristic and then
descends down to a definite time band. The vertical band typically has an adjustable pickup
from 2 to 10 times the sensor current rating. Three or four definite time bands are typically
provided with the middle of the bands at 0.15, 0.25 and 0.4 seconds. Sometimes a fixed or
switched I2t curve capability is provided which alters the (flat) definite time bands to I2t bands
which typically will better coordinate with downstream fuses.
Instantaneous trip - A vertical tolerance band which meets the long time or short time
characteristic at a pickup setting adjustable from 1.5 to 10 times the breaker sensor rating.
The top of the fixed time tolerance band typically is is in the area from 0.02 to 0.05 seconds.
On molded case or insulated case breakers the instantaneous may be a fixed override set at a
given kiloamp current level.
Page 4-9 - Rev 0, 9/9/2014
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Section 4 - Discussion of Coordination Study Results
Ground Fault trip - The ground fault trip characteristic is very similiar to the short time
characteristic in terms of it's shape, definite time band delays and switchable I2t capability.
The difference is in it's pickup setting range where a much more sensitive setting range from
20% to 60% of the breaker current sensor is typical.
All of the above characteristics are plotted with tolerance bands which include circuit breaker
operating time so that in coordinating these devices no additional margin must be left between
characteristics.
Page 4-10 - Rev 0, 9/9/2014
September 5, 2014
To:
Jason Korn
GE Energy
Industrial Solutions
Phone # (806) 252-4037
Fax # (214) 481-2007
E-Mail: Jason.korn@ge.com
RE:
From:
Christopher R. Gray, P.E.
AEP – Southwestern Electric Power
6130 Union Street
Shreveport, LA 71108-3932
Phone # (318) 862-2028
E-Mail: crgray@aep.com
Fault Current – BCWTP South Intake
Jason,
The following maximum fault currents are for the BCWTP South Intake in Bossier City, Louisiana. These
fault currents were calculated by computer model (CYMDist 5.02).
Overcurrent protection should be a C14, 65A Fault-Sensing Bay-O-Net fuse (RTE #4000353C14, or
equivalent) for the transformer, and an 80K riser fuse (Cooper/McGraw # FL6K80, or equivalent).
Note: If design changes are made that change the length/size of secondary wire, size/voltage of the
transformer, length/size of primary line, or source of primary power, the following fault currents would no
longer be correct.
Location
Transformer Information
Cumulative
System
Impedance
(Ohms)
Single Phase
to Ground
Fault Current
(Amps)
Three Phase
Fault Current
(Amps)
Transformer Primary
Terminals
12,470GndY/7,200 V
(Nominal)
R1=0.3078
X1=1.1000
(X/R=3.57);
R0=0.5331
X0=1.6048
(X/R=3.01).
R1=0.0013
X1=0.0104
(X/R=7.80);
R0=0.0017
X0=0.0112
(X/R=6.69).
5,706 A
8,618 A
27,031 A
27,705 A
Shed Road 7530
Transformer
Secondary Terminals
(Point of Service)
Shed Road 7530
Chris Gray
1,500 kVA,
12,470GndY/7,200480GndY/277 V,
Three Phase Padmounted
Transformer
(Z = 5.75%)
TIB-102
TECHNICAL INFORMATION BULLETIN
Alternator Data Sheet
Alternator Model:
5M4030
* Voltage refers to wye (star) connection, unless otherwise specified. Kohler Co. reserves the right to change the design or specifications
without notice and without any obligation or liability whatsoever.
TIB-102
5M4030 60 Hz 4/09k
1
City of Bossier City South Inland Raw Water Pump Station, Bossier City, LA
Cable Data Request - Please complete blank fields.
Call Paul Klein with FEC if you need additional information 318-68
Phase Cable
Copper or
Circuit
Magnetic or
From
To
Qty/Ph
Size
Aluminum Cable
Distance
Non-Mag Conduit
RWP-XF-001
RWP-SWB-010
6
500MCM
Copper
90'
Non-Mag Conduit
GENERATOR
RWP-SWB-010
3
500MCM
Copper
70'
Non-Mag Conduit
RWP-SWB-010
RWP-VFD-401
2
250MCM
Copper
25'
Non-Mag Conduit
RWP-SWB-010
RWP-VFD-402
2
250MCM
Copper
25'
Non-Mag Conduit
RWP-SWB-010
RWP-VFD-403
2
250MCM
Copper
25'
Non-Mag Conduit
RWP-SWB-010
RWP-MCP-420
1
#2AWG
Copper
40'
Non-Mag Conduit
RWP-SWB-010
RWP-PNL-030
1
4/OAWG
Copper
25'
Non-Mag Conduit
Corrected
RWP-PNL-030
RWP-XF-040
1
#4AWG
Copper
10'
Metal
Added to S
RWP-VFD-401
RWP-P-401
1
4/OAWG
Copper
100'
Non-Mag Conduit
RWP-VFD-402
RWP-P-402
1
4/OAWG
Copper
105'
Non-Mag Conduit
RWP-VFD-403
RWP-P-403
1
4/OAWG
Copper
110'
Non-Mag Conduit
RWP-MCP-420
RWP-AC-421
1
#4AWG
Copper
10'
Metal
RWP-XF-040
RWP-PNL-040
1
#2AWG
Copper
10'
Metal
Corrected
Service Pole
RWP-XF-001
140'
Non-Mag Conduit
Added to S
AEP/Swepco-Chris Gray 318-862-2023
SECTION
5
Bossier City South Inland Pump Station
Bossier City, Louisiana
Distributor: Rexel
Contractor: Feazel Electrical
Section 5
Trip Device Setting Sheets
Page 1 of 2
LOW VOLTAGE CIRCUIT BREAKER TRIP DEVICE SETTING SHEET
Bossier City South Inland Pump Station, Bossier City, Louisiana
Main 480V Switchboard RWP-SWB-010
Circuit Breaker
Trip Device
Circuit
Unit
Designation
RWP-SWB-010 MAIN
Plug
Cur Set
Type
(S)
(X)
PU (C)
Delay
PU
GE
SS
EGTU
2000
2000
1.00
C1
1.5
1
GE
SS
EGTU
2000
2000
1.00
C5
2.5
GE
SGLA
RMS
BREAKER
PU
PU
Delay
I2t
OFF
15.0
0.60
2
1
4
OFF
15.0
-
-
-
500
-
Fixed
Fixed
Tracks
Fixed
Fixed
MIN
-
-
-
Fixed
Fixed
MIN
-
-
-
Fixed
Fixed
MIN
-
-
-
LSI
Inst
GE
SGLA
RMS
500
-
Fixed
Fixed
BREAKER
RWP-SWB-010 MAIN BR3
Delay I2t
LSIG
BREAKER
RWP-SWB-010 MAIN BR2
Ground Fault
Inst.
Type
BREAKER
RWP-SWB-010 MAIN BR1
Sensor
Short Time
Mfg.
BREAKER
RWP-SWB-010 MAIN EMER
Long Time
Tracks
Inst
GE
SGLA
RMS
500
-
Fixed
Fixed
Tracks
Inst
Note: Set all downstream GE feeder breakers with RMS trips on "Max" if settings are otherwise not provided.
For motor starters, magnetic only breakers should have their instantaneous devices set no higher than 13 x Motor full load amps.
Rev 0 - 9/9/2014 - Initial Issue
30034550 Settings Rev 0.xls!RWP-SWB-010
Page 2 of 2
LOW VOLTAGE CIRCUIT BREAKER TRIP DEVICE SETTING SHEET
Bossier City South Inland Pump Station, Bossier City, Louisiana
480V Generator
Circuit Breaker
Trip Device
Circuit
Unit
Designation
GEN CB
BREAKER
Mfg.
Type
SQUARE P-FRAME
D
1.0L
Long Time
Ground Fault
Sensor
Plug
Cur Set
Inst.
Type
(S)
(X)
PU (C)
Delay
PU
PU
Delay
I2t
PG
1000
-
1.00
Fixed
2.0
-
-
-
LI
Note: Set all downstream GE feeder breakers with RMS trips on "Max" if settings are otherwise not provided.
For motor starters, magnetic only breakers should have their instantaneous devices set no higher than 13 x Motor full load amps.
Rev 0 - 9/9/2014 - Initial Issue
30034550 Settings Rev 0.xls!GEN
SECTION
6
Bossier City South Inland Pump Station
Bossier City, Louisiana
Distributor: Rexel
Contractor: Feazel Electrical
Section 6
Time Current Curve Plots
CASE 1
1000
Utility XFMR
100
COF
TIME IN SECONDS
Utility XFMR
RWP-SWB-010 MAIN
10
RWP-SWB-010 MAIN BR1
1
RWP-P-401
TX Inrush
0.10
10
10K
1
8626 A
1K
0.01
0.5
100
26143 A
CURRENT IN AMPERES
Reference Voltage: 480
South Inland Raw Water Pump Station
GE Engineering Services, Dallas, Texas
Current Scale x 100
Proposed
TCC Title: RWP-P-401
Bossier City, LA
September 9, 2014
1000
RWP-XF-040
RWP-SWB-010 MAIN
RWP-SWB-010 MAIN BR8
100
TIME IN SECONDS
RWP-PNL-030 MAIN
RWP-PNL-030 BR
RWP-XF-040
10
RWP-PNL-040 MAIN
1
RWP-PNL-040 BR
TX Inrush
0.10
10
1K
1
100
0.01
0.5
10K
26143 A
23169 A
1680 A
CURRENT IN AMPERES
Reference Voltage: 480
South Inland Raw Water Pump Station
GE Engineering Services, Dallas, Texas
Current Scale x 10
Proposed
TCC Title: RWP-PNL-030
Bossier City, LA
September 9, 2014
1000
100
TIME IN SECONDS
RWP-SWB-010 MAIN BR1
10
RWP-SWB-010 MAIN GF
1
0.10
10
10K
1
1K
0.01
0.5
100
26143 A
CURRENT IN AMPERES
Reference Voltage: 480
South Inland Raw Water Pump Station
GE Engineering Services, Dallas, Texas
Current Scale x 100
Proposed
TCC Title: RWP-SWB-010 GF
Bossier City, LA
September 9, 2014
CASE 2
1000
GEN-0001
100
TIME IN SECONDS
Gen SC
10
GEN-0001
GEN O/L
GEN CB
RWP-SWB-010 MAIN EMER
1
RWP-SWB-010 MAIN BR1
RWP-P-401
0.10
9136 A
10
10K
1
1K
0.01
0.5
100
8789 A
CURRENT IN AMPERES
Reference Voltage: 480
South Inland Raw Water Pump Station
GE Engineering Services, Dallas, Texas
Current Scale x 100
Proposed
TCC Title: RWP-P-401 EMER
Bossier City, LA
September 9, 2014
1000
GEN-0001
100
TIME IN SECONDS
Gen SC
GEN-0001
GEN O/L
10
GEN CB
RWP-SWB-010 MAIN EMER
RWP-SWB-010 MAIN BR8
RWP-PNL-030 MAIN
1
RWP-PNL-030 BR
0.10
8144 A
9136 A
10
10K
1
1K
0.01
0.5
100
8789 A
CURRENT IN AMPERES
Reference Voltage: 480
South Inland Raw Water Pump Station
GE Engineering Services, Dallas, Texas
Current Scale x 100
Proposed
TCC Title: RWP-PNL-030 EMER
Bossier City, LA
September 9, 2014
SECTION
7
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, Houston, Texas
Section 7 - Summary and Discussion of Arc-Flash Calculations
Contents:
7.0
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.12
Introduction
Discussion of Results
Study Procedures
Introduction to Arc-Flash Fundamentals
Definitions from NFPA 70E
Definitions from IEEE Std. 1584-2002
Systems Covered by IEEE Std. 1584-2002
IEEE Std. 1584 - Arc-Flash Hazard Analysis Procedure
Arc-Flash Hazard Study Computer Output Explanation
Arc-Flash Hazard Labels
Occupational Safety and Health Administration (OSHA)
Methods for Decreasing Arc-Flash Incident Energies
Appendixes:
•
7.0
Arc-Flash Label Assignments for Normal Settings, (1 - 11” x 17” sheet).
Introduction
This section of the report documents the results of arc-flash calculations and discusses the
latest arc-flash study procedures and definitions. The calculations were performed utilizing the
Power*Tools™ software by SKM Systems Analysis Inc. The Arc-flash study results can be
reviewed in the spreadsheet result summaries contained at the rear of this section of the report.
The latest NFPA 70E standard requires that arc-flash calculations be performed at the
maximum fault condition, as well as a minimum fault condition with the reduced minimum
available from the utility and all plant motors out of service. The 12470 Volt system minimum
and maximum fault available information at the Central Plant was obtained from a study by this
author of the Central Plant Revamp that was performed in the last two years. In addition, the
central plant feeder relays were represented based on information from that same study. It is
likely that some sort of fuse protection is provided in the selector switch arrangement on the
building 2500 kVA transformer primary, but no information on these fuses could be provided so
they could not be represented in this study.
The latest NFPA 70E standard requires that arc-flash calculations be performed at the
maximum fault condition, as well as a minimum fault condition with the reduced minimum
available from the utility and all plant motors out of service. The “MAX” source short-circuit
magnitude was obtained by using the minimum -7.5% ANSI manufacturing tolerance, which for
the 5.75% nominal design impedance transformer is 5.32%. The “Min” source short-circuit
magnitude was obtained by using the maximum +7.5% ANSI manufacturing tolerance, which for
the 5.75% nominal design impedance transformer is 6.18%.
Consequently, the calculation cases specified in Table 7-1 have been performed, and the worst
case for each location summarized in the table provided at the rear of this section of the report.
Page 7-1, Rev 0, 9/12/14
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, Houston, Texas
Section 7 - Summary and Discussion of Arc-Flash Calculations
Table 7-1 - Arc-Flash Calculation Cases Considered
7.1
Case
Fault
Available
ATS
Switching
Firepump
Motor
S0
MAX
Normal
On
S1
MIN
Normal
OFF
S2
MAX
Emergency
On
Discussion of Results
The table at the rear of this section of the report summarizes the arc-flash incident energies
present in the system at various system locations within the scope of the study. Clearly the
results are very good or very bad. At the downstream locations with good breaker protection,
the panelboards are 3.8 Cal/cm^2 or less, except for SDB which is at an energy of 8.8
Cal/cm^2.
However, at the upstream locations including the 1000A busway tap feeder, Swbd GSB and
Switchgear MDS, all arc-flash incident energies are above 40 Cal/cm^2 and this equipment
cannot be worked on energized.
For almost all the 480 Volt panelboards and ATS equipment downstream of the main
switchboards, arc-flash energies are very low – mostly at Category 0 or 1 with just ATS-CPSA
and ATS-CPSB at Category 2. Similarily, the VFDs, all of which are fed by feeder circuit
breakers with instantaneous devices are at low Category 0 levels, except for the CH-1-2 VFD
which is barely into Category 1. Even the 2000 amp bus riser bus plugs, although protected by
a relatively large 2000 ampere circuit breakers, are all at reasonable Category 2 energy levels.
As is typical in the industry, there is an issue on the secondary of the larger 120/208 volt
transformers. Because of the long operating times of the primary protection for low magnitude
secondary faults, higher Category 3 energies result.
However, at upstream locations, energies naturally tend to rise because of higher available
arcing fault currents and in some cases, longer device operating times. At the MSA/MSB main
switchboard, energies are Category 3 in the feeder sections where the energy is controlled by
the main breaker. However, in the main breaker section faults must be interrupted by the utility
line fuses which take a relatively long time to operate for transformer secondary faults, and the
results are above Category 4, with arc-flash energies at 103.9 cal/cm2, and this area of the main
switchboard equipment cannot be working on energized. At the downstream CPSA and CPSB
switchboards, arc-flash energies are very well controlled at Category 2 by the 2000 ampere
main switchboard feeder breakers and/or the main breakers.
The situation on the emergency system switchboards is difficult because the restricted fault
magnitudes result in longer operating times and high arc-flash energies in the upstream
switchboards. At Switchboard ESA, energies are well controlled by the 1600 amp GSA feeder
breaker and ESA main breaker to a relatively low Category 2. However, at Switchboard GSA
and the generator circuit breakers energies are in excess of 40 cal/cm2, and this equipment
cannot be working on energized. For standby emergency equipment however, this typically is
not a problem since any needed work activities can normally be conducted on a non-energized
basis.
Page 7-2, Rev 0, 9/12/14
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, Houston, Texas
Section 7 - Summary and Discussion of Arc-Flash Calculations
The main breakers for switchboards MSA/MSB, CPSA, CPSB and ESA are all equipped with
RELT switches. When put into the maintenance mode they lower arc-flash energies for
locations downstream of the circuit breaker. For the MSA/MSB feeder sections energies are
reduced from Category 3 to 2 and at CPSA/CPSB and ESA, Categories are reduced from 2 to
1. Unfortunately, their use of course does nothing to lower arc-flash energies on the incoming
circuit on the line side of the circuit breakers.
7.2
Study Procedures
Within a lineup of electrical equipment a number of different potential arc energies may be
present. The incoming line and line side terminals of a main breaker will have arc energies
dependent on the timing of the remote upstream protective device. The main equipment bus
will have energies based on the main breaker arc duration times, and the load side of every
feeder will have arc energies which result from the feeder protective device timing
characteristics. However, the information specified on the equipment arc-flash labels will also
be dependent on the physical construction and level of isolating barriers present in the
equipment. Most panelboards, switchboards and motor control centers with no effective
metalclad barriers will have a single label, or multiple labels with the same energy levels, based
on the upstream device operation. Metalclad Switchgear which has physically isolated incoming
line/terminals may have two different labels – one for the main incoming unit, and another for
the remainder of the switchgear where exposure to feeder terminals also results in exposure to
the main bus. Fully compartmentalized metalclad switchgear could have rear access to cable
terminals only, so it is conceivable that individual labels could be provided for these
compartments based on feeder relay timing. However, this is sometimes not done in practice in
order to simplify the number of different arc-flash classifications present. Also, the most
common operation involving exposure to uninsulated conductors, the racking of circuit breakers,
always involves line side, (or bus), and load side stabs, so that the higher line or bus side fault
energy level must be used for all feeders.
The arc-flash results in this study are based upon the following clarifications of arc-flash
calculation procedures:
1) IEEE Std. 1584-2002 equations were used in all arc-flash hazard calculations. IEEE
Std. 1584a-2004–Amendment 1 requires that the second arc current equal to 85% of the
original arc current be calculated only for system voltages under 1000V. The larger of the
two incident energies calculated was used in this study.
2) The following assigned working distances were used in this study for each voltage level
in the scope of the study:
ng D
Voltage
Distance
480 Volt Switchgear
24”
480 Volt Swbds, Panels & MCCs
18”
3) IEEE Standard 1584-2002 specifies that arc-flash calculations do not have to be
performed on 240 or 208 Volt systems which receive power from transformers less than
125 kVA.
Page 7-3, Rev 0, 9/12/14
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, Houston, Texas
Section 7 - Summary and Discussion of Arc-Flash Calculations
4) Informative Annex B of IEEE Std. 1584-2002 states “If the time is longer than two
seconds, consider how long a person is likely to remain in the location of an arc flash. It is
likely that the person exposed to an arc flash will move away quickly if it is physically
possible and two seconds is a reasonable time for calculations. A person in a bucket truck
or a person who has crawled into equipment will need more time to move away.” For this
study, a 2 second maximum time was used in the arc-flash calculations.
5) The arc-flash energies calculated in this report are only valid if the relay settings, trip
device settings and any fuse size changes recommended in the coordination study portion
of this report are fully implemented.
6) Equipment arc-flash labels will be furnished once this arc-flash study has been
reviewed and approved.
It is recommended that this study be repeated whenever any system changes are made that
would affect the fault current levels or the protective device opening times, or in five years as
required by NFPA 70E®, whichever occurs sooner.
Page 7-4, Rev 0, 9/12/14
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, Houston, Texas
Section 7 - Summary and Discussion of Arc-Flash Calculations
7.3
Introduction to Arc-Flash Fundamentals
An arc-flash hazard is a dangerous condition associated with the release of energy caused by
an electrical arc. An arc-flash hazard study should be performed as part of an overall electrical
safety program that determines safety-related work practices before someone approaches
exposed energized electrical conductors or circuit parts. The National Fire Protection
Association, Inc. (NFPA®) includes items such as shock hazard analysis, arc-flash hazard
analysis, arc-flash hazard and shock hazard labels, safety training, and work permits as part of
the requirements of NFPA 70E® – Standard for Electrical Safety in the Workplace®, 2012
Edition. The arc-flash hazard study is a continuation of the short-circuit analysis and protective
device coordination of an electrical system. The short-circuit analysis is used to determine the
first-cycle currents (also called close and latch or momentary), interrupting currents and shortcircuit (withstand) rating of electrical equipment (IEEE Std. 141-1993 – Red Book and IEEE Std.
551-2006 – Violet Book). Results of the protective device coordination study are used to
determine the time required for protective devices to isolate overload or short-circuit conditions
(IEEE Std. 242-2001 – Buff Book). Both the short-circuit study and the protective device
coordination study results are required to perform arc-flash hazard calculations. The outcomes
of the arc-flash hazard study include the incident energy at assigned working distances
throughout the electrical system and the arc-flash protection boundary (IEEE Std. 1584-2002,
IEEE Guide for Performing Arc-Flash Hazard Calculations and its Amendment 1, IEEE Std.
1584a-2004, and Amendment 2 – Changes to Clause 4, IEEE Std. 1584b-2011). The PPE
(personal protective equipment) required can then be specified based on the incident energy
that was calculated by referring to NFPA 70E.
Workers can be killed or seriously injured by arcing faults even without direct contact.
Arcing involves high temperatures of up to or beyond 35,000 degrees Fahrenheit at the
arc terminals, or about four times hotter than the surface temperature of the sun.
Tremendous energy can be released in a very brief time at the initiation of the arc.
Clothing is ignited at distances of several feet caused by the resulting thermal energy.
Severe or fatal burns at distances of 10’ are common.
Arc-Blast: When an arcing fault occurs, thermal escalation of the air and vaporization of metal
can create a very loud explosion and tremendous pressures. Conductors can vaporize resulting
in ionized gases, hot vapors, molten metal and shrapnel being violently expelled from the arc
area.
This can result in ruptured eardrums, collapsed lungs, and forces that violently knock
workers backwards. Copper expands as it becomes vaporized by the intense heat. Its volume
expands to 67,000 times the volume of solid copper.
Personal Protective Equipment (PPE) for shock and arc-flash hazards includes the
clothing, gloves, footwear and headwear that help to mitigate the effects of an arc-flash
event for a worker who is exposed. PPE is generally determined to protect the head and
body against thermal effects that would cause severe burns. It does not necessarily
protect from the possible impact of any harmful light, sound, or pressure impulses, toxic
gas by-products or ejected debris.
NFPA 70E® – Standard for Electrical Safety in the Workplace®, 2012 Edition addresses arcflash and shock hazards, including these excerpts. Several definitions are provided after these
excerpts.
Page 7-5, Rev 0, 9/12/14
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xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, Houston, Texas
Section 7 - Summary and Discussion of Arc-Flash Calculations
Arc Flash Hazard Analysis. “A study investigating a worker’s potential exposure to arc
flash energy, conducted for the purpose of injury prevention and the determination of safe
work practices, arc flash boundary, and the appropriate levels of PPE.” Article 130.5 states
that “An arc flash hazard analysis shall determine the arc flash boundary, the incident
energy at the working distance, and the personal protective equipment that people within the
arc flash boundary shall use.”
Article 130.3(B) Working Within the Limited Approach Boundary of Exposed Electrical
Conductors or Circuit Parts that Are or Might Become Energized addresses the Electrical
Hazard Analysis. “If the energized electrical conductors or circuit parts operating at 50
volts or more are not placed in an electrically safe work condition, other safety-related work
practices shall be used to protect employees who might be exposed to the electrical hazards
involved.” It goes on to require that work practices protect employees from arc flash and
from coming into contact with energized electrical conductors or circuit parts. It states that
“Appropriate safety-related work practices shall be determined before any person is
exposed to the electrical hazards involved by using both shock hazard analysis and arc
flash hazard analysis.”
Shock Hazard. “A dangerous condition associated with the possible release of energy
caused by contact or approach to energized electrical conductors or circuit parts.” Article
130.4(A) states that, “A shock hazard analysis shall determine the voltage to which
personnel will be exposed, boundary requirements, and the personal protective equipment
necessary in order to minimize the possibility of electrical shock to personnel.
130.5(B) Protective Clothing and Other Personal Protective Equipment (PPE) for
Application with an Arc Flash Hazard Analysis. This covers, among other things, the
uses and types of personal protective clothing and equipment required when working on
energized electrical equipment within the arc flash boundary. It states that one of two
methods shall be used for the selection of protective clothing and other PPE. The first
method is the Incident Energy Analysis. “The incident energy analysis shall determine, and
the employer shall document, the incident energy exposure of the worker (in calories per
square centimeter). The incident energy exposure level shall be based on the working
distance of the employee’s face and chest areas from a prospective arc source for the
specific task to be performed. Arc-rated clothing and other personal protective equipment
(PPE) shall be used by the employee based on the incident energy exposure associated
with the specific task. Recognizing that incident energy increases as the distance from the
arc flash decreases, additional PPE shall be used for any parts of the body that are closer
than the distance at which the incident energy was determined.” An informational note
references Informative Annex H for selection of arc-rated clothing and other PPE,
specifically, Table H.3(b)
The second method that is permitted by 130.5(B)(2) to be used to select personal protective
equipment and other protective equipment is through use of the Hazard/Risk Categories by
using Tables 130.7(C)(15) and 130.7(C)(16). Note that to use Tables 130.7(C)(15) and
130.7(C)(16), the parameters inside the table must be followed that indicate the maximum
short-circuit current, fault clearing time, and minimum working distance for which the results
are valid. They also state the potential arc flash boundary.
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130.7(C)(6) Body Protection. “Employees shall wear arc-rated clothing whenever there is
possible exposure to an electric arc flash above the threshold incident energy level for a
second-degree burn, [5 J/cm2 (1.2 cal/cm2)].”
130.7(C)(1) INFORMATIONAL NOTE NO. 2: “The PPE requirements of this section are
intended to protect a person from arc flash and shock hazards. While some situations could
result in burns to the skin, even with the protection described in Table 130.7(C)(16), burn
injury should be reduced and survivable. Due to the explosive effect of some arc events,
physical trauma injuries could occur. The PPE requirements of this article do not address
protection against physical trauma other than exposure to the thermal effects of an arc
flash.”
7.4
Definitions from NFPA 70E
From Article 100 – Definitions:
Boundary, Arc Flash Protection – “When an arc flash hazard exists, an approach limit at a
distance from a prospective arc source within which a person could receive a second
degree burn if an electrical arc flash were to occur.”
Note: The onset of a second-degree burn is assumed to be when the skin receives 5.0
J/cm2 (1.2 cal/cm2) of incident energy (skin temperature remains less than 80 degrees C,
176 degrees F).
Boundary, Limited Approach – “An approach limit at a distance from an exposed energized
electrical conductor or circuit part within which a shock hazard exists.”
Boundary, Restricted Approach – “An approach limit at a distance from an exposed
energized electrical conductor or circuit part within which there is an increased risk of shock,
due to electrical arc-over combined with inadvertent movement, for personnel working in
close proximity to the energized electrical conductor or circuit part.”
Boundary, Prohibited Approach – “An approach limit at a distance from an exposed
energized electrical conductor or circuit part within which work is considered the same as
making contact with the electrical conductor or circuit part.”
Qualified Person – “One who has skills and knowledge related to the construction and
operation of the electrical equipment and installations and has received safety training to
recognize and avoid the hazards involved.”
Arc Rating – “The value attributed to materials that describes their performance to exposure
to an electrical arc discharge. The arc rating is expressed in cal/cm2 and is derived from the
determined value of the arc thermal performance value (ATPV) or energy of breakopen
threshold (EBT) (should a material system exhibit a breakopen response below the ATPV
value). Arc rating is reported as either ATPV or EBT, whichever is the lower value.
Arc Rating Informational Note No. 1: Arc-rated clothing or equipment indicates that it
has been tested for exposure to an electric arc. Flame-Resistant (FR) clothing without
an arc rating has not been tested for exposure to an electric arc.
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Arc Flash Suit – “A complete arc-rated clothing and equipment system that covers the entire
body, except for the hands and feet.”
Arc Flash Suit Informational Note: “An arc flash sutie may include pants or overalls, a
jacket or a coverall, and a beekeeper-type hood fitted with a face shield.”
7.5
Definitions from IEEE Std. 1584-2002
Flash hazard analysis – “A method to determine the risk of personal injury as a result of
exposure to incident energy from an electrical arc-flash.”
Shock hazard – “A dangerous condition associated with the possible release of energy
caused by contact or approach to live parts.”
Exposed (live parts) – “Capable of being inadvertently touched or approached nearer than a
safe distance by a person. It is applied to parts that are not suitably guarded, isolated, or
insulated.”
Electrical Hazard – “A dangerous condition in which inadvertent or unintentional contact or
equipment failure can result in shock, arc-flash burn, thermal burn, or blast.”
Incident Energy – “The amount of energy impressed on a surface, a certain distance from
the source, generated during an electrical arc event. Incident energy is measured in joules
per centimeter squared (J/cm2).” [Note: A joule is defined as a watt second. J/cm2 in the SI
system is divided by 4.184 to obtain the CGS system unit of calories per centimeter squared
(cal/cm2)]
Burn Definitions (not a part of 1584): The skin is made up of two layers, the surface layer called
the epidermis, and the more sensitive dermis underneath. Burns that only affect the epidermis
are known as first-degree burns and are the least severe type of burns. The area may be red,
slightly swollen and sensitive to the touch, but blisters do not form. Within a few days, the skin
heals and the damaged layer of sin may peel off. Once the epidermis has been destroyed, the
more sensitive lower dermis layer is vulnerable to damage. Damage to both of these two layers
is known as a second-degree burn and is usually very painful. The skin becomes red and
covered with large blisters filled with clear fluid. After about three days the pain usually
decreases, and most second-degree burns should be fully healed within 14 days. Third degree
burns are the most severe type of burns and extend into deeper tissue. (Burn definitions were
taken from American College of Physicians Complete Home Medical Guide, 1999)
7.6
Systems Covered by IEEE Std. 1584-2002
This arc-flash hazard study was performed utilizing equations from IEEE Std. 1584-2002, Guide
for Performing Arc-Flash Hazard Calculations and its amendments, IEEE Std. 1584a-2004 and
IEEE Std. 1584b-2011. The guide is based on the use of test data and is designed for systems
having:
•
•
•
Voltages in the range of 208 V – 15,000 V, three phase
Frequencies of 50 Hz or 60 Hz
Bolted fault current in the range of 700 A – 106,000 A
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•
•
•
•
7.7
Grounding of all types and ungrounded
Equipment enclosures of commonly available sizes
Gaps between conductors of 13 mm – 152 mm
Faults involving three phase
IEEE Std. 1584 - Arc-Flash Hazard Analysis Procedure
The process for performing an arc-flash hazard study is as follows:
1. Data collection. Obtain up-to-date one-line diagram, short-circuit study, protective
device coordination study or collect all the necessary data to perform them along with
the needed arc-flash data. This data includes but is not limited to all impedance data, i.e.
transformers, generators, motors, cables, busways, transmission lines; all protective
devices, i.e. circuit breakers, protective relays and their CTs, fuses, switches; specific arcflash information such as system grounding configuration, conductors enclosed or in
open air, class of equipment, and gap distance between conductors (table lookup by
voltage). IEEE Std. 1584b-2011 states in Section 4.2 Step 1: “Equipment below 240 V
need not be considered unless it involves at least one 125 kVA or larger transformer in its
immediate power supply.” In Section 9.3.2 it states: “The arc-flash hazard need only be
considered for large 208 V systems: systems fed by transformers smaller than 125 kVA
should not be a concern.” IEEE Std. 1584b-2011 also directs, “Obtain the minimum and
maximum available fault MVA and power angle or X/R ratio from the utility supplying
service or for the separately derived power system. Do not use overly conservative
bolted fault current values.”
2. Identify the various operating modes. Identify utility feeders in/out of service, main and
tie breaker positions, Unit Subs and MCCs fed from multiple sources, generators in
parallel or in standby mode, utility system normal switching set for maximum possible
fault MVA; utility system normal switching configured for minimum possible fault MVA;
separately derived sources (generators)—maximum capacity on-line; separately derived
sources (generators) minimum number on line. The short-circuit study should identify the
minimum and maximum fault currents for the available switching conditions.
3. Calculate the bolted fault currents and X/R ratios at each bus.
4. Calculate the arcing fault currents utilizing equations 1 and 2 found in section 5.2 of IEEE
Std. 1584-2002.
For applications with a system voltage under 1000V:
lg I a = K + 0.662 lg I bf + 0.0966 V + 0.000526 G + 0.5588 V (lg I bf )
where:
− 0.00304 G (lg I bf )
lg
Ia
K
(Section 5.2, Equation 1)
is the log 10
is arcing current (kA)
is –0.153 for open configurations and
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is –0.097 for box configurations
is bolted fault current for three-phase faults (symmetrical RMS) (kA)
is system voltage (kV)
is the gap between conductors, (mm) (see Table 4 of IEEE Std. 1584)
I bf
V
G
For applications with a system voltage of 1000 V and higher:
(Section 5.2, Equation 2)
lg I a = 0.00402 + 0.983 lg I bf
The high-voltage case makes no distinction between open and box configurations.
Convert from lg:
I a = 10
lg I a
(Section 5.2, Equation 3)
For application with a system voltage under 1000 V**, calculate a second arc current
equal to 85% of I a , so that a second arc duration can be determined. See the discussion
in section 9.10.4 of IEEE Std. 1584. It talks about the difficulties in predicting arc current
accurately, and that a minor change in current could make a major change in operating
time–hence changing the incident energy.
** IEEE Std. 1584a-2004 change
Table 4 of IEEE Std. 1584 (renumbered Table 3 by inference in 1584b)
Factors for equipment and voltage classesa
System
voltage (kV)
Typical gap between
Distance x
conductors (mm)
factor
Open air
10 – 40
2.000
Switchgear
32
1.473
0.208 – 1
MCC and panels
25
1.641
Cable
13
2.000
Open air
13-102
2.000
>1–5
Switchgear
13-102
0.973
Cable
13
2.000
Open air
13-153
2.000
> 5 – 15
Switchgear
153
0.973
Cable
13
2.000
a - The distance x factor is used in Section 5.3, equation 6
and Section 5.5, equation 8 as a distance exponent.
Equipment type
5. Find the protective device characteristics and the duration of the arcs. A recent
coordination study is best. Fuse clearing times are used. For fuses with only average
melt times shown, add 10%, plus 0.004 seconds to that time to determine total clearing
time. If the total clearing time at the arcing fault current is less than 10 milliseconds, use
0.01 seconds for the time.
If low-voltage power circuit breakers are equipped with retrofit kits, the time-current
curve may, or may not include the breaker operating time. If the curve only shows the
trip unit’s operating time, a breaker operating time of 0.05 seconds should be added.
For relays operating in their instantaneous region, allow 16 milliseconds (60 Hz systems)
for operation. The circuit breaker opening time must then be added after consulting the
manufacturer’s literature. For low-voltage (<1 kV) relay operated power circuit breakers
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(non-integral trip), the interrupting times is typically 0.05 seconds (three cycles).
Interrupting times for MV and HV breakers can be verified by consulting the
manufacturer’s literature or the breaker nameplate data.
6. Document the system voltages and classes of equipment.
Table 2 of IEEE Std. 1584 (renumbered Table 1 in 1584b)
Classes of equipment and typical bus gaps
Classes of equipment
15 kV switchgear
5 kV switchgear
Low-voltage switchgear
Low-voltage MCCs and panelboards
Cable
Other
Typical bus gaps (mm)
152
104
32
25
13
Not required
Typical bus gaps (in)
6
4
1.25
1
0.5
Not required
7. Select the working distances.
The incident energy level on the person’s head and torso at the working distance, not the
incident energy on the hands or arms is what is calculated. The degree of injury in a burn
depends on the percentage of a person’s skin that is burned. The head and torso make
up a large percent of the total skin surface area and injury to these areas is much more
life threatening than burns on the extremities.
Table 3 of IEEE Std. 1584 (renumbered Table 2 in 1584b)
Classes of equipment and typical working distances
Classes of equipment
Typical working
Typical working
distancea (mm)
distancea (in)
15 kV switchgear
910
36
5 kV switchgear
910
36
Low-voltage switchgear
610
24
Low-voltage MCCs and panelboards
455
18
Cable
455
18
Other
To be determined in field
To be determined in field
aTypical working distance is the sum of the distance between the worker standing in front of the equipment,
and from the front of the equipment to the potential arc source inside the equipment.
8. Calculate the incident energy for all equipment.
The basic equations are found in section 5.3 of IEEE Std. 1584 – equations 4, 5, 6, & 7.
lg En = K1 + K 2 + 1.081 lg I a + 0.0011 G
Where:
En
K1
K2
G
Then:
En = 10
lg En
(Section 5.3, Equation 4)
is incident energy (J/cm2) normalized for time and distance*
is –0.792 for open configuration (no enclosure) and
is –0.555 for box configuration (enclosed equipment)
is 0 for ungrounded and high-resistance grounded systems and
is –0.113 for grounded systems
is the gap between conductors (mm) (see Table 4, IEEE Std. 1584)
* - measurement utilized in test laboratories was cal/cm2
(Section 5.3, Equation 5)
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Finally, convert from normalized:
x 

 t   610 
E = 4.184 C E 

f
n
 0.2   D x 


Where:
E
Cf
En
t
D
x
(Section 5.3, Equation 6)
is incident energy (J/cm2)
is a calculation factor
1.0 for voltages above 1kV, and
1.5 for voltages at or below 1kV
is incident energy normalized
is arcing time (seconds)
is distance from the possible arc point to the person (mm)
is the distance exponent from IEEE Std. 1584’s Table 4
Also, the theoretically derived Lee method is utilized for cases over 15kV, or gap is outside
the range of the model. Ralph Lee developed a theory-based model of the arc flash that
served for many years as the only method available, even though it did not include a
method of finding arc current.
Lee Method:
E = 2.142 X 10 6 V I
Where:
E
V
t
D
I bf
bf
 t 


 2
D 
(Section 5.3, Equation 7)
is incident energy (J/cm2)
is system voltage (kV)
is arcing time (seconds)
is distance from the possible arc point to person (mm)
is bolted fault current
For voltages over 15kV, arc fault current is considered to be equal to the bolted fault
current.
It is important to realize that in evaluating the incident energy at an arcing fault location
in the system, the protective device upstream from the point of the fault must be
considered. An integral ‘main’ overcurrent protective device may be considered in the
calculation if it is adequately isolated from the bus to prevent escalation to a line-side
fault. When the integral main overcurrent protective device is not adequately isolated
from the bus, the upstream protective device must be considered as protecting the main
and bus.
9. Calculate the flash-protection boundary for all equipment.
The equations are found in section 5.5 of IEEE Std. 1584, equations 8 and 9.
For the IEEE Std. 1584-2002 empirically derived model:
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1
 x

 t   610

DB = 4.184 Cf En 
 
 0.2   EB 

x
(Section 5.5, Equation 8)
For the Lee method:
 t 
6

DB = 2.142 X 10 V I bf 
 EB 
Where:
DB
Cf
En
EB
t
x
I bf
(Section 5.5, Equation 9)
is the distance of the boundary from the arcing point (mm)
is a calculation factor
1.0 for voltages above 1kV, and
1.5 for voltages at or below 1kV
is incident energy normalized*
is incident energy in J/cm2 at the boundary distance
is time (seconds)
is the distance exponent from IEEE Std. 1584’s Table 4
is bolted fault current
E B can be set at 5.0 J/cm2 for bare skin (no hood) or at the rating of proposed PPE.**
* Measurement utilized in test laboratories was cal/cm2
** 5.0 J/cm2 = 1.2 cal/cm2
7.8
Arc-Flash Hazard Study Computer Output Explanation
In this study, GE performed the arc-flash hazard calculations using the IEEE Std. 1584-2002
equations with the IEEE Std. 1584a-2004 Amendment 1 and IEEE Std. 1584b-2011
Amendment 2. This typically results in more conservative results than other methods, hence
requiring greater PPE (personal protective equipment). The selection of PPE should be based
on NFPA 70E, 2012 Edition’s Table H.3(b) that provides guidance on selection of proper PPE.
Arc Fault Bus Name – Uniquely identifies the system location where the three-phase bolted fault is calculated.
Arc Fault Bus kV – Nominal line-to-line kV rating for the faulted bus.
Upstream Trip Device Name – For each bus at least one and sometimes more data lines will be provided.
There will be a unique device name on each line. The arc-flash calculations use the clearing time for the
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protective device named on this line. There can be more than one device for a given bus since alternate arcflash calculations may be performed for alternate relay actions. For instance, a bus may have arc-flash
calculations for clearing times based on 87B-Bus Differential operation or on 51-Time Overcurrent relay
operation of the main breaker. The fault current will be the same in each case but the incident energy will be
much worse for the latter relay because of its longer operating time.
Upstream Trip Device Function – ANSI Standard Device Function Number
Equipment Type – IEEE Std. 1584 arc-flash calculations assume bus separation distances based on the
equipment type and voltage rating categories
Gnd – Arc-Flash “Ground” Status. This column shows a Y for “yes,” or N for “no” depending if the system is
solidly-grounded and an arc-flash reduction is taken (per IEEE Std. 1584).
Arc Gap (mm) – This is the arc gap distance derived from Standards based on the equipment type and voltage
rating.
Bolted Fault (kA) – The calculated first-cycle symmetrical bolted three-phase fault current in kiloamps (branch
current).
Est. Arc Fault (kA) – The estimated first-cycle three-phase arcing fault current in kiloamps. If this value is
preceded by an asterisk (*), it indicates that a second arc-flash calculation made with an arcing fault current
different from 100% found a worst-case incident energy. Arc-flash calculations are made at 100% of
estimated arcing fault current and typically at 85% of estimated arcing fault current for buses less than 1000
V, per IEEE Std. 1584a.
Trip Time (sec) – The protective device operating time.
Opening Time (sec) – The circuit breaker operating time. For fuses and low-voltage breakers the operating
time will be zero since the opening timing is already taken into account in the “Trip Time (sec).”
Arc Time (sec) – This is simply the sum of the device tripping time plus the circuit breaker opening time and is
the arcing fault duration for purposes of the incident energy calculations.
Est. Arc Flash Boundary (inches) – The Arc-Flash Boundary is an approach limit at a distance from live parts
that are uninsulated or exposed, within which a person could receive a second-degree burn. More specifically,
this is the distance where the incident energy level equals 1.2 cal/cm2. When live parts are exposed, any
personnel who come within this boundary must wear appropriate arc-flash protection clothing.
Working Distance (inches) – The distance from the possible arc point to the head and torso of the worker
positioned in place to perform the assigned task. For low voltages, this is typically assumed to be the distance
from the fingers to the main body parts such as the face and chest, approximately 18”. The working distance
varies with equipment operating voltage. Unless the customer provided different working conditions, typical
working distances found in IEEE Std. 1584b Table 2 (up to 15 kV) and the IEEE National Electric Safety Code Table
441-1’s phase to ground approach distances (in inches) were used in this study. The arc-flash hazard table
shows the working distance used for each calculation.
Summary of Working Distances from the Various Standards
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Voltage
0.050 – 0.300 kV
0.301 – 0.750 kV
0.751 – 5.0 kV
5.1 –15.0 kV
15.1 –36.0 kV
36.1 –46.0 kV
46.1 –72.5 kV
72.6 – 121 kV
121.1 – 145 kV
145.1 – 169 kV
169.1 – 242 kV
242.1 – 362 kV
362.1 – 550 kV
550.1 – 800 kV
Enclosed
Working
Distance
18 ”
18 ”
36 ”
36 ”
36 ”
31 ”
35 “
37 “
42 “
48 “
63 “
101 “
133 “
179 “
Open Air
Working
Distance
18 ”
18 ”
26 ”
26 ”
29 ”
31 ”
35 “
37 “
42 “
48 “
63 “
101 “
133 “
179 “
Standard*
IEEE 1584-2002
IEEE 1584-2002 / Min. 18 ”
IEEE 1584-2002 / C2-2012
IEEE 1584-2002 / C2-2012
Min. 36 ” / IEEE C2-2012
IEEE C2-2012
IEEE C2-2012
IEEE C2-2012
IEEE C2-2012
IEEE C2-2012
IEEE C2-2012
IEEE C2-2012
IEEE C2-2012
IEEE C2-2012
*IEEE Std. 1584-2002, Table 2, Classes of equipment and typical working distances
For LV Switchgear use 18” rather than 24” to be conservative, or provide two distances
*IEEE Std. C2-2012, National Electrical Safety Code, Table 441.1, AC live work minimum
approach distance
Enclosed Working Distances that are shaded don’t exist. Could use same as Open Air
Incident Energy (cal/cm2) – The result of the AF calculations provide the needed incident energy so that
Personal Protective Equipment may be selected that is greater than this calculated value. It is the amount of
energy impressed on a surface, a certain distance from the source, generated during an electrical arc event.
When the value in the column exceeds 40.0 cal/cm2, the cell is highlighted in yellow and its text is changed to
red to indicate an Extreme Danger condition.
Note: When the incident energy calculated is greater than 40 cal/cm2, the arc-flash and shock hazard
warning labels show “EXTREME DANGER – Do Not Work on Equipment Energized” in their Appropriate
PPE section of the label.
The following tables from NFPA 70E-2012 are shown on the next pages: Table H.3(b), Guidance on Selection of
Arc-Rated Clothing and Other PPE (used with the calculated method) and Table 130.7*(C)(16), Protective
Clothing and PPE (used with the Hazard/Risk Task Table method.
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Section 7 - Summary and Discussion of Arc-Flash Calculations
NFPA 70E — Table H.3(b)
Guidance on Selection of Arc-Rated Clothing and Other Personal Protective Equipment (PPE) for
Use When Incident Energy Exposure is Determined by a Hazard Analysis
Incident Energy Exposure
Protective Clothing and PPE
Less than or Equal to 1.2 cal/cm2
Protective clothing, nonmelting (in accordance with
Shirt (long sleeve) and pants (long) or coverall
ASTM F 1506-08) or untreated natural fiber
Other personal protective equipment
Face shield for projectile protection (AN)
Safety glasses or safety goggles (SR)
Hearing protection
Heavy-duty leather gloves or rubber insulating gloves with
leather protectors (AN)
Greater than 1.2 cal/cm2 to 12 cal/cm2
Arc-rated clothing and equipment with an arc rating
Arc-rated long-sleeve shirt and arc-rated pants or arc-rated
equal to or greater than the incident energy
coverall or arc flash suit (SR) (See Note 3.)
Arc-rated face shield and arc-rated balaclava or arc flash
determined in a hazard analysis (See Note 3.)
suit hood (SR) (See Note 1.)
Arc-rated jacket, parka, or rainwear (AN)
Other personal protective equipment
Hard hat
Arc-rated hard hat liner (AN)
Safety glasses or safety goggles (SR)
Hearing protection
Heavy-duty leather gloves or rubber insulating gloves with
leather protectors (SR) (See Note 4.)
Leather work shoes
Greater than 12 cal/cm2
Arc-rated clothing and equipment with an arc rating
Arc-rated long-sleeve shirt and arc-rated pants or arc-rated
equal to or greater than the incident energy
coverall and/or arc flash suit (SR)
Arc-rated arc flash suit hood
determined in a hazard analysis (See Note 3.)
Arc-rated gloves
Arc-rated jacket, parka, or rainwear (AN)
Other personal protective equipment
Hard hat
Arc-rated hard hat liner (AN)
Safety glasses or safety goggles (SR)
Hearing protection
Rubber insulating gloves with leather protectors (SR) (See
Note 4.)
Leather work shoes
AN: As needed [in addition to the protective clothing and PPE required by 130.5(B)(1)].
SR: Selection of one in group is required by 130.5(B)(1).
Notes:
(1)
Face shields with a wrap-around guarding to protect the face, chin, forehead, ears, and neck area required by
130.8(C)(10)(c). For full head and neck protection, use a balaclava or an arc flash hood.
(2)
All items not designated “AN” are required by 130.7(C).
(3)
Arc ratings can be for a single layer, such as an arc-rated shirt and pants or a coverall, or for an arc flash suit or a
multi-layer system consisting of a combination of arc-rated shirt and pants, coverall and arc flash suit.
(4)
Rubber insulating gloves with leather protectors provide arc flash protection in addition to shock protection.
Higher class rubber insulating gloves with leather protectors, due to their increased material thickness, provide
increased arc flash protection.
Editorial note (from GE): Table H.3(a) specifies that Heavy-duty leather work shoes are required for exposures > 4 cal/cm2 and
“As Needed” for exposures ≤ 4 cal/cm2.
Page 7-16, Rev 0, 9/12/14
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Section 7 - Summary and Discussion of Arc-Flash Calculations
From NFPA 70E 2012 Edition –
130.7(C)(16) Protective Clothing and Personal Protective Equipment (PPE)
Hazard/Risk
Category
0
1
2
3
4
Protective Clothing and PPE
Protective Clothing, Nonmelting or Untreated Natural Fiber
(i.e., untreated cotton, wool, rayon, or silk, or blends of these materials) with a Fabric Weight of at Least 4.5
oz/yd2
Shirt (long sleeve)
Pants (long)
Protective Equipment
Safety glasses or safety goggles (SR)
Hearing protection (ear canal inserts)
Heavy duty leather gloves (AN) (See Note 1.)
Arc-Rated Clothing, Minimum Arc Rating of 4 cal/cm2 (See Note 3.)
Arc-rated long-sleeve shirt and pants or arc-rated coverall
Arc-rated face shield (See Note 2) or arc flash suit hood
Arc-rated jacket, parka, rainwear, or hard hat liner (AN)
Protective Equipment
Hard hat
Safety glasses or safety goggles (SR)
Hearing protection (ear canal inserts)
Heavy duty leather gloves (See Note 1.)
Leather work shoes (AN)
Arc-Rated Clothing, Minimum Arc Rating of 8 cal/cm2 (See Note 3.)
Arc-rated long–sleeve shirt and pants or arc-rated coverall
Arc-rated flash suit hood or arc-rated face shield (See Note 2) and arc-rated balaclava
Arc-rated jacket, parka, rainwear, or hard hat liner (AN)
Protective Equipment
Hard hat
Safety glasses or safety goggles (SR)
Hearing protection (ear canal inserts)
Heavy duty leather gloves (See Note 1.)
Leather work shoes
Arc-rated Clothing, Selected so That the System Arc Rating Meets the Required Minimum Arc Rating of 25
cal/cm2 (See Note 3.)
Arc-rated long–sleeve shirt (AR)
Arc-rated pants (AR)
Arc-rated coverall (AR)
Arc-rated arc flash suit jacket (AR)
Arc-rated arc flash suit pants (AR)
Arc-rated arc flash suit hood
Arc-rated jacket, parka, rainwear, or hard hat liner (AN)
Protective Equipment
Hard hat
Safety glasses or safety goggles (SR)
Hearing protection (ear canal inserts)
Leather work shoes
Arc-Rated Clothing, Selected so That the System Arc Rating Meets the Required Minimum Arc Rating of 40
cal/cm2 (See Note 3.)
Arc-rated long–sleeve shirt (AR)
Arc-rated pants (AR)
Arc-rated coverall (AR)
Arc-rated arc flash suit jacket (AR)
Arc-rated arc flash suit pants (AR)
Arc-rated arc flash suit hood
Arc-rated gloves (See Note 1.)
Arc-rated jacket, parka, rainwear, or hard hat liner (AN)
Page 7-17, Rev 0, 9/12/14
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Section 7 - Summary and Discussion of Arc-Flash Calculations
Protective Equipment
Hard hat
Safety glasses or safety goggles (SR)
Hearing protection (ear canal inserts)
Leather work shoes
N = As needed (optional)
AR = As required
SR = Selection required
Table 130.7(C)(16) Notes
(1) If rubber insulating gloves with leather protectors are required by Table 130.7(C)(15)(a) and Table
130.7(C)(15)(b), additional leather or arc-rated gloves are not required. The combination rubber
insulating gloves with leather protectors satisfies the arc flash protection requirement.
(2) Face shields are to have a wrap-around guarding to protect not only the face but also the forehead,
ears, and neck, or alternatively, an arc-rated flash suit hood is required to be worn.
(3) Arc rating is defined in Article 100 and can be either the arc thermal performance value (ATPV) or energy
of break open threshold (EBT). ATPV is defined in ASTM F 1959, Standard Test Method for Determining
the Arc Thermal Performance Value of Materials for Clothing, as the incident energy on a material, or a
tested specimen is predicted to cause the onset of a second-degree skin burn injury based on the Stoll
curve, in cal/cm2. EBT is defined in ASTM F 1959 as the incident energy on a material or material system
that results in a 50 percent probability of breakopen. Arc rating is reported as either ATPV or EBT,
whichever is the lower value.
Note: ASTM International = Organization formerly known as American Society for Testing and Materials, today
provides technical standards for materials, products, systems, and services
NFPA 70E, 2012 Edition Article 130.7(C)(6) addresses Body Protection. 130.7(C)(5) Body Protection.
“Employees shall wear arc-rated clothing whenever there is possible exposure to an electric arc flash
above the threshold incident energy level for a second degree burn, [5 J/cm2 (1.2 cal/cm2)].” See also
130.7(C)(9)(a) for layering requirements.
See NFPA 70E, Article 130.7(C)(9) for details regarding factors in selection of protective clothing.
130.7(C)(9)(a) regarding outer layers states, “Garments worn as outer layers over arc-rated clothing,
such as jackets or rainwear, shall also be made from arc-rated material. 130.7(C)(9)(b) states,
“Meltable fibers such as acetate, nylon, polyester, polypropylene, and spandex shall not be permitted
in fabric underlayers (underwear) next to the skin.”
7.9
Arc-Flash Hazard Labels
NFPA 70®, National Electrical Code® (NEC®), 2011 Edition, in Article 110.16 on Arc Flash
Hazard Warning requires that equipment be field marked to warn qualified persons of potential
electrical arc flash hazards.
“Electrical equipment, such as switchboards, panelboards, industrial control panels,
meter socket enclosures, and motor control centers, that are in other than dwelling units,
and are likely to require examination, adjustment, servicing, or maintenance while
energized shall be field marked to warn qualified persons of potential electric arc flash
hazards. The marking shall be located so as to be clearly visible to qualified persons
before examination, adjustment, servicing, or maintenance of the equipment.”
NFPA 70E, 2012 Edition in Article 130.5(C) requires Equipment Labeling.
“Electrical equipment, such as switchboards, panelboards, industrial control panels,
meter socket enclosures, and motor control centers that are in other than dwelling units,
and are likely to require examination, adjustment, servicing, or maintenance while
energized, shall be field marked with a label containing all the following information.
Page 7-18, Rev 0, 9/12/14
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
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Section 7 - Summary and Discussion of Arc-Flash Calculations
(1)
(2)
(3)
At least one of the following:
i. Available incident energy and the corresponding working distance
ii. Minimum arc rating of clothing
iii. Required level of PPE
iv. Highest Hazard/Risk Category (HRC) for the equipment
Nominal system voltage
Arc flash boundary
Exception: Labels applied prior to September 30, 2011, are acceptable if they contain
the available incident energy or required level of PPE.”
Arc-Flash Hazard labels (and the arc-flash hazard study) are only part of the overall facility
safety program and as such should not be relied upon to “assess” a hazard or select PPE to
perform energized work based solely on the information found on the label. NFPA 70E 130.1
should be followed which includes:
•
•
130.2-Electrically Safe Working Conditions. Justifying why the work on any exposed
energized electrical conductor of equipment at 50 volts or more must be performed
energized using one of the two permitted explanations for not creating an electrically
safe work condition (de-energizing would result in an increased, additional, or greater
hazard or increased risk; or is infeasible due to equipment design or operational
limitations). This is also required by OSHA 1910.333(a)(1).
Completing the work permit process identifying and assessing all hazards and selecting
PPE. A sample work permit is found in NFPA 70E Informative Annex J. The person(s)
signing the permit is authorizing the work and is accepting responsibility for the
exposure. A Hazard Analysis, Risk Estimation, and Risk Evaluation Procedure appears
in NFPA 70E Informative Annex F.
The information found on the Arc-Flash Hazard labels should be used as one input into the
overall hazard assessment and PPE selection.
Page 7-19, Rev 0, 9/12/14
Electrical Power System Short-Circuit, Coordination & Arc-Flash Studies for the
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, Houston, Texas
Section 7 - Summary and Discussion of Arc-Flash Calculations
GE’s Arc-Flash and Shock Hazard labels have the following
Shock Hazard approach boundaries
[as found in Table 130.4(C)(a) of NFPA 70E]
Approach Boundaries to Energized Electrical Conductors or Circuit Parts
for Shock Protection for Alternating-Current Systems
(All dimensions are distance from energized electrical conductor
or circuit part to employee)
See NFPA 70E for the complete table
Nominal System
Voltage Range
(Phase to Phase)
50 V – 300 V
301 V – 750 V
751 V – 15 kV
15.1 kV – 36 kV
36.1 kV – 46 kV
46.1 kV – 72.5 kV
72.6 kV – 121 kV
138 kV – 145 kV
161 kV – 169 kV
230 kV – 242 kV
345 kV – 362 kV
500 kV – 550 kV
765 kV – 800 kV
Limited
Approach
Boundary
3' - 6"
3' - 6"
5' - 0"
6' - 0"
8' - 0"
8' - 0"
8' - 0"
10' - 0"
11' - 8"
13' - 0"
15' - 4"
19' - 0"
23' - 9"
Restricted
Approach
Boundary
Avoid Contact
1' - 0"
2' - 2"
2' - 7"
2' - 9"
3' - 3"
3' - 4"
3' - 10"
4' - 3"
5' - 8"
9' - 2"
11' - 10"
15' - 11"
Prohibited
Approach
Boundary
Avoid Contact
0' - 1"
0' - 7"
0' - 10"
1' - 5"
2' - 2"
2' - 9"
3' - 4"
3 - 9"
5' - 2"
8' - 8"
11' - 4"
15' - 5"
The limited approach boundary shown in the table above is to an exposed fixed circuit part, not
an exposed movable conductor as overhead line conductors supported by poles would be. The
restricted approach boundary includes inadvertent movement adder.
Note that if arc-flash and shock hazard labels are provided in this work scope, only equipment
within the scope of this study had labels provided. NFPA 70E requires labels at all locations
that have an arc-flash hazard incident energy level greater than 1.2 cal/cm2. The Table Method
(NFPA 70E 2012 Edition Table 130.7(C)(15) should be used with writable labels to audit and
label the remaining system locations that have an arc-flash hazard that were not within the
scope of this study.
7.10
Occupational Safety and Health Administration (OSHA)
OSHA has not specifically addressed arc-flash hazards, however, there exists adequate safety
requirements for employers to follow to ensure the safety of the worker in the workplace
(General Duty clause).
OSHA 29 CFR 1910.269(l)(6)(iii) states that “The employer shall ensure that each employee
who is exposed to the hazards of flames or electric arcs does not wear clothing that, when
exposed to flames or electric arcs, could increase the extent of injury that would be sustained by
the employee.”
Page 7-20, Rev 0, 9/12/14
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xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, Houston, Texas
Section 7 - Summary and Discussion of Arc-Flash Calculations
OSHA 1910.132(d)(1) — The employer shall assess the workplace to determine if hazards are
present, or are likely to be present, which necessitate the use of personal protective equipment
(PPE). If such hazards are present, or likely to be present, the employer shall:
OSHA 1910.132(d)(1)(i) — Select, and have each affected employee use, the types of PPE
that will protect the affected employee from the hazards identified in the hazard assessment;
OSHA 1910.132(d)(1)(ii) — Communicate selection decisions to each affected employee;
and,
OSHA 1910.132(d)(1)(iii) — Select PPE that properly fits each affected employee. Note:
Non-mandatory Appendix B contains an example of procedures that would comply with the
requirement for a hazard assessment.
In response to an inquiry on OSHA’s stand on arc-flash hazard, Dean Y. Ikeda, the Regional
Administrator for Occupational Safety and Health, US Department of Labor for Region X in
Seattle, concluded as follows:
“Although OSHA does not, per se, enforce the NFPA standard, 2012 Edition, OSHA
considers NFPA standard a recognized industry practice. The employer is required to
conduct assessment in accordance with CFR 1910.132(d)(1). If an arc-flash hazard is
present, or likely to be present, then the employer must select and require employees to
use the protective apparel. Employers who conduct the hazard/risk assessment, and
select and require their employees to use protective clothing and other PPE appropriate
for the task, as stated in the NFPA 70E standard, 2012 Edition, are deemed in
compliance with the Hazard Assessment and Equipment Selection OSHA standard.”
Of course, the safest course of action is to de-energize the equipment first as the following
OSHA regulation limits the situations in which work is performed near or on equipment or
circuits that are or may be energized.
OSHA 1910.333(a)(1) — "De-energized parts." Live parts to which an employee may be
exposed shall be de-energized before the employee works on or near them, unless the
employer can demonstrate that de-energizing introduces additional or increased hazards or is
infeasible due to equipment design or operational limitations.
7.11
Methods for Decreasing Arc-Flash Incident Energies
There are measures which can be taken to lower the incident energy and decrease the arc-flash
boundary distance at a given system location. Some of these methods obviously may apply on
some systems more than others.
1. Lower the available fault current at that location. On systems equipped with differential
relaying, which will operate in the same amount of time for a reduced magnitude fault, arcflash incident energies will be reduced. While this can be a consideration when designing a
new electrical distribution system, it normally is not practical to consider reducing fault
current available on an existing system. In addition to the relatively high cost of changing
out transformers for higher impedance units or adding current limiting reactors, increasing
impedance will degrade voltage regulation performance within the system. In new systems,
consideration should be given to reducing the transformer sizes, thereby reducing available
fault current. Additional transformers would need to be purchased for the same loads. Limit
the ampere rating sizes of new mains and feeders where possible, i.e. split large feeders
into two feeders.
Page 7-21, Rev 0, 9/12/14
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Section 7 - Summary and Discussion of Arc-Flash Calculations
2. Raise the available fault current at that location. This is not a contradiction to point 1.
There may be locations in an electrical system which would have had a lower NFPA
Hazard/Risk Category if there were a higher fault current present sufficient to operate a fuse
in its current limiting region or sufficient to operate a short-time or instantaneous trip device.
On longer circuit lengths, this could involve adding parallel conductors to the circuit to raise
the downstream fault levels.
3. Determine a realistic but not overly conservative working distance for various classes
of equipment rather than simply using an arbitrary value like 18”, which is the typical
distance from a person’s fingers to their chest or face. Always confirm the assigned working
distances with the owner.
4. Decrease total fault clearing times. This approach can take a number of forms and offers
the best promise for an effective and yet reasonably economic method for reducing arc-flash
incident energies.
a) A protective device coordination study could be performed with the intent to decrease
the incident energies by compromising selectivity between devices. On 480V circuits, it
may be possible to lower the short time and/or instantaneous settings creating a lower
arc-flash incident energy. Realistically however, limited improvement will be possible
assuming the same fundamental coordination philosophies are utilized. Typically,
maximum coordination selectivity is desired to minimize the loss of load when clearing a
given fault. The steps necessary to achieve this selectivity run counter to what is
necessary to reduce arc-flash incident energies – i.e. lower current pickup settings and
time delays.
b) One approach would be to lower protective device settings only when maintenance had
to be performed on energized equipment. This would probably not be a reasonable
approach with older electro-mechanical relaying schemes. However, with modern digital
relaying, an alternate slate or “setpoint group” of settings may be entered and enabled
only when maintenance is performed. If it is desired that the relay not be disturbed, this
change to an alternate set of maintenance settings may be accomplished by having a
control switch wired into the relay with a “Normal” and “Maintenance” position.
c) The most significant impact on arc-flash incident energies can be realized by adding
high-speed pilot wire or differential (transformer, bus, line) relaying to the system.
Unfortunately, this can be costly and disruptive, not so much because of the relays
themselves, but due to the addition of the current transformers that would also be
necessary.
d) Replacing electromagnetic induction disk relays with digital relays for tighter relay-torelay coordination margins, faster fault clearing.
•
Electromagnetic Relay margins with 5 cycle breakers: 0.3–0.35 seconds
•
Static Relay margins with 5 cycle breakers: 0.2–0.25 seconds (source IEEE Buff
Book)
e) Zone selective interlocking can be utilized on systems using 480V breakers where this
optional feature has been ordered with solid-state trip devices.
Hard-wire
communications between the circuit breaker trip devices allow the normally time-delayed
short time or ground fault functions on an upstream breaker to operate in the minimum
Page 7-22, Rev 0, 9/12/14
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Section 7 - Summary and Discussion of Arc-Flash Calculations
time band when it senses a fault and the same fault is not sensed at any downstream
breakers.
f)
Add ground fault trip devices to breakers other than the Mains, which is mandated by the
Code. Since the determination of worst-case incident energies is based on three-phase
faults, this would not impact the need to provide ground fault protection. However, since
the majority of faults on a system are single-line-to-ground faults, on a practical basis,
arc-flash risks will be mitigated as the current is interrupted at lower stages of fault
development, prior to the bolted-fault condition.
g) Consider low or high-resistance grounding rather than solid grounding. Caution should
be exercised in adopting high-resistance grounding since a facility may not have the
maintenance staff to respond in a timely fashion to ground fault alarms.
h) Use current-limiting overcurrent protective devices such as current limiting MCCBs,
fuses, and fuses on circuit breakers. Use of current-limiting fuses and instantaneous
functions on low-voltage feeder breakers would sacrifice some selectivity but reduce the
incident energy.
i)
Size the current limiting branch circuit overcurrent protective devices as low as possible.
j)
Set the instantaneous setting for circuit breakers as low as possible to maintain selective
coordination.
k) Remote breaker operation including insertion and withdrawal as well as remote control,
metering and monitoring.
l)
Use of arc-resistant switchgear in new installations. Note that it is only arc-resistant if all
the panels and doors are closed.
Page 7-23, Rev 0, 9/12/14
Summary of Arc Flash Study Results for Equipment Labeling
Page 1 of 1
Bossier City South Inland Pump Station, Bossier City, Louisiana
Warning: The following Arc-Flash "IEEE Std. 1584" results are based on theoretical equations, derived from measured test results. The test results are a function of specific humidity, barometric pressure, temperature, arc distance, and many other variables. These parameters will NOT be
the same in your application. These results should be applied only by experienced engineers in the application of arc-flash hazards. The software developers make no warranty concerning the accuracy of these results as applied to real-world scenarios. PPE recommended by any calculation
method will NOT provide complete protection for all arc hazards. Injury can be expected when wearing recommended PPE.
Equipment Descriptions
Protective
Bus
Bus
Bus
Prot Dev
Prot Dev
Trip/
Breaker
Device
kV
Bolted
Arcing
Bolted
Arcing
Delay
Opening
Fault
Fault
Fault
Fault
Time
Time
(sec.)
Bus Name
Name
Grd
Equip
Arc
Arc Flash
Working
Incident
Worst Case
Type
Gap
Boundary
Distance
Energy
Scenario
(mm)
(in)
(in)
(cal/cm2)
Volts
Bus
Equipment
Label Description
(kA)
(kA)
(kA)
(kA)
(sec.)
480
RWP-SWB-010
AV5 Swb
RWP-SWB-010, Sec 1
ATS NORM (RWP-SWB-010 MAIN LineSide)
COF
0.48
23.25
11.46
23.25
11.46
0.313
0
Yes
PNL
25
73.5
18
12.0
S3
480
RWP-SWB-010
AV5 Swb
RWP-SWB-010, Sec 2
ATS NORM (RWP-SWB-010 MAIN LineSide)
COF
0.48
23.25
11.46
23.25
11.46
0.313
0
Yes
PNL
25
73.5
18
12.0
S3
480
RWP-SWB-010
AV5 Swb
RWP-SWB-010, Sec 3
ATS NORM (RWP-SWB-010 MAIN LineSide)
COF
0.48
23.25
11.46
23.25
11.46
0.313
0
Yes
PNL
25
73.5
18
12.0
S3
480
Generator Bus
Generator
Generator Bus
GENERATOR BUS (GEN CB LineSide)
GEN O/L
0.48
5.78
4.1
5.56
3.95
2
0
Yes
PNL
25
113.5
18
24.5
S2
480
RWP-SWB-030
Panelboard
RWP-SWB-030
RWP-PNL-030
RWP-PNL-030 MAIN
0.48
23.17
13.44
23.17
13.44
0.025
0
Yes
PNL
25
17.5
18
1.1
S1
Rev 0 - 9-9-14
Labels!30034550 Arc Flash Rev 0.xls
CASE 1
CASE 2
CASE 3
Utility
Isc 3P 4309.0 Amps
Isc SLG 5706.0 Amps
COF
Frame/Model 353C14
Sensor/Trip 65.0 A
GEN-0001
750 kVA
X"d 0.2 pu
P
S
GEN O/L
Frame/Model Am pSentry
Utility XFMR
Size 1500.00 kVA
Pri Wye-Ground
Sec Wye-Ground
%Z 5.7500 %
X/R 6.5
GEN CB
Frame/Model PG
Sensor/Trip 1000.0 A
CBL-0002
(6) Size 500 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 90.0 ft
Non-Magnetic
Ampacity 2580.0 A
GENERATOR BUS
480.0 V
CBL-0003
(3) Size 500 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 70.0 ft
Non-Magnetic
Ampacity 1290.0 A
RWP-SWB-0 10 MAIN
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 2000.0 A
RWP-SWB-0 10 MAIN GF
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 2000.0 A
RWP-SWB-010 MAIN EMER
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 1000.0 A
ATS NORM
480.0 V
N
City of Bossier City
South Inland Raw Water Pump Station
Bossier City, Louisiana
Proposed - Minimum Utility
ATS EMER
480.0 V
E
AUTO-0003
RWP-SWB-010
480.0 V
RWP-SWB-010 MAIN BR1
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0004
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-401
CBL-0007
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 100.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-401
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-SWB-0 10 MAIN BR2
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0005
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-402
CBL-0008
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 105.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-402
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-SWB-010 MAIN BR3
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0006
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-403
RWP-SWB-010 MAIN BR7
Frame/Model SELA
Sensor/Trip 80.0 A
CBL-0010
(1) Size 2 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 40.0 ft
Non-Magnetic
Ampacity 130.0 A
RWP-SWB-0 10 MAIN BR8
Frame/Model SFLA
Sensor/Trip 225.0 A
CBL-0011
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-AC-4 21
30.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-PNL-030 MAIN
Frame/Model SFHA
Sensor/Trip 225.0 A
CBL-0009
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 110.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-403
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-PNL-030
480.0 V
RWP-PNL-030 BR
Frame/Model TEYH
Sensor/Trip 60.0 A
P
S
RWP-XF -040
Size 30.00 kVA
Pri Delta
Sec Wye-Ground
%Z 4.8000 %
X/R 2.7
RWP-PNL-040 MAIN
Frame/Model THQB
Sensor/Trip 100.0 A
RWP-PNL-040
208.0 V
RWP-PNL-040 BR
Frame/Model THQB-C
Sensor/Trip 50.0 A
CASE 4
Utility
Isc 3P 8618.0 Amps
Isc SLG 5706.0 Amps
COF
Frame/Model 353C14
Sensor/Trip 65.0 A
GEN-0001
750 kVA
X"d 0.2 pu
P
S
GEN O/L
Frame/Model Am pSentry
Utility XFMR
Size 1500.00 kVA
Pri Wye-Ground
Sec Wye-Ground
%Z 6.1800 %
X/R 6.5
GEN CB
Frame/Model PG
Sensor/Trip 1000.0 A
CBL-0002
(6) Size 500 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 90.0 ft
Non-Magnetic
Ampacity 2580.0 A
GENERATOR BUS
480.0 V
CBL-0003
(3) Size 500 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 70.0 ft
Non-Magnetic
Ampacity 1290.0 A
RWP-SWB-0 10 MAIN
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 2000.0 A
RWP-SWB-0 10 MAIN GF
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 2000.0 A
RWP-SWB-010 MAIN EMER
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 1000.0 A
ATS NORM
480.0 V
N
City of Bossier City
South Inland Raw Water Pump Station
Bossier City, Louisiana
Proposed - Maximum Operation
ATS EMER
480.0 V
E
AUTO-0003
RWP-SWB-010
480.0 V
RWP-SWB-010 MAIN BR1
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0004
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-401
CBL-0007
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 100.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-401
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-SWB-0 10 MAIN BR2
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0005
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-402
CBL-0008
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 105.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-402
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-SWB-010 MAIN BR3
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0006
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-403
RWP-SWB-010 MAIN BR7
Frame/Model SELA
Sensor/Trip 80.0 A
CBL-0010
(1) Size 2 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 40.0 ft
Non-Magnetic
Ampacity 130.0 A
RWP-SWB-0 10 MAIN BR8
Frame/Model SFLA
Sensor/Trip 225.0 A
CBL-0011
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-AC-4 21
30.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-PNL-030 MAIN
Frame/Model SFHA
Sensor/Trip 225.0 A
CBL-0009
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 110.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-403
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-PNL-030
480.0 V
RWP-PNL-030 BR
Frame/Model TEYH
Sensor/Trip 60.0 A
P
S
RWP-XF -040
Size 30.00 kVA
Pri Delta
Sec Wye-Ground
%Z 4.8000 %
X/R 2.7
RWP-PNL-040 MAIN
Frame/Model THQB
Sensor/Trip 100.0 A
RWP-PNL-040
208.0 V
RWP-PNL-040 BR
Frame/Model THQB-C
Sensor/Trip 50.0 A
CASE 5
Utility
Isc 3P 8618.0 Amps
Isc SLG 5706.0 Amps
COF
Frame/Model 353C14
Sensor/Trip 65.0 A
GEN-0001
750 kVA
X"d 0.2 pu
P
S
GEN O/L
Frame/Model Am pSentry
Utility XFMR
Size 1500.00 kVA
Pri Wye-Ground
Sec Wye-Ground
%Z 6.1800 %
X/R 6.5
GEN CB
Frame/Model PG
Sensor/Trip 1000.0 A
CBL-0002
(6) Size 500 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 90.0 ft
Non-Magnetic
Ampacity 2580.0 A
GENERATOR BUS
480.0 V
CBL-0003
(3) Size 500 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 70.0 ft
Non-Magnetic
Ampacity 1290.0 A
RWP-SWB-0 10 MAIN
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 2000.0 A
RWP-SWB-0 10 MAIN GF
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 2000.0 A
RWP-SWB-010 MAIN EMER
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 1000.0 A
ATS NORM
480.0 V
N
City of Bossier City
South Inland Raw Water Pump Station
Bossier City, Louisiana
Proposed - Minimum Short Circuit
ATS EMER
480.0 V
E
AUTO-0003
RWP-SWB-010
480.0 V
RWP-SWB-010 MAIN BR1
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0004
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-401
CBL-0007
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 100.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-401
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-SWB-0 10 MAIN BR2
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0005
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-402
CBL-0008
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 105.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-402
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-SWB-010 MAIN BR3
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0006
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-403
RWP-SWB-010 MAIN BR7
Frame/Model SELA
Sensor/Trip 80.0 A
CBL-0010
(1) Size 2 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 40.0 ft
Non-Magnetic
Ampacity 130.0 A
RWP-SWB-0 10 MAIN BR8
Frame/Model SFLA
Sensor/Trip 225.0 A
CBL-0011
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-AC-4 21
30.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-PNL-030 MAIN
Frame/Model SFHA
Sensor/Trip 225.0 A
CBL-0009
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 110.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-403
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-PNL-030
480.0 V
RWP-PNL-030 BR
Frame/Model TEYH
Sensor/Trip 60.0 A
P
S
RWP-XF -040
Size 30.00 kVA
Pri Delta
Sec Wye-Ground
%Z 4.8000 %
X/R 2.7
RWP-PNL-040 MAIN
Frame/Model THQB
Sensor/Trip 100.0 A
RWP-PNL-040
208.0 V
RWP-PNL-040 BR
Frame/Model THQB-C
Sensor/Trip 50.0 A
CASE 6
Utility
Isc 3P 8618.0 Amps
Isc SLG 5706.0 Amps
COF
Frame/Model 353C14
Sensor/Trip 65.0 A
GEN-0001
750 kVA
X"d 0.2 pu
P
S
GEN O/L
Frame/Model Am pSentry
Utility XFMR
Size 1500.00 kVA
Pri Wye-Ground
Sec Wye-Ground
%Z 5.3200 %
X/R 6.5
GEN CB
Frame/Model PG
Sensor/Trip 1000.0 A
CBL-0002
(6) Size 500 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 90.0 ft
Non-Magnetic
Ampacity 2580.0 A
GENERATOR BUS
480.0 V
CBL-0003
(3) Size 500 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 70.0 ft
Non-Magnetic
Ampacity 1290.0 A
RWP-SWB-0 10 MAIN
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 2000.0 A
RWP-SWB-0 10 MAIN GF
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 2000.0 A
RWP-SWB-010 MAIN EMER
Frame/Model SS
Sensor/Trip 2000.0 A
Plug 1000.0 A
ATS NORM
480.0 V
N
City of Bossier City
South Inland Raw Water Pump Station
Bossier City, Louisiana
Proposed - Maximum Short Circuit
ATS EMER
480.0 V
E
AUTO-0003
RWP-SWB-010
480.0 V
RWP-SWB-010 MAIN BR1
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0004
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-401
CBL-0007
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 100.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-401
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-SWB-0 10 MAIN BR2
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0005
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-402
CBL-0008
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 105.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-402
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-SWB-010 MAIN BR3
Frame/Model SGLA
Sensor/Trip 500.0 A
CBL-0006
(2) Size 250 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 580.0 A
RWP-VF D-403
RWP-SWB-010 MAIN BR7
Frame/Model SELA
Sensor/Trip 80.0 A
CBL-0010
(1) Size 2 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 40.0 ft
Non-Magnetic
Ampacity 130.0 A
RWP-SWB-0 10 MAIN BR8
Frame/Model SFLA
Sensor/Trip 225.0 A
CBL-0011
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 25.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-AC-4 21
30.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-PNL-030 MAIN
Frame/Model SFHA
Sensor/Trip 225.0 A
CBL-0009
(1) Size 4/0 AWG/kcmil
Copper 3 Wire+Grnd
THHN, 110.0 ft
Non-Magnetic
Ampacity 260.0 A
RWP-P-403
250.000 hp
Load Factor 1.00
X"d 0.17 pu
RWP-PNL-030
480.0 V
RWP-PNL-030 BR
Frame/Model TEYH
Sensor/Trip 60.0 A
P
S
RWP-XF -040
Size 30.00 kVA
Pri Delta
Sec Wye-Ground
%Z 4.8000 %
X/R 2.7
RWP-PNL-040 MAIN
Frame/Model THQB
Sensor/Trip 100.0 A
RWP-PNL-040
208.0 V
RWP-PNL-040 BR
Frame/Model THQB-C
Sensor/Trip 50.0 A