SHORT CIRCUIT CALCULATION DOC

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Short-Circuit Calculations

A Handboo

k to Accompany the

Online Short-Circuit

Calculation Program from

www.arcadvisor.com

August 25, 2006

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Introduction

Determining available short circuit fault currents is one of the most important aspects of designing power

distribu-tion systems. Short circuits and their effects must be considered in selecting electrical equipment, circuit protecdistribu-tion

tion systems. Short circuits and their effects must be considered in selecting electrical equipment, circuit protection

devices, carrying out arc flash analysis. The short circuit calculator presented on

devices, carrying out arc flash analysis. The short circuit calculator presented onwww.arcadvisor.comwww.arcadvisor.comweb-site isweb-site is

offered in effort to satisfy the need for a convenient, compre

offered in effort to satisfy the need for a convenient, comprehensive method of calculahensive method of calculating fault currents. It is intendedting fault currents. It is intended

for radial and looped low-and medium-voltage circuits. The calculator allows to quickly and easily obtain accurate

potential short circuit currents at each node (bus) in a power distribution system.

This program, other programs, or hand c

This program, other programs, or hand calculation can be used to pealculation can be used to perform short-circuit calculations. Any methodrform short-circuit calculations. Any method

used requires spe

used requires specific data on the pcific data on the power distributioower distribution system. All this data is converted to short cin system. All this data is converted to short circuit MVrcuit MVA A valuesvalues

(SC MV

(SC MVA) for each component in the system. This paper describA) for each component in the system. This paper describes the data needed for each type of circuit coes the data needed for each type of circuit compo-

mpo-nent and how to obtain the da

nent and how to obtain the data. It also describes method and advantages of using the ta. It also describes method and advantages of using the online short circuit program toonline short circuit program to

calculate available

calculate available short-circuishort-circuit currents.t currents.

Utility

The first step in analyzing a power system is to get the data for the powe

The first step in analyzing a power system is to get the data for the power available at the site, the utility data. Thisr available at the site, the utility data. This

data can be

data can be obtained from the power company. When calling the power company, explain the type of informationobtained from the power company. When calling the power company, explain the type of information

you need and ask for the engin

you need and ask for the engineering department. It may be helpful to eeering department. It may be helpful to explain why you need the information.xplain why you need the information.

The power company will be able to supply this information for the point in the power system where their

respon-sibility for the power system end

sibility for the power system ends and the customers and the customer’s responsibility starts. A ’s responsibility starts. A common locacommon location for this point is thetion for this point is the

secondary of a pole

secondary of a pole or pad mounted or pad mounted transformertransformer. If the customer is . If the customer is responsible for the transformer, the transitionresponsible for the transformer, the transition

point would be the primary of the transformer. Sometimes a pole mounted disconne

point would be the primary of the transformer. Sometimes a pole mounted disconnect will be the transition point. Thect will be the transition point. The

power company will specify where in the system their responsibility ends.

The data needed is the line to line voltage (V

The data needed is the line to line voltage (V_LL_LL), short-circuit ), short-circuit MVMVA (SC MVA (SC MVA), and A), and X/R. Obtaining X/R. Obtaining the voltagthe voltage ise is

simple enough. SC MV

simple enough. SC MVA is the power available at a bolteA is the power available at a bolted three phase fault. d three phase fault. Bolted means all threBolted means all three phases con-e phases

con-nected togethe

nected together with no added impr with no added impedance. X/R is the edance. X/R is the ratio of reactancratio of reactance to resistance in the sue to resistance in the supplypply. SC MV. SC MVA and X/A and X/

R may need to be derived from other data.

Short-circuit current (I

Short-circuit current (I_SC_SC) is sometimes supplied b) is sometimes supplied by the power compay the power company rather than SC MVny rather than SC MVA. This current is theA. This current is the

current in one phase

current in one phase of a three of a three phase bolted fault. The SC phase bolted fault. The SC MVMVA can be calculated from the A can be calculated from the short-circuit current usingshort-circuit current using

the following equation:

SC MVA = 1.732 I

SC MVA = 1.732 I _SC_SCV V _LL_LL, where, whereI I _SC_SCis expressed in kA andis expressed in kA andV V _LL_LL- in kV- in kV

Power factor (PF) is sometimes specified instead

Power factor (PF) is sometimes specified instead of X/R. This must be the of X/R. This must be the short circuit power factor. Power factor short circuit power factor. Power factor

is defined as the cosine of the angle between voltage and curre

is defined as the cosine of the angle between voltage and current. X/R is the tangent of this same angle. X/R can bent. X/R is the tangent of this same angle. X/R can be

found from power factor by taking

found from power factor by taking the tangent of the tangent of the inverse cosine of the the inverse cosine of the power factorpower factor..

X/R

X/R= tan(cos= tan(cos-1-1_PF_PF₎₎

This is all the data

This is all the data needed for the uneeded for the utilitytility..

Transformers

Transformers are specified by outpu

Transformers are specified by output voltage (V), kVt voltage (V), kVA A rating, percenrating, percent impedance (%Z), and X/R ratiot impedance (%Z), and X/R ratio. The X/R . The X/R

ratio is the ratio of reactance to

ratio is the ratio of reactance to resistance. This information, with the exception of X/R, is resistance. This information, with the exception of X/R, is usually on the transformer usually on the transformer

nameplate.

If X/R is not

If X/R is not specified on the nameplate, the specified on the nameplate, the transformetransformer manufacturer may be able r manufacturer may be able to supply this. When contactingto supply this. When contacting

the transformer manufacturer

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check

check Appendix AAppendix Afor a typical value for a typical value that can be that can be used in the used in the calculations. Transfcalculations. Transformer short circuit MVormer short circuit MVA is calcu-A is

calcu-lated

lated from kVA from kVA and %and %Z:Z:

SC MVA = kVA x 10

SC MVA = kVA x 10 -3-3_{/ Zp.u.}_{/ Zp.u.}_{, where Zp.u.}_{, where Zp.u.}_{is equal to %Z / 100}_{is equal to %Z / 100} Cables

Cables

Data needed for cables is resistance, reactance and length. This data is available in cable standards and

manufacturer’s specifications.

manufacturer’s specifications.Also,Also,Appendix BAppendix Bshows values for resistance and reactance peshows values for resistance and reactance per hundred feet for r hundred feet for

most commonly used cable types. Lengths may be measured, paced off and estimated. The cable

most commonly used cable types. Lengths may be measured, paced off and estimated. The cable Short CircuitShort Circuit

MV

MVA is determined from the A is determined from the equation below:equation below:

SC MVA = n x kV

SC MVA = n x kV 22_/_/_Z,_Z,_where,_where,_n_n_{- number of cables in parallel,}_{- number of cables in parallel,}_{Z = (R}_{Z = (R}22_{+ X}_{+ X}22₎₎1/21/2_Ohm_Ohm Motors and Generators

Motors and Generators Motors are a source

Motors are a source of short-circuit current. They will act like of short-circuit current. They will act like generators when a generators when a short-circuishort-circuit occurs. At a mini-t occurs. At a

mini-mum, motors must be specified by

mum, motors must be specified by horsepower which will be listed on horsepower which will be listed on the motor nameplate. Motor specifications arethe motor nameplate. Motor specifications are

as follows:

kV

kV: Motor ra: Motor rated kV.ted kV.

HP

HP: Motor Horse Power. Motors may be represented individually or as a lumped : Motor Horse Power. Motors may be represented individually or as a lumped group.group.

FL

FLAA: The Full Load Amps.: The Full Load Amps.

PF

PF: Motor operating Pow: Motor operating Power Factor. er Factor. This is used with the Efficiency to deteThis is used with the Efficiency to determine kVrmine kVA. Motor groups shoulA. Motor groups should use and use an

average value of power factor.

EF

EFFF: Motor operating Efficien: Motor operating Efficiency. cy. This is used with the Power Factor field to deteThis is used with the Power Factor field to determine kVrmine kVA. Motor groups shouldA. Motor groups should

use an average

use an average value of efficiency.value of efficiency.

kVA/HP

kVA/HP: The motor or : The motor or motor group motor group kVkVA rating per horsepoweA rating per horsepower. r. This is a simpThis is a simple way of dele way of defining the fining the kVkVA when fullA when full

load amperes, or e

load amperes, or efficiency and power factor are fficiency and power factor are not known. Typical values for standard efficiency motors are listednot known. Typical values for standard efficiency motors are listed

below:

1.0 kV

1.0 kVA/HP - Induction < A/HP - Induction < 100 HP and 0.8 PF Syn 100 HP and 0.8 PF Syn MotorsMotors

0.95 kV

0.95 kVA/HP - Induction 100 < 9A/HP - Induction 100 < 999 HP99 HP

0.90 kV

0.90 kVA/HP - Induction > 10A/HP - Induction > 1000 HP00 HP

0.8 kV

0.8 kVA/HP - Synchronous A/HP - Synchronous 1.0 PF1.0 PF

X"dv

X"dv: Subtransient reactance in pe: Subtransient reactance in percent on the motor HP base. See Trcent on the motor HP base. See TableableA Appendix C for A Appendix C for for a typical valuefor a typical value

that can be used

that can be used in the calculations if accurate subtransient reactance cannot be obtainedin the calculations if accurate subtransient reactance cannot be obtained..

Table

TableB Appendix C B Appendix C displays ANSI displays ANSI Standard interrupting duty multipliers. Code numbeStandard interrupting duty multipliers. Code numbers are chosen accordingrs are chosen according

to the motor types, sizes and modeling method. Using the ANSI Code is the recommended method to determine

motor impedance Zp.u. used for short circuit ca

motor impedance Zp.u. used for short circuit calculations:lculations:

Zp.u.

Zp.u.= ( X”dv )( ANSI multiplier )= ( X”dv )( ANSI multiplier )

There are three wa

There are three ways to calculate motoys to calculate motor kVr kVA. Below the kVA. Below the kVA calculation methods are shoA calculation methods are shown in priority order:wn in priority order:

1) If the FLA is known, the motor kV

1) If the FLA is known, the motor kVA should be determined by the folloA should be determined by the following equation:wing equation:

KVA = (1.73)(FLA)(kV)

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2) If the FLA is not availa

2) If the FLA is not available and the ble and the kVkVA/HP is known, the motoA/HP is known, the motor kVr kVA should be determined froA should be determined from the followingm the following

equation:

KVA = (HP)(kVA/HP)

3) If both the

3) If both the FLA and the kVFLA and the kVA/HP are not availableA/HP are not available, the motor , the motor kVkVA should be determined froA should be determined from the followingm the following

equation:

KV

KVA = A = (HP)(0.746)/(EFF)(PF)(HP)(0.746)/(EFF)(PF)

Motor and ge

Motor and generator short circunerator short circuit MVit MVA is calculated from kVA is calculated from kVA rating and subtransient reaA rating and subtransient reactance:ctance:

SC MVA = kVA x 10

SC MVA = kVA x 10 -3-3 _{/ Zp.u.}_{/ Zp.u.}

X/R can be read off from the motor nameplate. If X/R is not specified on the nameplate, the motor manufacturer

may be able to supply this. If X/R cannot be obtained

may be able to supply this. If X/R cannot be obtained, check , check Appendix C Appendix C tablestablesC C andandDDfor a typical value that canfor a typical value that can

be used in the calculations.

About MV

About MVA method for short circuit anA method for short circuit analysis and ialysis and it’s program implementation t’s program implementation atat www.arcadvisor.comwww.arcadvisor.com

The MV

The MVA method developeA method developed by Moon Yd by Moon Yuen at Becuen at Bechtel in the 6htel in the 60’s is a modification of t0’s is a modification of the Ohmic mehe Ohmic method wherethod where

the impedance of a

the impedance of a circuit equals the sum of the impedances of circuit equals the sum of the impedances of components constituting the circuit. The method usescomponents constituting the circuit. The method uses

the admittance o

the admittance of each componef each component expressed as the nt expressed as the Short Circuit MVShort Circuit MVA (SC MVA (SC MVA) that could flow throA) that could flow through thatugh that

component from an infinite bus to a short circuit.

ArcAd’s online short circuit cal

ArcAd’s online short circuit calculator perfoculator performs vector additiorms vector addition of SC MVn of SC MVA A contributcontributed by system equipmened by system equipmentsts

with arbitrary X/R ratios at every point where they intersect. This provides an extremely acc

with arbitrary X/R ratios at every point where they intersect. This provides an extremely accurate analysis of shorturate analysis of short

circuit MV

circuit MVA any node can A any node can be subject be subject to.to.

By performing short circuit

By performing short circuit MVMVA analysis for positive, negative and A analysis for positive, negative and zero sequences, zero sequences, symmetrical three phase symmetrical three phase andand

unsymmetr

unsymmetrical phase-to-ground, phase-to-phasical phase-to-ground, phase-to-phase and e and double phase-to-ground fault currents can double phase-to-ground fault currents can be resolved.be resolved.

Y

Your online accoour online account gives you the advantaunt gives you the advantage of saving the entered system diagge of saving the entered system diagram. This is practical for systemsram. This is practical for systems

with multiple scenarios of interconnection

with multiple scenarios of interconnections where the system goes through ongoing changes where the system goes through ongoing changes over a period of time.s over a period of time.

Y

You may continue ou may continue your analysis without having to your analysis without having to re-enter your data from the re-enter your data from the beginning.beginning.

T

Typical commercial software has more interfaces and graphic conteypical commercial software has more interfaces and graphic content, which make them more appealing andnt, which make them more appealing and

expensive. ArcAd's on-line tool is user friendly, performs error propagation analysis - very important

expensive. ArcAd's on-line tool is user friendly, performs error propagation analysis - very important but widelybut widely

ignored issue, and is offered at a

ignored issue, and is offered at a reasonable price. Many other procedures do not reasonable price. Many other procedures do not take into account room for take into account room for errorerror,,

which can distort final values. A

which can distort final values. A lack of understanding of basic error analysis has led lack of understanding of basic error analysis has led some very bright scientists andsome very bright scientists and

engineers to make some incredible

engineers to make some incredible blunders. ArcAd's short circuit online calculator features input data analysis andblunders. ArcAd's short circuit online calculator features input data analysis and

hard coded error propagation rules ensuring that the results are not more

hard coded error propagation rules ensuring that the results are not more precise than justified by the accuracy of precise than justified by the accuracy of

input data.

W

We strongly believe that if a resulting fault current e strongly believe that if a resulting fault current margin of error can't be quantified, then margin of error can't be quantified, then it's not engineering, butit's not engineering, but

only a guess. As far as we are aware, none

only a guess. As far as we are aware, none of the available cof the available competing products performs proper eompeting products performs proper error analysis. Itrror analysis. It

wouldn't be a problem if

wouldn't be a problem if most accurate system equipment data were available. Experience shows that by most accurate system equipment data were available. Experience shows that by far mostfar most

real world studies are built upon approximate and therefore mo

real world studies are built upon approximate and therefore more or less accurate input data. The core or less accurate input data. The concept of ncept of

precision is very important indeed and can impact results in surprising ways.

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Example:

Step 1

Develop a comprehensive one-line radial diagram of the power sy

Develop a comprehensive one-line radial diagram of the power system being analized.stem being analized.It is recommendedIt is recommended

that you use a copy of the same one-line diagram which is applied when laying ou

that you use a copy of the same one-line diagram which is applied when laying out the distribution system. Thist the distribution system. This

approach provides the

approach provides the most complete system.most complete system.

Step 2

Convert the equipment data to Short Circuit MVA values for each component in the system.

Convert the equipment data to Short Circuit MVA values for each component in the system.Each basicEach basic

component with

component within the industrial electricin the industrial electrical distribution system is pre-assigned a sinal distribution system is pre-assigned a single the SCMVgle the SCMVA factor based on theA factor based on the

impedance it adds to the system. See sections above on how to do the conversion. For instance, the 5 MVA

%Z=6% tra

%Z=6% transformer lansformer labeled TX-beled TX-3 above 3 above has a SC MVhas a SC MVA = Rated MVA = Rated MVA / Z = 5 / 0.06 = 83.3 MVA. For the C-4A / Z = 5 / 0.06 = 83.3 MVA. For the C-4

conduit with R = 6.09 mOhm and X = 5.49 mOhm per 100 feet taken from manufactu

conduit with R = 6.09 mOhm and X = 5.49 mOhm per 100 feet taken from manufacturer spec sheet, its short circuitrer spec sheet, its short circuit

MV

MVA is equal tA is equal to (kV)o (kV)22_{/ Z = 13.8}_{/ Z = 13.8}22_{/ ( 0.0115}_{/ ( 0.0115}22_{+ 0.0128}_{+ 0.0128}22₎₎1/21/2_{= 11050, where 0.0115 and 0.0128}_{= 11050, where 0.0115 and 0.0128}_{are resistance and}_{are resistance and}

reactance values in Ohms per 210 feet:

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If approximate or typical values are used,

If approximate or typical values are used, SC MVSC MVA error and X/R error should be specified. Leave the error equalA error and X/R error should be specified. Leave the error equal

to 0 when

to 0 when most accurate equipment data is available.most accurate equipment data is available.

Step 3

Develop a hierarchical tree in terms

Develop a hierarchical tree in terms of database records.of database records.The system equipment tree should be broken intoThe system equipment tree should be broken into

levels, with each level being more focused than the last. The tree consists of nodes connected to each

levels, with each level being more focused than the last. The tree consists of nodes connected to each other byother by

branches. Please note that a node may have on

branches. Please note that a node may have one or more “children”, but can have only one “parent”e or more “children”, but can have only one “parent”. Equipment. Equipment

parent

parentid id equals the id of the upstream device feeding the equipment. In oequals the id of the upstream device feeding the equipment. In our example, TX-1 is fed from PSE. Theur example, TX-1 is fed from PSE. The

TX-1 is assigned parent

TX-1 is assigned parentid id of "1" which equals the PSE id value. PSE is a root feeding the system, its parentof "1" which equals the PSE id value. PSE is a root feeding the system, its parentid id isis

assigned "0" by default. Y

assigned "0" by default. You will need the reference ou will need the reference table such as the ontable such as the one below to input the e below to input the data for short circuitdata for short circuit

calculations: calculations: ID ID LLA A B B E E LL DESCRIPTION DESCRIPTION V V ooll ttaa ggee ,, kkV V S S C C M M V V A A S S C C M M V V A A eerr rroo rr,, % % X X //R R X X //R R eerr rroo rr,, % % P P A A R R E E N N T T 1 1 _P_PS_SE_E _P_PS_SE_E--S_SO_OU_UT_TH_{H 2}₂₀₀₀₀₀_0M_MV_VA_{A S}_S..E_E._. ₁₁₁₁₅₅ ₂₂₀₀₀₀₀₀ ₀₀ ₇₇ ₀₀ ₀₀ 2 2 _T_TX_X--1₁ _T_TX_X--1_{1 2}₂₀_{0 M}_MV_VA_{A Z}_Z=₌₈_8%_{% D}_D--Y_YR_RG_G ₁₁₃_3..8₈ ₂₂₅₅₀₀ ₀₀ ₂₂₂_2..3₃ ₀₀ 11 3 3 _C_C--4₄ ₁_1--1_1//C_C--4_4//0_{0 A}_AW_WG_{G 2}₂₁₁₀_{0 F}_FE_EE_ET_{T C}_CU_U ₁₁₃_3..8₈ ₁₁₁₁₀₀₅₅₀₀ ₀₀ ₀_0..9₉ ₀₀ ₂₂ 4 4 _C_C--5₅ ₁_1--1_1//C_C--2_2//0_{0 A}_AW_WG_{G 4}₄₀₀₀_{0 F}_FE_EE_ET_{T C}_CU_U ₁₁₃_3..8₈ ₄₄₂₂₀₀₅₅ ₀₀ ₀_0..6₆ ₀₀ ₂₂ 5 5 _C_C--1₁ ₁_1--1_1//C_C--4_4//0_{0 A}_AW_WG_{G 3}₃₀₀₀_{0 F}_FE_EE_ET_{T C}_CU_U ₁₁₃_3..8₈ ₇₇₇₇₃₃₅₅ ₀₀ ₀_0..9₉ ₀₀ ₂₂ 6 6 _T_TX_X--3₃ _T_TX_X--3_{3 5}_{5 M}_MV_VA_{A Z}_Z=₌₆_6%_{% D}_D--Y_YR_RG_G ₂_2..4₄ ₈₈₃_3..3₃ ₀₀ ₁₁₂_2..6₆ ₀₀ 33 7 7 TTXX--4 4 TTXX--4 4 00..3 3 MMVVA A ZZ==44% % DD--YYG G 00..448 8 77..5 5 0 0 33..7 7 00 44 8 8 TTXX--2 2 TTXX--2 2 1 1 MMVVA A ZZ==66% % DD--YYG G 00..448 8 1166..667 7 0 0 55..7 7 00 55 9 9 MM--2 2 339988KKVVA A 1166..77%%Z Z 1177..6622XX//R R 22..4 4 22..338 8 0 0 1177..6 6 00 66 1 10 0 MM--3 3 999966KKVVA A 1166..77%%Z Z 2244..9977XX//R R 22..4 4 55..996 6 0 0 225 5 00 66 1 11 1 MM--4 4 11449944KKVVA A 1166..77%%Z Z 2288..4433XX//R R 22..4 4 88..994 4 0 0 2288..4 4 00 66 1 12 2 PPNNLL--1 1 0 0 SSCCMMVVA A 448800V V PPAANNEEL L 00..448 8 0 0 0 0 0 0 0 0 77 1 13 3 CC--3 3 22--11//CC--33550 0 MMCCM M 11225 5 FFEEEET T CCU U 00..448 8 6666..8 8 0 0 1 1 0 0 88 1 14 4 CC--2 2 22--11//CC--33550 0 MMCCM M 11225 5 FFEEEET T CCU U 00..448 8 6666..8 8 0 0 1 1 0 0 88 1 15 5 MMCCCC--1 1 444466KKVVA A 1166..77%%Z Z 44..55XX//R R 00..448 8 22..667 7 0 0 44..5 5 0 0 1133 1 16 6 MM--1 1 224477KKVVA A 1166..77%%Z Z 1144..2211XX//R R 00..448 8 11..447 7 0 0 1144..2 2 0 0 88 LLA A B B E E LL DESCRIPTION DESCRIPTION V V ooll ttaa ggee ,, kkV V S S C C M M V V A A S S C C M M V V A A eerr rroo rr,, % % X X //R R X X //R R eerr rroo rr,, % % P PSSE E PPSSEE--SSOOUUTTH H 22000000MMVVA A SS..EE. . 11115 5 2200000 0 0 0 7 7 00 T TXX--1 1 TTXX--1 1 220 0 MMVVA A ZZ==88% % DD--YYRRG G 1133..8 8 22550 0 0 0 2222..3 3 00 C C--4 4 11--11//CC--44//0 0 AAWWG G 22110 0 FFEEEET T CCU U 1133..8 8 111100550 0 0 0 00..9 9 00 C C--5 5 11--11//CC--22//0 0 AAWWG G 44000 0 FFEEEET T CCU U 1133..8 8 4422005 5 0 0 00..6 6 00 C C--1 1 11--11//CC--44//0 0 AAWWG G 33000 0 FFEEEET T CCU U 1133..8 8 7777335 5 0 0 00..9 9 00 T TXX--3 3 TTXX--3 3 5 5 MMVVA A ZZ==66% % DD--YYRRG G 22..4 4 8833..3 3 0 0 1122..6 6 00 T TXX--4 4 TTXX--4 4 00..3 3 MMVVA A ZZ==44% % DD--YYG G 00..448 8 77..5 5 0 0 33..7 7 00 T TXX--2 2 TTXX--2 2 1 1 MMVVA A ZZ==66% % DD--YYG G 00..448 8 1166..667 7 0 0 55..7 7 00 M M--2 2 339988KKVVA A 1166..77%%Z Z 1177..6622XX//R R 22..4 4 22..338 8 0 10 177..6 6 00 M M--3 3 999966KKVVA A 1166..77%%Z Z 2244..9977XX//R R 22..4 4 55..996 6 0 0 225 5 00 M M--4 4 11449944KKVVA A 1166..77%%Z Z 2288..4433XX//R R 22..4 4 88..994 4 0 20 288..4 4 00 P PNNLL--1 1 0 0 SSCCMMVVA A 448800V V PPAANNEEL L 00..448 8 0 0 0 0 0 0 00 C C--3 3 22--11//CC--33550 0 MMCCM M 11225 5 FFEEEET T CCU U 00..448 8 6666..8 8 0 0 1 1 00 C C--2 2 22--11//CC--33550 0 MMCCM M 11225 5 FFEEEET T CCU U 00..448 8 6666..8 8 0 0 1 1 00 M MCCCC--1 1 444466KKVVA A 1166..77%%Z Z 44..55XX//R R 00..448 8 22..667 7 0 0 44..5 5 00 M M--1 1 224477KKVVA A 1166..77%%Z Z 1144..2211XX//R R 00..448 8 11..447 7 0 0 1144..2 2 00 M MCCCC--2 2 224477KKVVA A 1166..77%%Z Z 44..55XX//R R 00..448 8 11..448 8 0 0 44..5 5 00

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Step 4

Create an online account if you don't already have one, and log onto the page where you can add components one

by one to build up

by one to build up a radial electrical distribution system.a radial electrical distribution system.YYour account gives you our account gives you the advantage of the advantage of saving the enteredsaving the entered

system diagram. This is practical for systems with multiple scenarios of interconnections where the system goes

through ongoing changes over a

through ongoing changes over a period of time.period of time.Run the analysis and docuRun the analysis and document the results.ment the results.The program willThe program will

output the hierarchical system equipment tree

output the hierarchical system equipment tree with short circuit MVwith short circuit MVA calculated at each node. A calculated at each node. Short circuits contrib-Short circuits

contrib-uted by upstream (red) and downstream (blue) equipment are

uted by upstream (red) and downstream (blue) equipment are listed across each node:listed across each node:

• • PSE[PSE[ 2000.002000.00(7.00X/R) +(7.00X/R) + 17.1417.14(13.2X/R) =(13.2X/R) = 2017.12017.1(7.03X/R) ](7.03X/R) ] o o TX-1[TX-1[ 222.32222.32(18.0X/R) +(18.0X/R) + 18.4018.40(12.8X/R) =(12.8X/R) = 240.7240.7(17.4X/R) ](17.4X/R) ]   C-4[C-4[ 223.14223.14(13.8X/R) +(13.8X/R) + 14.3114.31(21.5X/R) =(21.5X/R) = 237.4237.4(14.1X/R) ](14.1X/R) ]   TX-3[TX-3[ 60.6660.66(12.9X/R) +(12.9X/R) + 17.2817.28(25.1X/R) =(25.1X/R) = 77.977.9(14.5X/R) ](14.5X/R) ]   M-4[8.94]M-4[8.94]   M-3[5.96]M-3[5.96]   M-2[2.38]M-2[2.38]   C-1[C-1[ 231.5231.5(13.1X/R) +(13.1X/R) + 4.1304.130(5.37X/R) =(5.37X/R) = 236236(12.8X/R) ](12.8X/R) ]   TX-2[TX-2[ 15.5515.55(5.93X/R) +(5.93X/R) + 5.4915.491(5.27X/R) =(5.27X/R) = 21.021.0(5.93X/R) ](5.93X/R) ]   C-2[C-2[ 15.6615.66(3.17X/R) +(3.17X/R) + 1.481.48(4.50X/R) =(4.50X/R) = 17.117.1(3.26X/R) ](3.26X/R) ]   MCC-2[1.48]MCC-2[1.48]   C-3[C-3[ 14.9514.95(3.29X/R) +(3.29X/R) + 2.672.67(4.50X/R) =(4.50X/R) = 17.617.6(3.43X/R) ](3.43X/R) ]   MCC-1[2.67]MCC-1[2.67]   M-1[1.47]M-1[1.47]   C-5[C-5[ 232.9232.9(9.65X/R) +(9.65X/R) + 00(12.0X/R) =(12.0X/R) = 233233(9.65X/R) ](9.65X/R) ]   TX-4[TX-4[ 7.2687.268(3.78X/R) +(3.78X/R) + 0.000.00(0.00X/R) =(0.00X/R) = 7.277.27(3.78X/R) ](3.78X/R) ] PNL-1[0.00] PNL-1[0.00] Since short circuit

Since short circuit MVMVA values are added A values are added vectoriallyvectorially, ariphmetic a, ariphmetic addition of upstream ddition of upstream and downstream and downstream SC MVSC MVAA

does not generally equals the total SC MVA. Upstr

does not generally equals the total SC MVA. Upstream and downstream values eam and downstream values above contain one above contain one more significantmore significant

digit than required by error analysis rules. This digit is dropped off the final result (in green

digit than required by error analysis rules. This digit is dropped off the final result (in green color). In this manner,color). In this manner,

phenomeno

phenomenon known as "roundn known as "round-off error" is effectively avoide-off error" is effectively avoided. Divide total SC MVd. Divide total SC MVA values by 1.73 * kVA values by 1.73 * kV_LL_LLto getto get

3 phase short circuit current values in kA. Record the resulting sho

3 phase short circuit current values in kA. Record the resulting short circuit currents in the reference table:rt circuit currents in the reference table:

ID ID LLA A B B E E LL DESCRIPTION DESCRIPTION V V ooll ttaa ggee ,, kkV V S S C C M M V V A A rraa ttiinn gg S S C C M M V V A A eerr rroo rr,, % % X X //R R X X //R R eerr rroo rr,, % % P P A A R R E E N N T T C C aall cc.. S SCC M MV VA A C C aall cc.. IIS S C C ,,kk A A N N oodd ee 1 1 PPSSE E PPSSEE--SSOOUUTTH H 22000000MMVVA A SS..EE. . 11115 5 2200000 0 0 0 7 7 0 0 00 2017.12017.1 _10.13_{10.13 a)}_a) 2 2 TTXX--1 1 TTXX--1 1 220 0 MMVVA A ZZ==88% % DD--YYRRG G 1133..8 8 22550 0 0 0 2222..3 3 0 0 11 240.7240.7 _10.1_{10.1 b)}_b) 3 3 CC--4 4 11--11//CC--44//0 0 AAWWG G 22110 0 FFEEEET T CCU U 1313..8 8 111100550 0 0 0 00..9 9 0 0 22 237.4237.4 _9.93_{9.93 c)}_c) 4 4 CC--5 5 11--11//CC--22//0 0 AAWWG G 44000 0 FFEEEET T CCU U 1313..8 8 4422005 5 0 0 0..6 0 6 0 0 22 233233 _9.75_{9.75 d)}_d) 5 5 CC--1 1 11--11//CC--44//0 0 AAWWG G 33000 0 FFEEEET T CCU U 1313..8 8 7777335 5 0 0 0..9 0 9 0 0 22 236236 _9.87_{9.87 e)}_e) 6 6 TTXX--3 3 TTXX--3 3 5 5 MMVVA A ZZ==66% % DD--YYRRG G 2..4 24 8833..3 3 0 0 1122..6 6 0 0 33 77.977.9 _18.7_18.7 _f)_f) 7 7 TTXX--4 4 TTXX--4 4 00..3 3 MMVVA A ZZ==44% % DD--YYG G 00..448 8 77..5 5 0 0 33..7 7 0 0 44 7.277.27 _8.7_{8.7 g)}_g) 8 8 TTXX--2 2 TTXX--2 2 1 1 MMVVA A ZZ==66% % DD--YYG G 00..448 8 1166..667 7 0 0 55..7 7 0 0 55 2121 ₂₅_{25 h)}_h) 9 9 MM--2 2 339988KKVVA A 1166..77%%Z Z 1177..6622XX//R R 22..4 4 22..338 8 0 0 1177..6 6 0 0 66 1 10 0 MM--3 3 999966KKVVA A 1166..77%%Z Z 2244..9977XX//R R 22..4 4 55..996 6 0 0 225 5 0 0 66 1 11 1 MM--4 4 11449944KKVVA A 1166..77%%Z Z 2288..4433XX//R R 22..4 4 88..994 4 0 0 2288..4 4 0 0 66 1 12 2 PPNNLL--1 1 0 0 SSCCMMVVA A 448800V V PPAANNEEL L 00..448 8 0 0 0 0 0 0 0 0 77 1 13 3 CC--3 3 22--11//CC--33550 0 MMCCM M 11225 5 FFEEEET T CCU U 00..448 8 6666..8 8 0 0 1 1 0 0 88 17.617.6 _24.2_24.2 _i)_i) 1 14 4 CC--2 2 22--11//CC--33550 0 MMCCM M 11225 5 FFEEEET T CCU U 00..448 8 6666..8 8 0 0 1 1 0 0 88 17.117.1 _20.7_20.7 _j)_j) 1 15 5 MMCCCC--1 1 444466KKVVA A 1166..77%%Z Z 44..55XX//R R 00..448 8 22..667 7 0 0 44..5 5 0 0 1133 1 16 6 MM--1 1 224477KKVVA A 1166..77%%Z Z 1144..2211XX//R R 00..448 8 11..447 7 0 0 1144..2 2 0 0 88

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Appendix A

Primary Substation % Impedance

If specific information is not available use the following as a guide

For transfo

For transformers 501 trmers 501 to 10000o 10000kVkVA A 3 phase a3 phase and 501 to 5nd 501 to 5000kV000kVA 1 phaseA 1 phase

From American Standards As

From American Standards Association Standard C57.12.10-195sociation Standard C57.12.10-19588

(Included in NEMA T

(Included in NEMA Transformer Standaransformer Standard TR-1-1962)rd TR-1-1962)

* - generally pertains to all voltages 600V

* - generally pertains to all voltages 600V and belowand below

Secondary Substation Impedance Data:

Secondary Substation Impedance Data: High V

High Voltage 1oltage 15kV Max, Lo5kV Max, Low Vw Voltage 6oltage 600V Max00V Max

If specific information is not available use the following as a guide

Note: NEMA industry standards allow a maximum manufacturing tolerance of

Note: NEMA industry standards allow a maximum manufacturing tolerance of +/- 7.5% of the specified trans-+/- 7.5% of the specified

trans-former impedance value.

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Appendix B

Copper Conductor Cable Reactance and Resistance Data:

Copper Conductor Cable Reactance and Resistance Data: T

Typical Vypical Values - alues - Use ExacUse Exact data t data if Aif Available.vailable.

Line-To-Neutral mOhm per 100 feet

Square D Bus Duct Reactance and Resistance Data

Square D Bus Duct Reactance and Resistance Data Line-To-Neutral mOhm per 100 feet

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Appendix C

Motors and Generators

T

Table A. Percent able A. Percent values ovalues on machinn machine KVe KVA ratingA rating

Note: X" for induction motor groups >50 HP and <50

Note: X" for induction motor groups >50 HP and <50 HP are typically assumed equal toHP are typically assumed equal to

16.7%. Using the impedance multipliers, this corresponds to an equ

16.7%. Using the impedance multipliers, this corresponds to an equivalent motor contri-ivalent motor

contri-bution of 3.6 to 4.8

bution of 3.6 to 4.8 times the full load current.times the full load current.

T

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T

Table C. Tyable C. Typical X/R values for genepical X/R values for generators and synchronourators and synchronous motorss motors

T