Battery Sizing
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electrical...
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ELECTRICAL DESIGN PROCEDURES
BATTERY SIZING CALCULATIONS
DTP-E-GEN-1003-00
ROLTA INDIA LIMITED
EDS ELECTRICAL DESIGN PROCEDURES Battery Sizing Calculations Calculations DTP-E-GEN-1003-00 Revision History Revision Level
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Department Head (Approver)
This Document and all contained herein are proprietary of ROLTA INDIA LIMITED and is subjected to confidentiality restrictions
between ROTLA INDIA LIMITED and the Recipient. Copyright Reserved.
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Table of Contents Sr. No 1 2 3 4
5 6
Description
Page no.
Purpose & Scope Applicability References Procedure 4.1 General 4.2 Methodology of Calculation 4.3 User’s Manual 4.4 Sample Output Battery Sizing & Battery Charger Sizing Sample Calculation of Battery Sizing
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3 3 3 5 6 6 9 10 25
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1. Purpose & Scope The purpose of this ETP is to describe the methods, which should be used to size, or to verify the sizing of batteries and battery chargers and to determine the short circuit current available from the battery and from the charger. The purpose of this procedure is to provide:
A pre-approved calculation template to aid in calculating sizes and available short circuit currents for battery and charger.
User instructions for EL-105 “Battery Sizing, Battery Charger Sizing, and available Short Circuit Current,” for developing the user inputs and for performance of the calculation of the size and short circuit current contribution for battery and battery.
2. Applicability This procedure is applicable to all projects. 3. References 3.1 EL-105, “Battery & Battery Charger Sizing & Available Short Circuit Current,” Version 00, Level 00. 3.2 Mathcad Version 7, Mathsoft Inc., Cambridge, MA 3.3 “IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications,” IEEE Standard 485-1997. 3.4 “IEEE Recommended Practice for Design of the DC Auxiliary Power Systems for Generating Stations,” IEEE Standard 946-1992. 4. Procedure 4.1 General The Electrical and Control Systems Engineer shall prepare a calculation to size batteries and chargers and to determine available short circuit currents for all project procured DC systems. DC components procured as part of a vendor supplied system (such as a fire alarm system) where others are responsible for determining the electrical loads, do not require the preparation of a calculation by the Engineer.
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4.2 Methodology of Calculation
This ETP contains a pre-approved calculation EL-105, including battery sizing methodology adapted from IEEE 485, battery charger sizing methodology adapted from IEEE 946, and methodologies for calculating available short circuit current from the battery adapted from IEEE 946, Annex B, and available short circuit current from the battery charger adapted from IEEE 946, Annex D.
4.3 User’s Manual The EL-105 is divided into three sections: a) Input b) Calculation c) Results 4.3.1 Input Data: General: The input section of the EL-105 Mathcad template should be completely filled in. All input data necessary for this calculation shall be obtained from the project design criteria, specifications, or IEEE referenced standards. IEEE Standards 485-1997 and 946-1992 describe all necessary calculation procedures for the selection or development of input data. The user is prompted to input the battery duty cycle data, the design margins, battery manufacturer and battery cell data, and battery charger design parameters. All definition equations denoted by “:=” shall be filled in. The user can modify the information and text in the Input section.Text inputs shall be contained in quotations (“TEXT”). The technical basis and source of the inputs shall be properly documented in the body of the project calculation. Note: When entering data or text be careful that the cursor encompasses the data or text only and not the entire equation. Otherwise, the equation will be deleted when using “cut” or “backspace.” and cannot be undone. Should this occur, either start a new or copy the deleted formula from the original file and paste it in the working file. Load Duty Cycle The load duty cycle shall be developed following the instructions in IEEE 485. Enter the loads for each step of the battery duty cycle in matrix “A” and associated durations in matrix “M.” The input matrices should be adjusted for the number of periods needed for the duty cycle by using “CTRL M” and adjusting the number of rows in each matrix © Copyright 2008. Rolta India Limited. All Rights Reserved.
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accordingly. MathCAD will not handle a single element matrix. If the load duty cycle is a continuous value, such as for a UPS battery, use a 2 row by 1 column matrix and assign the value of zero to the second row element Enter random load, if required, and the associated time duration. Design, Aging Margin, & Battery Room Temperature Enter design margin, aging factor, and electrolyte temperature in degrees F. Design margin and temperature are project-determined values. IEEE 485 recommends a design margin of 10-15%. The temperature should be the lowest expected temperature for the battery room. Provide reference for design temperature. Battery Type Select a battery manufacturer and cell type and enter this text as shown on the template. Enter the nominal cell voltage, typically 2.00 Volts-per-cell. Enter the minimum cell voltage and total number of cells. Consult IEEE 485 or the specialist for direction in determining these values. Enter the values for time durations (all combinations) and lookup the associated Amperes-per-positive-plate (R factors) for each time. Enter these into matrix “R.” The user can look ahead to page 9 of the calculation to determine the needed values of time from the calculated time matrix “T,” and then enter the values in matrix “R.” Enter the total number of plates in the “TotalPlates” matrix based on the selected manufacturer’s cell data sheet. Enter the associated 8-hour Ampere-hour discharge ratings in the “BattSze_Ah,” matrix. If additional sizes or a change in the cell type needs to be made, this can be adjusted at any time. From the manufacturer’s initial voltage curve for the chosen battery cell type select two points and enter the voltage and Amperes-per-positive-plate values for each point. Battery Charger Design Parameters The battery charger input data should be entered as follows: 8 to 24 hours recharge time. Recharge efficiency factor of 1.1. Continuous load Amperes that must be served by the charger during normal plant © Copyright 2008. Rolta India Limited. All Rights Reserved.
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operations (ac restored) while the battery is being recharged. Largest combination of noncontinuous loads that would be likely to be connected to the bus simultaneously during normal plant operations. The “StdCharger” matrix lists the most commonly available charger sizes. If necessary, the user can add sizes to this matrix by using “CNTRL M.” 4.3.2. Calculation Template parameters are set. These parameters are not user adjustable without removing the lock on the pre-approved calculation. Special functions are defined to allow the creation of a graphical presentation of the load duty cycle entered. Calculation of Battery Size The template calculates the size of the battery using the positive plate method of calculation for sizing lead-acid batteries taken from IEEE 485. Temperature correction factors from IEEE 485 have been included in the template for automatic lookup by Mathcad. The number of positive plates is calculated using design margins from the input and a lookup feature determines the Ampere-hour size of the battery based on the input data. Calculation of Battery Charger Size The template calculates the size of the charger based on the calculation methodology of IEEE 946. This method compares the Ampere-hours from the battery with the sum of the continuous and non-continuous loads and selects the larger sized charger. The template calculates two charger sizes based on the IEEE 946 method comparing the “sum of the continuous and non-continuous loads” with each of the following: 1. The load duty Ampere-hours discharged from the battery. 2. The 8 hour Ampere-hour rating of the selected battery. Calculation of Battery and Charger Short Circuit Current Battery short circuit current is calculated automatically using the input data from the initial voltage curve of the battery. Battery charger short circuit current is calculated automatically using the input data, and in accordance with Annex D of IEEE 946, is based on 1.5 times the full load rated output. The values of short circuit current for both battery and charger are calculated at the nominal system voltage (typically 120 Vdc for a 60 cell battery) for use in the © Copyright 2008. Rolta India Limited. All Rights Reserved.
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DC system fault current analysis calculation.
4.3.3. Results The Calculation and Results sections of the MathCAD template is “locked” to prevent accidentally changing the equations from the qualified MathCAD template. The password to unlock the calculation section is “SW245.” If the calculation section is unlocked, the engineer shall review and check the entire calculation including the pre-approved areas. The date when the qualified Mathcad files were locked is Friday, September 4, 1998. In order to properly print the date stamp for the locked area on page 6 of the program, a non-postscript print driver must be used. The Results section repeats the essential input data and then prints the results of The template for each section of the calculation, “Battery Size,” Battery Charger Size,” and “Short Circuit Current Available.” This is done for convenience of viewing the input data with the results. 4.3.4. Program Limitations and General Instructions The methodology is based on sizing batteries of the lead-acid stationary battery type, which includes Lead-Calcium, Lead-Antimony, and Lead-Selenium. It is recommended to use the Lead-Calcium type for stationary battery use. It is not suitable for use in sizing Nickel-Cadmium type batteries. Refer to IEEE Standard 1115-1992 for guidance for this type of battery cell. The template calculates battery charger size in the following two ways: 1. The larger of the Ampere-hours discharged from the battery or the combination of continuous and non-continuous loads. 2. The larger of the rated Ampere-hour size of the selected battery or the combination of continuous and non-continuous loads. 3. The more conservative approach using the Ampere-hour rating of the battery is recommended in IEEE 946. The user should select the method that satisfies the project specification requirements. The template calculates the available short circuit currents for batteries and chargers at their terminals. This data is intended for use as input to a dc system fault analysis calculation. The value of charger short circuit current should be selected based on the associated sizing method. The calculation assumes the intercell connector resistance is included in the manufacturer’s initial voltage curve. If the intercell connector resistance is © Copyright 2008. Rolta India Limited. All Rights Reserved.
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not included in the input data, the resulting short circuit current at the terminals
of the battery will be a conservatively higher value. The resistance values of inter-rack and battery terminal cables shall be included in the DC system fault current analysis calculation and are not included in this calculation. The heading and footer of the template can be modified, except that the left hand section of the footer, “EL 105 V00 L00” shall not be changed. MathCAD Version 7.0 or later and Windows 95 operating system are required to run EL-105. The Page Setup feature for the Mathcad files is set to ensure proper printing as follows: a) Letter 8.5 x 11 inch b) Portrait c) Margins are set: Left and Right are 1.0 inch; Top is 1.5 inch; Bottom is 1.0 inch 4.4. Sample Output EL-105 The entire output of EL-105 should be included as an attachment to a project calculation. In the Methodology section of the project calculation, the following text shall be included to describe the methodology used in EL105. Attachment A (Note: Attachment A should represent the actual battery and charger sizes calculated and not the appendix A example attached to this ETP) is the output of EL-105, “Battery Sizing, Battery Charger Sizing, and Available short Circuit Current,” a MathCAD template. Attachment A includes a run of sample battery sizing, charger sizing, and short circuit calculations. The battery data used is taken from the sample calculations in IEEE 485, Figures A1 and A4.
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5.
BATTERY SIZING CALCULATIONS
DTP-E-GEN-1003-00
BATTERY SIZING, BATTERY CHARGER SIZING AND AVAILABLE SHORT CIRCUIT CURRENT References: 1. IEEE 485 - 1997, “IEEE Recommended Practice for Sizing Lead-Acid Batteries for
Stationary Applications.” 2. IEEE 946 -1992, “IEEE Recommended Practice for the Design of DC Auxiliary Power Systems for Generating Stations.” I.
INPUT A. Load Duty Cycle The load duty cycle is developed per instructions contained in IEEE 485. Loading of each section of battery discharge, in Amperes ( Column 2 in IEEE 485, worksheet Figure A-4).
Time duration of each section of battery discharge, in minutes (Column 4 in IEEE 485,workshe -et Figure A-4).
320 100 280
A=
1 29 30 B=
200 40 120
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60 59 1
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Note: Use CTRL "M" to insert or delete rows and columns in the above matrices. .Random A := 100 Random Current, A Random M :=1 Time duration of random current, minutes B. Design, Aging Margin, & Battery Room Temperature
DesignMargin ----------------AgingFactor ----------------Electrolutye temp Low-------C. Battery Type
1.15 1.25 65 °F
(USER TO MODIFY - TEXT IN QUOTES)
The battery manufacturer's type of cell is selected as follows: Reference -------------------- "ABC-123" Manufacturer----------------- "ABC" Cell Type-------------------"XYZ" Cell Voltage-----------------2.00 Volts-per-cell, nominal open circuit. Minimum_Cell_Voltage--1.75 ----- Volts-per-cell Total Number Cells = 60 R factor for battery: 1 st Column is the time duration associated with a specific R factor. 2 nd Column is R factor (Item 6A of Column 6 discharge period in IEEE 485, Sample Worksheet Figure A-4).
Cell Type ="XYZ" Available battery sizes, in terms of the total number of plates and Ampere-hour ratings for an 8 hour . 1
R=
104
11
30 55.4
13
59 40
15
60 40
17
TotalPlates=
90 32.5 119 27.5
19 21
120
27.5
23
150
24.0
25
179
21.5
27
180
21.5
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400
480 560
Batt Size_Ah=
640 720 800
880 960
64
1040
Note: Use CTRL "M" to insert or delet rows and columns in theabove matrices Select two points on the manufacturer's initial voltage curve (V1,I1) and (V2, I2) that will be used for the calculation of short circuit current: (Ref. IEEE 946-1992, Fig. B.1) V1
1.90
V2
1.50
Volts
I1=60
Volts
I1=370
Amperes per positive plate Amperes per positive plate
D. Battery Charger Design Parameters(Reference IEEE 946-1992, Sample A.3) Tc8
Time to recharge the battery to approximately 95% of capacity (in hours) (This is same as the symbol "T" in equation 1 of IEEE Std 946, which was modified to avoid confusion with the use of "T" in battery sizing).
C=1.1
Constant that compensates for battery losses.
L c 50
Continuous dc load (Amperes), including future load growth (1.30 factor), in Amperes.
L n 60
The largest combination of noncontinuous loads in Amperes (as defined in IEEE Std 485) that would likely be connected to the bus simultaneously during normal plant operations. 3 6 12 25 50 75
StdCharger = © Copyright 2008. Rolta India Limited. All Rights Reserved.
100 150
Standard Charger Sizes, Amperes DC
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200 300 400 432 500 600 800 1000
II. Calculation A. Template Parameters
the
see= rows A)
sec 6
i= 1 sec
j= 1 sec
m= 1 sec
n= 1 sec
Lookup num A1 A2) = for return
S
ORIGIN=1
i €1 last A1)
This defines a function called Vector "A,"
A2 if
value in the is returned.If "A",then the messa -ge "NF" (not found) is returned.
A1inum
i "NF"
Replicate A s) =
k
0 for
i €1 last A)
Creates a function called "Replicate" which doubles the size of matrix A, repeating the value of each element.
for j €1 s TkjAi k k 2
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+ T
LookupCol Vector sF) = for
i €1 last Vector)
return
S
Similar to "Lookup" function, except only the first column is used. Vector if
"Out of Range"
B Duty Cycle Curve Plot CREATING THE "CURRENT" VECTOR AA
= Replicate (A, 2)
Double the size of the current "A" matrix and call it "AA" matrix.
AA rows (AA)+1 : = 0 q :=1 ( rows AA)+1 )
Add an additional element to "AA" matrix at the end and set it equal to zero so that current curve will return to zero.
AAAq :=if ( q =1,0,AA q-1
Current Vector"AAAq"
CREATING THE "TIME" VECTOR
r:= 2 rows (M) time1 := M1
Set first element of "time" matrix to first element of "M" Add the next element of "M" matrix to the previous element of "time" matrix.
timer : =Mr + time r-1 Dbl_time := Replicate (time ,2 )
q := 1 ( rows (Dbl_time)+1 )
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"Time" matrix is now doubled and called "Dbl_time."
Add additional element to "Dbl_time" matrix at the beginning, and set it equal to 0.
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Dbl_timeplusq := if (q =1, 0
DTP-E-GEN-1003-00
Dbl_time q-1)
q := 1 ( rows (Dbl_timeplus) + 1 )
Repeat above step to add one additional 0
element. DDbl_timeplusq := if (q= 1, 0Dbl_timeplus q-1) C. Change in Load
∆Ai :=if [i = 1, Ai,Ai - A (i-1) ] Change in load Amperes of present section load compared with the previous section load (Column 3 in IEEE 485 example.
320 -220
180
∆A =
-80
80
∆A_testi : = if (i= sec, Ai, Ai – Ai+1) 220
Change in load Amperes of previous section load compared with present
∆A_test section
load.
160
-80 120
D. Time to End of Section (minutes) T(i i) := 0 T1, j := if [ j= 1, M1Mj + T1(j -1) Ti,j :=if [ i= 1 ,Ti,jT(i – 1j) – M (i-1)] . Tij := if ( Ti,j ≤ 0,0, Ti,j ) Ti,j := if ( ∆ - testj < 0,0,Ti,j )
Eliminates section calculation if load duration of
the next section is greater than present section,
i.e., Ai+1 is greater than Ai
1 0 60 120 0 180 ime to end of section, in minutes. 0 0 30 90 0 150 Columns represent each section;
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ELECTRICAL DESIGN PROCEDURES T=
BATTERY SIZING CALCULATIONS
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rows represent the period within each section.
0 0 0 60 0 120 0 0 0 0 0 60 0 0 0 0 0 1
E. IEEE 485 Temperature Correction Factors The first column is the electrolyte temperature in degrees F. The second column is the correction factor from Table 1 of IEEE 485.
Table 1a =
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25
1.520
78
0.980
30
1.430
79
0.987
35
1.350
80
0.980
40
1.300
81
0.976
45
1.250
82
0.972
50
1.190
83
0.968
55
1.150
84
0.964
60
1.110
85
0.960
65
1.080
86
0.956
66
1.072
87
0.952
67
1.064
88
0.948
Table 1b =
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1.056
89
0.944
69
1.048
90
0.940
70
1.040
95
0.930
71
1.034
100
0.910
72
1.029
105
0.890
73
1.023
110
0.880
74
1.017
115
0.870
75
1.011
120
0.860
76
1.006
125
0.850
77
1.000
DTP-E-GEN-1003-00
Table1 := stack (Table 1a,Table1b ) TempCorrFactor := Lookup ( ElectrolyteTempLow Table11 ) TempCorrFactor 1.11 F. Battery Size - Positive Plate Method (R Factor) R1 : =R Rmatrix i,j
R2 := R
Divides the 2 column matrix, "R," into two vectors.
: = if ( Ti,j = 0, 0,Lookup (Ti,j ,R1,R2 ))
This is matrix of R factor of each value of time in the matrix ‘T’. If the time in “T” is zero, then the value in “RMatrix” is set to zero. If a value in “T” is not found in matrix “R”, an input, then “NF” (Not Found) is reported. The user has to then to correct his input matrix R by inserting missing value(s).
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This replicates DA into a matrix of identical columns.
This calculates the required section size (Column 7 in IEEE 485) , the number of positive plates for each period in each section.
This is the section size of each section.The subtotal of each column of matrix “Col 7” in Ampere-hours. MaximumSectionSize = max (SubtotalCol7) This is maximum section size, in positive plates. MaximumSectionSize 7.1748
Positive plates, maximum section size
Random A
This is the number of positive plates
Random Section Size: = Lookup (Random M R1R2) © Copyright 2008. Rolta India Limited. All Rights Reserved.
required for the random load.
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RandomSectionSize 0.962
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Positive plates, random load.
UncorrSizeRFactor: = MaximumSectionSize + RandomSectionSize UncorrSizeRFactor: = 8.136 Uncorrected total number of positive plates. PositivePlatesRq: = UncorrSizeRFactor X TempCorrFactor X DesignMargin X AgingFactor PositivePlatesRq: = 12.63 PositivePlates: = ceil (PositivePlatesRq) PositivePlates: = 13 Total number of positive plates required. Plates: = (2 X PositivePlates) + 1 Plates = 27 Total number of plates required. AmpHour_SizeR:= Lookup (Plates TotalPlates BattSze_Ah) AmpHour_SizeR = 1040 Ampere-hour size of battery required (R factor) G. Charger Size
Charger size based on Ampere-hours discharged from the battery:
Total ampere hours discharged from the battery during its specified duty cycle, Ampere-Hours. I 1= L c + C Ah
I1 = 144.971
Minimum required charger size,Ampere
Tc I 2 = Lc + L n
(Equation 1 from IEEE 946 ). I2 = 21.78
I 3= if (I 1, I 2I 1 I 2 )
Sum of continuous and noncontinuous loads, Amperes (Equation 2 from IEEE 946). Larger of the two above sizes.
I3 = 144.971
Charger_Size:= LookupCol (StdCharger I 3 1) Charger_Size 150
Amperes DC, based on Ampere-Hours discharged from the battery.
Charger size based on the rated size of the selected battery: Minimum required charger size, based on Ampere-hours size of selected battery © Copyright 2008. Rolta India Limited. All Rights Reserved.
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(Equation 1 from IEEE 946).
Sum of continuous & noncontinuous loads, Amperes (Equation 2 from IEEE 946) Larger of the two above sizes.
Selected_Charger_Size:= LookupCol( StdCharger , I 5 , 1) Selected_Charger_Size 200
Amperes DC, based on rated Ampere-hours of the selected battery.
H. DC SOURCE SHORT CIRCUIT CONTRIBUTION Battery (Based on IEEE Standard 946, Annex B): The internal resistance of a cell is calculated from the slope of the initial volts line of the Published discharge characteristic curve of the manufacturer. The internal resistance is Determined as follows: PositivePlates = 13 Rp=( V1 (I2
Number of positive plates
- V2)
Rp =1.29 x10-9
I1) Rp= Rp Positive plates
Ohms per positive plate.
-
Rt =9.926 x10-5
Rb Rt Total_Number_Cells
Total internal resistance of cell
Rb 5.955 x10-3 Ohms,total battery resistance.
The short circuit current available at the cell terminals is found from Ohm's law as follows: CellVoltage 2.00
Volts/cell, nominal cell voltage
Batt_Voltage = CellVoltage Total_Number_Cells Batt_Voltage 120
Volts, nominal battery voltage
Ic1 20150
Amperes, available short circuit current
2. Battery Charger (Based on IEEE Standard 946, Annex D): The maximum battery charger available continuous short circuit current is 1.5 times the full load current rating of the charger. Charger Voltage: = Batt_Voltage Charger Voltage = 120 Volts, DC © Copyright 2008. Rolta India Limited. All Rights Reserved.
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Charger based on the larger of the the Ampere-hours discharged from the battery or the combination of continuous and non-continuous loads: Charger_Size 150 Amperes Icharger_fault=1.5 charger_Size Icharger_fault =225 Amperes Charger based on the larger of the rated Ampere-hour size of the battery or the combination of continuous and non-continuous loads: Selected_Charger_Size = 200 Amperes Icharger_Selected_fault:= 1.5 Selected_Charger_Size. Icharger_Selected_fault = 300 Amperes
A. Battery Size: 1. Inputs: Load Duty Cycle Section
Amperes Time (minutes)
320 1 100 29 280 A=
M=
30
200
60 59
40 1 120
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For load duration curve see the following curve-----
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DesignMargin =1.15 AgingFactor =1.25 ElectrolyteTempLow =65 Degrees F, lowest electrolyte temperature TempCorrFactor =1.08 2. Results:
Minimum_Cell_Voltage =1.75
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Volts per cell end voltage
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Total_Number_Cells = 60
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Total number of cells
PositivePlates =13
Number of positive plates
Plates =27
Total number of plates required.
AmpHour_SizeR =1040
Ampere-hours for an 8 hour discharge to the specified Volts-per-cell end voltage.
Manufacturer ="ABC"
Cell_Type ="XYZ"
B. Battery Charger Size: 1. Inputs: T c= 8
Hours, recharge time
C =1.1
Recharging efficiency constant
L c =50
Amperes, continuous DC load
L n= 60
Amperes, largest combination of noncontinuous loads
2. Results: Charger_Size =150
Amperes DC, based on the larger of the the Ampere-hours discharged from the battery or the combination of continuous and non-continuous loads.
Selected_Charger_Size =200
Amperes DC, based on the larger of the rated Ampere-hour size of the selected battery or the combination of continuous and non-continuous loads.
C. Short Circuit Current Available 1. Inputs: CellVoltage =2.00 Volts per cell, nominal
Initial Voltage Curve Data V1 = 1.90
Volts
I1 = 60
Amperes per positive Plate.
V2 = 1.50
Volts
I2 = 370 Amperes per positive Plate.
2. Results : © Copyright 2008. Rolta India Limited. All Rights Reserved.
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ELECTRICAL DESIGN PROCEDURES
BATTERY SIZING CALCULATIONS
DTP-E-GEN-1003-00
a. Battery Short Circuit Current Batt Voltage = 120 Volts, DC, nominal battery short circuit voltage. Ic1 = 20150
Amperes, available battey short circuit current
b. Battery Charger Short Circuit Current Charger Voltage = 120 Volts, DC, nominal charger short circuit voltage. Charger based on the larger of the Ampere-hours discharged from the battery or the combination of continuous and non-continuous loads. Icharger Fault = 225
Amperes, available charger short circuit current
Charger based on the larger of the rated Ampere-hour size of the battery or the combination of continuous & non-continuous loads: Icharger Selected Fault = 300 Amperes, available charger short circuit current.
6.SAMPLE CALCULATION OF BATTERY SIZING 1.0 Site and system Conditions Ambient temp. : Max: 46.6°C, Min: -0.7°C Design ambient temp. : Max: 45°C, Min: 10°C (for battery sizing) Maximum voltage : 220, +10% 242V (as per Bid package)
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ELECTRICAL DESIGN PROCEDURES Minimum voltage End cell voltage
BATTERY SIZING CALCULATIONS
DTP-E-GEN-1003-00
: 220, -10% = 198 V (as per Bid. package) : 1.16V (as per Bid package)
2.0. Battery sizing calculation 2.1 No of cells Number of battery cells shall be based on the following No.of cells : Maximum allowable system voltage/Float charging voltage per cell =242V/ 1.41 = 171.63 = 172 Minimum system voltage ≥ No of cells x End cell voltage = 172 x 1.16= 199.52V No of cells selected : 172 2.2 Calculation of load cycle 2.2.1 Calculation of continuous electrical loads (I2)
S.NO
DESCRIPTION
QTY
TOTAL NO OF PANEL
LOAD(W) UNIT ITEM
TOTAL LOAD(W)
1
Indicating lamps for HV sw.bd (6.6kV & 33kV)
3 per panel
34
2.5
255
2
Indicating lamps for MV sw.bd
3 per breaker feeder
70
2.5
525
3
86 relay
2 per sw.bd
10
3.0
60
4
Aux.relay
1 per bkr feeder
100
3
300
5
Motor protection relay
50% of HV and MV motors
13
15
195
6
Motor diff. relay
As per project design data
3
15
45
7
Under voltage relay
4nos per sw.bd
5
15
300
8
ELR for motors rated above 22KW
50% of motors
I2
3
36
9
Annunciation panel loads
As per design data
—
—
—
10
DC lighting load
As per plan layout
-
-
2200
11
Misc.loads such as EPABX,LCP etc.
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As applicable
-
-
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-
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ELECTRICAL DESIGN PROCEDURES
BATTERY SIZING CALCULATIONS
12
Owner’s load for critical lighting
-
-
-
1000
13
Owner’s DC load for Elect. Control
.
-
-
2000
14
ECS Load
15
Any other load
DTP-E-GEN-1003-00
2000 -
-
-
-
Total load = 8916 watts TotaI current (I2) 40.55 Amps 2.2.2 Calculation of electrical load (I4) S.NO
DESCRIPTION
QTY
TOTAL NO OF PANEL
LOAD(W) UNIT ITEM
TOTAL LOAD(W)
1
HV incomer bkr tripping on U/V
2 no. per swbd
2
300
600
2
MV incomer bkr tripping on U/V
2 no. per swbd
7
200
1400
3
Breaker fed motor tripping on U/V
50% HV and MV motors
13
6 nos. - 300W (HV) & 7 nos. – 200W(MV)
3200
4
Aux.relay
1 per HV panel + 4 per PCC / EPMCC
46
3
138
5
Closing of EPMCC incomer
1No.
1
200
200
6
Any other load
-
-
-
-
Total load = 5538 watts TotaI current (I4) = 25.173 Amps 2.2.3 Calculation of electrical load (I5)
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ELECTRICAL DESIGN PROCEDURES
BATTERY SIZING CALCULATIONS
DTP-E-GEN-1003-00
DESCRIPTION
QTY
TOTAL NO OF PANEL
LOAD(W) UNIT ITEM
TOTAL LOAD(W)
I
Closing of main HV incomer bkr
2 nos. per substation
2
300
600
2
Closing of main MV incomer bkr
2 nos. per substation
2
200
400
3
Breaker spring charging motor
2 nos. per substation
2
400
800
4
Aux.relay
1 per HV panel + 4 per PCC / EPMCC
46
3
138
5
Any other load
-
-
-
-
S.NO
Total load = 1938 watts TotaI current (I5) = 8.809 Amps 2.24 Calculation of random electrical load (IR) IR = load expected during any period of the duty cycle = NIL Amps. Electrical Loads for various duty cycle are First minute duty cycle I1 =I2 + I4 = 40.53 + 25.173 = 65.703 for duration of’ M 1 minutes 66A for 1 min. Next duty cycle I2 = I2 = 40.53 A for duration of M2 minutes = Approx. 41A for 118 min cycle I3=I2+I5 = 40.53 + 8.809 = 49.339 for duration of’ M3 minutes = Approx. 50A for 1 min IR = lR for duration of MR minutes - NIL
= Approx. Last minute duty Random load if any
Loads and time duration is tabulated as shown below
2.3 Duty cycle diagram S. NO
LOADS(A)
DURATION(MIN)
1.0
I1
1
66
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REMARKS
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ELECTRICAL DESIGN PROCEDURES
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BATTERY SIZING CALCULATIONS
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DTP-E-GEN-1003-00
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