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Transcript of 25 - Battery Sizing & DischarBattery Sizing & Discharge.pdfge
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Battery Sizing &
©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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When does a battery kick in?
• Load in DC System exceeds the battery
•
• ower s os genera y e wors case
scenario]
Slide 2©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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IEEE 485- Definitions
• Battery Duty Cycle
specified period of time (sum of all individual loads)
• Cell Size
– Rated capacity of a lead acid battery or number of
positive plates in a cell
• Period
– Time interval for which the load is assumed to be
constant
• Vpc
Slide 3©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
– Volts per cell (individual cell voltage)
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Duty Cycle Classification
• Continuous Load (Non-Random)
– on-ran om oa s
– Normally carried by the battery charger
– Includes lighting, converters, indicating lights,
communications systems, continuously operating motors
• on- on nuous oa an om or on- an om
– Emergency pumps
– MOV operations
– Critical ventilation system motors
Slide 5©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
– Fire protection systems actuators
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Duty Cycle Classification
• Momentary Loads (Random or Non-Random)
– oa s w ura on a o no excee more an
one minute
– MOV with stroke of less than a minute
– Field flashing of generators
– Motor starting currents
– nrus curren s so eno s, re ay co s, e c
Slide 6©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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Individual Load Duty Cycles
• Static Loads
• Motor loads
• DC Lump Loads
• Elementary Elementary Diagram
• DC to AC Inverters
Slide 7©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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Guidelines for Battery Duty
yc es
be higher or equal to one minute
• First identify the non-random load battery
duty cycle
• Find worst case scenario
• Include the random load duty cycle
•
Slide 8©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
conservative combination of the two
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Duty Cycle Example A
Slide 9©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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Duty Cycle Example B
Slide 10©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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Battery Modeling
• Battery voltage based on manufacturer
• Enter batter characteristic curves in batter
library
• nterpo at on extrapo at on s per orme to
obtain battery size and discharge voltage
pro e
Slide 11©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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Characteristic Curves
Battery Characterist ic Curves
1000.00 1.5
1.6
1.67
100.00
e ( m i n . ) 1.75
1.78
10.00 T i m
.
1.84
1.88
1.00
10.00 100.00 1000.00
1.92
1.96
Slide 12©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
Amps per Positi ve Plate
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Interpolation Methods
Slide 13©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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Battery Sizing Study Case
• Load Summation
– s a e oa u y cyc es
– Generally more conservative for systems with more
• Load Flow Method – Adds all the load duty cycles, but performs a load flow
calculation at every time step to account for systemlosses more realistic results
– Generally more conservative for systems with moreconstant power loads
Slide 14©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
– Load model type based on load type or duty cycle type
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• Load Duty Cycles
– eren sys em u y cyc es
• Correction factors
– Battery minimum temperature
– Aging compensation
– Initial capacity
– Design margin
• Voltage Requirements
– Maximum system voltage deviation (charging voltage)
– Minimum system voltage deviation (depends on finalVpc)
Slide 15©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
– Battery minimum discharge voltage (final Vpc)
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Battery Discharge Page
• Vd Calculation Parameters
– Time step and maximum voltage limit• Correction Factors
– Same as battery sizing (no design margin)
• Load Flow Parameters
–
– Precision
Slide 16©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
– Initial conditions and motor load handling
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Displayed Results
• Tabulated results for battery voltage, bus
system
• One-line diagram displayed results (similar
to DC load flow)
• Complete set of plots that include battery
, ,flows
Slide 18©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
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Things to Consider
• Obtain as many battery characteristic curves
• Obtain specific curves for battery model and
type
•
methods
• Use most conservative approach for yoursystem (load flow method or load
Slide 19©1996-2010 Operation Technology, Inc. – Workshop Notes: Battery Sizing & Discharge
summation)