DC Supply System, Batteries,UPS - Copy.pdf

DC Supply
System &
Batteries
Manoj Barsaiyan
DGM, PMI

Battery Is Considered To Be The “HEART” Of
The Power Plant
 Battery provides the ultimate and
final DC back-up for emergency oil
pumps and other emergency
equipment.
 DC power for operation of all
switchgear protection and relays.
 Power for emergency lighting
within the generating station
building.
 Uninterrupted power for C & I
equipment and the ups systems.
 Power for vital communication
equipment (PLCC), essential for re-
synchronizing the unit with the grid
or for reviving the grid in the case
of a major grid failure.

What If The Battery Fails In An Emergency
 Unit Battery
 The emergency oil pump will not
operate which may lead to seizure of
the rotor bearings
 Loss of hundreds of crore of rupees
towards repairing the rotor and
generation revenue loss while the unit
is out of service.
 Switchgear associated with generator
may not trip which could lead to
generating transformer damage
 Failure of instrumentation and control
 Total darkness in the powerhouse

What If The Battery Fails In An Emergency
(contd.)
 Substation
 Switchgear and relays will not operate
causing extensive damage to
transformers and power lines
 PLCC
 Extremely difficult to resynchronize the
unit with the grid
 Major setback in the process of reviving
the grid in the event of a regional grid
failure
 If the battery fails while the unit is in
operation, it may become essential to
shutdown

DC SYSTEM IS
DESIGNED
• TO SUPPLY HIGH STANDARD OF RELIABLE &
SECURE DC POWER
• TO PROVIDE CONTINUOUS & QUALITY
POWER AS AND WHEN REQUIRED
• UNDER NORMAL & ABNORMAL OPERATING
CONDITIONS
• ULTIMATE & FINAL DC BACK-UP POWER TO
EQUIPMENT AND DC DRIVES WHEN TOTAL AC
SUPPLY FAILS
• HENCE THEY ARE BATTERY BACKED

DUTIES
• TO SUPPLY EQUIPMENT WHICH REQUIRES DC
DURING NORMAL CONDITIONS
• TO SUPPLY STANDBY EQUIPMENT/DC DRIVES
• TO SUPPLY STARTERS OF VARIOUS
EQUIPMENT
• TO SUPPLY EQUIPMENT WHEN AC SUPPLIES
HAVE BEEN LOST

Types of Power Supplies
In a Power Plant
• 11KV/3.3KV/415V AC Power Supply
• 415V AC Emergency Supply(DG)
• DC Power Supply
• UPS Supply

DC Power Supply
• Various Critical Drives
• Emergency DC Lighting
• Switchgear Control Supply for closing & tripping
• Control, Protection And Interlocks
• Indication, Annunciation & Alarm System
• Public Address System
• DAS And Communication System

DC Supplies……………Why?
• Emergency Lube Oil Pump
• Emergency Jacking Oil Pump
• Emergency Scanner Air Fan
• Emergency Seal Oil Pump
• Breaker/Unit Protections
• Emergency Lighting

The Ultimate Backup
In case of unit tripping / grid failure, either station
changeover takes place / DG would start.
Normally, grid supply would be restored in minimum
possible time and DG would shut down.
In case of DG failure, the DC backup comes in to
service to facilitate safe shut down.

Selection of voltage
DC POWER SUPPLY
• In power plant D.C. pumps, lighting require comparatively
high voltage due to their high power requirement. Hence as
a standard these applications are designed with 220V level.
• It is desirable to have comparatively lower voltage-
24V/48V/110V for control/indications/annunciation due to
safety reasons. However to avoid multiplicity of DC supplies
(particularly we require two control supplies), we have
adopted uniform 220V DC voltage for plant electrical
systems for switchgear control, protection and interlock
operation.

DC POWER SUPPLY
SCHEME
1. Earlier concept;
• 1X100% battery bank along with its chargers for each unit with inter-
unit interconnection through high capacity DC bus bar.
• In view of large size of above DC loads of each unit and the large unit
pitch it is necessary to provide a separate DC system (battery
+chargers) to enhance the plant’s overall reliability.
2) Present concept;
• In view of the reasons explained above 2x100% capacity DC system is
provided for each unit and switchyard separately.
• Minor DC loads of offsite areas in the plant i.e. WTP, Ash handling are
fed from plant DC system as it is now restricted to limited area
switchgear rooms, as control now no longer relay based.

The Single Most Important Feature Of Storage
Batteries For Power Sector and Other Critical
Standby Application Is
Reliability
 Reliable standby power source
 Deliver power as and when called for
 Full capacity at any point of time in service life
 Predictability

EITHER
SUDDEN DISRUPTION OF MAINS POWER TAKES PLACE
OR
CONVENIENT AVAILABILITY OF MAINS POWER IS NOT THERE
THIS CLEARLY DEFINES TWO REGIMES OF APPLICATION
STANDBY APPLICATION
CYCLIC APPLICATION
UPS, INVERTERS, TELEPHONE
EXCHANGES, POWER STATIONS,
SWITCHING
CELL PHONES, TOYS, FORK
LIFTS, ELECTRIC VEHICLES,
SOLAR PHOTOVOLTAICS
STORAGE BATTERY
WHEN ?

STORAGE BATTERY FUNDAMENTAL
An ELECTRICAL STORAGE CELL consists of two dissimilar electrodes immersed
in electrolyte. Stores Electrical Energy in the form of Chemical Energy.
When the circuit is made between its +ve & -ve electrodes, it triggers a chemical
reaction inside the cell & delivers electricity – Direct Current (D.C.) through the circuit.
CHEMICAL ENERGY ELECTRICAL ENERGY
Anode
Electrolyte
Cathode

A BATTERY is an array of similar/identical objects The
battery, we are talking about is an electrical storage
battery comprising of an array of electrical storage cells
STORAGE BATTERY FUNDAMENTAL

INDUSTRIAL
POWER
LEAD – ACID
NICKEL – CADMIUM
PORTABLE
POWER
LITHIUM ION
NICKEL – METAL HYDRIDE
NICKEL CADMIUM
HIGH END
APPLICATION –
TORPEDOES, SPACE
SILVER - ZINC
NICHE POWER
GENERATION
FUEL CELLS
Application Pattern:

LEAD ACID
NICKEL CADMIUM
General Battery Technologies
Most Popular Electrochemical Couples
used worldwide in Industrial Application

Types of Batteries
Lead Acid Nickel - Cadmium
Flat Plate
Tubular
Plante
VRLA
Pocket Plate
Tubular Plate
Sintered Plate

BASIC ELECTROCHEMISTRY
PbO2 + Pb + 2H2SO4 PbSO4 + PbSO4 + 2H2O
CHARGED DISCHARGED
ELECTROLYTE TAKES ACTIVE PART IN REACTION – SPECIFIC GRAVITY
CHANGES WITH STATE OF CHARGE – EASY MONITORING AND INDICATION
OF STATE OF CHARGE (SOC)
2NiOOH + 2H2O + Cd 2Ni(OH)2 + Cd(OH)2
NEG. NEG.
POS POS
DISCHARGED
CHARGED
ELECTROLYTE DOES NOT TAKE ACTIVE PART IN REACTION – SPECIFIC
GRAVITY DOES NOT CHANGE WITH STATE OF CHARGE – NO DIRECT &
EASY METHOD OF MEASURING STATE OF CHARGE
NEG. NEG.
POS POS
LEAD ACID
NICKEL CADMIUM

More than 90% of applications world-wide use
Lead-acid
Reasons:
 LOW COST
 APPLICATION VERSATILITY
 ABUNDANT RAW MATERIAL
 WELL DEVELOPED SERVICING RECYCLING
INFRASTRUCTURE
Advantage “Lead Acid”

Technology Wise Categorisation
Industrial Lead Acid Battery
FLOODED VRLA
FLAT TUBULAR PLANTE
The Lead-Acid Technology

LEAD ACID BATTERY AN OVERVIEW
ACTIVE
MATERIAL
TAKES ACTIVE PART IN
REACTION TO STORE &
SUPPLY ENERGY
SUPPORT
STRUCTURE
ENABLES ELECTRONIC
CONDUCTION
1
2
PROVIDES MECHANICAL
SUPPORT TO ACTIVE
MATERIAL
ACTIVE MATERIAL
SUPPORT STRUCTURE
PLATES ARE
CONSTITUTED
OF
FLAT PASTED POSITIVE AND NEGATIVE

FLAT PLATE
A CHEMICAL BONDING HOLDS THE ACTIVE
MATERIAL IN PLACE THROUGHOUT THE
SERVICE LIFE
WIRE-MESH LIKE SUPPORT
STRUCTURE – GRID CAST OF LEAD
ALLOY, ANTIMONY OR CALCIUM
ACTIVE MATERIAL
PASTED ON GRID -
EXTERNALLY

FLAT POSITIVE PLATE
MOST SUITABLE FOR HIGH CURRENT, SHORT DURATION
APPLICATION viz. SLI, SHALLOW DUTY INVERTER ETC.
ADVANTAGES
MINIMUM LEAD MOST ECONOMIC & HIGHEST
ENERGY DENSITY
EXCELLENT HIGH RATE
DISCHARGE PERFORMANCE
AND CHARGE ACCEPTANCE
LARGE ACTIVE
SURFACE AREA
LIMITATIONS
ACTIVE MATERIAL
SHEDDING
LIMITED CYCLING
CAPABILITY
EASY ACCESS OF
ACID TO LEAD GRID
EASY CORROSION – LOW
LIFE EXPECTANCY

THE SUPPORT STRUCTURE IS IN THE
FORM OF CAST ROD ELECTRODES
CALLED SPINES JOINED AT THE TOP BY
A BUS BAR. ALLOY USED IS MOSTLY
ANTIMONIAL LEAD.
INDIVIDUAL SPINES ENGULFED IN A
MICROPOROUS PLURITUBULAR
GAUNTLET
ANNULAR SPACE BETWEEN SPINE AND
GAUNTLET FILLED WITH ACTIVE
MATERIAL. BOTTOM OF THE GAUNTLET
SEALED WITH A PLASTIC PLUG CALLED
BOTTOM BAR
TUBULAR POSITIVE PLATE

 Active material is held around the spines with the help of polyester tubes called
gauntlet.
 Annular space between the spine & gauntlet is filled with active
material.
Spine
Gauntlet
Active Material
Plastic Bottom Bar
A
A’
B B’
Gauntlet
Active
Material
Spine
Section A A’
Section B B’
TUBULAR POSITIVE PLATE
Lead Top Bar

EXTENDED SERVICE LIFE. IT IS DESIGNED FOR DEEP CYCLING
LOOSE PACKING OF
ACTIVE MATERIAL
POSSIBLE
ADVANTAGES
NO ACTIVE MATERIAL
SHEDDING
BEST SUITED FOR
CYCLING – 1500 CYCLES
@ 80% DOD
SPINE DEEPLY
EMBEDDED IN ACTIVE
MATERIAL – LOW SPINE
CORROSION
EXTREME TEMPERATURE
OPERATION
RESISTANT TO OVER-
CHARGE
RECOVERY FROM DEEP
DISCHARGE
PSOC OPERATION
TUBULAR POSITIVE PLATE WHY ?

MODEST HIGH RATE DISCHARGE
PERFORMANCE.
REQUIRES PERIODIC EQUALIZING AND/OR
BOOST CHARGING
REQUIRES PERIODIC TOPPING UP
“ANTIMONY POISONING” LEADS TO SLOWLY
DECLINING VOLTAGE PROFILE AND
INCREASING WATER LOSS AS THE BATTERY
AGES.
TUBULAR POSITIVE PLATE WHY NOT ?
LIMITATIONS

CAST OF 99.99%
PURE LEAD
LAMELLAR GRID
STRUCTURE –
ENHANCED ACTIVE
SURFACE AREA
INTEGRAL GRID
ACTIVE MATERIAL
PLANTE
PLANTE POSITIVE PLATE

CAST OF 99.99%
PURE LEAD
LAMELLAR GRID
STRUCTURE –
ENHANCED ACTIVE
SURFACE AREA
INTEGRAL GRID
ACTIVE MATERIAL
PLANTE
Lug
Support Bar
Lamellar Surface
PLANTE POSITIVE PLATE

POSITIVE PLATE HANGING FROM
CONTAINER SHOULDER
GAP BETWEEN POSITIVE PLATE
BOTTOM & MUD RIB FOR CREEP
GROWTH ALLOWANCE
POSITIVE PLATE
HANGING FROM
CONTAINER SHOULDER
TO PROVIDE SPACE FOR
CREEP GROWTH
INEVITABLE TO PURE
LEAD POSITIVE
PLANTE
HANGING PLATE DESIGN

1. In case of loss of active material due to
shedding, next layer of pure lead is converted to
lead-dioxide thereby ensuring no loss of
capacity – feature of continuous regeneration of
active material.
1. Across its life time Plante cells therefore
perform at full capacity – there is no aging
unlike all other lead-acid products.
1. No aging factor required for capacity calculation
Integral Grid-Active Material
Plante

CONTINUOUS REGENERATION OF ACTIVE MATERIAL
PLANTE NO LOSS IN CAPACITY
TOTAL LEAD-DI-OXIDE CONTENT FAIRLY
CONSTANT THROUGHOUT THE LIFE
SPAN INDICATING A CONSTANT
CAPACITY OUTPUT
CAPACITY DEGRADATION OVER LIFE AGEING FACTOR
TUBULAR : 20% 1.25
VRLA : 20% 1.25
Ni-Cd : 20% 1.25
PLANTE : ZERO 1.00

HIGH SURFACE AREA
HIGH CHARGING RATES POSSIBLE.
CHARGING AT 0.25 C10 AMPS UPTO
2.4 VOLTS PER CELL WITHOUT
PROBLEM
NO ANTIMONY POISONING
HIGH FLOAT POTENTIAL POSSIBLE.
PLANTE FAST RECHARGE

LIFE EXPECTANCY OF 18 TO 20 YEARS PLUS.
PLANTE LONG LIFE
VERY THICK POSITIVE – ENOUGH CUSHION AGAINST
CORROSSION
LOW SUSCEPTIBILITY TO OVERCHARGE DUE TO
VERY LOW EQUILIBRIUM FLOAT CURRENT OF THE
ORDER OF 1 mA/AH UNDER NORMAL FLOAT
CONDITION
LOW FLOAT CURRENT AND HIGH PURITY OF LEAD
LOWERS THE CORROSSION RATE

RELIABILITY - REITERATED
PLANTE EASY MONITORING
TRANSPARENT SAN (STYRENE ACRYLONITRILE)
CONTAINER – EASY VISUAL MONITORING OF CELL INSIDE
ANY ODD BEHAVIOUR CAN BE MONITORED AND
CORRECTED MUCH BEFORE IT SHOWS UP AS A
FAILURE MODE
EASY CLEANING OF CELLS FROM UNAVODABLE
SLUDGE DEPOSITION TO AVOID SHORT CIRCUIT
AND RELATED TROUBLES

SEALED ! CAN BE KEPT IN ANY ORIENTATION.
NO TOPPING-UP REQUIRED EVER “MAINTENANCE-FREE”.
A ZERO EMISSION PRODUCT.
BATTERY COMES CHARGED.
COMPACT.
WHAT IS VRLA ?

1. No topping up ever
2. No emission of fumes
3. Supplied factory charged
4. Excellent ‘high rate discharge’ performance
5. Excellent charge acceptance
6. Excellent deep cycle life
7. Low Self-discharge
8. Designed to suit float and moderate cyclic duty
9. Compact – low foot print
10. Long Life
Advantage VRLA
VRLA

CONSTRUCTION OF A VALVE REGULATED LEAD ACID CELL
AGM Separator
PbO2 Positive Plate
Pb Negative Plate

1. No means of state-of-charge assessment
1. Vulnerable to prolonged operation at high
temperature
1. Sensitive to both under and over charge
1. Recovery from over discharged condition is
difficult
1. Can have a catastrophic failure in case of charger
malfunction and/or abnormally high
temperature operation – a failure mode known
as ‘thermal runaway’
VRLA Limitations
VRLA

The VRLA Mechanism
Some fundamental requirements of a VRLA
1. Absence of free electrolyte – this can be done by two
process
a. Gel b. AGM
2. Entire element is held under tight compression
Under the above circumstance an oxygen bubble
evolved at the positive electrode diffuses to negative
electrode to react with the freshly formed pure lead
as follows:
O2 + Pb  (PbO) + SO4 + H+  PbSO4 + H2O
This is unique to VRLA – PbSO4 forms on the negative
electrode both on discharge as well as on charge!

The Lead Acid VRLA ….contd
The preceding analysis explains the limitations of a VRLA:
The recharge voltage and/or operating temperature
has to be carefully regulated since a higher voltage or
the higher temperature will raise the potential of both
positive and negative electrodes leading to:
- Excessive recombination, rise in temperature, loss of
water, so far as oxygen is concerned
- As far as hydrogen is concerned there is no recombination
reaction for it thereby resulting in net loss of the gas and in
effect water i.e. accelerated aging shall take place.
- In effect, VRLAs charge ‘slow’ at float voltage only.

A note on “Gel” tubular VRLA
Gel tubular VRLA share most of the advantage features of
AGM VRLA except for:
a. High Rate Performance is modest
b. Charge acceptance is lower
c. Compatibility to fast charging is poor
d. Uses more lead, hence more bulky and expensive
On the positive side, Gel products are less affected by high
temperature operation – basic electrolyte content being
higher vis-à-vis VRLA and hence also eliminates the
possibility of catastrophic failure due to ‘thermal runaway’

Factors that limit the life of a lead-acid battery (conventional)
• Positive Grid/Spine Corrosion
• Degradation of Positive/Negative Active Material
• Corrosion of positive pillars, group bar
• Mechanical degradation of cover/lid leading to leakage etc.
• Internal shorts due to separator degradation
• Internal shorts due to excessive sedimentation
• Internal short/terminal damage due to plate growth

Factors that lead to ‘Premature’ Battery Failure
• Wrong type selection
• Wrong sizing of battery
• Improper operation - over discharge
- under/over charging
• Improper maintenance – topping up
- equalization/boost
• Poor quality acid/water

INTRODUCTION TO Ni-Cd BATTERIES

Nickel Cadmium Technologies
 Pocket Plate
 Sintered Plate
 Fibre Plate

Technologies
Nickel-cadmium development
 Pocket Plate (PP) – 1st generation (1893)
• Industrial applications
 Sintered Plate (SP) – 2nd generation (1934)
• Aviation applications
 Fibre Plate (FP) – 3rd generation (1978)
• AGV, Rail & Industry applications

Technologies
Nickel-cadmium chemistry
 Positive active material : Nickel Hydroxide
 Negative active material : Cadmium Hydroxide
 Electrolyte : Potassium hydroxide
(KOH)
 Nominal voltage : 1.2 volts
2NiO-OH + 2H2O +Cd= 2Ni(OH)2+ Cd(OH)2
When the cell is charged, the active material initially present as
hydroxides are changed. On discharge, the process is reversed.

Pocket Plate battery
Key features
 Proven technology
 Exceptional reliability and long lifetime
 Low internal resistance
 Wide operating temperature range
 Fast recharge capability
 Resistance to electrical and mechanical abuse
 Specific designs to applications
 Easy installation and low maintenance
 Environmentally safe

Key features : How?
 Do not suffer from sudden death failure
 Electrolyte does not participate in the electro-chemistry,
Its simply an ion carrier. No need to measure Sp. Gravity
in service
 All internal components are made with steel structure
 No component is affected by electrochemical reaction or
by electrolytic aging

Construction
Splash guard
Prevents electrolyte splashing and
possible short-circuit caused by
external objects accidentally falling
into the cell
Plate Groups
Welded construction imparts high
mechanical strength to withstand severe
vibrations
Plate
Made of Double perforated steel strips,
encompass the active materials
Fusion welded to lids, makes the cell
mechanically sturdy and facilitate visual
electrolyte level inspection
Translucent polypropylene
container
Nickel-plated terminal posts provide good
electrical conductivity
Prevents explosion & electrolyte
contamination
Polypropylene Grid Separator
Separates the plates and insulate the
frames from each other and allows free
electrolyte flow
Flame Arresting Vent
Terminal Arrangement

Operating features : Charge
 Ensures the readiness of battery in short time, after one
black out
 Flexible boost charge voltage 1.45 – 1.70V/cell
 Float voltage 1.40 – 1.42V/cell
 Discharge End voltage range from 1.14 – 0.65V/cell
 Tolerates deep discharges - can be deep cycled.
 Excellent low temperature discharge capability
 85% capacity available even at -20°C operation

Operating features : Lifetime
 Life of Ni-Cd batteries is more than 20 years under float
conditions with many number of industrial applications
 Cyclic life
 Excellent cyclic capability
Depth of Discharge Number of cycles
20% 8000
40% 3200
60% 2000
80% 1000
 Lesser the DOD, higher would be the cyclic life

Operating features : Installation
 A simple bolted connector assembly system
 Stepped arrangement for easy maintenance & electrolyte
visibility
 Various options for battery racks to fit into available room
space
 No need for special acid / alkali proof flooring
 Battery can be installed in the same room as other
electronic equipment

2 Step – 2 tier

4 Step – 1 tier

3 Step – 2 tier

Low maintenance
 No need of measuring of specific gravity
 Large electrolyte reserve
 Air conditioned environment is not essential
 Natural ventilation is sufficient
 “Flip open” vent caps to simplify topping-up
 Long topping-up intervals

Environmentally safe
 No emission of corrosive gases
 Low emission of explosive gases
 Explosion proof vents
 Protection against accidental shorts
 More than 99% of metals contained in batteries can be
recycled

Comparison of Batteries
Tubular VRLA PLANTE NI-CD
1.Application Ideal for float as well
as frequent charge/deep
discharge cycling
duties
For relatively short
time backup with
moderate depth of
discharge
Ideal for meeting
duty cycle in float
operation
Better suited for very
high rate of discharge
under extreme
condition/cyclic duty.
2.Reliability Quite reliable Generally reliable,
however prone to
unexpected
malfunctioning
Most reliable in
float operations
Reliable during routine
duty cycles
3.Monitoring
state of
charge
Can be done by
measuring electrolyte
specific gravity
Cannot be determined
externally, acts as a
blackbox
Can be done by
measuring
electrolyte specific
gravity,visual
monitoring through
transparent
containers
Cannot be determined
externally, acts as a
blackbox
4.Susceptibili
ty to high
temperatures
Satisfactory operations
up to 48/50 deg. C
electrolyte
temperature,Best
among lead acid.
Prolonged operation
at high temperature
curtails battery life
Satisfactory
operations up to
48/50 deg. C
electrolyte
temperature
Satisfactory operations
up to 48/50 deg. C
electrolyte
temperature.Wide
temperature range
5.Discharge
performance
Standard, but inferior to
Plante
Best Superior to Tubular
but inferior to
VRLA
Very Good

Tubular VRLA PLANTE NI-CD
6.Maintenance
requirement
Topping up upto 3-4
times/year
No topping up
required
Topping up upto
once in a year
Topping up upto
once in a year
7.Ageing Degrades gradually,
10-12 years service
life
Degrades
gradually,8-10 years
service life
No capacity loss,15-
20 years service life
Slight capacity
loss,15-20 years
service life
8.Sensitivity to over
charge and
undercharge
Moderately
sensitive ,Best
among lead acid
Extremely sensitive Moderately
sensitive
Better than lead
acid batteries
9.Thermal runaway Not susceptible Very susceptible Not susceptible Not susceptible
10.Space
requirement
High Low High Moderate
Comparison of Batteries – Contd.

Battery Manufacturers
Lead Acid NI-CD
Plante Tubular VRLA Pocket plate VR NI-CD
Exide,
Kolkata
HBL,
Hyderabad
AmaraRaja,
Tirupati
HBL,
Hyderabad
HBL,
Hyderabad
Exide,
Kolkata
HBL, Hyderabad AMCO Saft AMCO Saft
Kirloskar,
Bangalore
Exide, Kolkata
BUI,Pune

Comparison of Battery Prices
Lead Acid Plante 30-32/- Per AH
Tubular 13-14/- Per AH
VRLA 12-13/- Per AH
NI-CD Pocket plate 28-30/-Per AH
VR NI-CD 33-35/-Per AH

BATTERY SIZING
FOR STANDBY APPLICATION

SIZING FACTORS PARAMETERS
PRIMARY
LOAD CURRENT
LOAD DURATION
NOMINAL SYSTEM VOLTAGE
MINIMUM SYSTEM VOLTAGE
MINIMUM OPERATING TEMPERATURE
DESIGN MARGIN
AGING FACTOR
SECONDARY
FACTORS SPECIFIC TO APPLICATION

Selection Parameters
DEPTH OF DISCHARGE
FREQUENCY OF DISCHARGE
APPLICATION CRITICALITY
CHARGING CONSTRAINT
MAINTENANCE CONSTRAINT
OPERATING CLIMATIC CONDITIONS
SPACE AVAILABLITY
SELECTION OF THE RIGHT TYPE OF TECHNOLOGY AND
DESIGN PRECEDES THE SIZING EXERCISE
PARAMETERS
TO BE
CONSIDERED
FOR SELECTION

1. A storage battery can store electrical energy
and deliver it back when needed.
2. Capacity of a storage battery is expressed
in Ah at a particular rate of discharge.
3. Normally, for standby application, the capacity
of a storage battery is declared at 10 hour rate
of discharge or at C10.
.

5. A 1000 Ah battery at 10 hour rate of discharge
would mean that it can deliver 100 Amps current
for 10 hours continuously up to an end cell
voltage of 1.85 Volts per cell for flooded
batteries or 1.75 Volts per cell for VRLA
batteries.
6. However, this battery cannot supply 1000 Amps
current for 1 hour since this relationship is not
linear.
7. Higher the current, lower is the duration.

8. For a NDP cell, C10 capacity gets de - rated
to 50% at C1. In other words, 1000 Ah NDP
battery at C10 becomes 500 Ah at C1.
It means the same battery can deliver 500
Amps current for 1 hour and the end voltage
goes down to 1.75 volts.
9. Capacity available from a battery therefore
depends on the discharge current and the
end cell voltage.
Here comes the concept of K factors.

10. K factors estimate the available capacity at
different discharge rate and end cell voltages.
This factor is the ratio of rated capacity to the
amperes that can be supplied for ‘t’ minutes
to a given ecv.
Rated Capacity
K factor =
Required discharge current
1000
K factor for 1 hour discharge =
500
= 2

Battery sizing is all about calculating rated
capacity of a battery for a given discharge
current to an end cell voltage.
If we want to draw ‘I’ current for ‘t’ period
of time to an end cell voltage of ‘a’ volts
per cell, then the rated C10 capacity is
C10 = I x K, where K is the discharge
factor for ‘t’ duration to an end cell voltage
of ‘a’.

K-FACTOR DEPENDS ON:
• TYPE OF CELL
• END OF DISCHARGE VOLTAGE
• DURATION OF LOAD

Sizing Parameters
APPLICATION
PARAMETERS
DUTY CYCLE – LOAD CURRENT
AND DURATION PATTERN
OPERATING DC BUS VOLTAGE
WINDOW – MAXIMUM & MINIMUM
DC BUS VOLTAGES
MINIMUM AMBIENT TEMPERATURE
DESIGN MARGIN
BATTERY
PARAMETERS
CHARGING VOLTAGE REQUIREMENT
DISCHARGE CHARACTERISTICS
FACTOR FOR AGING PHENOMENON
FACTOR FOR STATE-OF-CHARGE IF
REQUIRED

79
SIZING OF STORAGE BATTERY FOR STANDBY FLOAT APPLICATION
STEP 1 CALCULATION OF NUMBER OF CELLS
:
NUMBER OF CELLS =
MAXIMUM DC BUS VOLTAGE
RECOMMENDED FLOAT VOLTAGE OF EACH CELL
NO OF CELLS FOR PLANTE =
242
2.25
= 108
NO OF CELLS FOR NICD = = 173
242
1.40

80
STEP 2 WORKING OUT END CELL VOLTAGE
:
END CELL VOLTAGE =
MINIMUM DC BUS VOLTAGE
NUMBER OF CELLS (FOUND FROM STEP NO 1)
END CELL VOLTAGE FOR PLANTE =
192
108
= 1.78
END CELL VOLTAGE FOR NICD = = 1.11
192
173

81
STEP 3 CALCULATION OF AH CAPACITY
:
AH CAPACITY = K FACTOR x LOAD CURRENT
STEP 4 : APPLY DESIGN MARGIN
DESIGN MARGIN IS BASICALLY THE FACTOR OF SAFETY AND
INSURANCE AGAINST ANY POSSIBLE INCREASE IN LOAD AND
LESS-THAN-OPTIMUM OPERATING CONDITIONS OF THE
BATTERY DUE TO IMPROPER MAINTENANCE, RECENT
DISCHARGE OR AMBIENT TEMPERATURES LOWER THAN
ANTICIPATED OR BOTH.

82
STEP 5 APPLY TEMPERATURE CORRECTION FACTOR
:
AT LOWER TEMPERATURE, CAPACITY OF ANY STORAGE BATTERY
DECREASES . SINCE THE SYSTEM MUST WORK PROPERLY AT LOWEST
AMBIENT TEMERATURE ALSO, RAW CAPACITY NEEDS TO BE
ADJUSTED BY APPLYING SUITABLE TEMPERATURE CORRECTION
STEP 6 APPLY AGING MARGIN
:
CAPACITY OF ANY STORAGE BATTERY (EXCEPT PLANTE)DECREASES
WITH AGE. SINCE THE SYSTEM REQUIREMENT DOES NOT CHANGE
AND A BATTERY SHOULD BE REPLACED WHEN IT REACHES 80%
VALUE, 25% AGING MARGIN IS CONSIDERED FOR TUBULAR, VRLA
AND NICD BATTERIES.

CALCULATION OF NUMBER OF CELLS & ECV
VMAX / VC
NUMBER OF CELLS (NC)
VMIN / NC
END OF DISCHARGE
VOLTAGE (ECV)
MIN. DC BUS
VOLTAGE (VMIN)
CHARGING
VOLTAGE PER
CELL (VC)
MAX. DC BUS
VOLTAGE (VMAX)

CALCULATION OF RAW CAPACITY
END CELL VOLTAGE (ECV)
BACK-UP DURATION
SELECTED CELL TYPE
CAPACITY FACTOR
‘F’
LOAD CURRENT ‘I’
BASIC RATED CAPACITY OF CELL
C = I x F

CALCULATION OF FINAL CAPACITY
BASIC RATED CAPACITY OF CELL
C = I x F
FINAL CALCULATED CAPACITY
CF = C x A x D x KT
AGING FACTOR, A
DESIGN MARGIN, D
TEMPERATURE
CORRECTION FACTOR,
KT

• ALL TYPES OF BATTERY LOSES CAPACITY WITH AGING
(EXCEPT PLANTE)
• THE END OF LIFE IS DEFINED AS THE TIME WHEN THE
BATTERY CAPACITY REACHES 80% OF ITS RATED CAPACITY
• THE BATTERY IS EXPECTED TO PERFORM THE DESIGNED
DUTY EVEN AT THE END OF LIFE SITUATION
• THE CAPACITY THUS NEEDS TO BE UPRATED TO TAKE CARE
OF THIS INEVITABLE DEGRADATION
AGING FACTOR
RELEVANCE OF FACTORS

MINIMUM OPERATING TEMPERATURE
• ENERGY OUTPUT FROM A BATTERY IS DIRECTLY
PROPORTIONAL TO THE AMBIENT TEMPERATURE
• AT LOWER AMBIENT CAPACITY DECREASES – SO DOES
THE BACK-UP AVAILABILITY
• CAPACITY RATED AT STANDARD AMBIENT THUS NEEDS
TO BE UPRATED FOR SAME OPERATION AT LOWER
AMBIENT
• A TEMPERATURE CORRECTION FACTOR THUS IS
REQUIRED TO TAKE CARE OF THIS INEVITABLE CAPACITY
LOSS

CORRECTION FACTOR FOR MINIMUM AMBIENT
TEMPERATURE OF T 0C
KT = 1+ {(27 – T) X FT} / 100
WHERE
KT = TEMPERATURE CORRECTION FACTOR
T = MINIMUM AMBIENT TEMPERATURE
FT = TEMPERATURE CO-EFFICIENT VALID FOR THE TYPE OF
BATTERY SELECTED IN % PER DEGREE C
• FOR TUBULAR 0.43% PER DEG. C @ C10 (AS PER IS1651)
• FOR PLANTE 0.9% PER DEG. C @ C10 (AS PER IS1652)
• FOR VRLA 0.43% PER DEG. C @ C10 (AS PER IS15549)

•AS A STANDARD PRACTICE, A BUILD-UP OF 10% - 15% IS
GENERALLY ACCEPTED.
DESIGN MARGIN
CATERS TO
A. UNPLANNED AUGMENTATION OF PLANT INSTALLATION.
B. ABERRATION OF EQUIPMENT PERFORMANCE/DUTY.
C. UNEXPECTED LOWER AMBIENT THAN DESIGNED FOR.

DC System
• Battery
• Battery Charger

DC SYSTEM
• BATTERY CHARGERS [TWO/THREE]
• BATTERY BANKS [ONE/TWO]
• DC DISTRIBUTION BOARDS [ONE/TWO]
• DC FUSE BOARDS
• UN EARTHED SYSTEM
• CHARGER TROUBLE, DC EARTH FAULT AND
DC VOLTAGE ABNORMAL ALARMS IN UCB

220 V DC SYSTEM
Charger I
440 V
220 V DC
Charger II
Battery
Bank
Battery
Bank
Feeders
440 V
220 V DC
Feeders
DCDB

Typical UPS System
Module
Power supply
440 V
AC
220 V
DC Battery 220 V DC
220 V
AC UPS
All Unit Controls
&
Protection
48 V, 15V, 24 V, DC
Converter
Inverter
ACDB

X X
X X
X X
X X
DG-1 DG-3 DG-2
DG SWGR-1 DG SWGR-2
UNIT EMER
SWGR-1 UNIT EMER
SWGR-2
UNIT EMER
SWGR-3
UNIT EMER
SWGR-4

220 V DC
• FSSS
• HT Breakers
• Vacuum Breakers
• HOTV/HORV
• Deaerator Overflow Valve
• GRP
• HP Heater Protections
• DC Fans & Pumps
• Extraction FCNRV V/V’s
• SADC
• Trim Device
• Load Shedding Relay
• Scanner Air Fan Outlet & Emergency Damper
• All DC Lights

220 V Supplies
EMCC USS
MAIN CHARGER RESERVE CHARGER
UPS CHARGER-1 UPS CHARGER -2
DAS UPS CHARGER –1 DAS UPS CHARGER-2
+/- 24 VA DC CHARGER +/- 24 VB DC
CHARGER
DG SET BATTERY
SYSTEM

UNINTERRUPTED POWER
SUPPLY
• An uninterruptible power supply (UPS),
uninterruptible power source or sometimes
called a battery backup is a device which
maintains a continuous supply of electric power to
connected equipment by supplying power from a
separate source when utility power is not available.

CAPACITY
• UPS units come in sizes ranging from units which
will back up a single computer without monitor
(around 200 VA) to units which will power entire
data centers or buildings (several megawatts).
• Larger UPS units typically work in conjunction with
generators.

UPS DESIGNS
• The general categories of modern UPS systems
are on-line or off-line, the latter often referred to as
standby.

ON-LINE UPS
• ON-LINE UPS SYSTEMS PROVIDE THE HIGHEST LEVEL OF
PROTECTION FOR MOST IMPORTANT EQUIPMENT.
• THESE SYSTEMS USE A COMBINED DOUBLE-CONVERSION(AC
TO DC/DC TO AC) WHICH CONTINUOUSLY POWERS THE
LOAD,TO PROVIDE BOTH CONDITIONED POWER AND OUTAGE
PROTECTION.
• THEY PROVIDE PROTECTION AND ISOLATION FROM ALL
TYPES OF POWER PROBLEMS,INCLUDING POWER
SURGES,HIGH VOLTAGE SPIKE,SWITCHING
TRANSIENTS,NOISE FREQUENCY VARIATION ETC.
• THESE SYSTEMS ARE OFTEN USED FOR MISSION-CRITICAL
APPLICATION THAT REQUIRE HIGH PRODUCTIVITY AND
SYSTEM AVAILABILITY.

MAJOR COMPONENTS OF UPS
• CHARGER
• BATTERY
• INVERTER
• STATIC SWITCH
• ALTERNATE SUPPLY

 Diode Rectifier
 Thyristor Rectifier
 Diode and DC/DC Converter
(Chopper)
 Active Rectifier (IGBT)
 SMPS – Switch Mode Power Supply
TECHNOLOGY ASSESSMENT

TECHNOLOGY COMPARISON
 Power Factor
 Efficiency
 Harmonic Distortion
 Reliability / Availability / Service
Support
 Space Requirements
 System Cost

POWER FACTOR COMPARISON
 Diode : Good
 Thyristor : Low
 Diode and Chopper : Good
 Active Rectifier : Best
 SMPS : Good

EFFICIENCY COMPARISON
 Diode : High
 Thyristor Medium : High
 Diode and Chopper : Low
 Active Rectifier Medium : Low
 SMPS : High

HARMONIC COMPARISON
 Diode : Medium
 Thyristor : High
 Diode and Chopper : Medium
 Active Rectifier : Low
 SMPS : Low

RELIABILITY COMPARISON
Based Upon Component Count of Rectifier
Devices
 Diode : High
 Thyristor : High
 Diode and Chopper : Low
 Active Rectifier : Medium
 SMPS : Medium

SERVICE SKILL COMPARISON
 Diode : Low
 Thyristor : Medium
 Diode and Chopper : High
 Active Rectifier : High
 SMPS : High

SYSTEM COST COMPARISON
 Diode Rectifier : 105%
 Thyristor Rectifier : 100%
 Diode & Chopper : 124%
 Active Rectifier : 115%
 SMPS : 105%
Based upon past projects, component count and further
developments.

SPACE COMPARISON
Diode : Average
Thyristor : Larger
– (with power factor compensation included)
Diode and Chopper : Larger
Active Rectifier : Average
SMPS : Less

CONCLUSIONS
Considerations :
 Total System Requirements
 Future Provision of System Requirements
 Customer’s Experience / Background
 Technology comparison for exact project
 All Technologies Will continue for near future

FLOAT CUM BOOST
CHARGERS-FCBC
• Voltage
• Current

SIZING IN FLOAT MODE
In float mode the charger shall be capable of meeting the
trickle charging of both the battery banks, station
continuous load current and starting current of largest DC
drive.

SIZING IN BOOST MODE
In boost mode charger shall be capable of boost charging a
fully discharged battery in 8-10 hours.

CHARGER OPERATION
• CHARGER-FLOAT/BOOST
• CONTROLLER -AUTO/MANUAL

CHARGER OPERATION
• Float mode/controller auto mode-charger supplies
at constant voltage(set),with current limiter in
function.
• Boost mode/controller in auto mode-charger
supplies at constant current(set),with voltage limiter
in function

PERFORMANCE FEATURES
• Soft start feature-set voltage in 15 sec.
• Load limiter-80%-100%
• AVR-better then 1% of set voltage
• Voltage limiter
• When energising the charger with fully charged
battery connected plus 10% load shall not result in
output voltage greater than 110% of voltage setting &
charger to stablise to set value in 15 sec.
• With change in load from 20% to 100 % and vice-
versa, the momentary output voltage shall remain
within 94% to 106% and should stablise in 2 sec.
• Ripple content-less than 1%

ANNUNCIATIONS
• A.C. Supply Failure
• Rectifier Fuse Failure
• Surge Circuit Fuse Failure
• Filter Fuse Failure
• Load Limiter Operated
• Charger Trip
• Battery On Boost

Battery Charger Manufacturers
•AMARRAJA ,Tirupati
•HBL,Hyderabad
•Chabi Electricals,Jalgaon
•Caldyne,Kolkata
•Dubas

Battery
Battery
Voltage
stabilizer
ACDB-1
ACDB-2
UNIT UNINTERRUPTED POWER SUPPLY
415 V AC
EMCC
CHARGER –2 INVERTER-2
STATIC SWITCH
CHARGER-1 INVERTER-1
USS
SSVS
240 V AC
ALT
SUPPLY
Manual
Bypass
switch

INVERTER
• Inverters takes an input 210 to 280 V DC from chargers
or battery and converts them to 240V AC.
• First the DC voltage is converted to square wave using
SCRs.
• The SCRs gate pulses can be controlled to slightly alter
frequency.
• In latest UPS inverters IGBTs are being used.

Battery Capacity
• Expressed in ampere hour(AH)
• Duration of discharge-10 hr for Plante/5 hr for Ni-
Cd
• End cell voltage-1.85 volt for Lead acid plante/1.0
volt for Ni-Cd
• Ambient temperature-27 deg cent.
• Electrolyte specific gravity-1.2+-.005 lead acid
plante cells

SELECTION OF BATTERY
TYPE IN POWER PLANT
• Power plant batteries standby duty require high discharge
performance with continuously connected on float mode operation.
• Expected Life of lead acid tubular is of the order of 8-10 years so in
a power plant life of 25 years minimum two replacement would be
required.
• Lead acid PLANTE and Ni-Cd (alkaline) have expected life of 15-20
years hence only one replacement would be required in whole plant
life.
• In addition lead acid plante have much better discharge
performance than tubular type for the specified emergency duration.
• In view of above plante type lead acid or Ni-Cd high discharge
batteries are specified for power plant applications.
• Wherever there is space constraints VRLA batteries may be an
option however this has also expected life of 8-10 years.

CHARGING OF BATTERIES
Nominal Voltage
Float Voltage
Boost Voltage
Float Current
Boost Current
Lead Acid - Plante Ni - Cd
2.0V
2.1V - 2.25V
2.3V - 2.7V
1.4mA / AH
140mA / AH
1.2V
1.40V - 1.42V
1.5V - 1.7V
2.0mA / AH
200mA / AH

220 V FLOAT CUM BOOST
BATTERY CHARGER
(i) Manufacture UPTRON POWERTRONICS LTD,Sahibabad
(ii) A.C. input 415 V ± 10%, 3 ø, 50 Hz±5%, 69.7 A
(iii) D.C. output voltage Float 220- 250 V
Boost 200- 300 V
Current Float 110A
Boost 80 A
(iv) Ripple 1% peak to peak without battery
(v) Efficiency at full load More than 85%
(vi) Voltage setting range
(manual)
220 – 300 V
(vii) Current setting range 50% to 100% of rated current
(viii) Cooling AN
(ix) Max. ambient temp. 500 C
(x) Response time Less than 750 mSec

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