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8/3/2019 Station Battery
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Station Batteries Battery is the heart of power system
control and protection.
All the power system control andprotection equipments andcommunication equipments work on D.C.
Supply.
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Station Batteries Station Battery should supply the load
under the following conditions.
A) When auxiliary A.C. supply fails.
B) Output of the battery charger isinterrupted.
C) Load on the D.C. system exceeds themaximum output of the charger.
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Purpose
Protection
Control
IndicationCommunication
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Control power supply
The control circuits of substations are
designed for 110 Volt /220 Volt DC
operation.
The individual cell voltage is 2 Volts and 55 /
110 cells are connected in series.
The substation is equipped with one or two
battery systems for the control, and
protection, indication schemes.
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The following factors shall be considered for selection of the
cells.
1) Voltage requirement of relays and protection system. (110 V / 220 V).
2) Load requirement. (100 Ah to 400 Ah).3) Type of Cells. Plante / VRLA4) Physical characteristics, such as size, weight, container
material etc.
5) Planned life of installation6) Frequency and depth of discharge
7) Ambient temperature
8) Maintenance requirements
Battery Selection Factors
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Loads on Station Battery
Continuous Loads
Indicating Lamps.Continuously energised coils.
Continuously operating motors.
Inverters.
Lighting load.
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Loads on Station Battery
Non-Continuous Loads
Emergency Lamps
Circuit Breaker MotorsCommunication system
Fire Protection system
Momenta
ry Load
sSwitchgear Operation
Motor starting currents
Motor-driven Valve Operation
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DC LOADS IN THE SUBSTATION
Number of points
Load Total load
220KV feeder
panels
2 50W 100W
110KV Feeder 6 50W 300W
100MVA
Transformer
2 50W 100W
10 Panel VCB
Panel
10 30W 300W
Total Load 800W.
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DC LOADS IN THE SUBSTATION
Total current - 800 /110 = 7.28A
Simultaneous tripping of breaker due to Busdifferential trip = 14
Total watts = 14×2×350 = 9800W
Current taken by the breaker = 9800 / 110= 9.9A
Emergency light loads = 10×60 = 600W Current = 600 /110 = 5.45A
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DC LOADS IN THE SUBSTATION
Spring charging current DC motor of VCB= 4× 300 = 1200W
Current = 1200 /110 = 10.9A
Total Current = 7.28 + 9.9 + 5.54 + 10.9
= 33. 53 A
Ah capacity of the battery for 10 Hrs. Back up time = 33.53×10 = 335.3Ah
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DC LOADS IN THE SUBSTATION
Considering the diversity of load andcapacity reduction of the battery for a lifespan of 10Y rs. 400 Ah, 110 V Plante leadacid battery is selected.
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Metallic lead
Metallic lead acts as a carrier for the active material
and as a current conductor.
Lead (Pb) and Lead dioxide (PbO2).This oxide is dark brown in colour and is the active
material in the positive electrode.
P
orous lead Also called spongy lead.
It is gray in colour and is the active material in the
negative plate. It is lead (Pb).
Substances in the lead-acid battery
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Pasted negative plates are used in virtually all lead-
acid battery designs.
In the pasted plate the carrier of the active material
is a lead alloy grid.
The thickness ranges from 1 to 5 mm, depending on
the application.
The grid is pasted with a mixture of lead oxides,
organic additives (expanders), sulphuric acid and
water.
The paste is converted in an electrochemical
process, called formation, to highly porous lead.
N
ega
tive Pla
tes
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Positive Plates
Lead Acid Station BatteryTypes of Cells
1. Plante Cells
2. Pasted Plate Cells3. Tubular Cells
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Station Battery
(Plante Battery)
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Station Battery
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The positive plates in this type are made up largely of pure
lead with lead casting as single sheet of pure lead or with
lead-antimony frame supporting pure lead inserts.
These cells have long life and highest levels of integrity and
reliability.
They provide constant capacity throughout service life and
maintenance requirements are very low.
As per IS.1652 , the cells shall be designated by letter Pfollowed by the standard rating, a letter indicating the type of
cell container, a hyphen and letters HDP for High Discharge
Performance.
Plante' Cells
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The positive plates are made by impressing an oxide paste
into a current collecting lead alloy grid.
The grid alloy is lead-antimony or lead-calcium.The paste forms active material of the plate.
Some improved varieties with lead-antimony-selenium alloys
or lead-calcium-tin alloys provide very low maintenance levels
and temperature tolerances.
These cells are of the lowest capital option.The output are good for short discharges.
Pasted positive plates are commonly used in valve-regulated
batteries and starter batteries.
Pasted Plate of Faure Cells
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In a tubular cell, the positive plate is constructed from a series of
vertical lead alloy µspines¶ or µfingers¶ resembling a comb.
Lead oxide, the active material is packed around each spine and is
retained by tubes of woven glass fibre protected by an outer sleeve
of woven polyester or perforated PVC.
This design enables the cells to withstand frequent
charge/discharge cycles.
Cells with Lead-Calcium alloy plates always demand less addition
of water than the cells with lead-antimony alloy plates.Designation shall be as in the case of Plante¶ cells, except that ³T´
indicates Tubular cell.
Tubular positive plates are used in traction, standby and submarine
batteries.
Tubular Cells
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Current multiplied by time to indicate the
capacity of the battery (after correction to 270C), when the cell is discharged at 10 hour
rate to a final voltage of 1.85 V.
Specific Gravity Readings.
Specific gravity of the battery taken with ahydrometer shall be entered in the log sheet.
The specific Gravity should be 1.21
Ampere-hour capacity (Ah)
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Battery Room. There should be enough space to accommodate
the stands provided for supporting the cells.
Exhaust fans for ventilation of gases. Adequate lighting shall be provided.
Room temperature should be in between 200Cto 350C.
Higher temperature decreases life of Battery.
Lower temperature reduces capacity.
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Control Power supply ± 110 V D.C.
55 Nos ± PLANTE type 400 AH Lead Acid Battery
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Installation Battery cells are kept on insulators placed on stand.
The cells should be stacked in such a way that thepositive terminal of one cell should be connected to thenegative terminal of the adjacent cell.
All copper connection works should be painted with acidresistant paint before filling the acid in the cells.
Acid proof ceramic tiles should be used on floor as wellas the four walls up to a height of 10 feet.
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Initial Charging Initial Charging will take from 50 to 90 hours.
Initial Charge is 3 times the capacity of the cell.
Eg: For a 300 AH battery 900 AH should be given.
30 Ampere for 30 Hrs.
Temperature of the electrolyte should be less
than 500 C. After completion of first charge rest should be
given for 1 to 12 hour.
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Initial Charging After rest battery should be again charged at
finishing rate for a period not less than 30 hours
till sign of completion of charge are observed.
Hourly readings of
Sp. gravity, Voltage, temperature, level are to
be taken. Final voltage per cell 2.75 V for 3 hours.
Discharging and charging should be repeated.
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D.C. Battery Charger
The function of the battery charger is to convert A.C. input to D.C. output and feeds the substation D.C. loads at thetime of charging the battery.
The Ampere requirement can be determined by: A= AH x 1.15 + L
T
Where, A - is the minimum rated ampere charger capacity.
AH - Ampere hour discharge from battery. T Time allowed for recharge in hours.
L Continuous connected load on the battery.
1.15 Efficiency charge factor.
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Battery Charger Eg: If a 100 AH battery is 50% discharged,
and it is to be recharged in 10 Hours , anda continuous load of 6 amps to besupplied, ampere requirement will be:
A= (100x0.5) x 1.15 + 6 = 11.75 A
10 The next standard rating is 15A.
30 Amp and 60 Amp chargers are commonly used.
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Battery Charger for Power stations
Dual Chargers are used.
The system consists of two identicalchargers of same capacity .
Bothe shall be capable of work as Boost or
float charger when required.
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Maintenance of Plante BatteryS
lNo ActivityP
eriod
1 Cell voltage of Pilot Cells D
2 Specific gravity of Pilot Cells D
3 Cell voltage of all cells M
4 Specific gravity of all cells M
5 Check for any excessive
gassing (Over heating of
cells)
D
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Maintenance of Plante Battery
Sl No Activity Period
6 Battery earth leakage D
7 Battery cleaning to remove
dust accumulated
W
8 Tightening of terminal
bolts, applying contactgrease.
M
9 Capacity measurement Y
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An equalising charge or a boost charge is a
special charge given to a battery, when non
uniformity in voltage or specific gravity has beendeveloped in the cells.
For lead-antimony and Plante¶ types, the
equalisation charges may be required once in 3
months. Any of the following voltages as shown in Table
and corresponding time period shall be applied.
Equalising Charge
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Equalising voltage / cell Time - Hrs.
1.24 80
2.27 60
2.30 48
2.33 36
Equalise once a year, even if the precedingconditions do not demand.
Equalising Charge
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Specific Gravity Readings
Specific gravity of the battery taken with ahydrometer shall be corrected to 270C and
entered in the log. Without temperature
correction, the reading is meaningless.
For each 10 0 C variation from 27 0 C, a
correction factor of 0.0007 shall be added or
subtracted .
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VRLA (Valve Regulated Lead Acid Battery)
In VRLA battery the oxygen gas is transported tothe Negative plate through a special type of
separator and it will react with the lead on thenegative electrode to form lead peroxide.
The oxygen is suppressing the Hydrogen Gasevolution at the Negative plate.
Hence hydrogen and oxygen will not escape fromthe cell. An automatic pressure relief vent is provided to
release the excess pressure if produced.
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400AH ±
VRLA, Battery
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Charging of VRLA batteries
Constant Voltage out put charging equipment
should be used.
Recommended float Voltage 2.3 V and 50 mACurrent
Recommended boost Voltage 2.35 V.
While charging OPEN CIRCUIT VOLTAGE
(OCV) readings should be taken.
The charging current should be as per the
instruction manual . (12 %).
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Maintenance of VRLA Battery
1)Boost Charge the batteries @ 2.3 Voltsper cell once in every six months for
32Hours. @ a current 10 % of the rated capacity.
Discharge the Batteries up 1.85 V per cellin every Year.
Clean the batteries weekly.
Note down the cell voltages Monthly after switching of the charger.
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55 Nos ±
VRLA type
400 AH LeadAcid Battery
Recommended