station battery

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.



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.



Purpose

Protection

Control

IndicationCommunication



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.



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



Loads on Station Battery

Continuous Loads

Indicating Lamps.Continuously energised coils.

Continuously operating motors.

Inverters.

Lighting load.



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



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.




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




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




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.



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



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



Positive Plates

Lead Acid Station BatteryTypes of Cells

1. Plante Cells

2. Pasted Plate Cells3. Tubular Cells



Station Battery

(Plante Battery)



Station Battery



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



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



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



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)



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.



Control Power supply ± 110 V D.C.

55 Nos ± PLANTE type 400 AH Lead Acid Battery



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.



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.



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.



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.



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.



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.



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



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



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



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



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 .



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.



400AH ±

VRLA, Battery



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 %).



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.



55 Nos ±

VRLA type

400 AH LeadAcid Battery

station battery

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