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BHARAT SANCHAR NIGAM LIMITED
O/o Chief General Manager Haryana
Ambala-133001
To
The G.M.T.D.
AB/FBD/GRG/HSR/JD/KRL/RWR/RTK/SPT
No.
OPN/Core group/2009-10/14
Dated at AB the
Sub:
General guidelines for Battery/ Power Plant/Earthing
24-12-09.
For better maintenance of battery/power Plant and earthing
guidelines for Battery/Power Plant and Earthing received from BSNL HQ & core group
are herby enclosed for kind information and requested to instruct all field units for
implement these in true spirit.
A compliance may be given to this office for kind perusal of
CGMT Haryana.
DA Encls: As above
Sd/(Davinder Kalra)
AGM(OP)
1. Maintenance guidelines: Batteries
The connection of the batteries in series and parallel will increase voltage
and capacity respectively.
Always store lead-acid in a charged condition. Never allow the open cell
voltage to drop much below 2.10 V. Apply a freshening charge every three
months or when recommended.
Avoid repeated deep discharges. Charge more often. Use a larger capacity
battery to reduce the depth of discharge.
Prevent sulphation and grid corrosion by choosing the correct charge and
float voltages. If possible, allow a fully saturated charge of 14 hours.
To reverse sulphation, raise the charge voltage above 2.33V/cell for a few
hours.
Avoid operating VRLA batteries at elevated ambient temperatures.
Connect the temperature sensor and activate in SMPS power plant the same.
1.1 Quarterly Check:
(a) Measurement of a mark deviation > 30% in the impedance or
conductance of the cell as compared to the one recorded at the time of
commissioning. Normally
change in impedance / conductance <15% indicates the health state of cell.
The reading taken at the time for partial test discharge, deviation >30% of
observed during installation put for further investigation.
(b) Note down individual cell voltage readings.
(c) When battery set is on float mode operation, once in every three months,
capacity test to be conducted for 3 to 4 hours on 10% current or Exchange
load.
1.2 Annual Check:
Carryout C/10 discharges on the battery string followed by a re-charge and
maintain a record to monitor the state of health.
Note :
1. After installation of the battery, the formats as per the Feed Back Report
on Battery to be maintained.
2. After successful installation of the Battery, during Maintenance, the
readings are to be recorded in the Service Record Format.
1.3 Installation Tips:
The batteries received, should be commissioned within six months from the
date of manufacture.
Also the following factors may be checked and followed during installation of
battery.
1. Manufacturer’s installation guidelines.
2. Cell matching (voltage, capacity and conductance)
3. Check whether inter-cell connection is proper and proper torque is applied.
4. Do not put the battery to load without fully recovering its capacity.
5. Normally float voltage will be 2.25V per cell and charge voltage will be 2.3
V per cell.
IMPORTANT Do’s and Don’ts for VRLA Batteries
1.4 Do’s:
1) Read the Manual of battery manufacturer carefully before use.
2) When battery is not in use, store it in a sheltered place. Charge the battery
at least every three months so that there will be no loss of capacity during
storage.
3) Use calibrated voltmeter with an accuracy of ± 0.01.
4) Keep sparks, flames, lighted cigarettes away from the battery.
5) After discharge, recharge the battery as soon as possible.
6) Erections to be complete at one go.
7) Clean the batteries as and when dust accumulates.
8) No Exchange load to be allowed in the battery bank, till A/T completed.
9) If battery set is not able to deliver its capacity due to improper charging,
during the service, this battery set needs to be charged by Constant Current
charger to recover its capacity.
10) It shall be ensured that the Temperature compensation Sensor is
connected to the each battery bank and activated in the SMPS Power Plant to
suit for the temperature variation.
11) Battery Health Monitoring Unit (if supplied as per PO), shall be connected
to the battery bank for monitoring the health of battery to avoid deep
discharge of battery.
1.5 Don’t’s:
1) Never place the battery near heat source.
2) Never short-circuit the terminals.
3) Never disassemble or reassemble the battery.
4) Do not connect or disconnect any cell without switching off circuit.
5) Do not discharge a battery below 1.75VPC.
6) Do not allow the battery to deep discharge which will hamper the life of
the battery.
7) Do not tamper the safety valve of the cell.
8) Never connect the VRLA battery directly to a power supply socket without
using Charger as a medium.
9) Do not add water or acid to the Cell.
10) Do not store the batteries in places exposed to direct sunlight, rain, dust
etc.
11) Do not mix the batteries of different capacities or make.
12) Do not mix normal convention / low maintenance batteries with sealed
maintenance VRLA batteries.
13) Do Not keep the battery continuously in undercharged condition. Keeping
continuously undercharged lead to sulphation of plates and cells may lose
capacity gradually.
14) Do not over charge the battery. Over discharging leads to abnormal
expansion of the active material in the plates. This may leads to recharging
problems, permanent damage and failure of cell / battery.
15) Do not connect different capacity battery sets in parallel.
16) Do not connect new and old battery sets is parallel.
17) Do not connect different makes of the battery sets is parallel.
Power Plant :
1. Procurement of AC/DC clamp meter for measurement of value of
charging/load current on each module & battery sets.
2. 100 % provisioning of low voltage cut off devices in exchanges/BTS
sites.
3. Floating voltage of power plant should be set at 54.2 +/- 0.5 V at battery
terminal, for avoiding memory effect on batteries due to low voltage of power
plant.
4. All the SMPS power plant modules should work in synchronized mode for
equal sharing of load current.
5. Power plant cabinet should be A.C earthed & not with exchange earth.
6. Positive terminal of power plant and battery should be connected to
exchange earth.
7. The A.C potential difference between neutral & earth point of cabinet-earth
(AC Earth) should be less than 6 volts. For this neutral of electric
transformer of commercial/dedicated supply should be checked periodically
for proper connectivity.
8. Calibration of voltmeter & Ammeter should be checked periodically.
9. The main control card, Temco card & selection switches should work
properly.
10. A.C and D.C connections of power plant modules should be done through
specified connectors only.
11. 100 % provisioning of high/low voltage disconnectors and timer on mains
supply & periodic check of their functioning.
12. Surge arrestors should be checked periodically to safeguard equipment from
lightening.
Earthing
1. Exchange earthing should be with in limit i.e < 0.5 ohm and should be measured
in dry season.
2. Earth value should be displayed near the Earth distribution plate and date of
measurement should be displayed.
3. Individual earth should be extended from Earth distribution plate to equipment
and should be marked on Earth distribution plate plate.
4. All electrical equipments should be earthed and its value is < 2 ohm and tower
earth is < 5 ohm.
5. Electrical and exchange earth should be at reasonable distance i.e > 60 feet..
6. Earth pit mouth should be opened and ensure regularly watering of earth pits.