SUBSTATION BATTERIES 1 SCOPE This Section of the Live

SUBSTATION BATTERIES 1 SCOPE This Section of the Live
PSLWM
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SUBSTATION BATTERIES
1
SCOPE
This Section of the Live Working Manual details the procedure to be followed when alkaline or
acid batteries of any voltage require to be worked on Live. The procedure applies the principles
established by the Electrical and Mechanical Safety Rules to achieve Safety from the System and
in particular Power Systems Safety Instruction 12 - Low Voltage Apparatus.
2
DEFINITIONS
Terms printed in bold type are as defined in the ScottishPower Safety Rules (Electrical and
Mechanical) 4th Edition.
3
ASSESSMENT
All work on or so near Live exposed LV conductors that Danger may arise requires assessment
before the commencement of work to ensure that Danger will not arise during the course of the
work. This assessment will be carried out by the Authorised Person who is to undertake the work.
In all cases, as part of the assessment, Apparatus shall be subjected to a visual inspection prior to
the start of any work to ensure that Danger will not arise due to the condition of the Apparatus.
Should this inspection reveal any significant deficiency in the Apparatus which could give rise to
Danger, no attempt shall be made to work on the Apparatus until a supervisor has been consulted
and assessed the situation.
4
DANGERS
The main dangers to Persons carrying out work or testing on batteries are explosion or burns arising
from:
4.1
The ignition of hydrogen gas which is given off by cells during the process of charging. The
gas may be ignited by naked flames and cigarettes or by sparks if cell terminals are accidentally
earthed.
4.2
Contact with electrolyte contained within the cells. Burns can result from contact with
either alkaline or acid electrolyte.
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4.3
Overheating and the expulsion of electrolyte from cells. This may occur if cells are
accidentally short-circuited (i.e. positive and negative terminals directly connected).
5
PROCEDURES
5.1
Procedure WL1.6 - Changing Battery Cells
While changing cells, Approved goggles and PVC gloves should be worn and only Approved
insulated tools used.
Where a defective cell(s) is to be changed in a battery which is physically small, it is preferable to
instal a temporary battery, and remove the entire existing battery with defective cell(s) from the
charger before attempting to replace the defective cell(s).
Where chargers are fitted with an auxiliary socket the temporary battery may be plugged into the
charger before work commences to change the existing battery. Otherwise, where a complete
battery is to be changed, the temporary battery should be connected in parallel to the existing battery
(i.e. with outgoing terminals of batteries connected positive/positive and negative/negative) before
the existing battery is removed from the charger.
Where it is impractical to instal a temporary battery, defective cells should only be changed one at a
time. While the cell is being changed, it is important that the battery can still perform its duty (e.g.
OCB tripping). To ensure this, cell connections should not be broken before a bypass is put in to
replace the defective cell. The current rating of the bypass required is dependent on the battery size.
For 50V or 30V Distribution batteries, a 10 sq. mm. bypass is required.
For 110V Distribution batteries a 25 sq.mm. bypass is required.
Where a temporary battery is to be installed:Step 1
Inform appropriate Persons before commencing work. This will include warning to the
PSMC when working in Primary/Grid substations.
Step 2
Switch off battery charger.
Step 3
Remove any gases by opening doors and thoroughly ventilating the area in which the
cells are placed.
Step 4
Install temporary battery, by plugging into charger where facilities are provided, or
connecting positive/positive and negative/negative across permanent battery.
Step 5
Remove permanent battery and replace defective cell(s).
Step 6
Replace refurbished battery.
Step 7
Remove temporary battery.
Step 8
Inform Regional Office or PSMC that work is complete, to allow remote alarms to be
cleared.
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Where an individual cell(s) is to be replaced:Step 1
Inform appropriate Persons before commencing work. This will include warning to the
PSMC when working in Primary/Grid substations.
Step 2
Switch off battery charger.
Step 3
Remove any gases by opening doors and thoroughly ventilating the area in which the
cells are placed.
Step 4
Remove any insulating boards covering terminals of cells on which work is to be done.
Step 5
Assemble three similarly rated cells with bypass leads and clamps to bypass out the
defective cell and each adjacent cell (see drawing NUMBER HQE10-0376).
Step 6
Clamp the bypass leads to the adjacent cell interconnectors, effectively bypassing the
defective cell and each adjacent cell.
Step 7
Disconnect the defective cell and replace with a healthy cell.
Step 8
Remove the bypass cell assembly.
Step 9
Replace any insulating boards which have been removed.
Step 10 Switch on charger. Check that charger is operating correctly and that charging rate and
battery voltage is correct.
Step 11 Inform Regional Office or PSMC that work is complete, so that any remote alarms can be
cleared.
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