Howard Small Power - Manual (Page 7)

Small Power Substation Transformers
Document 2.4.54 Revision 0
July 2006
7
INSTALLATION
Location and Mounting
The transformer should be mounted on a level
concrete foundation of sufficient strength to support
the weight of the completely assembled transformer.
If the transformer is not level, insulating fluid may
not circulate properly through the cooling assembly,
possibly causing overheating and reduced transformer
life. The mounting location should provide for adequate
ventilation and easy access for inspection. The
transformer should be located at least 24 inches from
any obstruction. When installing transformers designed
for indoor operation, adequate air inlets and outlets
must be provided for proper cooling. Avoid locating
transformers in corrosive areas.
Opening Transformer Tank
Transformers are usually shipped sealed and should
not be opened unless necessary.
!
DANGER : SLOWLY RELEASE INTERNAL
PRESSURE PRIOR TO REMOVING
TANK ACCESSORIES. FAILURE TO DO SO COULD
RESULT IN SEVERE PERSONAL INJURY, DEATH, OR
PROPERTY DAMAGE.
!
DANGER: TO AVOID DEATH FROM
SUFFOCATION NEVER ALLOW ANYONE
TO ENTER THE TRANSFORMER TANK UNLESS AN
ANALYSIS OF THE AIR IN THE TANK SHOWS AT
LEAST 19.5% OXYGEN. THE GAS SPACE IN AN
OPERATING TRANSFORMER USUALLY CONSISTS
OF NITROGEN GAS. WHENEVER ANYONE IS IN
THE TANK, A PERSON SHOULD BE STATIONED AT
THE HAND HOLE OUTSIDE THE TANK TO ENSURE
SAFETY OF THE PERSON INSIDE.
Transformer should not remain open for more than
12 hours at a time. If work is interrupted, the tank
should be resealed, evacuated, and filled with dry air or
nitrogen.
To prevent contamination of the transformer tank, do
not open the transformer in an unprotected area during
inclement weather or where the air may contain dirt
or other particles. Either of the above could cause
a transformer failure. The tank opening should be
protected against entry of foreign matter.
If it is necessary to remove some fluid from the tank to
allow for inspection or other work, the transformer must
be refilled with fluid after work is completed.
Personnel should not be permitted on top or inside the
transformer while it is open unless they have emptied
all pockets and checked for loose objects that might fall
into the tank. All tools should be accounted for after
work is completed. It is recommended that any tools
used on top of the transformer or inside the tank be
attached with safety cords to prevent them from being
lost inside the transformer.
Personnel must not stand directly on any electrical
insulation. Clean drop cloths should be used under
working areas in the transformer to prevent objects
from dropping into the core/coil assembly.
The following procedure should be used to remove the
hand hole cover.
1. Thoroughly clean the hand hole cover.
Remove all moisture, dirt, and grease to
avoid contaminating the transformer’s fluid
compartment.
2. Relieve internal tank pressure by manually
operating the pressure relief valve.
3. Remove cover fasteners.
4. Gently pry the cover upward, making sure that
the cover gasket does not fall into the tank.
Lift the cover vertically to prevent damage to
cover, bolts, and gasket.
5. Remove the gasket sections from the
hand hole flange. Record the location and
orientation of each gasket piece so they can be
reinstalled correctly.
The following procedure should be used to reinstall the
hand hole cover.
1. Place gasket sections in their original positions
and orientations.
2. Reinstall hand hole cover. Reinstall fasteners
and torque to 25 ft-lbs. After tightening all
fasteners, re-torque each one to ensure proper
torque.