GE Industrial Solutions Seconday Substation Transformer - Manual (Page 6)

6
Check pressure vacuum gauge daily the first
week of transformer operation. If pressure-
vacuum gauge stays at zero reading, it
indicates a faulty seal. If transformer cannot
be de-energized, be careful to not come into
contact with live parts such as bushing
terminals and leads.
Slowly add nitrogen or dry air AT LOW
PRESSURE until gauge reads 5 PSI. Apply
with a paint brush soapy water or detergent to
all seals above liquid level. Small bubbles will
indicate the location of the leak.
After leak is repaired, add sufficient dry air or
nitrogen to provide 0.5 PSI gauge pressure at
25 °C (top liquid temperature). Refer to curve
for normal pressure at other top liquid
temperatures.
ACCESSORIES
PRESSURE RELIEF DEVICE
When required by the specifications, a
mechanical automatic
resealable type
pressure relief device can be supplied. This
device requires no adjustment after it
operates. After relieving the pressure due to
the gas build-up in the tank, it automatically
recloses and reseals. Alarm contacts are
available if specified
PRESSURE-VACUUM BLEEDER DEVICE
When required by the specifications, a
pressure-vacuum bleeder can be supplied.
This device is designed to protect transformer
from a slow build-up of pressure. It will either
admit air or exhaust internal gases to
maintain a safe level of pressure/vacuum.
BUSHINGS
Porcelain is used as the major insulation in
sidewall bushings and upon receipt, an
inspection should be made for chips and
cracks. If there is evidence of damage or
rough handling, file a claim with the
transportation company promptly and notify
the nearest Sales Office of the General
Electric Company. If it becomes necessary to
replace a porcelain, the change can be made
externally after the liquid level has been
lowered below the bushing.
DETACHABLE-CABLE TYPE
To remove the porcelain on a detachable-
cable type bushing, bend locking collar back
and remove it along with hex-head nut.
Remove nuts, washers and clamp. Porcelain
can be removed and stud will remain attached
to the transformer leads from inside the tank.
When installing a new porcelain, be sure
gasket stop is in position, and torque nuts
from 10 to 17 foot-pounds (13.6 to 23 Newton
meters).
STUD TYPE
To replace the porcelain on a stud type
bushing, remove hex-head nut and flat
washer. Remove nut, lock and flat washers,
and clamp. Porcelain can then be removed
leaving terminal stud attached to the winding
leads. When installing a new porcelain be
sure gasket stop is in position, and torque
nuts from 10 to 17 foot-pounds (13.6 to 23
Newton meters).
FORCE AIR-COOLING EQUIPMENT
FOR LIQUID-FILLED TRANSFORMERS
CAUTION
THE EQUIPMENT COVERED BY THESE
INSTRUCTIONS SHOULD BE INSTALLED,
OPERATED, AND SERVICED ONLY BY
COMPETENT TECHNICIANS FAMILIAR
WITH GOOD SAFETY PRACTICES, AND
THESE INSTRUCTIONS ARE WRITTEN FOR
SUCH PERSONNEL AND ARE NOT
INTENDED AS A SUBSTITUTE FOR
ADEQUATE TRAINING AND EXPERIENCE
IN SAFE PROCEDURES FOR THIS TYPE
OF EQUIPMENT.