Dry-Out Of Transformers; Accessories - HPS DH Serie Guía De Instalación, Operación Y Mantenimiento

RECOMMENDED TORQUE VALUES FOR BOLTED
ELECTRICAL CONNECTIONS
BOLT SIZE CARBON ST.
GRADE 5
ft-lbs [Nm] ±5%
1/4-20 7 [10]
3/8-16 20 [27]
1/2-13 60 [70]
8 mm 20 [23]
12 mm 60 [70]
*Note: The above torque values are for dry, unlubricated bolts.

Dry-Out of Transformers

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION OR
ARC FLASH
Failure to follow the attached dry-out procedures
before energizing transformers previously exposed
to moisture will result in serious personal injury or
death and property damage.

Accessories

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION OR
ARC FLASH
When installing transformers (regardless of the
location) the installing contractor is responsible
for the proper installation in accordance with the
attached instructions and all applicable codes and
standards (including Seismic). Failure to do so
will result in serious personal injury or death and
property damage.
Installation, Operation, and Maintenance Guide - Low Voltage Transformers
BRASS S.S STEEL
ALLOY CU270 B8 OR B8M
ft-lbs [Nm] ±5% ft-lbs [Nm] ±5%
3.8 [5] 5 [6]
14 [18] 15 [20]
33 [45] 37 [50]
12 [14] 12 [14]
33 [45] 37 [50]
checked for proper torque values and any signs or oxidation,
arching and improper electrical connection. If any improper
connections are identified they must be corrected immediately.
Vacuuming or blowing of compressed air from the top
down is an accepted practice for removing dust from the ducts
of a transformer coil. Low pressure, dry air should be used to
avoid further contamination of the windings by foreign objects.
The ground connection should also be checked to ensure
a low impedance connection. The accumulation of ice, snow or
any other objects blocking the ventilation should be cleaned up
immediately during the operation of the transformer to ensure
proper ventilation.
On outdoor units where filters have been installed, their
continuous exposure to the outside atmosphere can cause the
filters to get dirty quickly. A periodic check of the filters will
help avoid filter clogging and thus transformer overheating.
Also, never run the transformer without the filters properly
installed.
In the event that transformers have been exposed to
moisture such as condensation or rain, it is required to dry-out
the transformer prior to energization.
Drying may be accomplished by using any hot or warmed
air, radiant heat or internal heat that is directed through the
windings. Heated air should be allowed to rise up through the
windings for a minimum of twenty four (24) hours after the
evidence of moisture is no longer visible.
Transformers that have been exposed to flood conditions,
direct rain or sprinklers, may not be able to be dried out
appropriately. The insulation resistance, core to primary, core
to secondary and primary to secondary, should be greater
than 10k ohms. Contact the transformer manufacturer for
appropriate action instructions.
Dry-type distribution transformers are available with a
number of accessories to facilitate installation. Consult your local
distributor for the purchase of any of the items accessories that are
stocked in inventory. Some frequently used accessories include:
1) Wall Mounting Brackets
Ventilated dry-type transformers are normally designed to be
floor mounted only. However, depending on the enclosure type
some ventilated units up to 112.5 kVA are supplied in
enclosures that have integral wall mounting capabilities or may
be wall-mounted using kits. These units can be conveniently
mounted on walls, beams or poles.
Conventional ventilated dry-type transformers have a bottom
screen for air convection. When transformers are mounted above
the ground surface a catcher plate should be installed under each
transformer as a safety precaution against any hot particles that
may fall through the screen in the event of a faulted condition.
Refer to Appendix B and C (page 15 and 16).
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