GE Industrial Solutions Dry-Type General Purpose Power Transformers - Manual (Page 7)

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10. Maintenance
Under normal environments and operating conditions, dry type transformers are virtually maintenance free. However, they do
require occasional internal cleaning, care and inspection. The frequency of inspection will depend on atmospheric and/or
environmental conditions at a given transformer installation or location.
CAUTION
ANY INTERNAL INSPECTION, ADJUSTMENT, CLEANING OR MAINTENANCE MUST BE DONE WITH THE
TRANSFORMER DE-ENERGIZED AND THE WINDINGS GROUNDED.
A continuously energized transformer needs periodic cleaning and maintenance only to remove accumulations of dust or dirt from
cooling ducts and other surfaces. Large accumulations may reduce cooling efficiency and lead to overheating. Cleaning is
recommended at least once a year in relatively clean installations and at more frequent intervals in more heavily contaminated
atmospheres.
Transformers that are de-energized for long periods of time generally require more frequent maintenance and cleaning to ensure
removal of contamination. Accumulation of dirt on insulating surfaces becomes a hazard when a considerable amount of moisture
is absorbed. Vacuuming is the recommended method for cleaning. Special attention should be given to cooling ducts within the
winding. Low-pressure dry air can be used if care is taken to avoid driving the contamination into insulation.
Moisture is detrimental to most insulation systems. It is advisable to dry out any transformer that has been exposed for long periods
of time to high humidity. Whenever moisture is visible on insulation surfaces, the unit must be dried before being energized. If
moisture is evident, the unit should be dried out by placing it in an oven, by blowing heated air over it, or by placing strip heaters
under the coil windings. The temperature of the heated air should not exceed 110C/230F. If strip heaters are used, the elements
should not be allowed to come in contact with the transformer. Heat should be applied to both the front and rear of the transformer.
Transformers may be subjected to flooding, direct rain or similar applications of water. In such cases, normal drying techniques
may not be adequate and the factory should be consulted.
Maintenance would include dust removal and/or drying, if applicable, as described above, tap changing, tightening of bolted
connections, general servicing and inspection of auxiliary devices. Additional information related to the installation and
maintenance of general-purpose transformers can be found in ANSI publication C57.94, “Guide for Installation and Maintenance of
Dry Type Transformers”.
Storage
Condensation and moisture absorption must be prevented during storage. Ventilated dry-type transformers should be stored in a
warm dry location having a uniform temperature to prevent condensation. Openings should be covered to keep out dust. If outdoor
storage cannot be avoided, the transformer must be protected to prevent the entrance of water, moisture, dust, birds and other
foreign material.
12. Renewal Parts
In most cases, field repairs to the core and coil are not recommended, are not economical and can be dangerous. Renewal parts are
available for all enclosure parts surrounding the core and coil assembly.
NOTE
These instructions do not purport to cover all details or variations in equipment nor to provide for every possible contingency to be
met in connection with installation, operation or maintenance. Should further information be desired or should particular problems
arise which are not covered sufficiently for the purchasers purpose, the matter should be referred to the manufacturer.