DRY TYPE TRANSFORMER INSTALLATION and MAINTENANCE

Published: 20th April 2010
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INSTALLATION
Dry type transformers can be mounted on various surfaces and with different methods of mounting. The transformer should be mounted in an upright position. This will permit the best effective ventilation
Be sure the surface to which the transformer is mounted is strong enough to handle the weight of the unit. Be sure to check the nameplate for the weight before installation.
In most cases it is best that the surface be flat and level, although this is not critical. If it is not flat and level, additional noise from vibrations may be heard.
Installation of a dry type transformer also involves another important consideration and that is the possible need to supply impulse protective devices such as arresters. Dry-types do not have the same impulse levels as their liquid filled counterpart. Where the units could be exposed to lightning strikes or heavy switching transients, proper protective equipment should be provided.
MAINTENANCE
Like all equipment transformers do require occasional maintenance to assure proper operation. Inspection to the unit should be made on regular intervals to evaluate whether corrective measures should be taken.
1. Frequency of inspections depend on the area of installation. If the area is normally clean and dry then an annual inspection may be enough. In other locations if the area is contaminated with dust or chemical concerns a three to six month interval may be better. To start check within three months to see if the unit is not experiencing any problems
2. With the transformer de-energized (be sure to always check the main switch to make sure) access the inside of the transformer by removing the external panels and putting them aside. Inspect for dirt on the coil surfaces and at areas where the air flow could be restricted. If excessive dirt is found on the windings and insulators, actions should be taken to clean the unit immediately. Dirt can cause tracking and poor air circulation causing overheating. Clean the winding ducts by forcing air through them. Also carefully clean the top, sides and bottom end of the coils. The use of a vacuum cleaner is the preferred method of cleaning the coils in the first step of the process. This can be followed by clean dry air from a compressor to blow out the coils. The air should not be over 30 psi.
3. Check for loose connections which could cause heating and loose of power. Check condition of the tap changer, terminal board and general condition of the transformer.
4. Observations should be made for signs of overheating of the insulation and of voltage creepage over the insulation surface. This over heating or creepage would be evident by change in color of insulation in some areas, tracing or tracking with carbonization.
5. Enclosure condition should also be monitored. If signs of rust or corrosion is evident, corrective measures should be taken where necessary.
6. If the unit is to be shut down for a period of 12-24 hours, in humid environments it would be best to install small strip heaters for avoiding the effects of possible condensation I the enclosure and on the coils.

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