Scope

This procedure describes requirements for extending the warranty on a transformer that has been stored for a prolonged period prior to energization. The transformer’s Instruction Book describes general storage conditions, the duration of normal storage, installation procedures and maintenance requirements.

If there is some doubt about the condition of the transformer after extended storage, an inspection and prescribed tests must be performed by the ABB Service Company or other ABB personnel.

If the inspection or tests identify any problems with the transformer or its components, the problems must be corrected, at the owner’s expense, before the warranty can be extended.

It is also useful to keep the inspection report and test results for comparison purposes during normal periodic maintenance and inspection of the transformer.

Send the inspection report and test results to the Reliability Department at Small Power Transformers. The Reliability Department will review all the data. Once the data has been approved and the transformer certified as serviceable, the warranty defined in the terms and conditions of the original sale will be extended.

When the transformer is removed from storage, the pre-energization tests and inspection outlined in the Instruction Book must be performed before the transformer is energized. A review of the previous data should be made to make sure there has been no deterioration during storage.

1

1

External Inspection of the Transformer

Are there any indications of external damage?

-Describe the location and extent of the damage.

Is the paint finish damaged?

-Describe the location and extent of the damage.

Are all the fittings still attached and undamaged?

-If not, describe the fittings that are loose and/or damaged.

Is there any evidence of fluid leakage?

-Note the location of the leak.

Are any of the bushings broken or damaged?

-Identify which bushing(s) are damaged.

Are all the parts that were shipped separate from the transformer

available and undamaged?

-If not, which are missing and/or damaged?

For wall-mounted bushings, is the black polyvinyl material covering the bushings torn or damaged?

-If it is torn or damaged, inspect the bushings for deterioration of the epoxy or spades. Replace if necessary.

If silica gel was placed in the control cabinet, is it fresh?

-Replace if necessary.

If the transformer was designed for indoor use, was it stored indoors?

-Contact the Small Power Transformers for further instructions if it was not stored indoors.

Contact Small Power Transformers or consult the transformer’s Instruction Book if there are any questions about the inspection procedures.

Transformer Test

1

  1. Record ambient temperature and barometric pressure for correction of test data.
  1. Pressure Test for six (6) hours at 4 psig to insure that the tank and fittings do not have any leaks. Repair any leaks that are discovered and test again. After completing the test, reduce the tank pressure to 2 psig.
  1. Test insulating liquid for dielectric strength and moisture content.
  1. Test insulation with a 1000 or 2500 volt megger.
  1. Check insulation using the power factor test.
  1. Test ratio in all tap position to insure proper tap changer operation.
  1. Verify liquid level by gauge reading.

1

Contact Small Power Transformers if any of the test results are unsatisfactory or if there are any questions abut the test procedures or the results.

1

If the transformer continues to be in storage during the warranty extension period, the following applies:

Extended Storage Guidelines

  1. Store transformer on a firm level foundation, preferably at the installation site.
  1. Transformer should be completely assembled, including the terminal chambers and switches, if any, to provide additional protection.
  • If the transformer has wall-mounted bushings and terminal chambers or switches have not been supplied, the bushings should be protected from the environment. A black polyvinyl material placed over the bushings will serve as protection. Check this material during other routine inspections to insure that the material is not damaged.
  • Cover-mounted bushings that are shipped un-mounted on the transformer do not have to be installed during storage. Stored the bushings in a clean, dry location in their original shipping cartons. When the transformer is ready to be put into service, the bushings should be physically inspected for damage before installation.
  1. Transformers designed for indoor use must be stored indoors.
  1. Parts that are shipped separate from the transformer must be stored in a clean, dry area.
  1. Space heaters, when supplied in switches, terminal chambers, control cabinets, or their cases, should be connected and energized at all times.
  1. For control cabinets only, if space heaters are not supplied or it is not practical to energize the heaters, silica gel packets should be placed in the cabinet.

Maintenance/Inspection

The following inspection should be made while the transformer is in extended storage. Record the results for comparison with previous data to insure that there has been no deterioration in the condition of the transformer.

Quarterly Inspection*

  1. Check the black polyvinyl material covering the bushings to be sure it is not damaged. Replace if necessary.
  1. Check the silica gel in the control cabinet and replace, if necessary.
  1. Record gauge readings, including the ambient temperature and barometric pressure.

Note: a. Pressure should be

maintained at two (2) psig,

taking into account

variances in barometric

pressure.

  1. If pressure or liquid level readings indicate a leak, pressure test according to the transformer Instruction Book. Repair leaks immediately.

*Perform the first inspection one month after the transformer has been stored.

Annual Inspection

  1. Check paint finish and touch-up as necessary.
  1. Test insulating liquid for dielectric strength and moisture content.
  1. Test insulation megger test.
  1. Check insulation power factor.

Omit tests #3 and #4 if the bushings have not been mounted on the transformer tank.

When the transformer is taken out of storage, the pre-energization tests and inspections identified in the Instruction Book must be performed. Review the storage records of the transformer to insure that there has been no deterioration in the condition of the transformer.

1