Monthly Archives: May 2018

Transformer Transport

Because of the brittleness of the rupture disk when the transformer is transported, the disc is packaged separately and must be mounted when the transformer is installed, following the procedures described below:

– Remove the screws on the flange of the blast tube, it is not necessary to lower the existing oil level;

– Remove the sealing flange;

– Place the rupture disc at the location of the sealing flange.    ORC6SBTHP63

The self-closing pressure relief valve is installed on insulated liquid transformers in order to protect them against possible deformation or rupture of the tank in cases of internal defect with high pressure.

The valve is very sensitive and quick, it closes automatically after the operation, thus preventing the entry of any external agent inside the transformer.

The sudden pressure relay and protective equipment for sealed type transformers installed above the maximum level of the liquid in the gas space between the liquid and the transformer cover.

The relay is designed to operate when transformer defects occur that produce abnormal internal pressure and its operation is caused only by rapid changes in internal pressure independent of the operating pressure of the transformer.

 

 

Degree of Polymerization

The mechanical tests proved that the GP is the test that more effectively informs about the actual aging conditions of the insulating kraft paper, helping with the results.

The condition of the insulation paper in the transformers is the determining factor of the life of these equipments and that 50% of the mechanical loss of this polymer is generally accepted as limiting condition for use.

In the classes used, the 50% decrease in paper strength at breakage was reached after 33 days of aging, and equates to an approximate GP value of 475. However, in the field, as paper sampling is done in some parts of the transformer, there is a risk of sampling the part of the paper that has not been punctured. An indirect methodology, such as the measurement of furanic compounds in the IMO, is applied for efficient evaluation of the state of the solid insulation.      HOR06FBYP34

Thermogravimetric assays (TGA) were also carried out on a new and aged Kraft paper sample for 35 days and the GPs for these samples were quite different, 1050 and 367 respectively, indicating the cleavage of the glucoside bonds of the biopolymer after aging. However, the results for thermogravimetric tests indicated only a small difference in temperatures where the degradation rate is maximal.