06.12.2013

Complete revision of a 6.3 MVA transformer

In addition to the development and production of new transformers in dry or oil design J. Schneider Elektrotechnik works on the business of the transformer revisions.

In particular, by installing a vacuum drying oven with internal dimensions of 3.200 x 2.300 x4.400 mm ( LxWxH) in the new plant at the Werner -von- Siemens-Straße , J. Schneider is capable of the comprehensive revision of power transformers up to a rating of about 7.5 MVA. Due to those conditions and years of experience in construction of oil-filled transformers J. Schneider could win a contract for the revision of several transformers of a company in early summer. 

In addition to transformers in the power range up to 2.5 MVA the contract also included a 6.3 MVA transformer with 21 kV on OS and a control range of + / - 10 x 1%.
 
As all transformers belonging to this order this about 17 to heavy transformer also was removed at the customer and transported to the factory in Offenburg by the specialists of J. Schneider. 
After the entrance control to identify any latent defects, the removal of the active part and the control switch from the boiler followed. Then an intensive visual inspection at the active of the coils, the electrical connections to the regulator switch and of the outgoing lines was carried out.
In parallel, employees of the company Maschinenfabrik Reinhausen reviewed the removed onload tap changer also in our factory. Subsequently, a drying of the active part, including the on-load tap changer was made in the vacuum oven. Herewith the moisture, which was stored in the built-in insulation materials during many years of operation, was extracted to a residual moisture <1%. Then the dried unit was installed in the vessel, which was meanwhile cleaned and equipped with all-new seals.

After filling the transformer with a new dried insulating oil the electrical tests were performed in the test area by J. Schneider. To meet the requirements of corrosion protection for more years operating in outdoor installation, the vessel and the radiators received at the end a new paint job. Of course, the installation of the transformer was also performed from Offenburg to the customer by the staff of the transformer specialists.