50 Years of continuous Operation
The nameplate on the out side of transformer no. 2790 at the transformer station Uirapuro near São Paulo tells us. Inside the light-gray, 5-MVA monstrosit y (utility: Rede Energia) is an MR, type D on-load tap-changer which is coupled to an MA 2 motor drive unit . The special thing about it: This pair has already been in operation for 50 years. Without any malfunctions at all. ON.LOAD was on the scene when service technicians Edvaldo Macedo and Marcelo Dantas of MR do Brasil did the complete maintenance job.
This dependable device has made a total of 168,871 switching operations since 1959. One thing is already clear after the diverter switch insert is removed and given an initial cleaning. Everything still looks very good. The same holds true when the device is taken apart. After checking for contact wear, the only things that have to be replaced are the main movable shunt contacts and the buffer springs and these are routine replacements. Nothing else. Afterwards the support plate for the buffer springs is installed. A painstaking check of the mechanical function of both the insert and the resistance values follows. "Everything's okay," says Edvaldo Macedo to his colleague. They can start putting everything back together again. Afterwards, the "spry" on-load tap-changer, wrapped in plastic foil, floats upward on a crane only to disappear again into the depths of the transformer.
The robust motor drive-unit also shows its exemplary quality. Only the energy accumulators must be replaced here. After a thorough cleaning, the unit runs just like it did on its first day of operation. The test switching operations must still be done. They reveal that the proven MR technology functions perfectly. Fit for another 50 years.