【technology】main Transformer Epoxy Resin Bushing Insulation Failure Analysis And Maintenance Methods

2.2 Second maintenance
epoxy bushing dismantling starts from the place where the general cap is installed at the top of epoxy resin bushing, remove the top nut, and be sure to use uniform force when removing the explosion-proof membrane; remove the epoxy resin cast bushing oil chamber nut and double nut, remove the oil chamber, measure the position of the spring nut (to facilitate the restoration of the installation), expose the internal structure of the top of epoxy bushing manufacturer, and remove the upper spring of epoxy bushing for transformer; after the spring is removed, prepare to start the lifting and remove the bushing, remove the bushing porcelain bottle; when hanging the porcelain insulator, make sure that the porcelain bottle is vertical to avoid damaging the capacitor core inside. The end of the capacitor core must be removed before the porcelain sleeve is removed. Be very careful when removing it because the end is very thin and fragile; remove the exposed capacitor core, remove the bottom equalizing ring, remove the end nut, remove the lower porcelain insulator of the bushing, and finally remove the installation flange.
The A-phase, B-phase, and C-phase bushings were disassembled. After each phase of bushing was disassembled, the capacitor core was hoisted into the container tank, transformer oil was injected into the bottom (to make the heating effect better), the lid was covered, and the oven was hoisted. The temperature was controlled at 100-130℃, and heating and vacuuming were carried out. The parts of each bushing were classified and stored in a special storage tray.
After drying, each phase bushing was installed, vacuumed, and oiled. Finally, the dielectric loss and insulation resistance tests were carried out. The test data obtained were very accurate. The dielectric loss value was comparable to the dielectric loss of some new bushings when they left the factory. The insulation resistance value was greatly improved compared to before the maintenance, and passed the communication withstand voltage test.
The bushing has undergone 2 maintenances, and the second maintenance fully met the standard requirements