The issue
The customer had to replace leaky, unrepairable hard paper bushings on a 36 kV transformer that had aged considerably over 25 years and were no longer safe to operate.
The primary conductor of the transformer feeder in the bushing was firmly connected to the bushing header by brazing.
During the replacement action, the level of the insulating oil in the transformer must first be lowered to slightly below the cover, but still standing above the winding.
The risk of such a replacement action is then during the desoldering of the conductor that the conductor no longer fits correctly on the new bushing despite all care and thus the conversion becomes very time-consuming and cost-intensive. The risk of damage to the transformer during on-site soldering should also not be underestimated and is very high if, despite all the care taken, parts should fall into the tank.
Successful exchange
A suitable bushing for replacement without risky desoldering or even cutting off the conductor was not available as standard.
SERD GmbH solved the problem. A modern silicone-insulated bushing of the type SERD STC with silicone insulator, adapted to the problem, was the solution. After dismantling the old bushing, this bushing allowed replacement without changing the conductor attachment.
After removal of the defective bushing, the conductor could be fastened directly to the SERD bushing.
The customer was convinced by the safe solution of risk-free replacement. The somewhat higher costs of the new bushing were far outweighed by the significantly reduced replacement costs.
An example for the lived customer orientation and flexibility of SERD GmbH:
Left:
The old bushing to be replaced
bushing with porcelain insulator.
Right:
The new SERD bushing
Type STC with silicone insulator
When replaced, the conductor fit and could be installed without any problems, the connection to the transformer remained unchanged.