The bushing flange is a very convenient place to install bushing chain transformers (TCB’s). The TCB’s have 500 to 5,000 turns in their secondary winding and are installed around the flange, wrapping the conductor. This location is called the TCB box.
In this case, in the transformers, the central conductor arranges the primary winding of a turn, and the turns of the TCB form the secondary winding. The secondary of the TCB will equip a small scale current, proportional to the current of the system, feeding instruments of protection and measurement.
The insulating oil of a transformer is intended, as informed by the manufacturer of these transformers, to isolate and cool the core and the coil. Therefore, contamination of the oil is a serious problem that must be considered and solved urgently, as it causes the insulating liquid to lose its dielectric properties and become useless for the function it has to perform. One of the most important elements to avoid this contamination is the oil preservation system, basically consisting of the main and auxiliary tanks of the transformers.