The electricity system operator needs to regulate voltage at certain nodes in the transmission grid. For this purpose, it regulates transformers under load, achieving the required voltage levels according to established operating procedures.

Transformers can be single-phase (usually forming a three-phase bank) or three-phase.

The design of a power transformer can be either shell-type or core-type. Its construction technology requires a robust and compact structural form of core and windings, allowing efficient heat dissipation and the ability to withstand internal short-circuit forces generated by faults in the grid, along with an insulation system that ensures its operation under both normal and transient conditions.