The double-break disconnector consists of one arm which is moved by the central insulator supporting it and closes the circuit on two fixed contacts, each of them placed on one of the two side insulators.

Two models are available:

• the TCB, where the arm moves only perpendicularly to the plane of the insulators up to direct engagement of the moving contacts into the fixed ones;
• the STC, where the arm, upon completing its movement perpendicularly to the plane of the insulators, rotates around its own longitudinal axis leading to complete engagement and locking of the moving contacts into the fixed ones.

The former (TBC) is characterized by an extremely simple design and it is rather cheap; the latter (STC) can provide very high performance levels, in particular under short-circuit conditions.

Rated voltage: 24 – 550 kV

Rated continuous current: up to 8000 A

Rated short-time withstand current: up to 75 kA (3 s)