The vertical-break disconnector consists of one arm which, by moving on the plane of the insulators supporting it, closes the circuit on a fixed contact located on the side insulator.

Since the movement of the arm takes place on the same plane as that of the insulators, the phase-to-phase spacing is minimized.

Two models are available:

• the SHD, where the arm is operated by a driving insulator directly connected to it, which moves on the same plane as that of the two post insulators;
• the SLOB, where the arm is operated by the rotation of the driving insulator around its own longitudinal axis, by means of a rod-crank system.

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

Two different types of the SLOB disconnector are available (depending on the rated voltage and the rated short-time withstand current): 

• “single-motion” type, where the arm of each pole moves only perpendicularly to its rotation axis up to direct engagement of the moving contact into the fixed one;
• “double-motion” type, where the arm, upon completing its movement perpendicularly to its rotation axis, moves along its longitudinal axis leading to complete engagement and locking of the moving contact into the fixed one.

Rated voltage: 17.5 – 550 kV

Rated continuous current: up to 6300 A

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