The LK-VLBS is a three phase vacuum interrupter switch with a high breaking capacity. It was primarily designed for power networks and substation systems where it could replace vacuum circuit breakers in selective applications.

On each phase, a vacuum interrupter performs the function of arc quenching. The vacuum interrupter is housed in an insulating shield. This reduces the size of the switch so that it can be housed in panels of sizes as small as 470mm wide x 900mm deep x 1900mm high.

The LK-VLBS is capable of interrupting fault current levels up to 20kA through the vacuum interrupter when the switch is controlled by a current protection relay system.The LK-VLBS interrupts short circuit currents at within less than 50ms of fault detection (excluding the processing time of the relay.). 

The LK-VLBS is also built to house HV HRC fuses. A stored energy mechanism on the LK-VLBS allows for shunt tripping and fuse triggered tripping. Hence, with fuses the LK-VLBS can achieve up to 50 kA in short circuit breaking capacity. With fuses, the speed of interruption can reach times of less than 10 ms, depending on the time/current characteristic of the fuse selected.

The three phases are mounted on a chasis which also mounts an optional isolator on the incoming end and a  fault-making earth switch on the out going end of the interrupter. These last two components are interlocked in an opposed operating sequence towards each other and at the same time interlocked with the vacuum interrupter to ensure proper operating sequence.

Like other vacuum switches, LK-VLBS have a high electrical enduarance of more than 10,000 times, and it is virtually maintainence free.

The vacuum interrupter switch when controlled by a current protection relay unit protects for overload and fault currents up to 20kA. Furthermore when used in combination with HV HRC fuses the fuses act as backup devices for fault current levels of up to 50 kA. In the event of  overloading, the current protection relay triggers the switch so that  the vacuum interrupter, in place of the fuse, breaks the current.  This overcomes the traditional shortfall of relying soley on fuses for overload protection whereby fuses are relatively insensitive towards small overload.

During short circuit, either the interrupter or the fuse breaks the current, depending on the current level. Selective discrimination between the fuse and the vacuum interrupter is achieved by coordinating the time/current curves of the relay and the fuses. Thus with the fuse combination double protection of downstream equipment is achieved, making the LK-VLBS superior as a choice for overload and fault protection equipment.