Use of umbilicals with Vacuum Circuit Breakers
Some misunderstanding but finally the question is clear I hope.
Before the vacuum breaker is isolated (disconnected from the rails) it must be deactivated. (Remote or locally). 

When thereafter the breaker is isolated (disconnected from the rails) all power connections are disconnected. The remote station is still able to communicate with the breaker with SCADA.

This to prevent the situation that the breaker is pushed back in an active state.(Could be very dangerous) both SCADA and mechanical measures are in place to make this impossible. 

Therefore the SCADA system must be able to communicate with the breaker as long as it is on the rails in the cubicle. This is realised with the umbilical (a flexible data cable) connected to the breaker.

When the breaker is racked out for further inspection or replacement (Removed from the cubicle) the umbilical needs to be disconnected and communication with SCADA is lost.

After the same or an replacement breaker is put back on the rails for service the umbilical needs to be connected before any further action. This way the remote station is informed about the status and the actions with the breaker.

When information from SCADA and the additional mechanical protections are released the breaker can be pushed back into the cubicle (breaker is still open). Thereafter the breaker can be activated locally or remote.

The expression umbilical comes from the possibility that the cable set can be plugged in and out.