The switching is done by using two auxiliary contacts on the busbar disconnectors. In case of failure of either of the transformers, busbars, cables or their associated switchgear, a changeover option between the two will be at hand to keep the loads up and running. At 1 ½ breakers system arrangements a 2-zone protection must be used as in the Figure 2. Metal-Clad Switchgear is the premium choice for high-reliability requirements. i mean if pt is not in operation position you can not close the circuit breaker. is it necessary? Interested in this topic? By joining CR4 you can "subscribe" to this discussion and receive notification when new. Busbar protection (BBP): Protection intended to detect and operate to clear faults on a busbar.