Obviously in the latter arrangement, relay protection (reclose or fuse) immediately outside the substation should be considered to minimize faults on the maintained line circuit from causing extensive station outages.
The cost of the main and transfer bus arrangement is more than the single bus arrangement because of the added transfer bus and switching devices. in addition, if a low-profile configuration is used, land requirements are substantially more.
Connections of lines to the station should not be very complicated. If a bus tie breaker is not installed, consideration as to normal line loading is important for transfers during maintenance. If lines are normally operated at or close to their capability, loads will need to be transferred or temporary generators provided similar to the single bus arrangement maintenance scenario.
The main and transfer bus arrangement is an initial stage configuration, since a single main bus failure can cause an outage of the entire station. As load levels at the station rise, consideration of a main bus tie breaker should be made to minimize the al11ount of load dropped for a single contingency.
Another operational capability of this configuration is that the main bus can be taken out-of-service without an outage to the circuits by supplying from the transfer bus, but obviously, relay protection (reclose or fuse] immediately outside the substation should be considered to minimize faults on any of the line circuit from causing station outages. Application of this type of configuration should be limited to low reliability requirement situations.