If one transformer of a closed delta bank is removed, what percentage of the original capacity can the remaining transformers handle?

In a closed delta transformer configuration, removing one transformer can significantly impact the capacity of the remaining transformers. Each transformer in a delta configuration contributes to the overall capacity and load handling.

When one transformer is taken out of service in a closed delta connection, the two remaining transformers can still operate, but their capacity to handle the original load is affected. The remaining two transformers will continue to support the load, but they only share the incoming load from the original three transformers. Specifically, each transformer in a delta arrangement can handle approximately 58% of the total capacity when one transformer is removed. This is because with only two transformers remaining, each will take on approximately 1.15 times the load it would normally handle individually if the system were still complete, thus they can't fully compensate for the loss of a third transformer.

This results in the capacity of the two remaining transformers being about 66% of the total delta capacity, effectively leading to the available capacity being around 58% of the original when the one transformer is removed. Thus, the correct response highlights the important calculations involved in transformer operations and load sharing in a delta configuration. Understanding this concept is essential for maintaining system reliability and efficiency in power distribution systems.