By the rules of the mathematical field of topology, two Spaces are considered equivalent if one can be bent, stretched, and perhaps folded until it looks like the other.

The BK9103 also enables a classic star topology to be set up. In this case the second port is not used. Both port interfaces are equivalent.

Current compensation superconducting fault current limiter is a novel topology of FCL which consists of an equivalent AC current source with a limiting resistance in parallel.