To provide a power line coupler, along with an apparatus and system for detection of a power line connection configuration, capable of facilitating confirmation of a connection configuration of power lines in a power distribution system.

The power line coupler includes: connecting an upstream-side power line with a downstream-side power line via a blocking filter; relaying a request signal arriving through the upstream-side power line to the downstream-side power line; receiving a connection configuration signal arriving through the downstream-side power line in response to the request signal, as a downstream-side identification information signal; and adding its own identification information to the downstream-side identification information signal to generate a connection configuration signal, which is supplied to the upstream-side power line.