Different Between Bus Riser and Bus Coupler?

Just look at the Switch board /schamitic drawings. You will understand it better.

Buscoupler connects two bus sections which being fed from two different Incomers,like Incomer-1 ---- Buscoupler -----Incomer-2

Busriser means When your outgoings or Incomers are busbars rather than cables,and it runs through an enclosed Busduct upto the destination.

Bus-coupler is a coupler breakers that installed between the Incomer-1 and Incomer-2 that connects two bus sections which being fed from two different Incomers or transformers.

Bus riser is a set of bus bar that connected from the coupler breakers, outgoing section enclose in the panel and connected to your incoming 1 or incoming 2 bus bar section. It depend which side is your outgoing from the bus bar coupler breakers or depend on your electrical design.

Yeah Wan is right...I took that in another way