Running load flow on three phase and single phase system.

[Dr. D. Karthikaikannan .]

Dear sir,
I want to conduct a load flow analysis using matpower in my college campus.
The three phase cables from the transformer goes to the different building
and there it is splitted into single phase system (R,Y,B). Suppose I know
the loading values of single phase loads. How can I merge three phase and
single phase in one mpc.