So I have this network in the figure below (100 MVA base) that I need to model with DC power flow line reactances and etc.

Im attempting to set up the estimation matrix and have the following, but not sure what the value for M3 and M2 would be.

M21 = 10Theta2 - 10Theta1 M23 = 4Theta2 M32 = -4Theta2

I'm thinking: M2 = M12 + M23 (should one be negative even though both are flowing out of bus 2?) M3 = M32 (do we consider M23 here at all?)

Any help is great appreciated, thank you!