Hi and welcome!
It is hard to tell what went wrong without a Minimum Working Example (see the forum guidelines), maybe you could provide one?
If branch is a variable, the problem could come from the indexing V[Int.(real(branch[:,1])),:].
Otherwise, my best guess is that SOCP constraints don’t accept multiplications (V .* I or squares P.^2) inside the constraint, since it is their job to square stuff. But I’m not sure about this.