Using variable values before the optimization is being solved

I want to solve an optimal power flow (OPF) problem using YALMIP. I am using a linear power flow (PF) method.

I can get the optimal solution from that optimization part without applying the PF part. However, the program is not run with the PF part. The reason is that I cannot get the values of the load variables to use in the PF part.

In other words, I am finding the best amount of bus loads in the optimization part, and I want to apply the values in the optimization part considering the operation security limitations of the grid. Therefore, I am using PF to check the security violation.

[If I wanted just to check that my optimal answers violate the security constraints, I could use security constraints outside of the optimization part. However, I want the optimization part to give me the answer which the security constraints are not violated.]

The load variables are set as sdpvar variables. I need to change the grid loading through the load variable values. However, the program takes the NAN value of the variables in the power flow part, and thus, I cannot check the constraints.

I was wondering how I can use the values of the variables in an internal part within the optimization process (without the optimization process is first being solved).