# Regarding assigning initial values for load flow analysis in NR method in runpf() function

```Hello,
I am Sayandev Ghosh, presently teaching power system in an undergraduate
engineering college. I have done my M.Tech on Energy Science from Jadavpur
University. I have been using MATPOWER for load flow analysis of till 118
bus by Newton Raphson method. While doing that I am not able to understand
the following area:-```
```

In the runpf() function while using Newton Raphson method  the initial
values of voltage magnitude and voltage angle have been assigned by the
following lines (line 177 - 183):

[image: Inline image 2]
I am having a bit problem in understanding this section. Why are we
considering the final values of Voltage magnitude and Voltage angle as the
initial guess? In the case files for eg. 'case57' the Vm and Va are
probably the final voltage magnitudes and voltage angles.

Shouldn't it be like assigning all the voltage magnitudes of PQ bus as 1.0
pu and voltage angles of all PV and PQ bus as 0 degree for a flat start.

Depending on the answer of this question I would like to convey my other
doubts/questions.