I have a single machine connected to an infinite bus with the following parameters:
- Sending end power = 3.75MW
- RL=5.18 ohms
- XL=130 ohms
- VS (Generator bus)=161kV
- VR (Infinite bus)=161kV
- Sending end voltage angle (delta) = 0.01877 (Angle which allows 3.75MW to be transferred)
Using these I want to calculate the amount of reactive power sent by the sending end as well.
I calculated it first without factoring in the line resistance (RL=0) Then got the result for Q as : 35.24kVAR
Next I calculated it with the line resistance factored in Then got the result for Q as: -114.77kVAR
When the line resistance is factored in, the answers for reactive power vary immensely. And when the resistance is factored in, the sign of Q is negative indicating the generator bus is absorbing VARS which doesn't seem to make sense.
Why are they so different? What am I doing wrong?
The equations I used are here
I derived these equations using Matlab to do the algebra, so it hopefully should be correct :)