In the case study, the author has taken a long line of 800 Km length ( mechanical length ) 735 KV and 0.932 mH/km and 12.2nF/km , and has shown that how the reactive power will wary at different points in the line.
The line is symmitrical . Meaning Vr=Vs , sending end voltage and receiving end voltage are same.When the line is uncompensated, the voltage distribution is as shown in Figure 2.7.
Po is the SIL of the line 1954 MW. P is the loading of the line. Voltage distribution is shown according to P/Po ratio.
When P=Po, the loading is according to SIL. So voltage profile is constant everywhere.
When P<Po, (P=0.8Po) there is light loading. So voltage profile is more than 1 pu.
When P>Po ( P=1.3Po ), heavy load condition is present. So voltage profile is lower than 1 pu .
When the controller is added at midpoint of the line, the Vm=1pu.
So the graph of voltage distribution becomes as shown in figure 2.9
Following points are concluded from the case study
- For the uncompensated line, loading is possible till 58% of the SIL.
- For the compensated line with VAR compensator at midpoint , loading can be increased.
- The VAR compensator should be capable of absorbing and supplying reactive power.