Question

A 300 km long 500 kV overhead transmission line connects a power plant to a grid substation. 

Per unit length parameters of the line are as follows: X=j0.32 Ω km^-1; y=j5.2 x 10^-6 S km^-1  peak and off- peak power and respective voltages at line ends are as given bellow 

	P, MW	V1, kV	V2, kV
Peak	1575	510	510
Off-peak	945	510	510

 

a)       For both peak and off-peak times  

i.             Determine current and reactive power at the receiving end of the line 

ii.           Calculate voltage, current and reactive power at points which are ¼, and ½ of the length of the line.

iii.         Sketch variation of each of above parameters along the line (v =f(l), I=f(l) and Q=f(l)

 

b)      If the power plants maximum reactive power limit is 200 MVar, what additional device are required to connect at the sending end of the line to keep 510 kV voltage at the ends of the line during the peak hours? Calculate the capacity of such device 

 

c)       State whether during the off-peak hours the voltage along the line is at the permissible range. If this requirement is not met, with necessary calculations suggest the measures required to bring the voltage of the line to a permissible range