Power System Analysis Part 2 .

ASSIGNMENT: Power system Analysis Part 2

ASSIGNMENT: Power system Analysis Part 2
Ans:
HVDC transmissions can be used for over long distance.In transmission line there is many parameters
are Important to calculate which voltage (KV) line we should use in transmission. Such Parameters are
distance (in km),line voltage (KV), resistance (ohm),series inductance, shunt capacitance, surge
impedance loading , Input and output power, active and reactive power, transmission parameters
(ABCD),efficiency, susceptance and compensators.
From given data overhead line is 280 km away from hydroelectric stations.
So,
Distance between lines: 280 Km
Full load: 1500 MW
Power factor cos (φ)=0.95 (lagging)
Φ=18.1949o
Line representation=π equivalent circuit with half the capacitance at either end.
Line compensation=40%
Synchronous compensation=300 MVAr
Maximum permissible voltage drop =10%
Transmission angle=30 o
From the table-1 we observed that , when overhead line voltages has increases from 132 Kv,275 Kv and
400 Kv, than the resistance is decreases, reactance is increases, susceptance is increases and surge
impedance is decreases.
All the parameters are in per phase per km.
Consider nominal π method:

ASSIGNMENT: Power system Analysis Part 2
Figure-1
Figure-2
Cos φR=receving end power factor (lagging)
VR=VR+j0
IR=IR(cos φR –jsin φR)
IC1=(jѽCVR)/2

ASSIGNMENT: Power system Analysis Part 2
IL=IR+IC1
VS=VR+IL(R+jX)
IC2= (jѽCVs)/2
Is=IL+IC2
Relation between distance and voltage in transmission line(V)=5.5 √0.62 L+(3 P/150)
From the table-1
L=280 Km
Line voltage= 5.5 √0.62∗ (280 ) +( 3∗1500000
150 )
=955 KV
So at 280 Km distance line voltage of overhead line can be 400 KV
Series compensation:
It improve system voltage. In this reactive power is inserted in series with the line for improving the
impedance of the system. It also improve power transfer capacity and stability.
If XC is connected in series with the line than the reactance of the line is reduces from XL to (XL-XC). The
power transfer to receiving end is given by:
P2= Vs VR sinα/(XL-XC) where α is angle between VR and VS
P2/P1= XL/( XL-XC)
=1/(1-(XC/XL))
= 1/(1-K)
Here k is degree of compensation
K=( XC/XL)*100
XL= total series inductive reactance