A 3-phase, 3-line, 100 Km long transmission line is loaded at 110 kV. If the loss per phase is 5 MW and the load is 150 MVA, the resistance of the line is.
A 3-phase, 3-line, 100 Km long transmission line is loaded at 110 kV. If the loss per phase is 5 MW and the load is 150 MVA, the resistance of the line is.
Right Answer is:
8.06 ohms per phase
SOLUTION
3 phase power loss can be calculated as
PL = 3 Vp Ip cosϕ
PL = √3 VL IL cosϕ
Where,
Vp = Phase voltage
Ip = Phase current
VL = Line voltage
IL = Line current
Power loss per phase-
PL = I2 x R
Calculation:
All the calculations are done in per phase only-
Now load current (I) can be calculated as
I = (150 x 106)/(√ 3(110 x 103)) per phase
I = (15 / 11√ 3) x 103
Now, using power loss Formula-
PL = I2 x R
5 x 106 = (225/121× 3) x106 x R
So, R = 8.06 ohm/phase