Page 230 - Handbook of Electrical Engineering

214 HANDBOOK OF ELECTRICAL ENGINEERING

is 33,700 V. The specific resistance r, inductive reactance x l and capacitance c are 0.100 ohm/km,
◦
0.110 ohm/km and 0.24 microfarad/km respectively at 90 C and 50 Hz. Find the percentage volt-drop
at the receiving end.
The cable.

The series impedance is:-

R = r.l = 0.100 × 25 = 2.50 ohms/phase
X l = x l .l = 0.110 × 25 = 2.75 ohms/phase
C = c.l = 0.24 × 25 = 6.00 µF/phase
10 6 10 6
X c = = = 530.52 ohms/phase
2πf C 2π × 50 × 6.0
The load.
The system nominal voltage V n is 33,000 volts.

The line current I r received at the load is,

Load MVA × 10 6 S L × 10 6
I r = √ = √
3 line voltage 3 V n
20.0 × 10 6
= √ = 349.91 amps/phase
3 × 33000.0
The load star connected impedance Z L is,

33000
V n
Z L = √ = √ = 54.45 ohms/phase
3I r 3 × 349.91
The resistive component R L is,

R L = Z L cos Ø = 54.45 × 0.95 = 51.728 ohms/phase

The inductive component X L is,

X L = Z L sin Ø = 54.45 × 0.3123 = 17.002 ohms/phase.

a) The ‘Tee’ equivalent circuit.
The two series elements are,
R X 1
+ j = 1.25 + j1.375 ohms/phase
2 2

The single shunt element is
X c =−j530.52 ohms/phase