Handbook of Electrical Engineering

214 HANDBOOK OF ELECTRICAL ENGINEERING

is 33,700 V. The specific resistancer, inductive reactancexland capacitancecare 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

Xl=xl.l= 0. 110 × 25 =2.75 ohms/phase

C=c.l= 0. 24 × 25 = 6. 00 μF/phase

Xc=

106

2 πf C

=

106

2 π× 50 × 6. 0

=530.52 ohms/phase

The load.

The system nominal voltageVnis 33,000 volts.

The line currentIrreceived at the load is,

Ir=

Load MVA× 106

√

3 line voltage

=

SL× 106

√

3 Vn

=

20. 0 × 106

√

3 × 33000. 0

=349.91 amps/phase

The load star connected impedanceZLis,

ZL=

Vn

√

3 Ir

=

33000

√

3 × 349. 91

=54.45 ohms/phase

The resistive componentRLis,

RL=ZLcos Ø= 54. 45 × 0. 95 =51.728 ohms/phase

The inductive componentXLis,

XL=ZLsin Ø= 54. 45 × 0. 3123 =17.002 ohms/phase.

a) The ‘Tee’ equivalent circuit.

The two series elements are,

R

2

+j

X 1

2

= 1. 25 +j1.375 ohms/phase

The single shunt element is
Xc=−j 530 .52 ohms/phase