ECE-380
INDIVIDUAL
SP2026
1. A 23-km,
Homework 3
Due - 4/21/2026
34
kV, 60Hz single-phase line has a per phase impedance z = 0.19 + j0.34 Ω/km. The
√3
single-phase load at the receiving end absorbs (10/3) MVA at
33
kV. Calculate:
√3
a. The ABCD model parameters
b. The sending-end voltage for a load power factor of 0.8 lagging.
c. The sending end voltage for a load power factor of 0.975 lagging.
Note: this is an unusual, (long) single-phase line…i.e. I’ve already converted to “single-phase” from
three-phase. All circuits are concerned with this for design purposes….you want to service a load –
e.g. what kind of source (at the sending end) is needed?
2. A 50-km, 220-kV, 60Hz three-phase overhead transmission line has a per-phase resistance of
0.2Ω/km , a per-phase inductance of 1.3481 𝑚𝐻/𝑘𝑚 and negligible shunt capacitance. Using the
short-line model:
i)
Find the sending end voltage
ii) Voltage regulation
iii) Sending end power
iv) Transmission line efficiency
When the line is supplying a three-phase load of:
a. 381 MVA at 0.8 power factor lagging at 220kV
b. 381 MVA at 0.8 power factor leading at 220kV
Note: three-phase specifications are in line-to-line voltages and total, 3 phase power –> check if the
system is balanced, convert to single-phase and line-to-neutral.