ECE 476 POWER SYSTEM ANALYSIS. Lecture 6 Development of Transmission Line Models Professor Tom Overbye Department of Electrical and Computer Engineering. Reading. For lectures 5 through 7 please be reading Chapter 4 we will not be covering sections 4.7, 4.11, and 4.12 in detail
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ECE 476POWER SYSTEM ANALYSIS
Lecture 6
Development of Transmission Line Models
Professor Tom Overbye
Department of Electrical andComputer Engineering
0.25 M
0.25 M
0.25 M
Consider the previous example of the three phases
symmetrically spaced 5 meters apart using wire
with a radius of r = 1.24 cm. Except now assume
each phase has 4 conductors in a square bundle,
spaced 0.25 meters apart. What is the new inductance
per meter?
Therefore in
general Dab
Dac Dbc
Unless something
was done this would
result in unbalanced
phases
Typical Transmission Tower
Configuration
230 kV wood pole H-frame
230 kV lattice steel tower double circuit
Source: Tom Ernst, Minnesota Power
Aerial or side view of conductor positions over the length
of the transmission line.
Answer: Dm = 12.6 m, Rb= 0.0889 m Inductance = 9.9 x 10-7 H/m, Reactance = 0.6 /Mile
Since D comes
radially out inte-
grate over the
cylinder bounding
the wire
A
C
B
Assume we have three
infinitely long conductors, A, B, & C, each with radius r
and distance D from the
other two conductors.
Assume charge densities such
that qa + qb + qc = 0
Inductance and Capacitance assume a Dm of 1 ft.
GMR is equivalent to r’
Term independent
of conductor with
Dm in feet.
Term from table assuming
a one foot spacing
Term independent
of conductor with
Dm in feet.
Term from table assuming
a one foot spacing
+/- 400 kV HVDC lattice tower
Source: Tom Ernst, Minnesota Power