From Handbook of Electric Power Calculations, Third Edition


Calculate the inductive reactance per phase at 377 rad/s for the bundled transmission line whose conductors are arranged in a plane shown in Fig. 9.6. Assume conductors are ACSR Crow.

Figure 9.6: A bundled transmission line.

Calculation Procedure

1. Determine GMD

Assume distances are between bundle centers and transposition of phases. Then, GMD=[(9 2)(18)] 1/3=11.07 m. From Table 9.2, GMR c=0.034 ft (0.01 m). The GMR should include all conductor spacings from each other in the usual product form with, in this case, three values of GMR c. Because of redundancy, GMR=(0.01 0.45 2) 1/3=0.127 m.

2. Calculate Inductive Reactance per Phase

X L=377 2 10 7 ln(11.07/0.127)=0.337 10 3 ?/m (0.544 ?/mi).

Related Calculations. For a two-conductor bundle, GMR=(GMR c D) 1/2 and for a four-conductor bundle, GMR=(GMR c D 32 1/2) 1/4. In each case, D is the distance between adjacent conductors.

For a two-conductor bundle, GMR=(GMR c D) 1/2, and for a four-conductor bundle, GMR=(GMR c D 32 1/2) 1/4. In each case, D is the distance between adjacent conductors. For an n-conductor bundle as depicted in Fig. 9.7, GMR=( n GMR c A n 1) 1/ n, where A is the radius of the bundle. Similarly, for an n-conductor bundle, r equiv=( n r A n 1)

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