Inductance of Three Phase Double Circuit with Unsymmetrical Spacing but Transposed

Inductance of Three Phase Double Circuit with Unsymmetrical Spacing but Transposed

Consider three phase double circuit having conductors which are unsymmetrically spaced. The line is transposed so that each conductor occupies the position of other conductor after certain interval length or distance of transmission line.

The transposition cycle is as shown in the Fig. 1.21.1.

Flux linkage of conductor x in position 1

Example 1.21.1 The Fig. 1.21.2 shows the spacings of a double circuit 3 phase overhead line. The conductor radius is 1.1 cm. Find the inductance per phase per kilometer.

AU : May-10, Marks 6; May-13, Marks 8

Solution :  

Example 1.21.2 Determine the inductance of a single phase transmission line consisting of three conductors of 2.5 mm radii in the ’go’ conductor and two conductors of 5 mm radii in the, return, conductor. The configuration of the line is as shown in Fig. 1.21.3

AU : May-01, 18, Marks 3 

Solution : Consider the side consisting of 3 wires.

Example 1.21.3 A 400 kV, 3-phase bundled conductor line with two sub-conductors per phase has a horizontal configuration as shown in Fig. 1.21.4. The radius of each sub-conductors is 1.6 cm. (1) Find the inductance per phase per km of the line (2) Compute the inductance of the line with only one conductor per phase having the same cross-sectional area of the conductor of each-phase.

AU: Dec.-08, Marks 10

Solution :

2) Now let us compute inductance of the line with only one conductor per phase having same cross sectional area of the conductor of each phase.

Review Questions

1. Derive an expression for a three phase double circuit line with unsymmetrical spacing but transposed.

2. Calculate the inductance per phase for a three phase double circuit line whose phase conductors have a radius of 5.3 cm with the horizontal conductor arrangement as shown in the Fig. 1.21.6.

4. The Fig.1.21.7 shows the spacing of a double circuit 3 phase overhead line. The conductor radius is 1.5.cm and line is transposed. Find the inductance per phase per kilometer.