Electric Power Generation, Transmission, and Distribution

21.1.1.8 Tape Shielded Cables

Figure 21.9 shows a simple detail of a tape shielded cable.
Parameters of Fig. 21.9 are

dc¼diameter of phase conductor (in.)

ds¼inside diameter of tape shield (in.)

dod¼outside diameter over jacket (in.)

T¼thickness of copper tape shield in mils

¼5 mils (standard)

Once again, Carson’s equations will be applied to calculate the self-impedances of the phase conductor
and the tape shield as well as the mutual impedance between the phase conductor and the tape shield.
The resistance and GMR of the phase conductor are found in a standard table of conductor data.
The resistance of the tape shield is given by

rshield¼

18 : 826

dsT

V=mile (21:41)

The resistance of the tape shield given in Eq. (21.41) assumes a resistivity of 100Vm and a temperature
of 50 8 C. The diameter of the tape shielddsis given in inches and the thickness of the tape shieldTis
in mils.
The GMR of the tape shield is given by

GMRshield¼

ds

2



T

2000

12

ft (21:42)

The various spacings between a tape shield and the conductors and other tape shields are as follows:
Tape shield to its own phase conductor

Dij¼GMRtape¼radius to midpoint of the shield (21:43)

Tape shield to an adjacent tape shield

Dij¼center-to-center distance of the phase conductors (21:44)

Tape shield to an adjacent phase or neutral conductor

Dij¼Dnm (21:45)

whereDnm¼center-to-center distance between phase conductors.

AL or CU Phase

Conductor

Insulation

dod ds dc

Jacket

T

CU Tape Shield

FIGURE 21.9 Taped shielded cable.