3-PHASE CABLE ARRANGEMENTS

RTD and CD design

There are no significant differences in the use of RTD type superconducting power cables and conventional cables. The cables can be arranged in a linear or triangular geometry. The distance between RTD phases is determined by the amount of magnetic field excerpted by the phases on each other. A typical distance would be 0.5 m. Smaller distances are possible but increase ac losses. Thermal considerations (as in copper cables) are not important.

CD design cables can be arranged as conventional cables, but also trefoil and concentric arrangements are possible.

Conventional arrangement

If each phase uses the CD design separately then standard arrangements (as above) can be used. As the superconducting screen shields all magnetic field from each phase separately there is no interaction between phases and they could be laid arbitrarily close together, or in metallic ducts.

Trefoil arrangement

Hereby all three phases are housed in the same thermal insulation. The phases are situated as close together as physically possible.

Light blue: coolant.
Dark blue: thermal insulation (cryostat).
Red: superconductor (both conductor and screen).
Yellow: electrical insulation.
Dark grey: cooling pipe.
Grey/black marbled: outer screen and protection layer.

Concentric arrangement

In contrast to the previous design here the 3 phases are situated concentric to a central cable axis. Thus there is only one cooling pipe, and the voltage that the dielectric has to withstand is the full phase to phase voltage. The advantage to the design is that it is ultra-compact, and uses the least amount of superconductor.

Light blue: coolant.
Dark blue: thermal insulation (cryostat).
Red: superconductor (both conductor and screen).
Yellow: electrical insulation.
Dark grey: cooling pipe.
Grey/black marbled: outer screen and protection layer.

In the figure an outer superconducting screen is shown. This screen is not absolutely necessary as with symmetrical load the currents and the magnetic fields in the phases cancel.

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	Triax
	Cable designs
	RTD design
	3-phase design
	Cooling
	Standard and norms
	Critical current
	Losses
	AC losses
	Overcurrent