Patent Application
20230411045
This application claims the benefit of priority from European Patent Application No. 22 305 601.1, filed on Apr. 22, 2022, the entirety of which is incorporated by reference.
The present invention relates to superconducting cable systems, in particular to 3-phase superconducting cable systems in which conductors of each phase of the cable system run in separate cryostats.
The electrical conductors of both low-temperature and high temperature superconductive cable systems must be cooled during operation in order to establish and maintain their desired superconducting properties. Low-temperature superconductors, typically metallic superconductors, may need to be cooled down to very low temperatures as low as 4 Kelvin or below to become superconducting, which can be achieved, e.g., by using liquid Helium as coolant. High temperature superconductors, typically ceramic superconductors, may need to be cooled down less deep, typically down to temperatures of 77 Kelvin and above, which can be achieved, e.g., using liquid Nitrogen (LN2) as coolant. The present disclosure is applicable for both and high and low temperature superconductors.
Similar to conventional cables, any phase conductor of 3-phase superconducting cables can be damaged at any time. This damage can be electrical, or hydraulic if there is a leak in the cryogenic envelope in which the coolant circulates. Repairs are time consuming, or in some cases not possible, so that components must be replaced. During this time, the entire 3-phase superconducting cable system cannot be operated.
It is, therefore, an object of the present invention to provide a superconducting cable system that can continue operation while one conductor or its cryogenic envelope is damaged or broken.
This object is achieved by the superconducting cable system of claim 1, and the method of operating the superconducting cable system of claim 8. Advantageous embodiments and developments are provided in the respective dependent claims.
A 3-phase superconducting cable system in accordance with a first aspect of the invention comprises four 1-phase superconducting cables, of which a first, a second and a third are electrically connected with a corresponding first, second and third electrical phase. Interrupting switches are arranged at respective first and second ends of a first, second and third of the 1-phase superconducting cables. First connecting switches and second connecting switches are connected at a first and a second end, respectively, of the fourth 1-phase superconducting cable in such a way, that a switchable connection between the first and second ends of the fourth superconducting cable and corresponding ends of each of the first, second and third superconducting cables exists. The interrupting switches and the first and second connecting switches are operable to selectively disconnect one of the first, second or third of the 1-phase superconducting cables from their respective current phase and to connect the fourth 1-phase superconducting cable to the previously disconnected current phase, effectively replacing the disconnected 1-phase superconducting cable.
In one or more embodiments each of the four 1-phase superconducting cables runs in a separate cryogenic envelope, and each of the separate cryogenic envelopes has shut-off valves at the respective first and second ends.
In one or more embodiments at least a first cooling system is provided, which feeds coolant into a first end of at least a first one of the four cryogenic envelopes, and receives coolant from a first end of at least a second one of the four cryogenic envelopes.
In one or more embodiments the second ends of the cryogenic envelopes are connected to a coolant router which is adapted to receive coolant from at least one of the four cryogenic envelopes and to feed coolant into at least another one of the four cryogenic envelopes.
In one or more embodiments a second cooling system is provided, which is adapted to receive coolant from the second ends of cryogenic envelopes coolant-fed by the first cooling system at their respective first ends, and which is adapted to feed coolant into the second ends of cryogenic envelopes, from which the first cooling unit receives coolant at their respective first ends.
In one or more embodiments a spare coolant line is provided between first cooling system and the coolant router or the second cooling system, respectively. The spare coolant line preferably has a the same hydraulic cross section or hydraulic properties as the cryogenic envelope of a superconducting cable.
In one or more embodiments each end of the four 1-phase superconducting cables is electrically shielded, and the shields are switchably connected to ground, at each respective end.
A method of operating a 3-phase superconducting cable system in accordance with the first aspect of the invention comprises detecting a damage to one of the first, second or third superconducting cable. If such damage is detected, the interrupting switches at the first and second end of the damaged superconducting cable are operated, for disconnecting it from the associated electrical phase. At the same time, or in a close temporal context, the respective first and second connecting switches associated with the damaged superconducting cable are operated, for connecting the fourth superconducting cable to the disconnected electrical phase. The close temporal context may comprise connecting the fourth superconducting cable to the disconnected electrical phase prior to disconnecting the damaged superconducting cable.
Disconnecting the damaged superconducting cable and connecting the fourth superconducting cable may comprise disconnecting and connecting the corresponding electrical shields.
During normal operation, i.e., none of the superconducting cables being damaged, the coolant will flow through all of the cryogenic envelopes, preferably symmetrically distributed.
In one or more embodiments the method further comprises closing the shut-off valves at both ends of the cryogenic envelope of the damaged superconducting cable. The damaged superconductor will then warm up and can be repaired or replaced.
In one or more embodiments the method further comprises if properties of a coolant flowing out of the first cooling system and/or into the first cooling system meet or exceed predetermined limit values. If the limit values are not met the method further comprises connecting the first cooling system and the coolant router, or the first cooling system and the second cooling system via a spare coolant line. The limit values may relate to one or more of a minimum flow, a maximum coolant return temperature, or the like. This embodiment permits compensating for an asymmetric coolant flow caused by closing the shut-off valves at both ends of the cryogenic envelope of the damaged superconducting cable, which otherwise would be symmetrically distributed over the cryogenic envelopes of the four superconducting cables in case the required low temperatures cannot be maintained through the asymmetric coolant flow.
After repair or replacement of the superconducting cable it will serve as a fourth, spare superconductor for any future damage to any of the other superconducting cables.
The superconducting cable system presented hereinbefore permits uninterrupted operation when one of the cables is damaged.
In the following section exemplary embodiments of the invention will be described with reference to the drawing, in which
In the figures similar or identical elements are referenced using the same reference designators.
In normal operation only three phases and their associated shields are connected via the corresponding switches. If the superconducting cable actively connected to one of the three phases is damaged, the spare fourth superconducting cable can be connected via the associated switches. The damaged superconducting cable and the corresponding shield is disconnected by the associated switches.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22305601.1 | Apr 2022 | EP | regional |
