Conduction-Cooled Superconducting Fault Current Limiter
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Solution Overview
Problem
Conventional fault current limiters (FCLs) face challenges in cost, timeliness, and recovery time, particularly in large and complex electrical distribution grids, with existing technologies relying on liquid cryogens and high capital costs, and requiring longer recovery times.
Innovation Solution
A liquid cryogen-free, conduction-cooled, resistive superconducting fault current limiter design using Magnesium diboride (MgB2) superconductors with a variable impedance element and a shunt resistor, allowing for rapid energy dissipation and minimal temperature rise during faults, enabling fast recovery times without the need for liquid cryogens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If liquid cryogen cooling is used for rapid heat removal during faults, then the energy removal rate is improved, but the system complexity and capital cost increase substantially
Solution Approach 1:
The patent extracts the liquid cryogen from the system entirely, replacing it with a solid-state conduction cooling system using heat sinks and thermal conduction paths through the FCL structure. This eliminates the complexity of liquid handling, pumping, and containment systems while maintaining effective heat removal through direct thermal conduction from the superconductor to heat sinks.
Solution Approach 2:
The patent introduces heat sinks as intermediary thermal management components that mediate between the superconductor and the ambient environment. These heat sinks provide a thermal conduction path that efficiently removes fault energy without requiring liquid cryogen circulation systems, thereby reducing system complexity while maintaining energy removal capability.
2Loss of time
If liquid cryogen cooling is used for rapid heat removal during faults, then the recovery time is improved, but the handling costs and engineering requirements increase
Solution Approach 1:
The patent removes liquid cryogen handling systems entirely, replacing them with passive or active conduction cooling through heat sinks. This eliminates the need for cryogen storage tanks, pumping systems, filtration, and safety handling infrastructure, substantially reducing manufacturing complexity and operational handling costs while achieving rapid recovery through efficient thermal conduction paths.
3Ease of manufacture
If inductive FCL design is used, then the capital cost is reduced, but the amount of superconductor wire required increases substantially
Solution Approach 1:
The patent changes the operational parameters of the superconductor by utilizing its resistive state during faults rather than relying on inductive effects. This parameter change allows the use of less superconductor material, as the limiting action comes from the resistive heating and quenching of a smaller superconductor volume rather than the inductive impedance of a large superconductor winding.
4Reliability
If conventional resistive FCL with liquid cryogen is used, then the fault current suppression is improved, but the temperature rise creates excessive thermal load
Solution Approach 1:
The patent incorporates heat sinks that are pre-cooled to cryogenic temperatures before fault events occur. These pre-cooled heat sinks act as thermal sinks that can rapidly absorb the heat generated during superconductor quenching without causing excessive temperature rises. The preliminary cooling of the heat sinks enables them to immediately absorb fault energy through thermal conduction.
Solution Approach 2:
The heat sinks serve as intermediary thermal management components between the superconductor and the environment. They provide a controlled thermal conduction path that limits temperature rise in the superconductor during faults by rapidly conducting heat away to the pre-cooled heat sink mass, thereby maintaining fault suppression capability while controlling thermal excursions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a cost-effective, rapid recovery system capable of withstanding large energy pulses and minimizing temperature excursions, allowing for multiple fault events within seconds to minutes, outperforming conventional systems in terms of recovery time and operational efficiency.
Implementation Method 1
a superconducting component which must be maintained at cryogenic temperatures
Implementation Method 2
conduction-cooled, fast acting, resistive, superconducting fault current limiter
Implementation Method 3
the superconductor quenches: it becomes a normal conductor as the temperature and thus the resistance rises sharply and quickly
Data Source
AI summary
Fault Current Limiters (FCL) provide protection for upstream and/or downstream devices in electric power grids. Conventional FCL require the use of expensive conductors and liquid or gas cryogen handling. Disclosed embodiments describe FCL systems and devices that use lower cost superconductors, require no liquid cryogen, and are fast cycling. These improved FCL can sustain many sequential faults and require less time to clear faults while avoiding the use of liquid cryogen. Disclosed embodiments describe a FCL with a superconductor and cladding cooled to cryogenic temperatures; these are connected in parallel with a second resistor across two nodes in a circuit. According to disclosed embodiments, the resistance of the superconducting components and its sheath in the fault mode are sufficiently high to minimize energy deposition within the cryogenic system, minimizing recovery time. A scheme for intermediate heat storage also is described which allows a useful compromise between conductor length enabled energy minimization and allowable number of sequential faults to enable an overall system design which is affordable, and yet allows conduction cooled (cryogen free) systems which have fast recovery and allows for multiple sequential faults.