A rapid opening device and method based on mutual inductance driving of a shielding layer of a direct current high temperature superconducting cable

Abstract

The application discloses a kind of based on DC high-temperature superconducting cable shield intertia drive's quick breaking device and method, it is related to DC high-temperature superconducting cable protection and DC quick breaking technical field, device includes: single-pole coaxial DC high-temperature superconducting cable, quick switch, current-limiting resistance, energy storage capacitor, first controlled switch, second controlled switch, voltage-limiting energy-absorbing element and auxiliary injection inductance;DC high-temperature superconducting cable includes superconducting layer and shield layer with intertia relationship;Selected shield conductor in shield layer is led out to form intertia drive conductor, remaining shield conductor keeps original connection mode;Quick switch is connected in series in main current channel, voltage-limiting energy-absorbing element is connected in parallel at its two ends;Energy storage capacitor is connected with first controlled switch and second controlled switch respectively;Second controlled switch is connected into main current channel by auxiliary injection inductance.The application is applicable to short-circuit protection of single-pole coaxial DC high-temperature superconducting cable and is conducive to controlling the current of shield layer and reducing heat production.

Description

Technical Field

[0001] This invention relates to the fields of DC high-temperature superconducting cable protection and DC fast interruption analysis, specifically to a fast interruption device and method based on mutual inductance driving of the shielding layer of a DC high-temperature superconducting cable. Background Technology

[0002] DC high-temperature superconducting cables are characterized by high current density, large transmission capacity, low line loss, and compact structure, and can be used in scenarios such as urban power grid capacity expansion, DC power transmission and distribution, high-current feeders, and interconnection of cryogenic power equipment. A typical monopole coaxial DC high-temperature superconducting cable includes a central support structure or cooling channel, a superconducting layer formed by wrapping REBCO high-temperature superconducting tape, a cryogenic insulation layer, a shielding layer, a liquid nitrogen or other cryogenic medium channel, and an outer sheath.

[0003] In the aforementioned cable structure, the shielding layer is typically composed of multiple high-temperature superconducting shielding tapes, metallic shielding conductors, or composite shielding conductors wrapped around the outside of the superconducting layer. Because the shielding layer spatially surrounds the superconducting layer, magnetic coupling and mutual inductance exist between them. During steady-state DC operation, the superconducting layer current remains essentially constant, and the voltage generated by mutual inductance within the shielding layer is relatively small. However, when a short-circuit fault, joint abnormality, sudden load change, or local quench occurs, the superconducting layer current and its rate of change increase, the magnetic flux linkage of the shielding layer changes, and induced voltage and current are generated in the shielding conductor.

[0004] Existing protection schemes for DC high-temperature superconducting cables mostly rely on external current sensors, external energy storage power supplies, independent triggering units, hybrid circuit breakers, or conventional mechanical switches. While these schemes can clear faults, there is usually no direct electromagnetic connection between the energy storage element and the fault current changes. Furthermore, the DC current lacks a natural zero-crossing point, and the fast switching process typically requires auxiliary current or other commutation measures. In addition, if all shielded conductors are directly connected to the external charging circuit, the induced current in the initial stage of a fault may be large, potentially increasing the local thermal load on the shielding layer and affecting the low-temperature insulation stability. Therefore, when utilizing the induced voltage of the shielding layer, it is necessary to limit the number of shielded conductors participating in external charging and constrain the charging current through series current-limiting elements.

[0005] In summary, there is an urgent need in the field of DC high-temperature superconducting cable protection to propose a new technical solution that can utilize the cable's own electromagnetic characteristics to achieve self-energy extraction from faults and solve key problems such as the inappropriate external extraction of the shielding layer induced current, the need to limit the charging current, and the need for auxiliary current coordination for fast DC switching. Summary of the Invention

[0006] The purpose of this invention is to provide a fast interruption device and method based on mutual inductance driving of the shielding layer of a DC high-temperature superconducting cable, aiming to solve the problem that the protection scheme for DC high-temperature superconducting cables is highly dependent on external current sensors, external energy storage power supplies, independent triggering units, hybrid circuit breakers or conventional mechanical switches.

[0007] In a first aspect, the present invention provides a fast breaking device based on mutual inductance driven by the shielding layer of a DC high-temperature superconducting cable, comprising a unipolar coaxial DC high-temperature superconducting cable, a fast switch, a current-limiting resistor, an energy storage capacitor, a first controlled switch, a second controlled switch, a voltage-limiting energy-absorbing element, and an auxiliary current-injecting inductor. The unipolar coaxial DC high-temperature superconducting cable includes a superconducting layer and a shielding layer. The shielding layer is wound around the outside of the superconducting layer, and there is a mutual inductance between the superconducting layer and the shielding layer. One end of the superconducting layer is electrically connected to the DC input terminal. One or a group of shielding conductors led out from the shielding layer form a mutual inductance driving element. The remaining shielding conductors in the shielding layer that are not led out maintain their original shielding connection method. The fast switch is connected in series in the main current channel of the unipolar coaxial DC high-temperature superconducting cable, with one end electrically connected to the other end of the superconducting layer and the other end connected to the DC output terminal. One end of the current-limiting resistor is connected to one end of the mutual inductance driving element, and the other end is connected to one end of the first controlled switch. One end of the energy storage capacitor is electrically connected to the other end of the mutual inductance driving element and the second end of the second controlled switch, and the other end is electrically connected to the second end of the first controlled switch and one end of the auxiliary current injection inductor. The control terminal of the first controlled switch is electrically connected to the detection and control unit and is used to receive the first control signal from the detection and control unit. The control terminal of the second controlled switch is electrically connected to the detection control unit and is used to receive the second control signal from the detection control unit; The pressure-limiting energy-absorbing element is connected in parallel across the two ends of the fast switch; The other end of the auxiliary current injection inductor is electrically connected to one end of the voltage limiting energy absorption element, the DC output terminal, and the other end of the fast switch.

[0008] Secondly, the present invention also provides a rapid disconnection method based on mutual inductance driving of the shielding layer of a DC high-temperature superconducting cable, comprising: During the normal flow phase: When the fast switch is closed, DC current flows in from the DC input terminal, and after being connected through the equivalent superconducting branches of the superconducting layer, it flows to the DC output terminal through the fast switch. When the total current of the superconducting layer is lower than the first preset threshold, or the rate of change of current is lower than the second preset threshold, or the induced voltage of the mutual inductance drive branch of the shielding layer is lower than the third preset threshold, the first controlled switch and the second controlled switch are controlled to remain in the off state. During the short-circuit fault and shielding layer mutual inductance driving stage: When the total current of the superconducting layer reaches a first preset threshold, or the rate of change of current reaches a second preset threshold, or the induced voltage of the mutual inductance drive branch of the shielding layer reaches a third preset threshold, it is determined that a short circuit fault has occurred in the superconducting layer, and the first controlled switch is turned on and the second controlled switch is turned off. At this time, the induced voltage of the mutual inductance drive branch of the shielding layer charges the energy storage capacitor through the first controlled switch, and the voltage of the energy storage capacitor gradually increases. In the energy storage stage: The current-limiting resistor limits the peak value and rising slope of the charging current of the energy storage capacitor. When the voltage of the energy storage capacitor continues to rise to a preset target value, the first controlled switch is controlled to remain off to prevent the energy storage capacitor from discharging prematurely into the mutual inductance drive branch of the shielding layer. During the capacitor discharge and auxiliary zero-crossing phase: The second controlled switch is turned on, and the energy storage capacitor releases auxiliary current through the auxiliary injection circuit; the auxiliary current flows through the branch where the fast switch is located and is superimposed on the fault current in the opposite direction, so that the combined current flowing through the fast switch is reduced to the breakable range or forms a current zero crossing point; the fast switch performs a tripping action when the current crosses zero or is reduced to the breakable range. During the recovery voltage limit and reset phase: After the fast switch is opened, the voltage limiting and energy absorbing element connected in parallel across the fast switch limits the recovery voltage across the fast switch and absorbs the remaining energy of the system. At this time, the second controlled switch is turned off, and the residual voltage of the energy storage capacitor is released through the current limiting resistor or a dedicated discharge branch. After the fault is cleared, the fast switch is closed again, returning to the normal current flow stage.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. Achieving self-generation of fault energy and reducing external dependence: This invention utilizes the mutual inductance between the shielding layer and the superconducting layer of a DC high-temperature superconducting cable to provide a charging voltage for the energy storage capacitor when the short-circuit fault current changes. This enables the extraction of energy from the fault current itself, eliminating the need for complex external energy storage power supplies or pre-charging circuits, and improving the independence and response speed of the protection device.

[0010] 2. Optimized shielding current distribution reduces thermal load risk: This invention connects only one or a group of conductors in the shielding layer to the charging circuit, rather than connecting the entire shielding layer to the external circuit. This design effectively reduces the thermal load risk caused by the entire induced current of the shielding layer being externally drawn, ensuring the thermal stability and insulation reliability of the shielding layer during fault transients.

[0011] 3. Precisely limit charging current and protect key components: The present invention sets a current-limiting resistor in the inductive charging branch of the shielding layer, which can effectively limit the peak value and rising slope of the charging current of the energy storage capacitor, thereby reducing the current surge borne by the first controlled switch, the energy storage capacitor and the selected shielding conductor, and improving the electrical stress resistance and service life of the entire device.

[0012] 4. Optimize control timing to prevent energy backflow: This invention effectively isolates the charging process of the energy storage capacitor from the auxiliary current injection process in terms of time and electrical circuit by coordinating the timing of the first and second controlled switches. The first controlled switch turns off before the second controlled switch, which avoids the energy storage capacitor from discharging back to the shielding layer inductive charging branch, thus ensuring energy utilization efficiency.

[0013] 5. Assisted DC interruption to enhance arc extinguishing capability: This invention injects an auxiliary current opposite to the fault current into the branch where the fast switch is located through an energy storage capacitor and an auxiliary current injection inductor. This reduces the combined current in the fast switch to the interruptible range or forms an artificial current zero-crossing point, creating favorable conditions for the arc extinguishing of the DC fast switch and significantly improving the interruption capability of DC faults. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the overall topology of a fast disconnection device based on mutual inductance driving of the shielding layer of a DC high-temperature superconducting cable according to an embodiment of the present invention. Figure 2 This is a circuit schematic diagram of the normal current-carrying stage according to an embodiment of the present invention; Figure 3 This is a circuit schematic diagram of the short-circuit fault and shielding layer mutual inductance driving stage according to an embodiment of the present invention. Figure 4 This is a circuit diagram illustrating the capacitor discharge and auxiliary zero-crossing stage according to an embodiment of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figure 1 As shown, this invention provides a fast switching device based on the mutual inductance drive of the shielding layer of a DC high-temperature superconducting cable, comprising the following components: a unipolar coaxial DC high-temperature superconducting cable, and a fast switch. Current limiting resistor Energy storage capacitor First controlled switch Second controlled switch Voltage limiting energy absorption element and auxiliary current injection inductor ; The single-pole coaxial DC high-temperature superconducting cable includes a superconducting layer and a shielding layer. The shielding layer is wound around the outside of the superconducting layer, and there is a mutual inductance relationship between the superconducting layer and the shielding layer. One end of the superconducting layer is electrically connected to the DC input end. One or a group of shielding conductors led out from the shielding layer form a mutual inductance driving element. The remaining shielding conductors in the shielding layer that are not led out maintain the original shielding connection method.

[0018] The superconducting layer is formed by multiple REBCO high-temperature superconducting tapes wrapped in parallel along the cable axis or helical direction, each tape... Each high-temperature superconducting tape corresponds to an equivalent superconducting branch. Each equivalent superconducting branch consists of a first inductor and a first resistor connected in series; each... The high-temperature superconducting tape is equivalent to the first inductor; the first resistance is per tape. The equivalent resistance of high-temperature superconducting tapes under fault or quench-free conditions. Specifically, such as... Figure 1 As shown, to This represents the first inductance of each parallel equivalent superconducting branch in the superconducting layer. to This represents the equivalent resistance of each equivalent superconducting branch under fault or quench-free conditions.

[0019] The shielding layer consists of multiple parallel high-temperature superconducting shielding strips, with only one or a group of shielding conductors connected to the energy storage capacitor as the mutual inductance drive branch of the shielding layer. A drive-side circuit is formed, and the remaining unextracted shielded conductors maintain their original shielded connection method.

[0020] The shielding layer mutual inductance drive branch includes a mutual inductance drive element and a current-limiting resistor. and the first controlled switch It is formed by leading out from one or a group of shielding conductors in the shielding layer, and then passing through a current-limiting resistor. and the first controlled switch With energy storage capacitor Electrical connections form a drive-side circuit.

[0021] quick switch Energy storage capacitor Auxiliary injection inductor Second controlled switch This forms an auxiliary injection loop.

[0022] quick switch It is connected in series in the main current channel of a single-pole coaxial DC high-temperature superconducting cable, with one end electrically connected to the other end of the superconducting layer and the other end electrically connected to the DC output terminal; Current limiting resistor One end is electrically connected to one end of the mutual inductance driving element, and the other end is connected to the first controlled switch. One end is electrically connected.

[0023] Energy storage capacitor One end is connected to the other end of the mutual inductance driving element and the second controlled switch. The second end is electrically connected, and the other end is connected to the first controlled switch. Second terminal, auxiliary injection inductor One end is electrically connected.

[0024] First controlled switch The control terminal is electrically connected to the detection and control unit, and is used to receive the first control signal from the detection and control unit, and the first controlled switch. This is a control switch for the drive side.

[0025] Second controlled switch The control terminal is electrically connected to the detection and control unit, and is used to receive the second control signal from the detection and control unit, and the second controlled switch. To assist the zero-crossing switch.

[0026] Both the first controlled switch and the second controlled switch are controllable power electronic switches.

[0027] Voltage limiting and energy absorbing element connected in parallel to fast switch The two ends.

[0028] Auxiliary current injection inductor The other end is connected to one end of the voltage limiting energy absorption element, the DC output terminal, and the fast switch, respectively. The other end is electrically connected.

[0029] Preferably, the voltage-limiting energy-absorbing element can be at least one of a metal oxide surge arrester, a nonlinear resistor, a RC snubber element, a diode clamping element, and a varistor element, used to limit fast switching. Voltage is restored at both ends.

[0030] In one optional embodiment, the mutual inductance driving element is formed by a second inductor and a second resistor, wherein the second inductor is the equivalent inductance corresponding to the led-out shielding conductor, and the second resistor is the equivalent resistance corresponding to the led-out shielding conductor. Specifically, as shown... Figure 1 As shown, For the second inductor, This is the second resistor.

[0031] This invention also provides a fast interruption method based on mutual inductance driving of the shielding layer of a DC high-temperature superconducting cable, comprising: During the normal flow phase: Control quick switch When closed, DC current flows in from the DC input terminal, converges through the equivalent superconducting branches of the superconducting layer, and then passes through a fast switch. Flows to the DC output terminal; When the total current of the superconducting layer i c Below the first preset threshold, or the rate of change of current di c / dt The voltage is lower than the second preset threshold, or the induced voltage of the shielding layer mutual inductance drive branch. u pn When the value is below the third preset threshold, control the first controlled switch. Second controlled switch Keep it off.

[0032] like Figure 2 As shown, quick switch In the closed state, the DC current enters the equivalent branches of each superconducting layer from the left DC input terminal, and then... , , to and its corresponding , , to After the parallel branches converge, the current is transferred through a closed fast switch. The current flows to the right-side DC output terminal. During this stage, the DC current is mainly borne by the superconducting layer, and the mutual inductance drive branch of the shielding layer does not undertake the main current transmission function.

[0033] During the normal current-carrying phase, the DC current is approximately stable, and the rate of change of the superconducting layer current is... The inductance is relatively low; although there is mutual inductance between the shielding layer and the superconducting layer, the second inductance of the selected shielding conductor is relatively low. Second resistor and current limiting resistor The induced voltage formed on It is in a low amplitude state. At this time, the detection and control unit determines that there is no short circuit fault in the superconducting layer, therefore the first controlled switch... Second controlled switch The energy storage capacitor remains off or has not formed an effective discharge path. Without a second controlled switch To fast switch The main current channel releases current. This is due to the energy storage capacitor. There is no effective discharge path between the energy storage capacitor and the main circuit. It will not participate in the main current transmission, nor will it change the normal current distribution of the superconducting layer cable.

[0034] During this stage, the shielding layer continues to function as the original cable structure. Although the selected shielded conductor has leads, its external drive-side circuit is not controlled by the first controlled switch. Once connected, the remaining unselected shielded conductors will maintain their original connection method.

[0035] During the short-circuit fault and shielding layer mutual inductance driving stage: When the total current of the superconducting layer i c Reaching the first preset threshold, or the rate of change of current. di c / dt The second preset threshold is reached, or the induced voltage of the shielding layer mutual inductance drive branch is reached. When the third preset threshold is reached, a short-circuit fault is determined to have occurred in the superconducting layer, and the first controlled switch is controlled. On, second controlled switch Turn off; at this time, the induced voltage of the shielding layer mutual inductance drive branch is transmitted through the first controlled switch. To energy storage capacitor Charging, energy storage capacitor The voltage gradually increases; Specifically, such as Figure 3 As shown, when a short-circuit fault occurs in the superconducting layer, the current in the main current channel increases rapidly. , , to The current and its rate of change in each equivalent superconducting branch increase synchronously. Because the shielding layer is wound around the outside of the superconducting layer, the magnetic flux change caused by the superconducting layer current change couples to the selected shielding conductor, thus increasing the second inductance. The branch in question generates an induced voltage.

[0036] During this stage, the detection and control unit adjusts the main current. Main current change rate Shielding layer induced voltage At least one of the quantities is used to determine the fault status. When the set action conditions are met, the first controlled switch... On, second controlled switch Keep it off. The induced voltage formed on the selected shielded conductor flows through the second inductor. Second resistor Current and resistance and the first controlled switch Acting on energy storage capacitors Energy storage capacitor Voltage at both ends With drive-side current Increase. Second controlled switch. Maintaining the circuit breaker off during this phase is to avoid damage to the energy storage capacitor. Send the fast switch ahead of time before the set threshold voltage is reached. The main current channel where it is located releases current.

[0037] Current limiting resistor Connected in series in the mutual inductance drive branch of the shielding layer, its function is to limit the drive-side current. Peak and energy storage voltage The current rise slope during the formation process. Let the current rise slope be the first current in the superconducting layer of the DC high-temperature superconducting cable. The equivalent superconducting branch current is The total current in the superconducting layer is The selected shielded conductor current is Superconducting layer The mutual inductance between the root equivalent branch and the selected shielded conductor is The equivalent self-inductance of the selected shielded conductor is Then we have: ; ; in, Given the magnetic flux linkage of the selected shielding conductor, according to the law of electromagnetic induction, the induced voltage in the selected shielding conductor can be expressed as: ; In engineering calculations, multiple superconducting branches can be equivalent to the total current. With equivalent mutual inductance The induced voltage in the selected shielded conductor at this time can be approximated as: ; When a short-circuit fault causes a localized resistance state in the shielding layer, the equivalent resistance of the selected shielding conductor can be written as: ,in To shield the additional resistance generated when the conductor transitions from a superconducting state to a resistive state. First controlled switch. The second controlled switch is on. When turned off, the selected shielding conductor and current-limiting resistor... First controlled switch and energy storage capacitors A charging circuit is formed. Let the energy storage capacitor be... The voltage across the terminals is The charging current is Then the charging circuit satisfies: ; ; Ignore this at this time The resulting short-time transient term is approximately satisfied by the charging current as follows: ; It is evident that the greater the rate of change of short-circuit current, the higher the induced voltage formed on the selected shielded conductor; if the current-limiting resistor... If the value is too small, the initial stage of the fault will be caused by the second inductor. The induced voltage may generate an excessively large drive-side current, causing damage to the selected shielded conductor and the first controlled switch. and energy storage capacitors Withstanding high current surges; if the current-limiting resistor If it is too large, the energy storage capacitor The voltage required for subsequent auxiliary injection may not be reached within the specified time. Therefore, the current-limiting resistor... The value should be related to the allowable current of the shielding conductor and the first controlled switch. Current resistance, energy storage capacitor The target voltage, the rate of change of fault current, and the equivalent resistance of the selected shielding conductor are matched together.

[0038] Its initial selection can be based on the maximum allowable charging current. Make an estimate: ; In this embodiment, only one or a group of shielding conductors are connected to the drive-side circuit; the entire shielding layer is not incorporated into the energy storage capacitor. The circuit in question utilizes the mutual inductance voltage between the shielding layer and the superconducting layer to power the energy storage capacitor. This generates an energy storage voltage while avoiding excessive induced current in the shielding layer and increased localized heating caused by simultaneously leading all shielding conductors outward.

[0039] When the energy storage capacitor Voltage When the preset target value is reached, the detection and control unit first turns off the first controlled switch. This enables the energy storage capacitor The path between the shielding layer and the mutual inductance drive branch is disconnected.

[0040] In the energy storage stage: Current-limiting resistor limits energy storage capacitor The peak value and rising slope of the charging current when the energy storage capacitor The voltage continues to rise to the preset target value, controlling the first controlled switch. Keep it off to prevent energy storage capacitors from being damaged. Discharge the mutual inductance drive branch of the shielding layer in advance.

[0041] During the capacitor discharge and auxiliary zero-crossing phase: Control the second controlled switch On, energy storage capacitor The auxiliary current is released through the auxiliary injection circuit; the auxiliary current flows through the fast switch. The current in the branch is superimposed in the opposite direction to the fault current, causing the current flowing through the fast switch to be superimposed. The combined current is reduced to the interruptible range or a current zero-crossing point is formed; fast switching. The circuit breaker will trip when the current crosses zero or drops to the breakable range. In one alternative implementation, during the capacitor discharge and auxiliary zero-crossing phase, the first controlled switch... The turn-off time precedes that of the second controlled switch. The conduction time is to avoid the energy storage capacitor Reverse discharge to the mutual inductance drive branch of the shielding layer.

[0042] like Figure 4 As shown, in the first controlled switch After being turned off, the second controlled switch On, energy storage capacitor Auxiliary current injection inductor Connect to fast switch The main current path in which it is located. After auxiliary current injection, rapid switching occurs. The synthetic current in the process is reduced, and the fast switching is achieved. The branch in which it is located can achieve a zero-crossing current condition. Energy storage capacitor. Capacity and auxiliary current injection inductor The values ​​should be verified during this process: energy storage capacitor Insufficient capacity will lead to insufficient auxiliary current duration, and the auxiliary current injection inductor... Too small will increase the number of second controlled switches. and energy storage capacitors Current surge, auxiliary injection inductor Excessive current will reduce the rate of rise of the auxiliary current.

[0043] Among them, energy storage capacitors The energy storage is: ; When the energy storage capacitor Auxiliary current injection inductor To fast switch When an auxiliary current is injected into the channel, under the approximate condition of neglecting loop damping, the auxiliary current can be estimated by the following formula: ; in, For the second controlled switch Energy storage capacitor at the moment of conduction Voltage at both ends, To assist in injecting current. Used for... and Preliminary parameter verification; actual current waveform is also affected by fast switching. The effects of arc voltage, voltage-limiting energy-absorbing elements, cable equivalent inductance, controlled switch voltage drop, and loop damping.

[0044] This stage involves rapid switching. The switching action is completed in conjunction with the auxiliary current. (Fast switch) For vacuum fast switches, a reduced or zero-crossing auxiliary current facilitates the extinguishing of the vacuum arc, and the reduced auxiliary current lowers the DC breaking current it can withstand. Fast switch The timing of the operation should be in conjunction with the energy storage capacitor. When the voltage reaches the preset target value, the second controlled switch... The turn-on timing and the auxiliary current formation timing are coordinated. Fast switching. After disconnection, the original parallel connection to the fast switch The voltage-limiting energy-absorbing elements at both ends limit the recovery voltage, absorb the remaining energy in the equivalent inductance of the DC system, and suppress fast switching. Overvoltage at both ends.

[0045] During the recovery voltage limit and reset phase: quick switch After tripping, it is connected in parallel to the fast switch. The voltage-limiting energy-absorbing elements at both ends limit the rapid switching. The voltage across the terminals is restored, and the remaining energy of the system is absorbed; at this time, the second controlled switch is controlled. Turn off, energy storage capacitor The residual voltage is limited by the current limiting resistor. Alternatively, a dedicated bleed branch can be used for release; after troubleshooting, the quick-closing switch can be re-closed. Then, it returns to the normal flow stage.

[0046] Specifically, quick switch After the interruption is completed and the system fault current is cleared, the second controlled switch Turn off, energy storage capacitor The residual voltage can be limited by the current-limiting resistor. Alternatively, a dedicated venting branch can be used to release the system to a safe range. If system maintenance is required, a quick-connect switch can be used. Keep the circuit open and switch on / off quickly. After successful tripping, the fault current is interrupted. At this time, the circuit breaker connected in parallel with the fast switch... The voltage-limiting energy-absorbing elements at both ends immediately engage, absorbing the energy stored in the residual inductance of the DC system and enabling rapid switching. The recovery voltage at both ends is clamped at a safe level to prevent overvoltage damage to the equipment.

[0047] Subsequently, control the second controlled switch. Turn off, energy storage capacitor The residual voltage through Alternatively, a dedicated bleeder resistor circuit can be used for release, preparing for the next operation. Once the fault has been eliminated and the system status meets the recovery conditions, the fast switch is reclosed. The device of the present invention returns to such Figure 2 The normal flow state shown indicates that a complete protection action cycle has been completed.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any equivalent substitutions, conventional modifications, or parameter adjustments made within the scope of this invention to different structures of DC high-temperature superconducting cables, superconducting layer tape forms, shielding layer conductor quantity, shielding layer wrapping direction, shielding conductor lead-out methods, current-limiting resistor parameters, energy storage capacitor parameters, auxiliary inductor parameters, controlled switch types, fast-switching structures, voltage-limiting energy-absorbing branch forms, detection and control methods, and the coordination methods between the shielding layer mutual inductance drive circuit and the fast switch, shall all fall within the protection scope of this invention.

Claims

1. A fast disconnection device based on mutual inductance driven by the shielding layer of a DC high-temperature superconducting cable, characterized in that, It includes a single-pole coaxial DC high-temperature superconducting cable, a fast switch, a current-limiting resistor, an energy storage capacitor, a first controlled switch, a second controlled switch, a voltage-limiting energy-absorbing element, and an auxiliary current-injecting inductor; The unipolar coaxial DC high-temperature superconducting cable includes a superconducting layer and a shielding layer. The shielding layer is wound around the outside of the superconducting layer, and there is a mutual inductance between the superconducting layer and the shielding layer. One end of the superconducting layer is electrically connected to the DC input terminal. One or a group of shielding conductors led out from the shielding layer form a mutual inductance driving element. The remaining shielding conductors in the shielding layer that are not led out maintain their original shielding connection method. The fast switch is connected in series in the main current channel of the unipolar coaxial DC high-temperature superconducting cable, with one end electrically connected to the other end of the superconducting layer and the other end electrically connected to the DC output terminal. One end of the current-limiting resistor is electrically connected to one end of the mutual inductance driving element, and the other end is electrically connected to one end of the first controlled switch. One end of the energy storage capacitor is electrically connected to the other end of the mutual inductance driving element and the second end of the second controlled switch, and the other end is electrically connected to the second end of the first controlled switch and one end of the auxiliary current injection inductor. The control terminal of the first controlled switch is electrically connected to the detection and control unit and is used to receive the first control signal from the detection and control unit. The control terminal of the second controlled switch is electrically connected to the detection control unit and is used to receive the second control signal from the detection control unit; The pressure-limiting energy-absorbing element is connected in parallel across the two ends of the fast switch; The other end of the auxiliary current injection inductor is electrically connected to one end of the voltage limiting energy absorption element, the DC output terminal, and the other end of the fast switch.

2. The apparatus according to claim 1, characterized in that, The superconducting layer consists of multiple strands High-temperature superconducting tapes are formed by parallel wrapping along the axial or helical direction of the cable, each tape... A high-temperature superconducting tape corresponds to an equivalent superconducting branch.

3. The apparatus according to claim 2, characterized in that, Each of the aforementioned equivalent superconducting branches consists of a first inductor and a first resistor connected in series; each of the aforementioned The high-temperature superconducting tape is equivalent to the first inductor; the first resistance is the resistance of each of the aforementioned tapes. Equivalent resistance of high-temperature superconducting tape under fault or quenching conditions.

4. The apparatus according to claim 1, characterized in that, The mutual inductance driving element is formed by a second inductor and a second resistor, wherein the second inductor is the equivalent inductance corresponding to the shielded conductor, and the second resistor is the equivalent resistance corresponding to the shielded conductor.

5. The apparatus according to claim 1, characterized in that, The first controlled switch and the second controlled switch are controllable power electronic switches. The first controlled switch is a drive-side control switch, and the second controlled switch is an auxiliary zero-crossing switch.

6. The apparatus according to claim 1, characterized in that, The voltage limiting and energy absorbing element is at least one of a metal oxide surge arrester, a nonlinear resistor, a RC absorption element, a diode clamping element, and a varistor element, used to limit the recovery voltage across the fast switch.

7. The apparatus according to claim 1, characterized in that, The mutual inductance driving element, The current-limiting resistor and the first controlled switch form a shielded mutual inductance drive branch; the fast switch, the auxiliary current-injecting inductor, the energy storage capacitor, and the second controlled switch form an auxiliary current-injecting circuit.

8. A fast interruption method based on mutual inductance driving of the shielding layer of a DC high-temperature superconducting cable, characterized in that, The method, employing the apparatus according to any one of claims 1 to 7, comprises: During the normal flow phase: When the fast switch is closed, DC current flows in from the DC input terminal, and after being connected through the equivalent superconducting branches of the superconducting layer, it flows to the DC output terminal through the fast switch. When the total current of the superconducting layer is lower than the first preset threshold, or the rate of change of current is lower than the second preset threshold, or the induced voltage of the mutual inductance drive branch of the shielding layer is lower than the third preset threshold, the first controlled switch and the second controlled switch are controlled to remain in the off state. During the short-circuit fault and shielding layer mutual inductance driving stage: When the total current of the superconducting layer reaches a first preset threshold, or the rate of change of current reaches a second preset threshold, or the induced voltage of the mutual inductance drive branch of the shielding layer reaches a third preset threshold, it is determined that a short circuit fault has occurred in the superconducting layer, and the first controlled switch is turned on and the second controlled switch is turned off. At this time, the induced voltage of the mutual inductance drive branch of the shielding layer charges the energy storage capacitor through the first controlled switch, and the voltage of the energy storage capacitor gradually increases. In the energy storage stage: The current-limiting resistor limits the peak value and rising slope of the charging current of the energy storage capacitor. When the voltage of the energy storage capacitor continues to rise to a preset target value, the first controlled switch is controlled to remain off to prevent the energy storage capacitor from discharging prematurely into the mutual inductance drive branch of the shielding layer. During the capacitor discharge and auxiliary zero-crossing phase: The second controlled switch is turned on, and the energy storage capacitor releases auxiliary current through the auxiliary injection circuit; the auxiliary current flows through the branch where the fast switch is located and is superimposed in the opposite direction with the fault current, so that the combined current flowing through the fast switch is reduced to the breakable range or forms a current zero crossing point; the fast switch performs a tripping action when the current crosses zero or is reduced to the breakable range. During the recovery voltage limit and reset phase: After the fast switch is opened, the voltage limiting and energy absorbing element connected in parallel across the fast switch limits the recovery voltage across the fast switch and absorbs the remaining energy of the system. At this time, the second controlled switch is turned off, and the residual voltage of the energy storage capacitor is released through the current limiting resistor or a dedicated discharge branch. After the fault is cleared, the fast switch is closed again, returning to the normal current flow stage.

9. The method according to claim 8, characterized in that, During the capacitor discharge and auxiliary zero-crossing phase, the first controlled switch turns off before the second controlled switch turns on, in order to prevent the energy storage capacitor from discharging in reverse to the mutual inductance drive branch of the shielding layer.

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