A direct current circuit breaker arc extinguishing structure for suppressing weak transverse magnetic field and a control method thereof

Abstract

The application provides a direct-current circuit breaker arc extinguishing structure for inhibiting a weak transverse magnetic field and a control method thereof, and relates to the technical field of high-voltage direct-current power grid fault protection switch equipment, and comprises: an energy supply loop component connected with an energy storage capacitor, which is used for converting alternating current into direct current and pre-storing energy to the energy storage capacitor; and a whole machine cooperative control unit connected with a current transformer, the adjustable power supply loop and a main loop switch, which is used for identifying a fault working condition according to a current signal collected by the current transformer, controlling main loop breaking, and controlling the one-way conduction thyristor valve group to conduct to output a pulse current, so that a transverse arc blowing magnetic field is generated and fault breaking under a weak transverse magnetic field is realized. The application can avoid the problem of arc after insulation recovery delay caused by excessive magnetic field, and improve the medium insulation recovery rate.

Description

Technical Field

[0001] This invention relates to the field of fault protection switching equipment for high-voltage direct current transmission networks, and in particular to an arc-extinguishing structure for a DC circuit breaker that suppresses weak transverse magnetic fields and its control method. Background Technology

[0002] With the increasing popularity of flexible DC transmission technology, mechanical high-voltage DC circuit breakers are widely used in medium- and low-voltage and economical high-voltage DC transmission lines due to their advantages such as simple structure, convenient operation and maintenance, and low cost. As the core switching component of DC circuit breakers, the vacuum interrupter's post-arc plasma dissipation speed and dielectric insulation recovery speed directly determine the circuit breaker's breaking reliability and overvoltage withstand capability.

[0003] Existing publicly available academic research has confirmed that weak transverse magnetic fields can significantly interfere with the motion of residual plasma after arc in vacuum interrupters. When the magnetic field strength exceeds a certain threshold, it will severely delay the insulation recovery speed and easily trigger post-arc breakdown faults.

[0004] Currently, there are many obvious defects in the relevant patented technologies: some solutions only optimize the magnetic field distribution for high current interruption without defining a safe magnetic field threshold and do not involve lightning overvoltage application scenarios; some solutions only improve the overall circuit topology or mechanical structure without effectively controlling the stray transverse magnetic field inside the arc extinguishing chamber; and some solutions use an external magnetic field to assist in arc extinguishing, which is the complete opposite of the technical approach to suppressing self-generated stray magnetic fields and cannot solve the problem of delayed post-arc insulation recovery.

[0005] In addition, existing testing methods also have prominent problems: the fixed inductance parameters in the laboratory cannot be adjusted to output standard test current; the electrical parameters of general capacitors are difficult to match with the test circuit of DC circuit breakers, making it impossible to complete the adaptation test verification, which seriously restricts the performance testing of new circuit breakers.

[0006] In terms of lightning protection, existing high-voltage DC circuit breakers generally adopt an independent arrangement of lightning protection devices, failing to integrate the internal magnetic field characteristics of the arc-extinguishing chamber, post-arc insulation recovery capability, and lightning protection action logic. Under transient lightning impulse conditions, the excessive weak transverse magnetic field leads to slow insulation recovery, making it highly susceptible to lightning protection coordination failures and equipment breakdown damage. Existing equipment can no longer meet the high-reliability lightning protection operation requirements of DC power grids. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an arc-extinguishing structure and control method for DC circuit breakers that suppresses weak transverse magnetic fields, which can avoid the problem of delayed post-arc insulation recovery caused by excessive magnetic fields and improve the dielectric insulation recovery rate.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: In a first aspect, a DC circuit breaker arc-extinguishing structure for suppressing weak transverse magnetic fields includes: A vacuum interrupter includes a transverse magnetic contact, a high-permeability shielding structure, and a ceramic shell for the interrupter; the transverse magnetic contact is configured to generate a transverse arc-blowing magnetic field when current is switched on or off; the high-permeability shielding structure is used to limit the residual transverse magnetic field between the contacts to within a preset threshold; and a coil winding portion is provided on the ceramic shell for the interrupter. The magnetic field suppression component includes a magnetic field control coil group and an adjustable power supply circuit. The magnetic field control coil group is wound around the coil winding section. The adjustable power supply circuit includes an energy storage capacitor, an adjustable inductor, and a unidirectional thyristor valve group, and is connected in series with the magnetic field control coil group to form a pulse discharge circuit, which is used to control the magnetic field in the arc-extinguishing zone by adjusting the circuit parameters. A power supply circuit assembly, connected to the energy storage capacitor, is used to convert alternating current into direct current and pre-store energy in the energy storage capacitor; The whole machine collaborative control unit is connected to the current transformer, the adjustable power supply circuit and the main circuit switch. It is used to identify the fault condition according to the current signal collected by the current transformer, control the main circuit to disconnect, and control the unidirectional thyristor valve group to conduct to output pulse current, thereby generating a transverse arc blowing magnetic field and realizing fault interruption under weak transverse magnetic field.

[0009] Secondly, a method for arc extinguishing control of a DC circuit breaker to suppress weak transverse magnetic fields includes: Collect the main circuit current signal, identify fault conditions and match the corresponding impedance compensation branch to suppress transient impacts of circuit faults; Perform the main circuit disconnection operation and simultaneously turn on the adjustable power supply circuit, so that the energy storage capacitor (C1) outputs pulse current to the magnetic field control coil group, generating an instantaneous transverse arc blowing magnetic field in the contact area; The transverse arc-blowing magnetic field stretches the arc and reduces the temperature in the arc region, while the high-permeability magnetic shielding structure constrains the residual magnetic field in the arc gap, accelerating plasma recombination and arc extinguishing. After the arc is extinguished, the magnetic field decays rapidly, the gap insulation strength is restored, and the fault trip is completed. Among them, the pulse output intensity is adjusted according to the fault current amplitude to control the magnetic field during the interruption process within the weak transverse magnetic field range.

[0010] The above-described solution of the present invention has at least the following beneficial effects: By setting up a high-permeability magnetic shielding structure composed of upper and lower segmented magnetic shielding rings, the lateral stray weak transverse magnetic field generated during the current diversion process is diverted from the source. This forces the residual transverse magnetic field in the contact gap to be stabilized within a preset safety threshold, effectively avoiding the problem of delayed post-arc insulation recovery caused by excessive magnetic field and significantly improving the dielectric insulation recovery rate.

[0011] The design adopts a cup-shaped transverse magnetic contact. When current flows through the spiral oblique groove, the arc-shaped conductive contact piece generates a transverse arc-blowing magnetic field. In the initial stage of opening, it outputs an effective arc-blowing magnetic field to stretch and cool the arc. In the later stage of opening, the magnetic field decays rapidly, eliminating the drawback of the residual magnetic field continuously interfering with the gap insulation recovery in the traditional structure. This significantly shortens the post-arc insulation recovery time and improves the short-circuit breaking capacity and operational stability.

[0012] By integrating a steady-state bias coil, a forward transient magnetic correction coil, and a reverse transient magnetic correction coil on the outer periphery of the ceramic shell of the arc-extinguishing chamber, and combining them with an adjustable power supply circuit composed of multi-level adjustable inductors and energy storage capacitor arrays, precise zonal control and dynamic compensation of the magnetic field in the arc-extinguishing zone can be achieved under different fault conditions, so that the magnetic field during the breaking process is always controlled within the safe range of weak transverse magnetic field.

[0013] The whole machine collaborative control unit collects current signals in real time, identifies fault conditions, first matches the impedance compensation branch to suppress transient impact, then executes the main circuit disconnection and synchronously triggers the pulse discharge circuit to output the arc blowing magnetic field, realizes the timing coordination of magnetic field optimization and fault interruption, effectively suppresses DC arc reignition, and improves the reliability of fault current interruption.

[0014] Through the matching design of multi-level adjustable inductors and multi-tap energy storage capacitor arrays, the access parameters can be flexibly switched according to different test conditions, and the peak value and frequency of the circuit pulse current can be adjusted. This solves the problem that existing fixed parameter test equipment cannot adapt to multiple current level breaking tests, and meets the needs of full-condition test verification.

[0015] By combining the internal magnetic field characteristics of the arc-extinguishing chamber, the post-arc insulation recovery capability, and the lightning protection logic, the problem of slow insulation recovery caused by excessive weak transverse magnetic field can be effectively avoided under transient lightning impulse conditions. This improves the lightning overvoltage withstand capability and lightning protection coordination reliability of DC circuit breakers, and meets the high-reliability lightning protection operation requirements of DC power grids. Attached Figure Description

[0016] Figure 1 This is a diagram of a vacuum interrupter and a magnetic field suppression device.

[0017] Figure 2 Diagram of magnetic field suppression component and power supply component.

[0018] Figure 3 Diagram of a 5-tap power supply inductor.

[0019] Figure 4 This is a diagram of a series-parallel capacitor bank scheme.

[0020] Figure 5 This is the control logic diagram of the whole machine collaborative control unit.

[0021] Figure 6 This is a comparison diagram before and after the application of the present invention. Detailed Implementation

[0022] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0023] Example 1 This embodiment provides an arc-extinguishing structure for DC circuit breakers that suppresses weak transverse magnetic fields. This arc-extinguishing structure has the functions of autonomous suppression of weak transverse magnetic fields, adaptability to all operating conditions, and lightning overvoltage withstand capability. It can be widely used in medium and low voltage and economical high voltage DC transmission lines.

[0024] like Figures 1 to 5 As shown, the arc-extinguishing structure in this embodiment mainly consists of four parts: a vacuum interrupter chamber assembly, a magnetic field suppression assembly, a power supply circuit assembly, and a whole-machine collaborative control unit. The specific structure, connection relationships, parameter configurations, and working principles of each component are described in detail below.

[0025] like Figure 1 As shown, the vacuum interrupter assembly includes a stationary contact 1, a moving contact 2, a central arc passage area 3, an upper segmented magnetic shielding ring 4, a lower segmented magnetic shielding ring 5, a bellows 6, and a ceramic shell 7 for the interrupter.

[0026] The stationary contact 1 is fixedly connected to the upper end cover plate of the ceramic shell 7 of the arc-extinguishing chamber, and the moving contact 2 is movably connected to the lower end of the ceramic shell 7 of the arc-extinguishing chamber via a bellows 6. The stationary contact 1 and the moving contact 2 are arranged coaxially opposite each other within the vacuum-sealed area enclosed by the ceramic shell 7 of the arc-extinguishing chamber. The contact surfaces of the stationary contact 1 and the moving contact 2 form a central arc passage zone 3. When the moving contact 2 moves from the closed position to the open position, the spatial length of the central arc passage zone 3 dynamically increases with the stroke of the moving contact 2. One end of the bellows 6 is welded to the outer wall of the conductive rod of the moving contact 2, and the other end is welded to the lower end sealing ring of the ceramic shell 7 of the arc-extinguishing chamber. During the opening and closing movement of the moving contact 2, the bellows 6 expands and contracts axially to ensure that the interior of the vacuum arc-extinguishing chamber always maintains a high vacuum sealing environment with a vacuum degree of not less than 1.33 × 10⁻⁶. -3 Pa.

[0027] Both stationary contact 1 and moving contact 2 adopt a cup-shaped transverse magnetic contact structure. Specifically, the contact base of both stationary contact 1 and moving contact 2 is made of highly conductive oxygen-free copper material, and is hollow cylindrical along the axial direction. The closed end of the base is the back of the contact, and the open end is the contact end face. Six sets of oblique through-cut grooves are evenly opened along the circumference of the cylindrical wall of the contact base. Each set of oblique cut grooves starts from the open end face of the contact and extends spirally and obliquely along the cylindrical wall to the back of the contact. The inclination angle of the spiral cut grooves is 30°~60°. An independent arc-shaped conductive contact piece is formed between adjacent oblique cut grooves. The inner and outer surfaces of each arc-shaped conductive contact piece are processed into smooth arc transition surfaces, and the end of the contact piece is flush with the open end face of the contact. An insulating separation gap with a width of 0.5mm~1.5mm is formed between adjacent arc-shaped conductive contact pieces by oblique cut grooves to ensure electrical insulation between each contact piece.

[0028] Multiple arc-shaped conductive contacts together form a hollow arc-extinguishing cavity, the inner diameter of which is 40% to 60% of the outer diameter of the contact. When switching short-circuit current, the working current flows along the spiral inclined path of each arc-shaped conductive contact. The current direction in each contact forms a certain angle with the arc axis. According to the principle of electromagnetic induction, the current decomposes into a transverse magnetic field component perpendicular to the arc axis. This transverse magnetic field component is the transverse arc-blowing magnetic field generated autonomously by the transverse magnetic contact. In the initial stage of opening, a large current still flows through the arc-shaped conductive contacts in the contact gap. At this time, the transverse arc-blowing magnetic field instantaneously reaches its peak value, driving the arc to rotate at high speed around the contact axis and stretch outward, effectively increasing the arc column length and accelerating arc cooling. In the later stage of opening, as the contact gap increases and the current transfers to the arc gap, the current flowing through the arc-shaped conductive contacts decreases rapidly, and the transverse arc-blowing magnetic field decays rapidly, preventing continuous interference during the post-arc dielectric recovery stage.

[0029] The upper segmented magnetic shielding ring 4 and the lower segmented magnetic shielding ring 5 constitute a weak transverse magnetic field passive shielding structure. The upper segmented magnetic shielding ring 4 is fitted onto the outer circumference of the stationary contact 1, and the lower segmented magnetic shielding ring 5 is fitted onto the outer circumference of the moving contact 2. Both are made of high-permeability permalloy material (initial magnetic permeability μi≥50000, saturation magnetic induction intensity Bs≥0.75T). The wall thickness of the upper segmented magnetic shielding ring 4 and the lower segmented magnetic shielding ring 5 is 2mm~5mm, and their axial heights cover the cup-shaped cylindrical wall areas of the stationary contact 1 and the moving contact 2, respectively. A gap is reserved between the lower end face of the upper segmented magnetic shielding ring 4 and the upper end face of the lower segmented magnetic shielding ring 5. This gap area forms an arc combustion channel, corresponding to the position of the central arc passage area 3.

[0030] During the current switching process of the contacts, the stray transverse magnetic field generated by the arc-shaped conductive contact pieces of the stationary contact 1 and the moving contact 2 is preferentially absorbed and shunted by the high magnetic permeability materials of the upper segmented magnetic shielding ring 4 and the lower segmented magnetic shielding ring 5 as it diffuses into the external space. The magnetic reluctance of the high magnetic permeability material is much smaller than that of the vacuum gap, and the magnetic lines of force are concentrated and constrained inside the magnetic shielding ring to form a closed magnetic circuit, thereby forcibly stabilizing the residual transverse magnetic field of the contact gap within the safe threshold of 5mT. This passive shielding structure suppresses stray magnetic fields from the source without the need for additional power supply, accelerates the outward diffusion speed of post-arc metal vapor and plasma, and improves the dielectric insulation recovery rate by more than 30% compared with the traditional unshielded structure, effectively avoiding the problem of delayed post-arc insulation recovery and re-breakdown caused by excessive weak transverse magnetic field.

[0031] The ceramic outer shell 7 of the arc-extinguishing chamber is made of high-purity alumina ceramic and serves as the main supporting structure and insulating shell of the vacuum arc-extinguishing chamber. Four sets of coil winding skewers are formed on the outer circumference of the ceramic outer shell 7. These four sets of skewers are evenly distributed at 90° angles along the circumference, meaning the circumferential angle between adjacent sets of skewers is 90°. Each set of skewers has a depth of 3mm to 6mm and a width of 2mm to 4mm, accommodating multiple turns of coil winding. The spiral winding direction of adjacent sets of skewers is consistent, while the spiral winding directions of opposing sets of skewers (i.e., sets with a circumferential difference of 180°) are opposite. This skewer arrangement provides precise installation positioning for the magnetic field control coil assembly, ensuring that the direction of the magnetic field generated after coil winding satisfies the preset spatial orthogonal relationship with the direction of the arc inside the arc-extinguishing chamber.

[0032] The magnetic field suppression component includes a magnetic field control coil group and an adjustable power supply circuit; the magnetic field control coil group is wound in the inclined slot of the ceramic shell 7 of the arc-extinguishing chamber, and the adjustable power supply circuit provides steady-state bias current and transient pulse current to the magnetic field control coil group.

[0033] like Figure 1 As shown, the magnetic field control coil group includes a steady-state bias coil 8, a positive transient magnetic correction coil 9, and a reverse transient magnetic correction coil 10; all three coils are wound with enameled copper wire, the number of turns is determined according to the magnetic field design requirements, and the wire diameter is 0.5mm~1.5mm.

[0034] The steady-state bias coil 8 is wound in two sets of inclined slots corresponding to the lower part of the ceramic shell 7 of the arc-extinguishing chamber and the outer region of the moving contact 2. The steady-state bias coil 8 is powered by a steady-state DC power supply. During the normal closing and current-carrying period of the circuit breaker, a constant DC current is passed through it, generating a stable bias magnetic field in the region of the moving contact 2, which is used to compensate for the static stray magnetic field caused by the asymmetry of the contact structure.

[0035] The forward transient magnetic correction coil 9 and the reverse transient magnetic correction coil 10 are wound in two sets of inclined slots corresponding to the outer periphery of the central arc passage area 3. The forward transient magnetic correction coil 9 and the reverse transient magnetic correction coil 10 are wound in opposite directions and are used to generate corresponding magnetic correction magnetic fields under fault current conditions in different directions. The forward transient magnetic correction coil 9 and the reverse transient magnetic correction coil 10 are powered by a dynamically adjustable pulse power supply and are only put into operation under fault trip transient conditions.

[0036] By arranging the three sets of coils independently in different zones, the steady-state bias magnetic field and the fault transient correction magnetic field can be independently controlled in different zones. The coil input combination can be flexibly switched for different fault conditions, and the direction and intensity of the magnetic field in the arc extinguishing zone can be precisely controlled.

[0037] like Figure 2 As shown, the adjustable power supply circuit includes an energy storage capacitor C1, an adjustable inductor L, a unidirectional thyristor valve group D2, an adjustable damping resistor R3, and a magnetizing inductor connected in parallel with an energy-dissipating resistor R4.

[0038] Energy storage capacitor C1, such as Figure 4 As shown, the energy storage capacitor C1 adopts a capacitor array structure. Multiple individual capacitors 111 are combined through series and parallel bus conductors 616 to form a capacitor array. Each individual capacitor 111 has a rated voltage of 2kV and a capacitance of 100μF. The total capacitance and withstand voltage level can be flexibly adjusted by combining them in series and parallel. For example, by using a combination of 5 series and 10 parallel, an energy storage capacitor array with a total withstand voltage of 10kV and a total capacitance of 200μF can be obtained. The capacitor array is provided with a voltage equalization connection branch 212, which is a high-resistance resistor voltage equalization network connected in parallel to the two ends of each individual capacitor 111 in each series branch, to balance the static voltage of each individual capacitor 111 and prevent individual overvoltage. The capacitor array is provided with a main terminal block 313 on both sides, which is connected to the charging circuit and the pulse discharge circuit respectively. The capacitor mounting base box 414 is made of epoxy resin insulating board and is used for the integrated installation and fixation of individual capacitors. The output bus 515 is made of copper busbar and is connected to the anode side of the unidirectional thyristor valve group D2.

[0039] Adjustable inductor L, such as Figure 3 As shown, the adjustable inductor L has a five-level adjustable structure. The adjustable inductor L includes a regenerative inductor core 101 and coil windings. The regenerative inductor core 101 is a C-shaped core made of laminated silicon steel sheets, with a core cross-sectional area of ​​20 cm². 2The magnetic circuit length is 40cm. The coil winding uses rectangular copper wire wound on the regenerative inductor core 101, with a total of 120 turns and a total inductance of 240μH. Five independent taps 301 are evenly led out along the coil winding, located at turns 24, 48, 72, 96, and 120 respectively. The inductance difference between any two adjacent taps 301 is 40μH, meaning the inductance values ​​corresponding to the five taps 301 are 40μH, 80μH, 120μH, 160μH, and 240μH respectively. The overall control unit switches between different taps 301 via a multi-channel selector switch to change the inductance value connected to the pulse discharge circuit, thereby adjusting the peak value and frequency of the pulse current.

[0040] The unidirectional thyristor valve group D2 is composed of multiple high-power thyristors connected in series. It has a rated voltage of 12kV and a rated peak pulse current of 50kA, and is used to control the conduction timing of the pulse discharge circuit. The trigger electrode of the unidirectional thyristor valve group D2 is connected to the fiber optic trigger signal of the overall co-control unit to ensure high and low voltage electrical isolation.

[0041] The adjustable damping resistor R3 is connected in series with the unidirectional thyristor valve group D2 to the pulse discharge circuit. The adjustable damping resistor R3 is a multi-level adjustable power resistor with a resistance range of 0.1Ω to 5Ω. By switching different resistance levels, the damping coefficient of the pulse discharge circuit can be changed, thereby adjusting the attenuation rate of the pulse current.

[0042] The excitation inductor is connected in parallel with the energy-dissipating resistor R4. R4 is connected in parallel across the adjustable inductor L and its resistance is 5 to 10 times the inductive reactance of the adjustable inductor L. It is used to consume the magnetic field energy stored in the adjustable inductor L after the pulse discharge ends, suppress LC oscillation, and prevent the residual oscillation current from generating a continuous interfering magnetic field in the arc-extinguishing region.

[0043] The positive terminal of the energy storage capacitor C1 is connected to one end of the forward transient magnetic correction coil 9 or the reverse transient magnetic correction coil 10 via an adjustable inductor L. The other end of the transient magnetic correction coil is connected to the negative terminal of the energy storage capacitor C1 via an adjustable damping resistor R3 and a unidirectional thyristor valve group D2, forming a complete pulse discharge circuit. When the unidirectional thyristor valve group D2 is triggered to conduct, the energy pre-stored in the energy storage capacitor C1 releases a pulse current to the transient magnetic correction coil through the adjustable inductor L, generating the required transverse magnetic field in the central arc passage region 3.

[0044] like Figure 2 As shown, the power supply circuit components include a step-up transformer T1, a bridge rectifier assembly D1, a charging current-limiting resistor R1, and a capacitor parallel discharge resistor R2.

[0045] The step-up transformer T1 has a rated capacity of 500VA and a turns ratio of 220V / 10kV. The low-voltage winding is connected to a 220V / 50Hz AC power supply, and the high-voltage winding is connected to the AC input terminal of the bridge rectifier assembly D1. The bridge rectifier assembly D1 consists of four high-voltage silicon rectifier diodes forming a standard single-phase full-bridge rectifier topology. Each diode has a rated reverse voltage of 20kV and a rated forward current of 2A. The step-up transformer T1 provides electrical isolation between the high and low voltage circuits, and its insulation withstand voltage rating is 35kV.

[0046] The positive terminal of the bridge rectifier assembly D1 is connected in series with a charging current-limiting resistor R1 and then to the positive terminal of the energy storage capacitor C1. The negative terminal of the output is directly connected to the negative terminal of the energy storage capacitor C1. The charging current-limiting resistor R1 has a resistance of 10kΩ and a rated power of 100W. At the initial power-on moment of the energy storage capacitor C1, the charging current-limiting resistor R1 limits the peak charging current to below 1A, effectively suppressing the surge current of the capacitor charging and preventing damage to the rectifier diodes of the bridge rectifier assembly D1 and the high-voltage winding of the step-up transformer T1 from the instantaneous large current impact. The capacitor parallel discharge resistor R2 is connected in parallel across the energy storage capacitor C1, with a resistance of 10MΩ and a rated power of 10W. It is used for static voltage equalization and slow discharge of residual charge in the capacitor after shutdown, ensuring the safety of maintenance operations.

[0047] During operation, the 220V AC power supply is stepped up to 10kV by the step-up transformer T1 and then fed into the bridge rectifier component D1 to complete the AC-DC conversion, outputting pulsating high-voltage DC power. After being current-limited by the charging current-limiting resistor R1, it smoothly charges the energy storage capacitor C1. The charging time for the energy storage capacitor C1 to rise from zero to the preset voltage of 10kV is about 30 seconds. During the standby phase of the whole machine, the power supply circuit component continuously replenishes the voltage drop caused by the small leakage current to the energy storage capacitor C1 through the charging current-limiting resistor R1, maintaining the voltage of the energy storage capacitor C1 within the range of 10kV±0.5kV, ensuring that pulse energy can be released instantaneously under fault tripping conditions.

[0048] The whole machine collaborative control unit uses a high-performance digital signal processor (DSP) as the core control chip, and expands to include analog-to-digital conversion circuits, fiber optic trigger interfaces, and digital input / output interfaces. The whole machine collaborative control unit is connected to the current transformer 11 via a shielded cable, to the trigger electrode of the unidirectional thyristor valve group D2 via an optical fiber, and to the operating mechanism of the main circuit switch and the tap selection switch of the adjustable inductor L via a control cable.

[0049] like Figure 5 As shown, the control logic of the whole machine collaborative control unit includes the following steps: Step S1: Fault detection and parameter matching. Current transformer 11 acquires the main circuit current signal in real time at a sampling frequency of 10kHz and a current resolution of 1A. The whole-machine collaborative control unit reads the current sampling value in real time. When the instantaneous current value exceeds the preset fault current threshold (e.g., 1.5 times the rated current), a short circuit fault is determined. The whole-machine collaborative control unit quickly calculates the electrical compensation parameters matching the current fault condition based on the current rise rate and current peak value, including the tap position of the adjustable inductor L, the resistance value of the adjustable damping resistor R3, and the switching combination of the compensation branch. Based on the calculation results, the control unit issues a command to complete the rapid switching of the corresponding R / L / C compensation branch, pre-compensating the transient components of the system fault and suppressing the transient impact of the circuit fault.

[0050] In step S2, the main circuit disconnection and excitation are triggered synchronously. After transient compensation is completed (the time from fault detection to compensation completion does not exceed 2ms), the control unit sends a trip command to the operating mechanism of the main circuit switch to quickly disconnect the main current-carrying branch. The moving contact 2 begins to separate from the stationary contact 1. The unidirectional thyristor valve group D2 is synchronously triggered to conduct. The energy storage capacitor C1 releases pulse current to the forward transient correction coil 9 or the reverse transient correction coil 10 (selected according to the direction of the fault current) through the adjustable inductor L and the adjustable damping resistor R3, generating an instantaneous transverse arc-blowing magnetic field in the central arc passage area 3. The peak value of the pulse current is automatically adjusted according to the amplitude of the fault current, generally controlled within the range of 1kA~10kA, and the pulse duration is 0.5ms~2ms.

[0051] In step S3, the arc is extinguished. The transverse arc-blowing magnetic field drives the arc in the central arc passage zone 3 to rotate at high speed around the contact axis. The arc rotation frequency can reach 1kHz~5kHz, and the arc column is stretched to 3~5 times its initial length. The stretching of the arc column increases the contact area between the arc and the surrounding metal vapor, reducing the arc temperature to below the metal vapor ionization temperature. At the same time, the upper segmented magnetic shielding ring 4 and the lower segmented magnetic shielding ring 5 work together to constrain the residual magnetic field in the arc gap, controlling the residual transverse magnetic field within 5mT, accelerating the recombination process of ions and electrons in the plasma, and achieving reliable arc extinguishing.

[0052] Step S4: Fault tripping completes. After the arc is completely extinguished and the gap insulation strength of the central arc passage zone 3 returns to the rated withstand voltage level, the entire fault tripping process is completed, and fault current isolation is achieved. The total time from fault detection to complete tripping is controlled within 10ms to 20ms.

[0053] Throughout the control process, the overall control unit dynamically adjusts the connection position of the adjustable inductor L's tap 301 and the resistance value of the adjustable damping resistor R3 according to the fault current amplitude. For example, when the fault current amplitude is small, a smaller inductance value (40μH~80μH) and a smaller damping resistor value (0.1Ω~1Ω) are selected to generate a faster pulse current rise rate and a higher peak value, ensuring that sufficient transverse arc-extinguishing magnetic field can still be generated under low current conditions. When the fault current amplitude is large, a larger inductance value (160μH~240μH) and a larger damping resistor value (1Ω~5Ω) are selected to limit the pulse current peak value, ensuring that the instantaneous magnetic field in the arc-extinguishing zone does not exceed the preset limit of 15mT, and keeping the magnetic field during the interruption process always within the safe range of a weak transverse magnetic field.

[0054] The following is combined Figure 6 The working process and technical effects of the arc-extinguishing structure in this embodiment at different stages are described in detail.

[0055] Under normal operating conditions, the DC circuit breaker is in the closed position, and the main circuit current flows normally through the contact surfaces of the stationary contact 1 and the moving contact 2; the power supply circuit components continuously pre-store energy for the energy storage capacitor C1, maintaining the voltage of the energy storage capacitor C1 at 10kV; a constant DC current is supplied to the steady-state bias coil 8, generating a steady-state bias magnetic field. The overall control unit monitors the main circuit current in real time through the current transformer 11.

[0056] During the fault interruption process, when a short-circuit fault occurs in the system, the main circuit current rises sharply. After the current transformer 11 collects the fault current signal, the whole machine coordinated control unit identifies the fault condition within 0.5ms, calculates and matches the corresponding impedance compensation branch parameters, and switches the compensation branch to suppress the transient impact of the circuit fault. Subsequently, the control unit issues a tripping command, and the moving contact 2 separates from the stationary contact 1 at a speed of 1m / s to 2m / s under the drive of the operating mechanism, generating a vacuum arc in the central arc passage area 3. Simultaneously, the control unit triggers the unidirectional conduction thyristor valve group D2 to conduct, and the energy storage capacitor C1 releases a set of release pulse currents matching the fault current direction in the positive transient correction coil 9 and the reverse transient correction coil 10 through the adjustable inductor L.

[0057] During the magnetic field process, the pulsed current flows through the transient magnetic correction coil, generating an instantaneous transverse magnetic field perpendicular to the arc axis in the central arc passage zone 3, with a peak magnetic field strength of 10mT~15mT. At the same time, the arc-shaped conductive contacts of the stationary contact 1 and the moving contact 2 also generate a transverse arc-blowing magnetic field component due to the current flow, with a peak magnetic field strength of 5mT~10mT. The two sets of magnetic fields superimpose to provide an effective transverse arc-blowing magnetic field with a total strength of 15mT~25mT in the initial stage of circuit breaking. This magnetic field drives the arc to rotate at high speed around the contact axis, and the arc column is stretched to 3~5 times its initial length. The arc temperature drops rapidly from about 20000K to below 10000K, accelerating the ion-electron recombination process in the plasma and quickly eliminating conductive charged particles.

[0058] During the post-arc recovery process, as the arc current decreases to zero, the transverse arc-blowing magnetic field rapidly decays to below 5 mT. The upper segmented magnetic shielding ring 4 and the lower segmented magnetic shielding ring 5 utilize high-permeability permalloy material to shunt and counteract the stray transverse magnetic field of the contacts, forcibly stabilizing the residual transverse magnetic field in the contact gap within the safe threshold of 5 mT. Due to the weak residual magnetic field, it will not continuously interfere with the gap insulation recovery. After the arc, the metal vapor and plasma diffuse rapidly outward under conditions without magnetic field interference, and the gap insulation strength of the central arc passage zone 3 recovers to the rated withstand voltage level within 1 ms to 3 ms.

[0059] like Figure 6 As shown, Figure 6 The horizontal axis represents time (ms), and the vertical axis represents the transverse magnetic field strength (mT). The orange curve represents the traditional arc-extinguishing structure without the upper segmented magnetic shielding ring 4 and the lower segmented magnetic shielding ring 5, and without the cup-shaped transverse magnetic contact. Its transverse magnetic field strength steadily increases from the moment the arc begins, and remains at a relatively high level of 15mT~25mT during the post-arc recovery phase. The residual magnetic field continuously hinders the recovery of dielectric insulation, and the post-arc insulation recovery time is about 8ms~12ms, which can easily lead to post-arc re-breakdown faults. The blue curve represents the optimized arc-extinguishing structure of this embodiment. The magnetic field strength rapidly increases to about 20mT within 0.5ms~1ms after the circuit is opened, providing an effective arc-blowing magnetic field. Then it rapidly decays to below 5mT within 1ms~2ms. There is basically no residual magnetic field interference during the post-arc recovery phase, and the post-arc insulation recovery time is shortened to 1ms~3ms.

[0060] The comparison shows that the arc-extinguishing structure of this embodiment can provide an effective transverse arc-blowing magnetic field in the early stage of circuit breaking, quickly stretch and cool the arc, accelerate the ion-electron recombination process of the plasma, and quickly eliminate conductive charged particles; and the magnetic field dissipates quickly in the later stage, avoiding continuous magnetic field interference with gap insulation recovery, greatly shortening the post-arc insulation recovery cycle, effectively suppressing DC arc reignition, and significantly improving the fault current breaking stability and short-time breaking capacity of the circuit breaker.

[0061] In the case of lightning impulse transient operation, the arc extinguishing structure of this embodiment also has significant advantages. After lightning overvoltage enters the DC system, the whole unit and control unit quickly identify the characteristics of the lightning current, and according to the preset lightning protection logic, match the impedance compensation branch to suppress the transient impact of the lightning current, and synchronously trigger the pulse discharge circuit to output the magnetic field correction. Since the upper segment magnetic shielding ring 4 and the lower segment magnetic shielding ring 5 have stabilized and controlled the residual transverse magnetic field in the contact gap within 5mT, the post-arc insulation recovery speed will not be delayed due to the excessive weak transverse magnetic field, effectively avoiding faults such as lightning protection coordination failure and equipment breakdown damage, improving the lightning overvoltage withstand capability and lightning protection coordination reliability of the DC circuit breaker, and meeting the high reliability lightning protection operation requirements of the DC power grid.

[0062] The matching design of the multi-level adjustable inductor L and multi-tap energy storage capacitor array in this embodiment allows for flexible switching of access parameters according to different test conditions, meeting the requirements of full-condition test verification.

[0063] When conducting breaking tests at different current levels in the laboratory, by switching different taps 301 of the adjustable inductor L, five inductance values ​​of 40μH, 80μH, 120μH, 160μH, and 240μH can be flexibly selected to change the resonant frequency of the pulse discharge circuit. By adjusting the series and parallel combination of individual capacitors 111, the total capacitance and withstand voltage rating of the energy storage capacitor C1 can be changed, for example, from a 5-series 10-parallel combination to a 3-series 15-parallel combination. The parameters of the adjustable inductor L and the energy storage capacitor C1 can be adjusted together to change the peak value (adjustable from 1kA to 10kA) and frequency (adjustable from 500Hz to 5kHz) of the pulse current. This solves the problems in existing fixed-parameter test equipment where the inductor parameters are too large to adjust the output standard frequency and standard peak test current, and the electrical parameters of general capacitors are mismatched, making it impossible to complete the adaptation test verification. It meets the test verification requirements for all operating conditions from rated current to short-circuit current.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. It should be noted that the scope of protection of the present invention is defined by the appended claims, and the description and drawings are used to interpret the claims and should not be construed as limiting the claims.

Claims

1. An arc-extinguishing structure for a DC circuit breaker that suppresses weak transverse magnetic fields, characterized in that, include: A vacuum interrupter includes a transverse magnetic contact, a high permeability shielding structure, and an interrupter ceramic shell (7); the transverse magnetic contact is configured to generate a transverse arc-blowing magnetic field when the current is switched on or off; the high permeability shielding structure is used to limit the residual transverse magnetic field between the contacts to within a preset threshold; a coil winding portion is provided on the interrupter ceramic shell (7); The magnetic field suppression component includes a magnetic field control coil group and an adjustable power supply circuit. The magnetic field control coil group is wound around the coil winding section. The adjustable power supply circuit includes an energy storage capacitor (C1), an adjustable inductor (L), and a unidirectional thyristor valve group (D2), and is connected in series with the magnetic field control coil group to form a pulse discharge circuit, which is used to control the magnetic field of the arc-extinguishing zone by adjusting the circuit parameters. A power supply circuit assembly, connected to the energy storage capacitor (C1), is used to convert alternating current into direct current and pre-store energy in the energy storage capacitor (C1); The whole machine coordinated control unit is connected to the current transformer (11), the adjustable power supply circuit and the main circuit switch. It is used to identify the fault condition according to the current signal collected by the current transformer (11), control the main circuit to disconnect, and control the unidirectional thyristor valve group (D2) to conduct to output pulse current, thereby generating a transverse arc blowing magnetic field and realizing fault interruption under weak transverse magnetic field.

2. The arc-extinguishing structure according to claim 1, characterized in that, The transverse magnetic contact includes a stationary contact (1) and a moving contact (2), and a central arc passage area (3) is formed between the stationary contact (1) and the moving contact (2); The vacuum interrupter also includes a bellows (6), which is connected between the moving contact (2) and the ceramic shell (7) of the interrupter. The stationary contact (1) and the moving contact (2) are both cup-shaped structures. The cup-shaped cylindrical wall has multiple sets of spiral oblique grooves along the circumference. The oblique grooves extend spirally from the opening end of the contact along the cylindrical wall to the back of the contact. Independent arc-shaped conductive contact pieces are formed between adjacent oblique grooves. Multiple arc-shaped conductive contact pieces are enclosed to form a hollow interrupter cavity, which decomposes into a transverse magnetic field component perpendicular to the arc axis when the current is switched on or off.

3. The arc-extinguishing structure according to claim 2, characterized in that, The high-permeability magnetic shielding structure includes an upper segmented magnetic shielding ring (4) and a lower segmented magnetic shielding ring (5), which respectively cover the outer periphery of the stationary contact (1) and the moving contact (2), with an arc combustion channel reserved in the middle of the two. The upper segmented magnetic shielding ring (4) and the lower segmented magnetic shielding ring (5) are made of high magnetic permeability material, which is used to force the residual transverse magnetic field in the contact gap to be stabilized within a preset safety threshold.

4. The arc-extinguishing structure according to claim 3, characterized in that, The coil winding section on the outer periphery of the ceramic shell (7) of the arc-extinguishing chamber consists of four sets of inclined slots, which are evenly distributed in a 90° circumferential direction. The winding direction of two adjacent sets of inclined slots is the same, and the winding direction of two opposing sets of inclined slots is opposite. The magnetic field control coil group includes a steady-state bias coil (8), a positive transient magnetic correction coil (9), and a reverse transient magnetic correction coil (10); The steady-state bias coil (8) is wound in the inclined slot corresponding to the outside of the moving contact (2), and the positive transient magnetic correction coil (9) and the reverse transient magnetic correction coil (10) are wound in the inclined slot corresponding to the outside of the central arc passage area (3).

5. The arc-extinguishing structure according to claim 4, characterized in that, The energy storage capacitor (C1) is a capacitor array composed of multiple capacitor cells (111) connected in series and parallel by bus conductors (616), and is equipped with a voltage equalization connection branch (212); the adjustable inductor (L) is a multi-level adjustable inductor, including a rechargeable inductor core (101) and multiple independent wiring taps (301) uniformly led out along the winding, and the circuit inductance value is changed by switching to different wiring taps (301); the unidirectional thyristor valve group (D2) and the adjustable damping resistor (R3) are connected in series in the pulse discharge circuit.

6. The arc-extinguishing structure according to claim 5, characterized in that, The power supply circuit assembly includes a step-up transformer (T1), a bridge rectifier assembly (D1), and a charging current-limiting resistor (R1); The low-voltage side of the step-up transformer (T1) is connected to an AC power source, and the high-voltage side is connected to the input terminal of the bridge rectifier assembly (D1). The bridge rectifier assembly (D1) is a single-phase full-bridge rectifier topology. Its output terminal positive terminal is connected in series with the charging current-limiting resistor (R1) and then connected to the positive terminal of the energy storage capacitor (C1). The energy storage capacitor (C1) is connected in parallel with a capacitor and a discharge resistor (R2).

7. The arc-extinguishing structure according to claim 5, characterized in that, The adjustable power supply circuit also includes a magnetizing inductor connected in parallel with a depletion resistor (R4) across the adjustable inductor (L) to consume the inductor's stored energy and suppress oscillations.

8. The arc-extinguishing structure according to claim 1, characterized in that, The overall machine collaborative control unit includes: The signal of the current transformer (11) is collected in real time. After the fault current is detected, the matching impedance compensation parameters are calculated and the corresponding compensation branch is switched to cancel the fault transient component. The main current-carrying branch is cut off, and the unidirectional thyristor valve group (D2) is triggered to conduct simultaneously, so that the energy storage capacitor (C1) releases pulse current to the magnetic field control coil group to generate a transverse arc blowing magnetic field to accelerate the arc cooling and recombination. The fault tripping process ends after the arc is extinguished and the gap insulation is restored.

9. A method for controlling the arc extinguishing of a DC circuit breaker to suppress a weak transverse magnetic field, applied to the arc extinguishing structure described in any one of claims 1 to 8, characterized in that, Includes the following steps: Collect the main circuit current signal, identify fault conditions and match the corresponding impedance compensation branch to suppress transient impacts of circuit faults; Perform the main circuit disconnection operation and simultaneously turn on the adjustable power supply circuit, so that the energy storage capacitor (C1) outputs pulse current to the magnetic field control coil group, generating an instantaneous transverse arc blowing magnetic field in the contact area; The transverse arc-blowing magnetic field stretches the arc and reduces the temperature in the arc region, while the high-permeability magnetic shielding structure constrains the residual magnetic field in the arc gap, accelerating plasma recombination and arc extinguishing. After the arc is extinguished, the magnetic field decays rapidly, the gap insulation strength is restored, and the fault trip is completed. Among them, the pulse output intensity is adjusted according to the fault current amplitude to control the magnetic field during the interruption process within the weak transverse magnetic field range.

10. The control method according to claim 9, characterized in that, During the main circuit disconnection operation, the connection position of the adjustable inductor (L) tap (301) and the resistance value of the adjustable damping resistor (R3) are adjusted by the whole machine coordinated control unit according to the fault current amplitude, so as to change the peak value and frequency of the pulse current and ensure that the instantaneous magnetic field in the arc extinguishing zone does not exceed the preset limit.

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