Method for realizing high arc voltage of vacuum mechanical switch in medium voltage DC hybrid circuit breaker

Abstract

The present application relates to a kind of medium voltage DC hybrid circuit breaker in vacuum mechanical switch high arc voltage implementation method, based on the basic principle of natural commutation of DC breaking, form arc voltage promotion method, propose the overall technical scheme based on high arc voltage vacuum fast mechanical switch, provide theory and technical basis for the research and development of natural commutation type medium voltage DC circuit breaker, engineering application.Through external transverse magnetic field (external transverse magnetic field, ETMF) to make up for the shortage of its own magnetic field.When vacuum switch is directly used for low voltage DC breaking, external transverse magnetic field control plays a crucial role.The effect of transverse magnetic field on vacuum arc is to improve the voltage of vacuum arc, force the current of DC loop to zero, thereby realizing the DC breaking of vacuum switch.Improve the rapidity and reliability of current transfer, expand the application scenario of natural commutation mode, improve the arc voltage of fast mechanical switch, improve commutation and breaking performance.

Description

Technical Field

[0001] This invention relates to the field of medium-voltage switchgear technology, and in particular to a method for achieving high arc voltage in a vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker. Background Technology

[0002] Traditional mechanical arc-extinguishing schemes based on arc cutting to establish the breaking voltage have slow breaking speeds, failing to meet the requirement of rapid fault clearing within milliseconds. For rapid fault clearing and protection in medium- and high-voltage DC systems, current-transfer DC breaking technology is typically employed, involving several parallel branches with different functions. During current interruption, the system current is transferred between these parallel branches. Currently, the mainstream current-transfer breaking technologies include hybrid breaking schemes and active current injection breaking schemes. Existing hybrid DC circuit breakers use vacuum fast mechanical switches and auxiliary control circuits for forced commutation DC breaking in their main branches. While the forced commutation method introduces auxiliary commutation equipment, improving the reliability of current transfer, it increases the cost and size of the DC circuit breaker and reduces its reliability, hindering the large-scale application of medium-voltage DC circuit breakers in IPS systems. To improve the speed and reliability of current transfer and expand the application scenarios of natural commutation methods, it is necessary to increase the arc voltage of the fast mechanical switches and improve commutation and breaking performance. Summary of the Invention

[0003] To address the aforementioned issues, a method for achieving high arc voltage in vacuum mechanical switches of a DC-DC hybrid circuit breaker is proposed.

[0004] The technical solution of this invention is as follows: A method for achieving high arc voltage of vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker, applied to a medium-voltage DC hybrid circuit breaker composed of a main branch, a transfer branch, and an energy-consuming branch connected in parallel, wherein the main branch is equipped with a fast vacuum mechanical switch, comprising the following steps: 1) At the start of the opening action of the fast vacuum mechanical switch, the magnetic blow-out coil discharge circuit is triggered synchronously, so that the pre-charged energy storage capacitor performs pulse discharge to the magnetic blow-out coils symmetrically arranged on both sides of the vacuum interrupter of the fast vacuum mechanical switch, and generates a strong pulse transverse magnetic field perpendicular to the direction of the arc current in the vacuum interrupter. 2) The strong pulsed transverse magnetic field acts on the vacuum arc, causing the charged particles in the arc to move laterally at high speed under the drive of the Lorentz force, which leads to the arc path being lengthened and the cooling effect being enhanced, thereby causing the arc voltage to rise rapidly. 3) When the arc voltage rises to exceed the on-state voltage drop of the transfer branch, the fault current is naturally switched from the main branch to the transfer branch, and then transferred to the energy-consuming branch to absorb the remaining energy of the system, thus completing the DC interruption; 4) When the energy storage capacitor finishes discharging, a low-impedance freewheeling path is provided to the magnetic blow-out coil through a freewheeling diode, so that the coil current and the strong pulse transverse magnetic field are steadily decayed to zero, so as to avoid interfering with the insulation recovery after the fast vacuum mechanical switch extinguishes the arc.

[0005] Furthermore, the magnetic blowout coil discharge circuit includes a charging power supply, an energy storage capacitor, a discharge switch, a freewheeling diode, a stray resistor and a stray inductor in the discharge circuit; the energy storage capacitor is connected in parallel across the two ends of the charging power supply, and its positive terminal is grounded after being connected in series with the stray resistor, stray inductor and magnetic blowout coil via the discharge switch; the anode of the freewheeling diode is grounded, and its cathode is connected in series with the stray inductor, stray resistor and magnetic blowout coil in sequence, and then connected to the connection node between the discharge switch and the positive terminal of the energy storage capacitor, forming a freewheeling circuit.

[0006] Furthermore, the trigger closing time of the discharge switch is synchronized with the starting time of the separation of the contacts of the fast vacuum mechanical switch, with a time deviation of ≤50μs; the total resistance and total inductance of the discharge circuit are configured to make the discharge current present as a rapidly rising pulse waveform, and the rising edge of the strong pulse transverse magnetic field is steep, which is rapidly established in the early stage of contact separation.

[0007] Furthermore, after the freewheeling diode is turned on, the magnetic energy stored in the magnetic blowout coil is consumed through the freewheeling diode and the coil internal resistance. The coil current decays smoothly to zero according to an exponential law, and the strong pulse transverse magnetic field disappears quickly, so as to eliminate the adverse effect of the residual magnetic field on the recovery of the dielectric insulation strength between the contacts of the fast vacuum mechanical switch.

[0008] Furthermore, the initial gap of the fast vacuum mechanical switch is 3mm; the arc voltage rises to above 150V within 2ms after the switch is opened, and the amplitude of the arc voltage is reliably greater than the on-state voltage drop of the power electronic switch in the transfer branch.

[0009] Furthermore, the strong pulsed transverse magnetic field is orthogonal to the direction of the arc current in the vacuum interrupter. Positive ions and free electrons in the arc drift laterally due to opposite charge signs and opposite directions of Lorentz force, driving the arc plasma as a whole to move laterally at high speed perpendicular to the current and magnetic field directions, thereby increasing the contact area between the arc and the contacts and the vacuum medium.

[0010] Furthermore, the natural commutation process does not require the introduction of auxiliary commutation capacitors or inductors, and relies entirely on the increase in arc voltage to force the transfer of DC circuit current; and the vacuum interrupter does not have a longitudinal magnetic field control structure inside, overcoming the defect that the longitudinal magnetic field has a limited effect on arc stretching.

[0011] Furthermore, the initial charging voltage of the energy storage capacitor is 1000V~1800V, and the capacitance value is 2000μF~4500μF; the magnetic blow-out coil is a symmetrically arranged double coil structure, with 30~40 turns on each side and a wire diameter of 2×5mm².

[0012] A high-arc voltage realization device for a vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker is applied to a medium-voltage DC hybrid circuit breaker consisting of a main branch, a transfer branch, and an energy-consuming branch connected in parallel. The main branch is equipped with a fast vacuum mechanical switch, comprising: At least one pair of magnetic blowout coils are symmetrically arranged on both sides of the vacuum interrupter chamber of the fast vacuum mechanical switch; A magnetic blowout coil discharge circuit, electrically connected to the magnetic blowout coil, is used to perform pulse discharge to the magnetic blowout coil after triggering; The control unit is connected to the opening drive mechanism of the fast vacuum mechanical switch and the discharge circuit of the magnetic blow-out coil, respectively. The control unit is configured to output a synchronous trigger signal at the same time as outputting the trip command, so that the magnetic blowout coil discharge circuit releases a pulse current to the magnetic blowout coil, thereby generating a strong pulse transverse magnetic field perpendicular to the direction of the arc current in the vacuum interrupter chamber. The strong pulse transverse magnetic field is configured to lengthen the arc path and enhance the cooling effect to increase the arc voltage, so that the arc voltage exceeds the on-state voltage drop of the transfer branch, thereby realizing the natural commutation of the fault current from the main branch to the transfer branch; the magnetic blowout coil discharge circuit is provided with a freewheeling diode, which is configured to conduct at the end of the discharge to release the coil magnetic energy and cause the strong pulse transverse magnetic field to decay rapidly.

[0013] Preferably, the magnetic blowout coil discharge circuit includes a charging power supply, an energy storage capacitor, a discharge switch, a freewheeling diode, and a stray impedance of the discharge circuit; the energy storage capacitor is connected in parallel with the charging power supply; the discharge switch, the stray impedance, and the magnetic blowout coil are connected in series to form a main discharge circuit; the freewheeling diode, the stray impedance in the main discharge circuit, and the magnetic blowout coil are connected in series to form a freewheeling branch, and the two ends of the freewheeling branch are respectively connected to the ground terminal of the main discharge circuit and the input terminal of the discharge switch.

[0014] Preferably, the control unit has a built-in hardware synchronization trigger module, which ensures that the time deviation between the starting edge of the tripping command and the rising edge of the synchronization trigger signal is ≤50μs; the stray impedance parameter of the discharge circuit is configured to ensure that the rise time of the pulse current is ≤0.5ms.

[0015] Preferably, the initial contact gap of the vacuum interrupter is 3mm; the initial voltage of the energy storage capacitor is 1000V to 1800V, and the capacitance value is 2000μF to 4500μF; the device is configured to raise the arc voltage to above 150V within 2ms after the circuit breaker is opened.

[0016] Preferably, the winding axis of the magnetic blowout coil is perpendicular to the central axis of the vacuum interrupter to generate a transverse magnetic field orthogonal to the arc current; the vacuum interrupter does not integrate a longitudinal magnetic field coil or permanent magnet array, and relies entirely on the strong pulsed transverse magnetic field for arc stretching and voltage boosting.

[0017] Preferably, the anode of the freewheeling diode is grounded, and the cathode is connected in series with the stray impedance of the discharge circuit and the magnetic blowout coil and then connected to the positive side of the energy storage capacitor; the freewheeling diode is configured to conduct forward when the voltage at the end of the energy storage capacitor is lower than the induced electromotive force of the coil, providing a low-impedance freewheeling path for the magnetic blowout coil, so that the magnetic field decays to less than 10% of the initial amplitude within 5ms after the arc is extinguished.

[0018] A medium-voltage DC hybrid circuit breaker system includes a vacuum mechanical switch high-arc voltage realization device in the medium-voltage DC hybrid circuit breaker, as well as a transfer branch and an energy-consuming branch; the transfer branch includes at least one power electronic switch, and the energy-consuming branch includes a metal oxide surge arrester or an energy-consuming resistor; the system is configured to utilize the arc voltage generated by the high-arc voltage realization device to complete the cascaded natural commutation of current from the main branch to the transfer branch and then to the energy-consuming branch, thereby achieving rapid clearing of DC faults without the need for auxiliary commutation equipment.

[0019] The beneficial effects of this invention are as follows: The method for realizing high arc voltage of vacuum mechanical switch in medium-voltage DC hybrid circuit breaker of this invention, based on the conventional vacuum mechanical switch of the original medium-voltage hybrid DC circuit breaker, carries out the analysis and modeling simulation of arc voltage characteristics of the tripping circuit, conducts in-depth research on the natural commutation mechanism, improves the speed and reliability of current transfer, expands the application scenarios of natural commutation mode, improves the arc voltage of fast mechanical switch, and improves commutation and breaking performance. Attached Figure Description

[0020] Figure 1 A simplified three-dimensional model of a 3mm magnetic blowout coil for rapid mechanical switch tripping according to an embodiment of the present invention; Figure 2 The magnetic blowout coil discharge circuit diagram of this invention; Figure 3 Structural diagram of a DC circuit breaker based on the vacuum magnetic blowout transfer principle of this invention; Figure 4A A schematic diagram of the fast vacuum mechanical switch of the present invention when the longitudinal magnetic field is used as the external magnetic field. Figure 4B A schematic diagram of the fast vacuum mechanical switch of the present invention when the transverse magnetic field is used as the external magnetic field. Figure 5A Schematic diagram of the effect of the external transverse magnetic field ETMF on the electric arc in this invention; Figure 5B Schematic diagram of ETMF generated by coil discharge in this invention; Figure 5C A schematic diagram of the permanent magnet generating ETMF in this invention. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0022] The first technical solution of this invention is based on the fundamental principle of natural commutation in DC interruption, forming an arc voltage boosting method and proposing an overall technical solution based on a high-arc voltage vacuum fast mechanical switch, providing a theoretical and technical foundation for the research, development, and engineering application of naturally commutated medium-voltage DC circuit breakers. The second solution compensates for the inadequacy of the vacuum's own magnetic field by using an external transverse magnetic field (ETMF). When the vacuum switch is directly used for low-voltage DC interruption, the external magnetic field control plays a crucial role. The transverse magnetic field's effect on the vacuum arc is to boost the arc voltage, forcing the DC circuit current to cross zero, thereby achieving DC interruption of the vacuum switch.

[0023] This invention generates a corresponding external transverse electric field by designing a magnetic blowout coil, which causes the arc inside the arc-extinguishing chamber to move rapidly laterally under the action of the Lorentz force generated by the external transverse magnetic field, resulting in arc lengthening and increased arc voltage.

[0024] 1. Design of the magnetic blowout coil: The magnetic blowout coil is a crucial component for generating high arc voltage. Its principle involves a storage capacitor discharging into the coil through a discharge device. The coil then generates a transverse magnetic field perpendicular to the current within the vacuum-sealed arc-extinguishing chamber. This magnetic field induces the transverse movement of electrons in the arc current within the chamber, thereby increasing the arc voltage drop. Since the magnitude and waveform of the magnetic field significantly influence the magnitude and variation of the arc voltage, the simulation and design of the magnetic field in the magnetic blowout coil are of great importance. Figure 1 A simplified three-dimensional model of a 3mm magnetic blow-out coil for a fast mechanical switch is provided. A set of magnetic blow-out coils 2 are placed symmetrically on both sides of the fast mechanical switch at the location of vacuum interrupter 1.

[0025] Since the relative permeability of each component inside the arc-extinguishing chamber is 1, which is the same as the relative permeability of air and vacuum, it will not affect the magnetic field distribution. The specific parameters of each material are shown in Table 1.

[0026] Table 1

[0027] The corresponding magnetic blowout coil discharge circuit design is as follows: Figure 2 As shown in Table 2, the specific electrical parameters in the circuit are as follows. After the power supply is connected in parallel with the energy storage capacitor C2, the positive terminal is connected in series with the resistor Rc and the energy storage capacitor C2. A freewheeling diode D2 is connected between the negative terminal of the power supply and the end of the energy storage capacitor C2 furthest from the resistor Rc, forming a discharge circuit. The negative terminal of the power supply is connected to the anode of the freewheeling diode D2 and grounded. Starting from the cathode, the freewheeling diode D2 is connected in series with the following components in sequence: the stray inductance Ls5 of the discharge circuit, the stray resistance Rs6 of the discharge circuit, the inductance L2 of the single-sided magnetic blow-out coil, the internal resistance R1 of the single-sided magnetic blow-out coil, the inductance L3 of the opposite-sided magnetic blow-out coil, and the internal resistance R2 of the opposite-sided magnetic blow-out coil before being grounded. The power supply provides the capacitor with the initial voltage V.

[0028] As the fast mechanical switch HSCB opens, the energy storage capacitor C2 begins to discharge into the magnetic blow-out coil through the discharge circuit. Due to the low total resistance and moderate inductance of the circuit, the discharge current exhibits a rapidly rising pulse waveform. This pulse current flows through the magnetic blow-out coil, generating a strong pulsed transverse magnetic field perpendicular to the direction of the arc current within the vacuum interrupter. When the energy storage capacitor C2 finishes discharging, the current in the magnetic blow-out coils L2 and L3 cannot change abruptly, resulting in a reverse induced electromotive force. At this time, the freewheeling diode D2 conducts forward, providing a low-impedance freewheeling circuit for the coil current. The magnetic energy stored in the magnetic blow-out coil is gradually consumed through D2 and the internal resistances R1 and R2 of the magnetic blow-out coil, causing the current to gradually decay to zero. The magnetic field then disappears rapidly, preventing interference with subsequent insulation recovery. This circuit utilizes the pulsed discharge of the capacitor's energy storage to generate a momentary strong current in the coil, thereby forming a sufficiently large and steeply rising transverse magnetic field within the vacuum interrupter, driving the arc to move at high speed to increase the arc voltage. The freewheeling diode is used to protect the switch and capacitor and control the magnetic field decay process.

[0029] Table 2

[0030] 2. High arc voltage implementation method: Figure 3 The key to the structure of a medium-voltage DC circuit breaker based on the vacuum magnetic blow-out transfer principle is that the main branch fast mechanical switch (HSCB) needs to rapidly trip to the insulation distance that can withstand the transient breaking voltage (TIV) within 2ms. Simultaneously, the HSCB must generate a high arc voltage to rapidly commutate the short-circuit current to the transfer branch, allowing the HSCB insulation to recover and withstand the transient breaking voltage (TIV). Therefore, the main challenges for the HSCB are rapid tripping operation and the generation of high arc voltage.

[0031] The high arc voltage implementation method proposed in this invention is applied to a naturally commutated medium-voltage DC circuit breaker. This circuit breaker topology consists of three parallel branches: a main branch, a transfer branch, and an energy dissipation branch. When the circuit breaker receives a tripping command, the fast mechanical switch (HSCB) contacts in the main branch begin to separate. Simultaneously, the magnetic blowout coil discharge circuit is triggered, generating a strong pulsed transverse magnetic field that drives the vacuum arc at high speed, causing the arc voltage to rise rapidly. Utilizing this high arc voltage, the fault current is pushed out of the main branch, thus achieving natural commutation to the transfer branch. As the arc voltage in the main branch rises and exceeds the on-state voltage drop of the transfer branch, the power electronic switches (D1-D4) in the transfer branch automatically turn on. Since the impedance of the transfer branch is significantly lower than that of the main branch under high arc voltage conditions, the fault current quickly transfers from the main branch to the transfer branch. After the fault current has completely transferred to the transfer branch, the power electronic switches remain on, but system energy needs to be absorbed. At this point, the current in the transfer branch begins to commutate to the energy dissipation branch (MOV), where the remaining energy stored in the system, including the magnetic energy in the line inductance and the commutation inductance, is absorbed. This completes the entire switching process.

[0032] 3. Principle of High Arc Voltage Implementation: The arc voltage of a traditional vacuum interrupter is only 20V~30V, which cannot guarantee that the current will be quickly commutated to the transfer branch during the DC circuit breaker interruption process. In order to significantly increase the arc voltage during the DC interruption process, an external transverse magnetic field ETMF is required. Under the action of the Lorentz force generated by the external transverse magnetic field, the arc inside the interrupter moves rapidly laterally, the arc is lengthened, and the arc voltage increases.

[0033] Figure 4A A schematic diagram of a vacuum interrupter structure controlled by a longitudinal magnetic field (hereinafter referred to as "longitudinal magnetic field") is shown. In the longitudinal magnetic field scheme, the direction of the magnetic field is parallel to the direction of the arc current. The function of the longitudinal magnetic field is to cause the charged particles in the arc to move spirally along the magnetic field lines, thereby constraining the arc and keeping it in a relatively concentrated and rotating state, preventing local overheating and erosion of the contacts. However, although the longitudinal magnetic field can improve the stability of the arc, its stretching effect on the arc length is limited. The arc voltage can usually only be increased to 30~50V, which is still far from sufficient to drive the fault current in the medium-voltage DC system to be quickly commutated to the transfer branch.

[0034] Figure 4BThe transverse magnetic field (hereinafter referred to as "transverse magnet") control scheme adopted in this invention is illustrated. In the transverse magnet structure, the direction of the magnetic field is perpendicular to the direction of the arc current. According to the Lorentz force law, charged particles are subjected to a force perpendicular to both the current and the magnetic field directions, driving the entire arc plasma to move laterally at high speed on the contact surface. The arc is violently elongated and twisted, significantly increasing the actual path length. At the same time, the cooling effect between the arc and the surrounding medium is enhanced, causing the arc voltage to rise sharply to over 150V.

[0035] Figures 5A-5C This invention relates to the principle of Lorentz force applied to the internal arc of a vacuum interrupter under the action of an external transverse magnetic field, and to a scheme for realizing the external transverse magnetic field ETMF. This scheme can quickly establish a high arc voltage in the vacuum interrupter, ensuring that the arc voltage is reliably greater than the on-state voltage drop of the transfer branch, thereby successfully completing the current transfer process after the switch is turned off. Figure 5A This illustrates the physical principle of the interaction between a transverse magnetic field and a vacuum arc. Inside the vacuum interrupter, the arc current... i arc The direction is from the anode of the contact to the cathode. When an external transverse magnetic field B, perpendicular to the current I, is applied into the contact gap, the charged particles (positive ions and free electrons) in the arc move at a velocity... v arc Moving along the direction of the current, the arc plasma is subjected to the Lorentz force. Since the positive ions and electrons have opposite charges, the forces acting on them are in opposite directions, causing the entire arc plasma to undergo a transverse motion perpendicular to both the current and the magnetic field. This transverse motion causes the arc to rotate at high speed on the contact surface, becoming violently elongated, significantly increasing the arc column length. Simultaneously, the contact area between the arc and the contact and the surrounding vacuum medium increases, enhancing the cooling effect and drastically increasing energy dissipation. This causes the arc voltage to rapidly climb from the traditional 20-30V to over 150V. The high arc voltage ensures that the arc voltage reliably exceeds the on-state voltage drop of the transfer branch, thus smoothly completing the natural commutation of current from the main branch to the transfer branch.

[0036] Figure 5B This invention demonstrates the scheme for generating an external transverse magnetic field using coils. A pair of magnetic blowout coils are arranged symmetrically on both sides of the vacuum interrupter. The coils are connected to an RLC discharge circuit consisting of an energy storage capacitor, a discharge switch, a freewheeling diode, etc. (see [link to relevant documentation]). Figure 2When the fast mechanical switch opens, the discharge switch closes, and the energy storage capacitor discharges into the coil, generating a strong pulse current with a steep rising edge. This current generates a momentary strong transverse magnetic field in the coil, with the magnetic field direction perpendicular to the arc current direction in the arc-extinguishing chamber. The advantages of this scheme include: 1. High magnetic field strength, which can be flexibly designed according to needs; 2. Precise synchronization between the magnetic field and the switch opening action, enabling rapid establishment of a high arc voltage in the early stages of contact separation; 3. The pulsed magnetic field decays rapidly after arc extinction through a freewheeling diode, avoiding adverse effects on insulation recovery. Therefore, the coil discharge scheme is particularly suitable for medium- and high-voltage, high-current DC breaking scenarios.

[0037] Figure 5C This paper demonstrates another ETMF generation scheme—the permanent magnet scheme. High-performance permanent magnets are directly installed on both symmetrical sides outside the vacuum interrupter, generating a constant transverse magnetic field in the contact gap. The advantages of this scheme are its simple structure, lack of need for additional discharge circuits and control timing, and low cost. However, it has significant drawbacks: 1. The magnetic field strength is fixed and cannot be adjusted according to the actual breaking current. 2. The constant magnetic field may be weakened or distorted by the magnetic field generated by the arc itself, especially when breaking large currents, where the self-generated magnetic field may interact with the permanent magnet magnetic field, reducing the strength of the effective transverse magnetic field. 3. The permanent magnet may demagnetize under high temperature, strong impact, or long-term use, affecting reliability. Therefore, the permanent magnet scheme is only suitable for low-voltage, low-current applications with less stringent requirements and is not suitable for the medium-voltage DC system targeted by this invention.

[0038] By comparison Figure 5B and Figure 5C Two implementation schemes are proposed. This invention selects the coil pulse discharge scheme as the core technology for generating the external transverse magnetic field ETMF. This scheme can quickly establish a high-intensity pulsed transverse magnetic field, driving the arc to move laterally at high speed. Within 2ms, the arc voltage of the vacuum interrupter is increased to over 150V, ensuring that the arc voltage is reliably greater than the on-state voltage drop of the transfer branch. This allows for the smooth completion of the current transfer process after the switch is turned off, achieving natural commutation DC interruption without the need for auxiliary commutation devices.

[0039] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for achieving high arc voltage of vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker, applied to a medium-voltage DC hybrid circuit breaker consisting of a main branch, a transfer branch, and an energy-consuming branch connected in parallel, wherein the main branch is equipped with a fast vacuum mechanical switch, characterized in that, Includes the following steps: 1) At the start of the fast vacuum mechanical switch's opening action, the magnetic blow-out coil discharge circuit is synchronously triggered, causing the pre-charged energy storage capacitor to pulse-discharge the magnetic blow-out coils symmetrically arranged on both sides of the vacuum interrupter of the fast vacuum mechanical switch, generating a strong pulsed transverse magnetic field perpendicular to the arc current direction within the vacuum interrupter; 2) The strong pulsed transverse magnetic field acts on the vacuum arc, causing the charged particles in the arc to move laterally at high speed under the Lorentz force, resulting in a lengthened arc path and enhanced cooling effect, thereby causing the arc voltage to rise rapidly; 3) When the arc voltage rises to exceed the on-state voltage drop of the transfer branch, the fault current naturally commutates from the main branch to the transfer branch, and then transfers to the energy-consuming branch to absorb the remaining energy of the system, completing the DC interruption; 4) When the energy storage capacitor finishes discharging, a low-impedance freewheeling path is provided to the magnetic blow-out coil through a freewheeling diode, so that the coil current and the strong pulse transverse magnetic field are steadily decayed to zero, so as to avoid interfering with the insulation recovery after the fast vacuum mechanical switch extinguishes the arc.

2. The method for realizing high arc voltage of vacuum mechanical switch in medium-voltage DC hybrid circuit breaker according to claim 1, characterized in that, The magnetic blowout coil discharge circuit includes a charging power supply, an energy storage capacitor, a discharge switch, a freewheeling diode, a stray resistor, and a stray inductor in the discharge circuit. The energy storage capacitor is connected in parallel across the charging power supply, and its positive terminal is grounded after being connected in series with the stray resistor, stray inductor, and magnetic blowout coil via the discharge switch. The anode of the freewheeling diode is grounded, and its cathode is connected in series with the stray inductor, stray resistor, and magnetic blowout coil before being connected to the connection node between the discharge switch and the positive terminal of the energy storage capacitor, thus forming a freewheeling circuit.

3. The method for achieving high arc voltage in a vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 1, characterized in that, The trigger closing time of the discharge switch is synchronized with the starting time of the separation of the contacts of the fast vacuum mechanical switch, with a time deviation of ≤50μs; the total resistance and total inductance of the discharge circuit are configured to make the discharge current present as a rapidly rising pulse waveform, and the rising edge of the strong pulse transverse magnetic field is steep, which is rapidly established in the early stage of contact separation.

4. The method for achieving high arc voltage in a vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 1, characterized in that, After the freewheeling diode is turned on, the magnetic energy stored in the magnetic blowout coil is consumed through the freewheeling diode and the coil internal resistance. The coil current decays smoothly to zero according to an exponential law, and the strong pulse transverse magnetic field disappears quickly, so as to eliminate the adverse effect of the residual magnetic field on the recovery of the dielectric insulation strength between the contacts of the fast vacuum mechanical switch.

5. The method for realizing high arc voltage of vacuum mechanical switch in medium-voltage DC hybrid circuit breaker according to claim 1, characterized in that, The initial gap of the fast vacuum mechanical switch is 3mm; the arc voltage rises to above 150V within 2ms after the switch is opened, and the amplitude of the arc voltage is reliably greater than the on-state voltage drop of the power electronic switch in the transfer branch.

6. The method for realizing high arc voltage of vacuum mechanical switch in medium-voltage DC hybrid circuit breaker according to claim 1, characterized in that, The strong pulsed transverse magnetic field is orthogonal to the direction of the arc current in the vacuum interrupter. Positive ions and free electrons in the arc drift laterally due to opposite charge signs and opposite directions of Lorentz force, driving the arc plasma to move at high speed in a transverse direction perpendicular to the current and magnetic field, increasing the contact area between the arc and the contacts and the vacuum medium.

7. The method for achieving high arc voltage in a vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 1, characterized in that, The natural commutation process does not require the introduction of auxiliary commutation capacitors or inductors, and relies entirely on the increase of the arc voltage to force the transfer of DC circuit current; and the vacuum interrupter does not have a longitudinal magnetic field control structure inside, overcoming the defect that the longitudinal magnetic field has a limited effect on arc stretching.

8. The method for achieving high arc voltage in a vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 1, characterized in that, The initial charging voltage of the energy storage capacitor is 1000V~1800V, and the capacitance value is 2000μF~4500μF; the magnetic blow-out coil is a symmetrically arranged double coil structure, with 30~40 turns on each side and a wire diameter of 2×5mm².

9. A high-arc voltage realization device for a vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker, applied to a medium-voltage DC hybrid circuit breaker consisting of a main branch, a transfer branch, and an energy-consuming branch connected in parallel, wherein the main branch is equipped with a fast vacuum mechanical switch, characterized in that, include: At least one pair of magnetic blowout coils are symmetrically arranged on both sides of the vacuum interrupter chamber of the fast vacuum mechanical switch; a magnetic blowout coil discharge circuit is electrically connected to the magnetic blowout coil and is used to pulse discharge to the magnetic blowout coil after triggering; a control unit is signal-connected to the tripping drive mechanism of the fast vacuum mechanical switch and the magnetic blowout coil discharge circuit respectively; the control unit is configured to output a synchronous trigger signal while outputting a tripping command, so that the magnetic blowout coil discharge circuit releases a pulse current to the magnetic blowout coil, thereby generating a strong pulsed transverse magnetic field perpendicular to the direction of the arc current in the vacuum interrupter chamber; the strong pulsed transverse magnetic field is configured to lengthen the arc path and enhance the cooling effect to increase the arc voltage, so that the arc voltage exceeds the on-state voltage drop of the transfer branch, realizing the natural commutation of the fault current from the main branch to the transfer branch; the magnetic blowout coil discharge circuit is provided with a freewheeling diode, configured to conduct at the end of the discharge to discharge the coil magnetic energy and make the strong pulsed transverse magnetic field decay rapidly.

10. The high-arc voltage realization device for vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 9, characterized in that, The magnetic blowout coil discharge circuit includes a charging power supply, an energy storage capacitor, a discharge switch, a freewheeling diode, and a stray impedance for the discharge circuit. The energy storage capacitor is connected in parallel with the charging power supply. The discharge switch, the stray impedance, and the magnetic blowout coil are connected in series to form a main discharge circuit. The freewheeling diode, the stray impedance in the main discharge circuit, and the magnetic blowout coil are connected in series to form a freewheeling branch. The two ends of the freewheeling branch are respectively connected to the ground terminal of the main discharge circuit and the input terminal of the discharge switch.

11. The high-arc voltage realization device for vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 9, characterized in that, The control unit has a built-in hardware synchronization trigger module, which ensures that the time deviation between the starting edge of the tripping command and the rising edge of the synchronization trigger signal is ≤50μs; the stray impedance parameter of the discharge circuit is configured to ensure that the rise time of the pulse current is ≤0.5ms.

12. The high-arc voltage realization device for vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 9, characterized in that, The initial contact gap of the vacuum interrupter is 3mm; the initial voltage of the energy storage capacitor is 1000V~1800V, and the capacitance value is 2000μF~4500μF; the device is configured to raise the arc voltage to above 150V within 2ms after the circuit breaker is opened.

13. The high-arc voltage realization device for vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 9, characterized in that, The winding axis of the magnetic blowout coil is perpendicular to the central axis of the vacuum interrupter to generate a transverse magnetic field orthogonal to the arc current. The vacuum interrupter does not integrate a longitudinal magnetic field coil or permanent magnet array, and relies entirely on the strong pulsed transverse magnetic field for arc stretching and voltage boosting.

14. The high-arc voltage realization device for vacuum mechanical switch in a medium-voltage DC hybrid circuit breaker according to claim 9, characterized in that, The anode of the freewheeling diode is grounded, and the cathode is connected in series with the stray impedance of the discharge circuit and the magnetic blowout coil, and then connected to the positive side of the energy storage capacitor. The freewheeling diode is configured to conduct forward when the voltage at the end of the energy storage capacitor is lower than the induced electromotive force of the coil, so as to provide a low-impedance freewheeling path for the magnetic blowout coil, and to reduce the magnetic field to less than 10% of the initial amplitude within 5ms after the arc is extinguished.

15. A medium-voltage DC hybrid circuit breaker system, characterized in that, The system includes a vacuum mechanical switch high arc voltage realization device in a medium-voltage DC hybrid circuit breaker according to any one of claims 9 to 14, as well as the transfer branch and the energy-consuming branch; the transfer branch includes at least one power electronic switch, and the energy-consuming branch includes a metal oxide surge arrester or an energy-consuming resistor; the system is configured to use the arc voltage generated by the high arc voltage realization device to complete the cascaded natural commutation of current from the main branch to the transfer branch and then to the energy-consuming branch, thereby achieving rapid clearing of DC faults without the need for auxiliary commutation equipment.

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