Short-circuit current self-driven fast switch and design and control method thereof

Abstract

The invention discloses a short-circuit current self-driven fast switch and a design and control method thereof, the short-circuit current self-driven fast switch comprises a vacuum arc-extinguishing chamber, an electromagnetic holding mechanism, an electromagnetic repulsion mechanism and a controller which are connected in parallel on a tested system, and the vacuum arc-extinguishing chamber is connected in parallel with a current limiting reactor connected on the tested system; the electromagnetic holding mechanism comprises a second current transformer of which the primary side is coupled with the tested system, a rectifying circuit connected in series with the secondary side of the second current transformer and a driving coil connected in series with the rectifying circuit, the driving coil is aligned with an armature of the vacuum arc-extinguishing chamber, and an air gap is formed between the armature and the driving coil; and the driving coil is arranged in the shell made of a ferromagnetic material. The invention aims to provide the short-circuit current self-driven quick switch, so that the current-limiting reactor can act immediately and can act for multiple times in a short time when the short-circuit current self-driven quick switch has a system short-circuit fault under any condition.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical switches, and in particular to a short-circuit current self-driven fast switch and a design and control method thereof. Background Art

[0002] With the continuous development of power construction, the continuous increase in power load and the close interconnection of AC and DC power grids in various regions, the short-circuit current level of the power system continues to increase, seriously threatening the breaking capacity of the circuit breaker. At present, the problem of excessive short-circuit current has become a common problem in load-intensive areas and power-intensive areas, restricting the development of power and the safe and stable operation of the power grid. In order to solve the above problems, it is necessary to suppress the short-circuit current. The principle is to increase the equivalent short-circuit impedance of the fault point. The conventional means mainly include: First, change the system structure or operation mode, including busbar segmented operation, line pull-out, line out of series, etc. These measures may cause large changes in the grid structure, sacrifice the integrity of the grid structure, and have a greater negative impact on the normal operation of the system. The second is to install current limiting reactors, mainly series reactors, split reactors, etc. Current limiting reactors can effectively reduce the short-circuit current level, but may cause uneven distribution of power flow, affecting the efficient use of the power grid; at the same time, high-voltage level current limiting reactors occupy a large area and are expensive. For load center substations, it is difficult to transform due to site restrictions and difficult to implement.

[0003] The fast switching fault current limiter composed of a fast switch in parallel with a current limiting reactor is currently a widely adopted current limiting method. When the power grid is operating normally, it controls the fast switch to close and bypass the current limiting reactor. After a short circuit fault occurs, it controls the fast switch to open and input the current limiting reactor within about one cycle to play the current limiting function. After the fault is removed, it controls the fast switch to reclose and bypass the current limiting reactor again. However, the existing fast switches have the following defects: 1. Since the driving current of the fast switch is generally provided by the energy storage capacitor, and the energy storage capacitor often takes several seconds to tens of seconds to charge, and can only prepare for the next action after charging is completed, the fast switch type current limiting reactor (FCL) cannot achieve continuous action. Generally, it will remain for 1-2 seconds after breaking, waiting for the completion of the reclosing procedure or the relay protection to remove the short-circuit fault, and the fast switch will resume the closed state; 2. The energy storage capacitor is charged by an external power supply or by taking power from the primary side of the system through an energy taking device. The external power supply method requires the design of an isolation transformer, an insulating rod-generator platform to connect the low-voltage power supply in the station and the high-voltage platform of the FCL, which has the problems of large size and high cost; if a CVT (capacitor voltage transformer) and other energy taking devices are used to take power from the primary side of the system, when the FCL is powered on for the first time after a power outage, once there is a short-circuit fault in the system, the energy storage capacitor will not have time to charge, and the FCL will not be able to act immediately, resulting in an increase in power failure losses. Summary of the invention

[0004] Technical problem to be solved by the present invention: In view of the above-mentioned problems in the prior art, a short-circuit current self-driven fast switch and a design and control method thereof are provided. The present invention aims to provide a short-circuit current self-driven fast switch which uses the fault current collected by a current sensor as the driving current, so that the current-limiting inductor of the short-circuit current self-driven fast switch can be immediately actuated and can be actuated multiple times in a short period of time when a system short-circuit fault occurs under any circumstances.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A short-circuit current self-driven fast switch comprises a vacuum interrupter connected in parallel to a system under test, an electromagnetic holding mechanism, an electromagnetic repulsion mechanism and a controller, wherein the vacuum interrupter is connected in parallel to a current limiting reactor connected to the system under test; the electromagnetic holding mechanism comprises a second current transformer coupled to the system under test on the primary side, a rectifier circuit connected in series to the secondary side of the second current transformer, and a drive coil connected in series to the rectifier circuit, the drive coil is aligned with the armature of the vacuum interrupter, and there is an air gap between the armature and the drive coil, and the drive coil is placed inside a shell of a ferromagnetic material; the electromagnetic repulsion mechanism is aligned with the armature of the vacuum interrupter, and the electromagnetic repulsion mechanism comprises a first current transformer coupled to the system under test on the primary side, a static repulsion coil, a dynamic repulsion coil and a bidirectional thyristor, the static repulsion coil is coupled to the secondary side of the first current transformer, the dynamic repulsion coil is coupled to the static repulsion coil, the dynamic repulsion coil is connected in series to the bidirectional thyristor, the bidirectional thyristor is electrically connected to the output end of the controller, and the input end of the controller is electrically connected to the first current transformer.

[0006] Optionally, the vacuum interrupter includes a switch circuit and a resistor-capacitor circuit connected in parallel, the armature is fixed on a movable arm of a switch on the switch circuit, and the resistor-capacitor circuit includes a resistor and a capacitor connected in series.

[0007] Optionally, the primary side coil of the second current transformer has 1 turn and a transformation ratio of 1500:1.

[0008] Optionally, the static repulsion coil is made of copper, and the dynamic repulsion coil is made of aluminum.

[0009] Optionally, the static repulsion coil and the dynamic repulsion coil are both double-layer coils.

[0010] Optionally, the double-layer coil has a coil height of 8 mm, an outer diameter of 250 mm, a single-turn thickness of the coil of 0.84 mm, and a total number of double-layer turns of 212 turns.

[0011] In addition, the present invention also provides a design method for the aforementioned short-circuit current self-driven fast switch, including determining the electrical parameters of the electromagnetic repulsion mechanism including the number of layers of the static repulsion coil and the dynamic repulsion coil, the coil height, the outer diameter, the single turn thickness and the total number of double-layer turns, and designing the electrical parameters of the electromagnetic repulsion mechanism based on the discharge mode of the vacuum arc: S101, calculate the electromagnetic repulsion between the static repulsion coil and the dynamic repulsion coil according to the following formula : , In the above formula, is the driving current, which is the fault current of the system to be tested; is the induced current of the dynamic repulsion coil; Represents the mutual inductance between the static repulsion coil and the dynamic repulsion coil; Indicates the distance between the static repulsion coil and the dynamic repulsion coil; S102, combining the electromagnetic repulsion between the static repulsion coil and the dynamic repulsion coil , calculate the acceleration a of the dynamic repulsion coil according to the following formula: , In the above formula, is the electromagnetic repulsion between the static repulsion coil and the dynamic repulsion coil, Indicates the resistance encountered by the movable part of the quick switch during operation; Indicates the mass of the movable part of the quick switch; S103, establishing a two-dimensional axisymmetric finite element simulation model of the electromagnetic repulsion mechanism: , In the above formula, represents the Hamiltonian operator; It indicates the magnetic field strength at a certain point of the dynamic repulsion coil; It represents the current density at that point of the dynamic repulsion coil; It represents the magnetic flux density at a point of the dynamic repulsion coil; Represents the vector magnetic potential at a point on the dynamic repulsion coil; represents the conductivity of the dynamic repulsion coil; It indicates the electric field strength at a certain point of the dynamic repulsion coil; It indicates the velocity of charge movement at a certain point in the kinetic repulsion coil; represents the conduction current density in the dynamic repulsion coil; Indicates the number of turns of the dynamic repulsion coil; Represents the single-turn current of the dynamic repulsion coil; Represents the cross-sectional area of ​​the dynamic repulsion coil; S104, using the steady-state magnetic field module of the simulation software to calculate the electromagnetic repulsion force exerted on the dynamic repulsion coil of the electromagnetic repulsion mechanism: , In the above formula, Indicates the electromagnetic repulsion force on the dynamic repulsion coil; according to the electromagnetic repulsion force between the static repulsion coil and the dynamic repulsion coil Verify the accuracy of the simulation software calculation. If the electromagnetic repulsion between the static repulsion coil and the dynamic repulsion coil , the electromagnetic repulsion force on the dynamic repulsion coil If they are equal, jump to the next step; S105, calculate the number of turns of the dynamic repulsion coil and the static repulsion coil:

[0012]

[0013] In the above formula, is the number of turns of the dynamic repulsion coil; is the outer diameter of the dynamic repulsion coil and the static repulsion coil; is the inner diameter of the dynamic repulsion coil and the static repulsion coil; is the thickness of the dynamic repulsion coil; is the number of turns of the static repulsion coil; is the thickness of the static repulsion coil; S106, under the premise that the average opening speed at the initial 75% opening distance is 1.8±0.2m / s, the current sensors of different coil layers, outer diameters, single turn thicknesses, and single turn heights of the dynamic repulsion coil and the static repulsion coil are simulated for different vacuum arc discharge modes, and the simulation results take the minimum capacity as the design goal to determine the optimal electrical parameters of the electromagnetic repulsion mechanism, including the number of layers, coil height, outer diameter, single turn thickness, and total number of double-layer turns of the static repulsion coil and the dynamic repulsion coil.

[0014] Optionally, the method further includes designing electrical parameters of the electromagnetic holding mechanism based on the set electromagnetic suction force, wherein the electrical parameters of the electromagnetic holding mechanism include an air gap width between the housing and the armature: S201, assuming that the air gap magnetic field between the housing of the electromagnetic holding mechanism and the armature is uniform, determine the function expression for calculating the electromagnetic attraction force of the electromagnetic holding mechanism as shown in the following formula: , In the above formula, It is the electromagnetic attraction between the shell of the electromagnetic holding mechanism and the magnetic pole of the armature. is the effective surface area of ​​the electromagnetic holding mechanism housing and the armature magnetic pole, is the magnetic induction intensity of the shell of the electromagnetic holding mechanism and the magnetic pole surface of the armature; is the vacuum permeability; S202, setting the magnetic induction intensity of the magnetic pole surface The relationship between the electromagnetic attraction force and the width of the air gap between the housing and the armature is proportional to the width of the air gap. The relationship between the electromagnetic attraction force and the width of the air gap between the housing and the armature is drawn using finite element simulation software in combination with the function expression for calculating the electromagnetic attraction force of the electromagnetic holding mechanism. S203, determining the width of the air gap between the housing and the armature based on the relationship curve between the electromagnetic attraction and the width of the air gap between the housing and the armature and the set electromagnetic attraction value , and the air gap width between the housing and the armature Not greater than the preset threshold.

[0015] Optionally, the method further includes designing electrical parameters of a first current transformer based on the set driving current and driving voltage, wherein the electrical parameters of the first current transformer include a core cross-sectional area: S301, determining a function expression for calculating the secondary side voltage of the first current transformer as shown in the following formula: , In the above formula, is the secondary side voltage of the first current transformer; The resistance encountered by the movable part during the rapid opening and closing process; is the number of turns on the secondary side of the first current transformer; is the maximum magnetic flux density allowed in the core of the first current transformer; is the core cross-sectional area of ​​the first current transformer; S302, determining a function expression for calculating the capacity of the first current transformer as shown in the following formula: , In the above formula, is the capacity of the first current transformer; is the secondary current of the first current transformer; is the primary side current of the first current transformer; is the number of primary turns of the first current transformer; S303: The primary side current of the first current transformer , the transformation ratio of the primary coil and the secondary coil, the secondary current , the capacity of the first current transformer , the maximum magnetic flux density allowed in the core of the first current transformer , the number of primary turns of the first current transformer , the number of turns on the secondary side of the first current transformer Substitute the function expression for calculating the capacity of the first current transformer into the formula to obtain the core cross-sectional area of ​​the first current transformer. .

[0016] In addition, the present invention also provides a control method for the aforementioned short-circuit current self-driven fast switch, comprising the following steps: When the system under test operates normally, the armature of the vacuum interrupter is closed, and the current flows through the vacuum interrupter to bypass the current-limiting reactor; When a short-circuit fault occurs in the measured system and the primary-side fault current of the first current transformer or the second current transformer is less than the set threshold, the bidirectional thyristor of the electromagnetic repulsion mechanism remains in a closed state, the armature of the vacuum arc chamber is closed, and the current-limiting reactor is bypassed; when a short-circuit fault occurs in the measured system and the primary-side fault current of the first current transformer or the second current transformer is greater than or equal to the set threshold, the controller controls the bidirectional thyristor of the electromagnetic repulsion mechanism to be disconnected, the static repulsion coil and the dynamic repulsion coil of the electromagnetic repulsion mechanism pass current, the electromagnetic repulsion mechanism generates electromagnetic repulsion, drives the armature of the vacuum arc chamber to separate, and thus puts the current-limiting reactor into the measured system; at the same time, if the primary-side coil current of the electromagnetic holding mechanism reaches the set threshold, the current value is reduced by the secondary coil and then coupled to the rectifier circuit, the driving coil is energized, and electromagnetic attraction is generated according to the principle of electromagnetic induction, attracting the armature of the vacuum arc chamber to remain in a disconnected state, and the current-limiting reactor is continuously put into use; When the short-circuit fault of the system under test is eliminated, the fault current disappears, the primary coil current of the electromagnetic holding mechanism decreases, the electromagnetic attraction decreases, the armature of the vacuum interrupter loses attraction and returns to the closed state, continuing to wait for the next fault to occur.

[0017] Compared with the prior art, the present invention mainly has the following beneficial effects: 1. No need to charge, it can restore to the non-current limiting state within tens of milliseconds after the fault is removed, and be ready to act again. If the system has a short circuit fault again or the relay protection is reclosed, as long as the fault current exceeds the set threshold, it can act multiple times in a short time; 2. Since the driving current comes directly from the system fault current, the current limiting reactor can act immediately in any case when a system short circuit fault occurs; 3. The energy storage capacitor and energy supply equipment are eliminated, the structure is relatively simple, the installation cost is low, the space occupied is small, and modular design can be realized, which has the advantages of short construction period and flexible configuration. When the short-circuit capacity of the system may be further improved, the number of current limiting units can be increased to meet future current limiting needs; at the same time, since it does not rely on external power supply, the cost of insulation to the ground is very low, especially when installed in ultra-high voltage power grids such as 500kV, it has great cost advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 4 is an equivalent circuit diagram of a short-circuit current self-driven fast switch in an embodiment of the present invention.

[0019] Figure 2Schematic diagram of the electromagnetic holding mechanism in an embodiment of the present invention.

[0020] Figure 3 Graph showing the relationship between the electromagnetic attraction force and the air gap width of the electromagnetic holding mechanism in an embodiment of the present invention.

[0021] Figure 4 Schematic diagram of the electromagnetic repulsion structure in an embodiment of the present invention.

[0022] Figure 5 Schematic diagram of the simulation of a short-circuit current self-driven fast switch in an embodiment of the present invention.

[0023] Legend: 1. Vacuum interrupter; 11. Armature; 2. Magnetic holding mechanism; 21. Second current transformer; 22. Rectification circuit; 23. Driving coil; 24. Housing; 3. Electromagnetic repulsion mechanism; 31. First current transformer; 32. Static repulsion coil; 33. Dynamic repulsion coil; 34. Bidirectional thyristor. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0025] It should be noted that the terms "include", "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0026] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings. In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0027] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. like Figure 1 As shown, the short-circuit current self-driven fast switch of this embodiment includes a vacuum interrupter 1 connected in parallel to the system under test, an electromagnetic holding mechanism 2, an electromagnetic repulsion mechanism 3 and a controller. The vacuum interrupter 1 is connected to the system under test (in Figure 1 In the equivalent circuit shown in FIG. 1 , the system under test is equivalent to a circuit formed by an equivalent power source, an impedance and a current-limiting reactor connected in parallel; Figure 2 As shown, the electromagnetic holding mechanism 2 includes a second current transformer 21 coupled to the measured system on the primary side, a rectifier circuit 22 connected in series with the secondary side of the second current transformer 21, and a drive coil 23 connected in series with the rectifier circuit 22, the drive coil 23 is aligned with the armature 11 of the vacuum interrupter 1, and there is an air gap between the armature 11 and the drive coil 23, and the drive coil 23 is placed inside a shell 24 of ferromagnetic material; the electromagnetic repulsion mechanism 3 is aligned with the armature 11 of the vacuum interrupter 1, and the electromagnetic repulsion mechanism 3 includes a first side coupled to the measured system The first current transformer 31, the static repulsion coil 32, the dynamic repulsion coil 33 and the bidirectional thyristor 34, the static repulsion coil 32 is coupled to the secondary side of the first current transformer 31, the dynamic repulsion coil 33 is coupled to the static repulsion coil 32, the dynamic repulsion coil 33 is connected in series with the bidirectional thyristor 34, the bidirectional thyristor 34 is electrically connected to the output end of the controller, and the input end of the controller is electrically connected to the first current transformer 31, thereby realizing the use of the first current transformer 31 to provide repulsion force for driving the dynamic repulsion coil 33 in the electromagnetic repulsion mechanism 3.

[0028] like Figure 1 As shown, the vacuum interrupter 1 in this embodiment includes a switch circuit and a resistor-capacitor circuit connected in parallel, the armature 11 is fixed on the movable arm of the switch on the switch circuit, and the resistor-capacitor circuit includes a resistor and a capacitor connected in series.

[0029] As an optional implementation, the number of turns of the primary side coil of the second current transformer 21 in this embodiment is 1 turn, and the transformation ratio is 1500:1. The second current transformer 21 is used to provide electromagnetic attraction to keep the armature 11 of the vacuum interrupter 1 in the open state, so its transformation ratio is 1500:1. The short-circuit current self-driven fast switch of this embodiment needs to consider the minimum short-circuit current. The first current transformer 31 provides the repulsive force to drive the dynamic repulsion coil 33 in the electromagnetic repulsion mechanism 3 to act, and the short-circuit current is set to 3.68kA, and the secondary side current is calculated according to the transformation ratio to be 184A.

[0030] As an optional embodiment, the static repulsion coil 32 in this embodiment is made of copper, and the dynamic repulsion coil 33 is made of aluminum. As an optional embodiment, the static repulsion coil 32 and the dynamic repulsion coil 33 in this embodiment are both double-layer coils. As an optional embodiment, the double-layer coil in this embodiment has a coil height of 8 mm, an outer diameter of 250 mm, a single-turn thickness of 0.84 mm, and a total number of double-layer turns of 212 turns.

[0031] In addition, this embodiment also provides a design method for the aforementioned short-circuit current self-driven fast switch, including determining the electrical parameters of the electromagnetic repulsion mechanism 3, including the number of layers, coil height, outer diameter, single turn thickness, and total number of double-layer turns of the static repulsion coil 32 and the dynamic repulsion coil 33, and designing the electrical parameters of the electromagnetic repulsion mechanism 3 based on the discharge mode of the vacuum arc: S101, calculate the electromagnetic repulsion between the static repulsion coil 32 and the dynamic repulsion coil 33 according to the following formula : , In the above formula, is the driving current, which is the fault current of the system to be tested; is the induced current of the dynamic repulsion coil 33; represents the mutual inductance between the static repulsion coil 32 and the dynamic repulsion coil 33; represents the distance between the static repulsion coil 32 and the dynamic repulsion coil 33; S102, combining the electromagnetic repulsion between the static repulsion coil 32 and the dynamic repulsion coil 33 , calculate the acceleration a of the dynamic repulsion coil 33 according to the following formula: , In the above formula, is the electromagnetic repulsion between the static repulsion coil 32 and the dynamic repulsion coil 33, Indicates the resistance encountered by the movable part of the quick switch during operation; represents the mass of the movable part of the fast switch; in this embodiment, the mass of the movable part of the fast switch mainly includes the mass of the dynamic repulsion coil 33, the mass of the armature 11 and the mass of the moving part of the vacuum interrupter 1; S103, establishing a two-dimensional axisymmetric finite element simulation model of the electromagnetic repulsion mechanism 3: , In the above formula, represents the Hamiltonian operator; represents the magnetic field strength at a certain point of the dynamic repulsion coil 33; represents the current density at this point of the dynamic repulsion coil 33; represents the magnetic flux density at a certain point of the dynamic repulsion coil 33; Represents the vector magnetic potential at a point at the dynamic repulsion coil 33; represents the conductivity of the dynamic repulsion coil 33; represents the electric field strength at a certain point of the dynamic repulsion coil 33; represents the velocity of charge movement at a point at the dynamic repulsion coil 33; represents the conduction current density in the dynamic repulsion coil 33; Indicates the number of turns of the dynamic repulsion coil 33; represents a single-turn current of the dynamic repulsion coil 33; represents the cross-sectional area of ​​the dynamic repulsion coil 33; S104, using a steady-state magnetic field module of a simulation software (such as COMSOL simulation software, etc.) to calculate the electromagnetic repulsion force exerted on the dynamic repulsion coil 33 of the electromagnetic repulsion mechanism 3: , In the above formula, Indicates the electromagnetic repulsion force of the dynamic repulsion coil 33; according to the electromagnetic repulsion force between the static repulsion coil 32 and the dynamic repulsion coil 33 Verify the accuracy of the simulation software calculation. If the electromagnetic repulsion between the static repulsion coil 32 and the dynamic repulsion coil 33 , the electromagnetic repulsion force on the dynamic repulsion coil 33 If they are equal, jump to the next step; S105, calculating the number of turns of the dynamic repulsion coil 33 and the static repulsion coil 32:

[0032]

[0033] In the above formula, is the number of turns of the dynamic repulsion coil 33; is the outer diameter of the dynamic repulsion coil 33 and the static repulsion coil 32; is the inner diameter of the dynamic repulsion coil 33 and the static repulsion coil 32; is the thickness of the dynamic repulsion coil 33; is the number of turns of the static repulsion coil 32; is the thickness of the static repulsion coil 32, such as Figure 4 As shown, wherein a is epoxy resin; S106, under the premise that the average opening speed at the initial 75% opening distance is 1.8±0.2m / s, for different vacuum arc discharge modes, the current sensors of the number of layers, outer diameter, single turn thickness, and single turn height of the dynamic repulsion coil 33 and the static repulsion coil 32 are simulated, and the simulation results are designed with the minimum capacity as the design target, so as to determine the optimal electrical parameters of the electromagnetic repulsion mechanism 3, including the number of layers, coil height, outer diameter, single turn thickness, and total number of double-layer turns of the static repulsion coil 32 and the dynamic repulsion coil 33. Among them, the discharge mode of the vacuum arc includes the following four main types: diffuse arc mode, dot spot mode, anode spot mode, and strong arc mode, among which the anode spot mode and dot spot mode appear at high current and long opening distance, at which time the armature is severely ablated, and the probability of breaking the short-circuit current is greatly reduced. And when the rapid switch opening speed is too fast, it is possible that there is already a large opening distance when the fault current limiting reaches the peak, and the conditions of large current and long opening distance are met at the same time, which is not conducive to the opening of the vacuum switch. The strong arc mode occurs when the armature opening distance is small, which will cause a certain amount of ablation on the armature, generating metal droplets or metal vapor. In this embodiment, simulations are performed on coils with single-layer and double-layer structures, and the opening speed and current transformer capacity under the single-layer coil structure are shown in Table 1, and the opening speed and current transformer capacity under the double-layer coil structure are shown in Table 2.

[0034] Table 1 Opening speed and current transformer capacity under single-layer coil structure

[0035] Referring to Table 1, according to the simulation results of the single-layer coil, at similar opening speeds, the current transformer capacity is smallest when the coil height is 14mm and the outer diameter is 250mm-300mm.

[0036] Table 2 Opening speed and current transformer capacity of self-driven fast switch under double-layer coil structure

[0037] Refer to Table 2. According to the simulation results of the double-layer coil, at a similar opening speed, the current transformer capacity is the smallest when the coil height is 8mm and the outer diameter is about 250mm. And the double-layer coil structure is better than the single-layer coil. This structure is the optimal structure of the electromagnetic repulsion mechanism. Finally, the number of layers of the static repulsion coil 32 and the dynamic repulsion coil 33 obtained in this embodiment is double-layer, the height of the double-layer coil is 8mm, the outer diameter is 250mm, the thickness of a single turn of the coil is 0.84mm, and the total number of double-layer turns is 212. The thermal diagram of the simulation results of the double-layer coil under this parameter is as follows: Figure 5 shown.

[0038] In addition, the design method of this embodiment also includes designing electrical parameters of the electromagnetic holding mechanism 2 based on the set electromagnetic attraction force. The electrical parameters of the electromagnetic holding mechanism 2 include the air gap width between the housing 24 and the armature 11: S201, according to Maxwell's suction formula, when the air gap between the drive coil and the armature is small, it is approximately considered that the air gap magnetic field is uniform. Therefore, it is assumed that the air gap magnetic field between the housing 24 of the electromagnetic holding mechanism 2 and the armature 11 is uniform, and the function expression for calculating the electromagnetic suction force of the electromagnetic holding mechanism 2 is determined as shown in the following formula: , In the above formula, is the electromagnetic attraction between the housing 24 of the electromagnetic holding mechanism 2 and the magnetic poles of the armature 11, is the effective surface area of ​​the magnetic poles of the housing 24 of the electromagnetic holding mechanism 2 and the armature 11, is the magnetic induction intensity between the housing 24 of the electromagnetic holding mechanism 2 and the magnetic pole surface of the armature 11; is the vacuum magnetic permeability; the electromagnetic attraction is proportional to the square of the magnetic induction intensity on the magnetic pole surface, that is, the magnetic potential generated in the coil F m Under the condition of no change, the magnetic resistance of the magnetic circuit R m The higher the magnetic flux φ The smaller the magnetic field intensity on the magnetic pole surface is, the smaller the magnetic field intensity is. B In the magnetic circuit, the air gap reluctance is much greater than the ferromagnetic material reluctance, so the magnetic induction intensity on the pole surface is B Mainly affected by air gap d Air Gap d When the magnetic resistance decreases, R m Decrease, the magnetic induction intensity on the pole surface B Increase, electromagnetic attraction F Increase; S202, setting the magnetic induction intensity of the magnetic pole surface The relationship between the electromagnetic attraction and the air gap width between the housing 24 and the armature 11 is proportional to the air gap width. The relationship between the electromagnetic attraction and the air gap width between the housing 24 and the armature 11 is plotted using finite element simulation software in combination with the function expression for calculating the electromagnetic attraction of the electromagnetic holding mechanism 2, as shown in FIG. Figure 3 As shown; S203, determining the width of the air gap between the housing 24 and the armature 11 based on the relationship curve between the drawn electromagnetic attraction and the width of the air gap between the housing 24 and the armature 11 and the set electromagnetic attraction value , and the air gap width between the housing 24 and the armature 11 Not greater than the preset threshold. Figure 3 It can be seen that when the air gap width d increases from the minimum value, the electromagnetic suction force drops sharply. Therefore, the electromagnetic holding mechanism only works when the distance between the electromagnet and the armature is very close, that is, when the armature opening distance of the fast switch is large; when the air gap width d is large, the electromagnetic suction force generated by the electromagnetic holding mechanism is very small. When the air gap width d is greater than 10mm, it almost does not work. This characteristic of the electromagnetic holding mechanism can enable the self-driven fast switch to achieve the functions of opening and holding and automatic recovery. Therefore, the air gap width d in step S24 is not greater than 10mm.

[0039] In addition, the design method of this embodiment also includes designing electrical parameters of the first current transformer 31 based on the set driving current and driving voltage, and the electrical parameters of the first current transformer 31 include the core cross-sectional area: S301, determine the function expression for calculating the secondary side voltage of the first current transformer 31 as shown in the following formula: , In the above formula, is the secondary side voltage of the first current transformer 31; The resistance encountered by the movable part during the rapid opening and closing process; is the number of turns on the secondary side of the first current transformer 31; is the maximum magnetic flux density allowed in the core of the first current transformer 31; is the core cross-sectional area of ​​the first current transformer 31; S302, determining a function expression for calculating the capacity of the first current transformer 31 as shown in the following formula: , In the above formula, is the capacity of the first current transformer 31; is the secondary side current of the first current transformer 31; is the primary side current of the first current transformer 31; is the number of primary turns of the first current transformer 31; S303: The primary side current of the first current transformer 31 , the transformation ratio of the primary coil and the secondary coil, the secondary current , the capacity of the first current transformer 31 , the maximum magnetic flux density allowed in the core of the first current transformer 31 , the number of turns on the primary side of the first current transformer 31 , the number of turns on the secondary side of the first current transformer 31 Substitute into the function expression for calculating the capacity of the first current transformer 31, so as to obtain the core cross-sectional area of ​​the first current transformer 31 Specifically, in this embodiment, the primary side current of the first current transformer is =3.68kA, the transformation ratio of the primary coil to the secondary coil is 1:20, and the secondary current =184A, capacity =47kVA, =0.2T, =6, =120, substitute into the function expression for calculating the capacity of the first current transformer 31, and obtain =0.05mm 2 .

[0040] This embodiment also provides a control method for the aforementioned short-circuit current self-driven fast switch, comprising the following steps: When the system under test operates normally, the armature 11 of the vacuum interrupter 1 is closed, and the current flows through the vacuum interrupter 1 to bypass the current-limiting reactor; When a short circuit fault occurs in the measured system and the primary side fault current of the first current transformer 31 or the second current transformer 21 is less than the set threshold, the bidirectional thyristor 34 of the electromagnetic repulsion mechanism 3 remains in a closed state, the armature 11 of the vacuum interrupter 1 is closed, and the current limiting reactor is bypassed; when a short circuit fault occurs in the measured system and the primary side fault current of the first current transformer 31 or the second current transformer 21 is greater than or equal to the set threshold, the controller controls the bidirectional thyristor 34 of the electromagnetic repulsion mechanism 3 to be disconnected, and the electromagnetic repulsion mechanism 3 is closed. The static repulsion coil 32 and the dynamic repulsion coil 33 of the mechanism 3 pass current, and the electromagnetic repulsion mechanism 3 generates electromagnetic repulsion, driving the armature 11 of the vacuum interrupter 1 to separate, thereby putting the current limiting reactor into the measured system; at the same time, if the primary side coil current of the electromagnetic holding mechanism 2 reaches the set threshold value, the current value is reduced by the secondary coil and then coupled to the rectifier circuit 22, and the driving coil 23 is energized, and electromagnetic attraction is generated according to the principle of electromagnetic induction, attracting the armature 11 of the vacuum interrupter 1 to remain in the disconnected state, and the current limiting reactor is continuously put into use; When the short-circuit fault of the measured system is eliminated, the fault current disappears, the primary coil current of the electromagnetic holding mechanism 2 decreases, the electromagnetic attraction decreases, the armature 11 of the vacuum interrupter 1 loses attraction and returns to the closed state, and continues to wait for the next fault to occur.

[0041] To sum up, the short-circuit current self-driven fast switch, design method and control method based on the current transformer in this embodiment can effectively utilize the fault current collected by the current sensor as the driving current. In any case, when a system short-circuit fault occurs, the current limiting reactor can be operated immediately and can be operated multiple times in a short time.

[0042] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application can take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the process Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0043] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A short-circuit current self-driven fast switch, characterized in that: The invention comprises a vacuum interrupter (1) connected in parallel to a system under test, an electromagnetic holding mechanism (2), an electromagnetic repulsion mechanism (3) and a controller, wherein the vacuum interrupter (1) is connected in parallel to a current limiting reactor connected to the system under test; the electromagnetic holding mechanism (2) comprises a second current transformer (21) coupled to the system under test on the primary side, a rectifier circuit (22) connected in series with the secondary side of the second current transformer (21), and a drive coil (23) connected in series with the rectifier circuit (22); the drive coil (23) is aligned with an armature (11) of the vacuum interrupter (1), and there is an air gap between the armature (11) and the drive coil (23); the drive coil (23) is placed in a housing (24) made of ferromagnetic material. ) inside; the electromagnetic repulsion mechanism (3) is aligned with the armature (11) of the vacuum interrupter (1), and the electromagnetic repulsion mechanism (3) comprises a first current transformer (31) coupled to the measured system on the primary side, a static repulsion coil (32), a dynamic repulsion coil (33) and a bidirectional thyristor (34), the static repulsion coil (32) is coupled to the secondary side of the first current transformer (31), the dynamic repulsion coil (33) is coupled to the static repulsion coil (32), the dynamic repulsion coil (33) is connected in series with the bidirectional thyristor (34), the bidirectional thyristor (34) is electrically connected to the output end of the controller, and the input end of the controller is electrically connected to the first current transformer (31).

2. The short-circuit current self-driven fast switch according to claim 1, characterized in that: The vacuum interrupter (1) comprises a switch circuit and a resistor-capacitor circuit connected in parallel, the armature (11) is fixed on a movable arm of a switch on the switch circuit, and the resistor-capacitor circuit comprises a resistor and a capacitor connected in series.

3. The short-circuit current self-driven fast switch according to claim 2, characterized in that: The number of turns of the primary side coil of the second current transformer (21) is 1 turn, and the transformation ratio is 1500:

1.

4. The short-circuit current self-driven fast switch according to claim 3, characterized in that: The material of the static repulsion coil (32) is copper, and the material of the dynamic repulsion coil (33) is aluminum.

5. The short-circuit current self-driven fast switch according to claim 4, characterized in that: The static repulsion coil (32) and the dynamic repulsion coil (33) are both double-layer coils.

6. The short-circuit current self-driven fast switch according to claim 5, characterized in that: The double-layer coil has a coil height of 8 mm, an outer diameter of 250 mm, a single-turn thickness of 0.84 mm, and a total number of double-layer turns of 212 turns.

7. A design method for a short-circuit current self-driven fast switch according to any one of claims 1 to 6, characterized in that: The method includes determining the electrical parameters of the electromagnetic repulsion mechanism (3), including the number of layers, coil height, outer diameter, single turn thickness, and total number of double turns of the static repulsion coil (32) and the dynamic repulsion coil (33), and designing the electrical parameters of the electromagnetic repulsion mechanism (3) based on the discharge mode of the vacuum arc: S101, calculate the electromagnetic repulsion between the static repulsion coil (32) and the dynamic repulsion coil (33) according to the following formula: : ， In the above formula, is the driving current, which is the fault current of the system to be tested; is the induced current of the dynamic repulsion coil (33); represents the mutual inductance between the static repulsion coil (32) and the dynamic repulsion coil (33); represents the distance between the static repulsion coil (32) and the dynamic repulsion coil (33); S102, combining the electromagnetic repulsion between the static repulsion coil (32) and the dynamic repulsion coil (33) , calculate the acceleration a of the dynamic repulsion coil (33) according to the following formula: ， In the above formula, is the electromagnetic repulsion force between the static repulsion coil (32) and the dynamic repulsion coil (33), Indicates the resistance encountered by the movable part of the quick switch during operation; Indicates the mass of the movable part of the quick switch; S103, establishing a two-dimensional axisymmetric finite element simulation model of the electromagnetic repulsion mechanism (3): ， In the above formula, represents the Hamiltonian operator; represents the magnetic field strength at a certain point of the dynamic repulsion coil (33); represents the current density at that point of the dynamic repulsion coil (33); represents the magnetic flux density at a point of the dynamic repulsion coil (33); represents the vector magnetic potential at a point of the dynamic repulsion coil (33); represents the conductivity of the dynamic repulsion coil (33); represents the electric field strength at a certain point of the dynamic repulsion coil (33); represents the velocity of the charge at a point in the dynamic repulsion coil (33); represents the conduction current density in the dynamic repulsion coil (33); represents the number of turns of the dynamic repulsion coil (33); represents a single-turn current of the dynamic repulsion coil (33); represents the cross-sectional area of ​​the dynamic repulsion coil (33); S104, using the steady-state magnetic field module of the simulation software to calculate the electromagnetic repulsion force exerted on the dynamic repulsion coil (33) of the electromagnetic repulsion mechanism (3): ， In the above formula, represents the electromagnetic repulsion force exerted on the dynamic repulsion coil (33); according to the electromagnetic repulsion force between the static repulsion coil (32) and the dynamic repulsion coil (33) Verify the accuracy of the simulation software calculation. If the electromagnetic repulsion between the static repulsion coil (32) and the dynamic repulsion coil (33) , the electromagnetic repulsion force on the dynamic repulsion coil (33) If they are equal, jump to the next step; S105, calculating the number of turns of the dynamic repulsion coil (33) and the static repulsion coil (32): In the above formula, is the number of turns of the dynamic repulsion coil (33); is the outer diameter of the dynamic repulsion coil (33) and the static repulsion coil (32); is the inner diameter of the dynamic repulsion coil (33) and the static repulsion coil (32); is the thickness of the dynamic repulsion coil (33); is the number of turns of the static repulsion coil (32); is the thickness of the static repulsion coil (32); S106, under the premise that the average opening speed at the initial 75% opening distance is 1.8±0.2 m / s, for different vacuum arc discharge modes, the current sensors of different coil numbers, outer diameters, single turn thicknesses, and single turn heights of the dynamic repulsion coil (33) and the static repulsion coil (32) are simulated, and the simulation results are designed with the minimum capacity as the design goal, so as to determine the optimal electrical parameters of the electromagnetic repulsion mechanism (3), including the number of layers, coil height, outer diameter, single turn thickness, and total number of double-layer turns of the static repulsion coil (32) and the dynamic repulsion coil (33).

8. The design method of the short-circuit current self-driven fast switch according to claim 7, characterized in that: The method also includes designing electrical parameters of the electromagnetic holding mechanism (2) based on the set electromagnetic suction force, wherein the electrical parameters of the electromagnetic holding mechanism (2) include an air gap width between the housing (24) and the armature (11): S201, assuming that the air gap magnetic field between the housing (24) of the electromagnetic holding mechanism (2) and the armature (11) is uniform, determine the functional expression for calculating the electromagnetic attraction force of the electromagnetic holding mechanism (2) as shown in the following formula: ， In the above formula, is the electromagnetic attraction between the housing (24) of the electromagnetic holding mechanism (2) and the magnetic poles of the armature (11), is the effective surface area of ​​the magnetic poles of the housing (24) of the electromagnetic holding mechanism (2) and the armature (11), is the magnetic induction intensity of the housing (24) of the electromagnetic holding mechanism (2) and the magnetic pole surface of the armature (11); is the vacuum permeability; S202, setting the magnetic induction intensity of the magnetic pole surface The electromagnetic attraction force of the electromagnetic holding mechanism (2) is proportional to the width of the air gap, and a curve diagram of the relationship between the electromagnetic attraction force and the width of the air gap between the housing (24) and the armature (11) is drawn using finite element simulation software in combination with a function expression for calculating the electromagnetic attraction force of the electromagnetic holding mechanism (2); S203, determining the width of the air gap between the housing (24) and the armature (11) based on a plotted relationship curve between the electromagnetic attraction force and the width of the air gap between the housing (24) and the armature (11) and a set electromagnetic attraction force value , and the air gap width between the housing (24) and the armature (11) Not greater than the preset threshold.

9. The design method of the short-circuit current self-driven fast switch according to claim 8, characterized in that: The method also includes designing electrical parameters of a first current transformer (31) based on the set driving current and driving voltage, wherein the electrical parameters of the first current transformer (31) include a core cross-sectional area: S301, determining a function expression for calculating the secondary side voltage of the first current transformer (31) as shown in the following formula: ， In the above formula, is the secondary side voltage of the first current transformer (31); The resistance encountered by the movable part during the rapid opening and closing process; is the number of turns on the secondary side of the first current transformer (31); is the maximum magnetic flux density allowed in the iron core of the first current transformer (31); is the core cross-sectional area of ​​the first current transformer (31); S302, determining a function expression for calculating the capacity of the first current transformer (31) as shown in the following formula: ， In the above formula, is the capacity of the first current transformer (31); is the secondary side current of the first current transformer (31); is the primary side current of the first current transformer (31); is the number of turns on the primary side of the first current transformer (31); S303, the primary side current of the first current transformer (31) , the transformation ratio of the primary coil and the secondary coil, the secondary current , the capacity of the first current transformer (31) , the maximum magnetic flux density allowed in the core of the first current transformer (31) , the number of turns on the primary side of the first current transformer (31) , the number of turns on the secondary side of the first current transformer (31) Substitute into the function expression for calculating the capacity of the first current transformer (31), thereby obtaining the core cross-sectional area of ​​the first current transformer (31): .

10. A control method for a short-circuit current self-driven fast switch according to any one of claims 1 to 6, characterized in that: The steps include: When the system under test operates normally, the armature (11) of the vacuum interrupter (1) is closed, and current flows through the vacuum interrupter (1) to bypass the current-limiting reactor; When a short circuit fault occurs in the system under test and the primary side fault current of the first current transformer (31) or the second current transformer (21) is less than a set threshold value, the bidirectional thyristor (34) of the electromagnetic repulsion mechanism (3) remains in a closed state, the armature (11) of the vacuum interrupter (1) is closed, and the current limiting reactor is bypassed; when a short circuit fault occurs in the system under test and the primary side fault current of the first current transformer (31) or the second current transformer (21) is greater than or equal to the set threshold value, the controller controls the bidirectional thyristor (34) of the electromagnetic repulsion mechanism (3) to be disconnected, and the electromagnetic repulsion mechanism (3) is closed. When current passes through the static repulsion coil (32) and the dynamic repulsion coil (33) of the mechanism (3), the electromagnetic repulsion mechanism (3) generates electromagnetic repulsion, driving the armature (11) of the vacuum interrupter (1) to separate, thereby putting the current limiting reactor into the measured system; at the same time, if the primary coil current of the electromagnetic holding mechanism (2) reaches a set threshold value, the current value is reduced by the secondary coil and then coupled to the rectifier circuit (22), the driving coil (23) is energized, and electromagnetic suction is generated according to the principle of electromagnetic induction, attracting the armature (11) of the vacuum interrupter (1) to remain in a disconnected state, and the current limiting reactor is continuously put into operation; When the short-circuit fault of the system under test is eliminated and the fault current disappears, the primary coil current of the electromagnetic holding mechanism (2) decreases, the electromagnetic attraction decreases, and the armature (11) of the vacuum interrupter (1) loses the attraction and returns to the closed state, and continues to wait for the next fault to occur.

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