Switch closing holding device and vacuum switch

Abstract

The application relates to a switch closing and holding device and a vacuum switch. The device comprises a piezoelectric actuator, a power taking coil mounted on a main circuit of the vacuum switch, and first and second parallel friction surfaces; wherein the input end of the piezoelectric actuator is connected with the output end of the power taking coil, the output end of the piezoelectric actuator is connected with the first friction surface, and the second friction surface is fixed on a transmission rod of an operating mechanism of the vacuum switch; the power taking coil is used for inducting a current signal on the main circuit and outputting a corresponding voltage signal to the piezoelectric actuator according to the current signal; the piezoelectric actuator is used for applying a driving force to the first friction surface when the change amplitude of the voltage signal is greater than a preset threshold; and the driving force is used for driving the first and second friction surfaces to generate a friction force, so that the vacuum switch can be kept in a closing state under a short circuit fault. The device can ensure that the switch maintains the closing state during the fault.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vacuum switch structure, in particular to a switch closing holding device and a vacuum switch. BACKGROUND

[0002] A vacuum switch, especially a vacuum circuit breaker, is one of the most widely used switching devices in medium and high voltage power systems. Its core function is to safely turn on or turn off the circuit under normal or fault (such as short circuit) conditions. Vacuum switch uses vacuum environment as insulation and arc extinguishing medium, has the advantages of strong arc extinguishing ability, small contact opening distance, long electrical life, small maintenance workload, etc. With the continuous improvement of power grid requirements for power supply reliability and power quality, higher requirements are put forward for the breaking speed of switching devices. Fast vacuum switch emerges as the times require, its goal is to complete the breaking operation in a very short time (usually within a few milliseconds) to quickly isolate the fault current, limit the release of fault energy, protect subsequent devices, and maintain system stability. The shorter the breaking time, the shorter the fault isolation time, and the better the stability of the power grid system. The breaking time of the current fast switch can be as low as 1ms or less, but further shortening the breaking time is limited by the closing holding force.

[0003] In order to provide stable and reliable closing holding force, the current mainstream vacuum switch mainly uses a holding mechanism based on contact spring or bistable spring, however, in this scheme, the closing holding force is always provided by a component (compressed spring or permanent magnet) in a high potential state during the entire closing period. Long-term mechanical stress can cause material fatigue, elastic potential decay, and mechanical wear, thereby reducing the mechanical reliability and service life of the entire operating mechanism. SUMMARY

[0004] Therefore, it is necessary to provide a switch closing holding device and a vacuum switch to solve the above technical problems.

[0005] In a first aspect, the present application provides a switch closing holding device, which is installed in a vacuum switch, and the device comprises: a piezoelectric actuator, a power taking coil installed on a main circuit of the vacuum switch, and a first friction surface and a second friction surface placed in parallel; wherein the input end of the piezoelectric actuator is connected with the output end of the power taking coil, the output end of the piezoelectric actuator is connected with the first friction surface, and the second friction surface is fixed on an operating mechanism transmission rod of the vacuum switch.

[0006] The power taking coil is used to induce a current signal on the main circuit, and output a corresponding voltage signal to the piezoelectric actuator according to the current signal;

[0007] The piezoelectric actuator is used to apply a driving force to the first friction surface when the detected voltage signal change amplitude is greater than a preset threshold; the driving force is used to drive the first friction surface and the second friction surface to generate friction, so that the vacuum switch remains closed under short-circuit fault.

[0008] In one embodiment, the device further includes a control module, wherein the output terminal of the energy harvesting coil and the input terminal of the piezoelectric actuator are connected through the control module;

[0009] The control module is used to process the voltage signal output by the energy harvesting coil and send the processed voltage signal to the piezoelectric actuator.

[0010] In one embodiment, the control module includes a rectifier and filter unit; the voltage signal is an AC voltage signal.

[0011] The rectifier and filter unit is connected to the output terminal of the energy harvesting coil and the input terminal of the piezoelectric actuator, respectively, and is used to convert the AC voltage signal into a DC voltage signal and send the DC voltage signal to the piezoelectric actuator.

[0012] In one embodiment, the control module further includes an electronic switch;

[0013] The electronic switch is installed at both ends of the piezoelectric actuator and is used to turn on when a tripping command is received, so that the piezoelectric actuator stops applying driving force to the first friction surface;

[0014] The tripping command is sent by the protection system of the vacuum switch when it determines that a fault needs to be cut off; when the piezoelectric actuator stops applying driving force to the first friction surface, the friction between the first friction surface and the second friction surface disappears, causing the vacuum switch to trip.

[0015] In one embodiment, the piezoelectric actuator is a piezoelectric ceramic stack structure.

[0016] In one embodiment, the second friction surface is fixed to the side of the non-motion path of the operating mechanism transmission rod.

[0017] In one embodiment, the magnitude of the frictional force is positively correlated with the signal strength of the current signal induced by the energy harvesting coil in the main circuit.

[0018] In one embodiment, at least one of the first and second friction surfaces is provided with a friction enhancement layer.

[0019] In one embodiment, the energy harvesting coil includes a toroidal iron core and an induction coil wound around the toroidal iron core;

[0020] The main circuit passes through the central through hole of the annular iron core.

[0021] Secondly, this application also provides a vacuum switch, wherein the vacuum switch is equipped with the switch closing and holding device provided in the first aspect.

[0022] The aforementioned switch closing and holding device and vacuum switch include a piezoelectric actuator, an energy harvesting coil mounted on the main circuit of the vacuum switch, and a first friction surface and a second friction surface placed in parallel. The input end of the piezoelectric actuator is connected to the output end of the energy harvesting coil, and the output end of the piezoelectric actuator is connected to the first friction surface. The second friction surface is fixed to the transmission rod of the operating mechanism of the vacuum switch. The energy harvesting coil is used to sense the current signal in the main circuit and output a corresponding voltage signal to the piezoelectric actuator according to the current signal. The piezoelectric actuator is used to apply a driving force to the first friction surface when the detected voltage signal change amplitude is greater than a preset threshold. The driving force is used to drive the first friction surface and the second friction surface to generate friction, so that the vacuum switch remains closed under short-circuit fault conditions. The energy harvesting coil directly senses the current signal of the main circuit of the vacuum switch, which can quickly capture the sudden change characteristics of the main circuit current during a short circuit. The energy harvesting coil drives the piezoelectric actuator, which applies normal pressure to the first friction surface, so that the first friction surface and the second friction surface generate friction. The friction locks the transmission rod of the operating mechanism, effectively preventing the electrodynamic force generated by the short circuit current from causing the switch to trip unexpectedly, and ensuring that the switch remains closed during a fault. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a structural diagram of the switch closing and holding device in one embodiment;

[0025] Figure 2 This is a structural diagram of the switch closing and holding device in another embodiment;

[0026] Figure 3 This is a detailed structural diagram of the switch closing and holding device in one embodiment. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application. In the description of this application, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0029] The serial numbers assigned to components in this application, such as "first" and "second," are merely for distinguishing the described objects and have no sequential or technical meaning. Unless otherwise specified, the term "connection" in this application includes both direct and indirect connections. It should be understood that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are used only for the convenience of describing this application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0030] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. In this application, the distinction between elements is not based on differences in name, but rather on differences in function.

[0031] In the design of vacuum switches, a crucial parameter is the "closing holding force." When the switch is closed, its moving and stationary contacts are in close contact. Once a large current (especially a short-circuit fault current) flows through the contacts, according to electrodynamic principles, a huge electrodynamic repulsive force is generated between the two parallel current-carrying conductors (contacts). The magnitude of this repulsive force is proportional to the square of the current flowing through it. If the closing holding force is insufficient to resist this repulsive force, the contacts will momentarily separate and immediately reclose as the current decreases; this process is called "contact bounce." Contact bounce can cause severe arc erosion and contact welding, greatly damaging the performance and lifespan of the vacuum interrupter, and may even lead to switch failure, causing grid instability and large-scale power outages. Therefore, all vacuum switches must be designed with sufficient closing holding force to ensure that the contacts maintain stable contact even when subjected to the maximum short-circuit current surge. To provide a stable and reliable closing holding force, most mainstream vacuum switches currently employ holding mechanisms based on contact springs or bistable springs. The contact spring solution is currently the most common approach, and its typical implementation is as follows: When the operating mechanism of the switch pushes the moving contact to the closed position via the drive linkage, it simultaneously compresses one or more strong closing holding springs (often called "overtravel springs"). After the contacts are fully engaged, the operating mechanism continues to move a short distance (called "overtravel"), further compressing the springs. Subsequently, a mechanical locking device (such as a pin, roller, or linkage mechanism) locks the operating mechanism in the current position. At this time, the compressed spring continuously applies a strong pressure to the moving contact through the mechanical transmission system; this pressure is the closing holding force. When opening is required, the trip unit (usually an electromagnet) is triggered, releasing the mechanical lock. The energy of the compressed spring and other opening mechanisms (such as the opening spring) work together to drive the contacts apart. This solution requires waiting for the trip unit to trigger and the contact spring to release during opening, with a typical opening time exceeding 10ms, which cannot meet the requirements for fast switching.

[0032] In the bistable spring scheme, the switch's drive system relies on a set of bistable springs to provide the closing and holding forces during operation. For example, in the closed position, the bistable springs provide a holding force in the closing direction to maintain the contacts closed. When opening is required, the opening device provides a sufficiently large driving force to further compress the bistable springs. Once the bistable springs have passed their dead point, they switch to providing a force in the opening direction. This force continues to be provided after the switch reaches the open position to keep it in that position. The advantage of this scheme is that it eliminates the need to wait for the contact springs to release during opening, significantly reducing the opening time to 1-3 ms. However, it still requires the opening force provided by the opening device to exceed the closing holding force provided by the bistable springs before the opening operation can be completed, limiting further reduction in opening time. It also results in the opening device requiring a huge driving force to overcome the closing holding force, significantly increasing operating power, increasing the size and cost of the operating mechanism, and reducing reliability.

[0033] Furthermore, in some vacuum circuit breakers driven by permanent magnet mechanisms, the permanent magnet provides a strong attractive force as the closing holding force, while a mechanical spring is used for energy storage and buffering. When opening, the permanent magnet needs to be demagnetized, and the typical demagnetization time is on the order of milliseconds, which also cannot meet the requirements for fast vacuum switching.

[0034] In summary, the existing solution relies on a single component (a compressed spring or permanent magnet) in a high potential energy state to provide the closing holding force throughout the entire closing process. This inherent characteristic leads to the following two insurmountable drawbacks:

[0035] 1. Limitation on further improvements in tripping speed: While the closing holding force ensures closing reliability, it also becomes a significant obstacle to overcome during tripping. After the tripping command is issued, the tripping drive mechanism must first output sufficient energy and force to counteract this powerful closing holding force before the moving contact can begin to separate. This "unlocking" and "reverse loading" process consumes valuable time and energy, constituting a major bottleneck in the rapid tripping response time, making it difficult to further compress the tripping time to its maximum potential.

[0036] 2. Limited Mechanical Reliability and Lifespan: Throughout the entire closing period of the switch (which may be over 99% of its lifespan), the closing holding spring and related latches and transmission components are continuously under high stress. Long-term mechanical stress leads to material fatigue, elastic potential energy decay, and mechanical wear, thereby reducing the mechanical reliability and lifespan of the entire operating mechanism. To ensure long-term reliability, these components must use high-performance materials and incorporate redundant designs, increasing manufacturing costs and complexity.

[0037] To address the aforementioned problems in the prior art, this application provides a switch closing and holding device, such as... Figure 1The diagram shown is a schematic representation of the switch closing and holding device provided in this embodiment of the application. The switch closing and holding device is installed in a vacuum switch and includes: a piezoelectric actuator 101, an energy harvesting coil 102 installed on the main circuit of the vacuum switch, and a first friction surface 103 and a second friction surface 104 placed in parallel. The input end of the piezoelectric actuator 101 is connected to the output end of the energy harvesting coil 102, and the output end of the piezoelectric actuator 101 is connected to the first friction surface 103. The second friction surface 104 is fixed to the transmission rod of the operating mechanism of the vacuum switch. The energy harvesting coil 102 is used to sense the current signal in the main circuit and output a corresponding voltage signal to the piezoelectric actuator 101 according to the current signal. The piezoelectric actuator 101 is used to apply a driving force to the first friction surface 103 when the detected voltage signal change amplitude is greater than a preset threshold. The driving force is used to drive the first friction surface and the second friction surface to generate friction, so that the vacuum switch remains closed under a short-circuit fault.

[0038] The vacuum switch can be a fast vacuum switch, which includes a main circuit, a vacuum interrupter chamber, and an operating mechanism transmission rod; the vacuum interrupter chamber is provided with a stationary contact and a moving contact connected to the operating mechanism transmission rod.

[0039] Piezoelectric actuators are typically stacked piezoelectric ceramics and exhibit the inverse piezoelectric effect, meaning they produce minute but precise displacements and large output forces when a voltage is applied. The piezoelectric actuator is mounted on a fixed support. The power harvesting coil is an electromagnetic induction component, consisting of a toroidal iron core and an induction coil wound around it; the main circuit passes through a central through-hole in the toroidal iron core. It is used for non-contact sensing of the main circuit current and outputs a voltage or current signal proportionally; it constitutes the system's sensor and energy source.

[0040] The first and second friction surfaces are mechanically locked components, employing a parallel planar structure. At least one of the friction surfaces has a friction-enhancing layer, such as reinforced rubber or ceramic matrix composites. The first friction surface is a movable component, rigidly connected to the output end of the piezoelectric actuator, and undergoes normal motion under driving force to compress the second friction surface and generate friction. The second friction surface is a fixed component, fixed to the side of the transmission rod of the operating mechanism that is not in motion.

[0041] It should be noted that under normal conditions, the piezoelectric actuator is unenergized and at its natural length, maintaining zero contact pressure or a very small preload pressure between the first and second friction surfaces. However, when a short-circuit fault occurs in the system, the current in the main circuit rises sharply to tens or even hundreds of kiloamperes within a very short time (usually less than 1 ms). With this surge in current, the output voltage of the power extraction coil also increases instantaneously and proportionally. This high-voltage signal is applied to both ends of the piezoelectric actuator. Due to the inverse piezoelectric effect, the piezoelectric actuator instantly elongates, pushing the first friction surface to press firmly against the second friction surface with tremendous pressure. This generates a strong static friction force between the two friction surfaces, reliably preventing contact bounce and separation, and ensuring the stability of the switch during short circuits. This is a completely passive, adaptive process with an extremely fast response speed (the response speed of piezoelectric ceramics is in the microsecond range).

[0042] In one embodiment, the magnitude of the frictional force is positively correlated with the signal strength of the current signal induced by the energy harvesting coil in the main circuit. The intensity of the current signal induced by the energy harvesting coil (such as the current amplitude) directly determines the amplitude of its output AC voltage signal. The more severe the short-circuit fault, the larger the short-circuit current in the main circuit, the higher the current signal strength, the more energy coupled by the energy harvesting coil, and the higher the amplitude of the output AC voltage. The output driving force of the piezoelectric actuator is positively correlated with the amplitude of the input DC voltage. Based on the piezoelectric effect, the higher the voltage, the greater the deformation of the piezoelectric ceramic, and the stronger the output mechanical driving force. The first friction surface is in contact with the second friction surface under the driving force of the piezoelectric actuator, and the normal force between them is positively correlated with the driving force. According to the friction formula, the maximum static friction force is approximately equal to the product of the normal force and the coefficient of friction, and the dynamic friction force is equal to the product of the normal force and the coefficient of friction. With a fixed coefficient of friction, the greater the normal force, the greater the frictional force generated. Different short-circuit faults have different severity levels, resulting in different electrodynamic forces. By employing a design where frictional force is positively correlated with current signal strength, the more severe the fault, the greater the frictional force automatically increases. This precisely counteracts the larger electrodynamic force, ensuring a stable closed state under various short-circuit scenarios and preventing locking failure due to insufficient friction. Furthermore, in cases of minor short-circuit faults or small current fluctuations, the frictional force decreases synchronously, eliminating the need for excessive driving force. This reduces the crushing wear on the first and second friction surfaces, while also preventing the piezoelectric actuator from bearing excessive loads for extended periods, reducing component fatigue wear, and extending the overall service life of the device.

[0043] The aforementioned switch-closing holding device includes a piezoelectric actuator, an energy harvesting coil mounted on the main circuit of the vacuum switch, and a first friction surface and a second friction surface placed in parallel. The input end of the piezoelectric actuator is connected to the output end of the energy harvesting coil, and the output end of the piezoelectric actuator is connected to the first friction surface. The second friction surface is fixed to the transmission rod of the operating mechanism of the vacuum switch. The energy harvesting coil is used to sense the current signal in the main circuit and output a corresponding voltage signal to the piezoelectric actuator according to the current signal. The piezoelectric actuator is used to apply a driving force to the first friction surface when the detected voltage signal change amplitude is greater than a preset threshold. The driving force is used to drive the first friction surface and the second friction surface to generate friction, so that the vacuum switch remains closed under a short-circuit fault. The energy harvesting coil directly senses the current signal of the main circuit of the vacuum switch, which can quickly capture the sudden change characteristics of the main circuit current during a short circuit. The energy harvesting coil drives the piezoelectric actuator, which applies normal pressure to the first friction surface, so that the first friction surface and the second friction surface generate friction. The friction locks the transmission rod of the operating mechanism, effectively preventing the electrodynamic force generated by the short circuit current from causing the switch to trip unexpectedly, and ensuring that the switch remains closed during a fault.

[0044] In one embodiment, in Figure 1 On the basis of, such as Figure 2 As shown, the switch closing and holding device also includes a control module 105. The output terminal of the energy harvesting coil and the input terminal of the piezoelectric actuator are connected through the control module 105. The control module is used to process the voltage signal output by the energy harvesting coil and send the processed voltage signal to the piezoelectric actuator. The control module is connected between the energy harvesting coil and the piezoelectric actuator. The voltage signal generated by the energy harvesting coil directly sensing the main circuit current may contain noise (such as grid harmonics, electromagnetic interference, etc.) or have waveform distortion. The control module processes the original signal through filtering, rectification, amplification, etc., to convert it into a stable and accurate voltage signal.

[0045] In addition, the control module includes a rectifier and filter unit; the voltage signal is an AC voltage signal; the rectifier and filter unit is connected to the output terminal of the energy harvesting coil and the input terminal of the piezoelectric actuator, respectively, to convert the AC voltage signal into a DC voltage signal and send the DC voltage signal to the piezoelectric actuator. The voltage signal output by the energy harvesting coil based on the principle of electromagnetic induction is an AC signal (which changes synchronously with the alternating characteristics of the main circuit current), while the piezoelectric actuator usually requires DC voltage to achieve controllable mechanical deformation, such as continuous output driving force. The rectifier unit converts the alternating AC voltage into a unidirectional pulsating DC voltage through a diode rectifier bridge (half-wave or full-wave rectification), making the voltage direction uniform and meeting the basic power supply requirements of the piezoelectric actuator. The rectified DC voltage has obvious pulsation, such as periodic waveform fluctuations. If directly input to the piezoelectric actuator, it may cause instability in its output driving force, such as fluctuating friction force, affecting the reliability of the closing and holding. The filtering unit typically uses capacitor filtering (such as electrolytic capacitors) or filtering circuits to absorb pulsating components through energy storage elements, converting pulsating DC into smooth and stable DC voltage, ensuring that the piezoelectric actuator obtains continuous and uniform electrical energy input, thereby outputting constant driving force, ensuring close contact between the first and second friction surfaces and stable friction force.

[0046] Furthermore, to ensure rapid tripping of the vacuum switch upon fault disconnection, in one embodiment, the control module also includes an electronic switch. The electronic switch is installed across the piezoelectric actuator and is used to turn on upon receiving a tripping command, causing the piezoelectric actuator to stop applying driving force to the first friction surface. The tripping command is sent by the vacuum switch's protection system when it determines that a fault needs to be disconnected. When the piezoelectric actuator stops applying driving force to the first friction surface, the friction between the first and second friction surfaces disappears, causing the vacuum switch to trip. The electronic switch can be a semiconductor switching device such as a thyristor. The electronic switch is connected in parallel or series across the piezoelectric actuator and is normally in an open state, not affecting the piezoelectric actuator's ability to receive voltage signals and output driving force. When the vacuum switch's protection system, such as a relay protection device, determines that the fault has been isolated and tripping is necessary, it sends a tripping command to the electronic switch, triggering the electronic switch to turn on.

[0047] When the electronic switch is turned on, it effectively provides a short-circuit loop for the piezoelectric actuator. If the electronic switch is connected in parallel across the piezoelectric actuator, its conduction will short-circuit the DC voltage input to the actuator, causing the voltage across it to drop sharply to zero. As the piezoelectric actuator loses its voltage input, the piezoelectric effect disappears, the mechanical deformation recovers, the driving force quickly disappears, and the first and second friction surfaces separate, reducing the frictional force to zero. At this point, the operating mechanism's transmission rod of the vacuum switch is released from its locking constraint and completes the opening action under the action of the opening force, achieving reliable disconnection of the faulty line. The electronic switch has a fast response speed (microseconds), far superior to mechanical unlocking mechanisms. It can instantly cut off the driving force of the piezoelectric actuator upon receiving the opening command, ensuring zero delay in the opening action. Furthermore, its action is controlled solely by electrical signals and is unaffected by mechanical wear or environmental interference, resulting in higher reliability during opening.

[0048] Based on the switch closing and holding device provided in the above embodiments, in one embodiment, a vacuum switch is provided, in which the above-mentioned switch closing and holding device is installed. Based on this vacuum switch, this application embodiment also provides a control method for closing and opening the vacuum switch. When the vacuum is in the closed and normal operation state, the vacuum switch is in the closed position, and the moving contact and stationary contact are closed. At this time, the rated operating current flows in the main circuit. This current is small, and the electrodynamic repulsive force generated is much smaller than the self-closing force provided by the bellows and other structures of the vacuum interrupter itself. The current signal induced by the energy harvesting coil is very weak, and after processing by the control module, it is insufficient to drive the piezoelectric actuator to produce an effective action. Therefore, the piezoelectric actuator does not extend, there is almost no contact pressure between the first friction surface and the second friction surface, and the generated friction holding force can be ignored. The entire system is in a low-stress state. When a short-circuit fault occurs in the system, the current in the main circuit rises sharply to tens or even hundreds of kiloamperes in a very short time (usually less than 1 ms). With the surge in current, the output voltage of the energy harvesting coil also increases sharply and proportionally. The high-voltage signal, after being rectified and filtered by the control module, is applied to both ends of the piezoelectric actuator. Due to the inverse piezoelectric effect, the piezoelectric actuator momentarily elongates, pushing the first friction surface to press firmly against the second friction surface with tremendous pressure. This generates a strong static friction force between the two friction surfaces, reliably preventing contact bounce and separation, thus ensuring the closing stability of the switch during short circuits. Figure 3 The diagram shown is a detailed structural diagram of the switch closing and holding device provided in an embodiment of this application.

[0049] During the short circuit, the protection system determines that the fault needs to be cut off and sends a tripping command signal to the electronic switch. The tripping command signal triggers the electronic switch to turn on instantaneously. After the switch closes, it is equivalent to directly short-circuiting the two electrodes of the piezoelectric actuator. Since the piezoelectric actuator is essentially a capacitor, the short circuit causes its stored charge to be discharged in an extremely short time (microseconds), and the voltage across its terminals drops rapidly to zero. As the voltage disappears, the piezoelectric actuator instantly loses its driving force and returns to its original length. The contact pressure between the first and second friction surfaces disappears instantly, and the holding friction force also disappears. At this point, not only is there no additional holding force to overcome, but the huge electrodynamic repulsive force becomes a powerful "tripping booster force." Under the combined action of the operating mechanism's own tripping driving force and this repulsive booster force, the moving contact can begin to separate with an extremely high initial acceleration, thus achieving ultra-fast tripping much faster than existing technologies.

[0050] The above method converts the linear output force of the piezoelectric actuator into a tangential locking force (static friction) on the transmission system of the operating mechanism through a pair of friction surfaces. The structure is simple and reliable. It utilizes the extremely fast response speed (microseconds), large output force, and lack of mechanical moving parts of the piezoelectric actuator to achieve rapid establishment of the closing holding force. Furthermore, by short-circuiting the electrodes of the piezoelectric actuator with an electronic switch, the stored charge is rapidly discharged using its capacitive characteristics, thereby removing the holding force within microseconds and creating conditions for ultra-fast opening. During opening, not only is the holding force that needs to be overcome in traditional solutions eliminated, but the originally harmful electrodynamic repulsive force generated by the short-circuit current is transformed into a beneficial driving force to assist opening, further improving the opening speed.

[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0052] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A switch closing and holding device, characterized in that, The device is installed in a vacuum switch and includes: a piezoelectric actuator, an energy harvesting coil installed on the main circuit of the vacuum switch, and a first friction surface and a second friction surface placed in parallel; wherein, the input end of the piezoelectric actuator is connected to the output end of the energy harvesting coil, the output end of the piezoelectric actuator is connected to the first friction surface, and the second friction surface is fixed on the transmission rod of the operating mechanism of the vacuum switch; The energy harvesting coil is used to sense the current signal in the main circuit and output a corresponding voltage signal to the piezoelectric actuator according to the current signal. The piezoelectric actuator is used to apply a driving force to the first friction surface when the detected voltage signal change amplitude is greater than a preset threshold; the driving force is used to drive the first friction surface and the second friction surface to generate friction, so that the vacuum switch remains closed under short-circuit fault.

2. The apparatus according to claim 1, characterized in that, The device further includes a control module, through which the output end of the energy harvesting coil and the input end of the piezoelectric actuator are connected; The control module is used to process the voltage signal output by the energy harvesting coil and send the processed voltage signal to the piezoelectric actuator.

3. The apparatus according to claim 2, characterized in that, The control module includes a rectifier and filter unit; the voltage signal is an AC voltage signal. The rectifier and filter unit is connected to the output terminal of the energy harvesting coil and the input terminal of the piezoelectric actuator, respectively. The rectifier and filter unit is used to convert the AC voltage signal into a DC voltage signal and send the DC voltage signal to the piezoelectric actuator.

4. The apparatus according to claim 3, characterized in that, The control module also includes an electronic switch; The electronic switch is installed at both ends of the piezoelectric actuator. The electronic switch is used to turn on when a trip command is received, so that the piezoelectric actuator stops applying driving force to the first friction surface. The tripping command is sent by the protection system of the vacuum switch when it determines that a fault needs to be cut off; when the piezoelectric actuator stops applying driving force to the first friction surface, the friction between the first friction surface and the second friction surface disappears, causing the vacuum switch to trip.

5. The apparatus according to any one of claims 1-4, characterized in that, The piezoelectric actuator is a piezoelectric ceramic stack structure.

6. The apparatus according to any one of claims 1-4, characterized in that, The second friction surface is fixed to the side of the non-movement path of the transmission rod of the operating mechanism.

7. The apparatus according to any one of claims 1-4, characterized in that, The magnitude of the frictional force is positively correlated with the signal strength of the current signal induced by the energy harvesting coil in the main circuit.

8. The apparatus according to any one of claims 1-4, characterized in that, At least one of the first friction surface and the second friction surface has a friction enhancement layer on its surface.

9. The apparatus according to any one of claims 1-4, characterized in that, The energy harvesting coil includes a toroidal iron core and an induction coil wound around the toroidal iron core; The main circuit passes through the central through hole of the annular iron core.

10. A vacuum switch, characterized in that, The vacuum switch is equipped with the switch closing holding device as described in any one of claims 1-9.

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