A fast overtravel measurement method for fast mechanical switches based on high-speed camera image processing

Abstract

The present invention discloses a method for measuring the overtravel of a fast mechanical switch based on high-speed camera image processing. The present invention uses a signal sensor to accurately obtain the instant of just-separation of the breaker contact by recording the trigger signal with a high-speed camera, and obtains the complete motion process of the mechanical switch by setting the pre-recording function of the high-speed camera. By calculating the frame difference between the moment when the light-emitting diode emits light and the moment when the just-separation signal is triggered, the time for the switch to complete the overtravel can be obtained, and data such as the total travel, opening distance, and overtravel of the switch can be accurately obtained. Studying the overtravel of the switch is of great significance for ensuring the safety, reliability, and lifespan of the mechanical switch.

Description

Technical Field

[0001] A fast mechanical switch overtravel measurement method based on high-speed camera image processing relates to the technical field of DC breaker opening and closing. Background Art

[0002] A circuit breaker is one of the most important high-voltage switchgears in the power system. As an important component of it, the reliability of the mechanical switch directly affects the safe and stable operation of the power grid. With the vigorous construction of the smart grid, in order to avoid unnecessary losses caused by switch mechanical failures, the mechanical characteristic detection of the switch becomes particularly important.

[0003] The contact stroke-time characteristic curve of the switch is an important characterization of its health status. In order to obtain the contact stroke curve, it is necessary to measure the total stroke and overtravel of the switch. The previous method was to install a displacement sensor on the circuit breaker body. Currently, the main displacement sensors for measuring the contact stroke of the circuit breaker include linear displacement sensors, differential transformer displacement sensors, incremental rotary optical encoders, etc. Among them, the linear displacement sensor is installed at the lower end of the insulating rod to directly collect the displacement signal of the moving contact. However, it is difficult to install, has poor accuracy, low anti-interference ability, and also destroys the original structure of the circuit breaker, affecting the insulation performance; the differential transformer displacement sensor is installed on the main shaft of the circuit breaker. The displacement of the contact changes the distribution of the spatial magnetic field, causing different electromotive forces to be induced in the secondary winding. The contact stroke displacement is measured by measuring the magnitude of the output voltage. However, the sensor has a large volume and is not suitable for medium-voltage circuit breakers; the incremental rotary optical encoder installed on the main shaft of the circuit breaker not only occupies less space, but also does not affect the insulation performance of the circuit breaker and has strong anti-interference ability. However, it outputs digital signals and cannot directly reflect the stroke characteristics of the circuit breaker, and a corresponding measurement circuit needs to be designed to cooperate for measurement. Summary of the Invention

[0004] In view of the above problems and technical requirements, the present invention proposes a fast mechanical switch overtravel measurement method based on high-speed camera image processing. The fast mechanical switch overtravel measurement method based on high-speed camera image processing of the present invention can directly reflect the mechanical stroke characteristics of the switch, including the total stroke, contact stroke, and overtravel. The purpose of detecting the switch performance through such a method of testing its mechanical performance is to eliminate potential hazards as early as possible through detection means, thereby avoiding the occurrence of serious accidents. It is the key to ensuring the safe and reliable operation of the switch and the stable operation of the system.

[0005] The technical solution of the present invention is as follows: A fast mechanical switch overtravel measurement method based on high-speed camera image processing includes the following steps:

[0006] Step 1: The high-speed camera is in the recording state but not caching images. The recording object is the repulsive disk of the mechanical switch. The repulsive disk of the mechanical switch is in the closing position, i.e., the initial state of the opening operation, and the opening energy storage capacitor is charged.

[0007] Step 2: Use a thyristor to control the opening operation. The opening energy storage capacitor discharges. At this time, the light-emitting diode emits light, indicating the moment of the opening control signal.

[0008] Step 3: The opening coil generates a pulsed current, generating an electromagnetic repulsive force on the repulsive disk.

[0009] Step 4: When the mechanical switch completes the over-travel during opening, it is in the initial state where the moving and static contacts of the mechanical switch are separated. At this time, the electrical connection is disconnected, and the edge of the line state change triggers the just-opened signal. The just-opened signal is transmitted to the high-speed camera, meeting the image caching condition of the high-speed camera for image caching.

[0010] Step 5: By calculating the set frame difference between the moment of the opening control signal when the light-emitting diode emits light and the cached image of the just-opened signal of the high-speed camera, calculate the over-travel completion time of the mechanical switch, and obtain the total stroke, opening distance, and over-travel of the circuit breaker contacts.

[0011] The beneficial effects of the present invention are as follows:

[0012] (1) The present invention can intuitively reflect the mechanical stroke characteristics of the switch, including the total stroke, contact stroke, and over-travel. It avoids the influence of factors such as difficult installation, poor accuracy, and low anti-interference ability of traditional displacement sensors on the results.

[0013] (2) The present invention detects the mechanical performance of the mechanical switch in the DC circuit breaker and eliminates potential hazards early to avoid the occurrence of serious accidents. It is the key to ensuring the safe and reliable operation of the switch and the stable operation of the system.

[0014] (3) The present invention uses a signal sensor to accurately obtain the just-opened point of the circuit breaker contacts by triggering the signal recorded by the high-speed camera, and obtains the complete movement process of the mechanical switch through the setting of the high-speed camera's early recording function. By calculating the frame difference between the moment when the light-emitting diode emits light and the moment when the just-opened signal is triggered, the time for the switch to complete the over-travel can be obtained, and data such as the total stroke, opening distance, and over-travel of the switch can be accurately obtained. Studying the over-travel of the switch is of great significance for ensuring the safety, reliability, and lifespan of the mechanical switch. Description of the Drawings

[0015] Figure 1 It is a component diagram of the mechanical switch of the present invention;

[0016] Figure 2 It is an equipment layout diagram of the present invention;

[0017] Figure 3This is the target diagram for image detection of the present invention.

[0018] In the figure, the reference numerals are: 1 - static contact, 2 - vacuum interrupter, 3 - moving contact, 4 - first busbar, 5 - porcelain bushing, 6 - bellows, 7 - flexible connection, 8 - upper pull rod, 9 - insulator, 10 - permanent magnet for closing hold, 11 - armature, 12 - permanent magnet for opening hold, 13 - opening coil, 14 - repulsion disc, 15 - closing coil, 16 - repulsion mechanism, 17 - second busbar, 18 - disc spring, 19 - lower pull rod, 20 - thyristor for opening control, 21 - thyristor for closing control, 22 - opening energy storage capacitor, 23 - closing energy storage capacitor, 24 - charging power supply, 25 - isolation transformer, 26 - light emitting diode, 1 - 1 - mechanical switch, 1 - 2 - high-speed camera, 1 - 3 - computer. Specific embodiments

[0019] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, the present invention adopts the following technical solutions.

[0020] As Figure 1As shown in the figure, the mechanical switch 1-1 consists of a vacuum interrupter 2 and a repulsive force mechanism 16. A moving contact 3 and a static contact 1 are arranged inside the vacuum interrupter 2. The moving contact 3 and the static contact 1 perform closing and opening operations. The upper end of the vacuum interrupter 2 is connected to the first busbar 4. The outside of the vacuum interrupter 2 is surrounded by a porcelain bushing 5 for insulation. The vacuum interrupter 2 is also provided with a bellows 6. The bellows 6 is used to ensure the movement of the moving contact 3 within a certain range and maintain the function of high vacuum for a long time. The repulsive force mechanism 16 provides the repulsive force and suction force required for the closing and opening of the moving contact 3 and the static contact 1. Among them, the repulsive force disk 14 and the opening coil 13 and the closing coil 15 provide repulsive force and suction force for each other. The closing coil 15 acts on closing, and the magnetic force generated by the combined component of the closing holding permanent magnet 10 and the armature 11. Both ends of the upper pull rod 8 are respectively connected to the moving contact 3 and the upper end of the insulator 9. A disc spring 18 is placed between the upper end of the insulator 9 and the upper pull rod 8. The disc spring 18 forms an over-travel buffer function. The moving contact 3 and the static contact 1 are separated until the arc is extinguished to complete the opening operation. The lower end of the insulator 9 is directly connected to the lower pull rod 19. The lower pull rod 19 is firmly connected to the armature 11 and the repulsive force disk 14 and keeps the same movement state. The lower pull rod 19 and the armature 11 overcome the reaction force of the disc spring 18 and the gravity of the moving parts, and prevent mis-opening caused by the electrodynamic force or mechanical vibration caused by the short-circuit fault current, and provide an effective holding force at the closing position and maintain the initial state of the opening operation. The repulsive force disk 14 generates a current opposite to the opening coil 13 under the influence of the eddy current effect, thereby generating an electromagnetic repulsive force, so that the repulsive force disk 14 drives the moving parts connected thereto to move in the opening direction, and the other parts are fixed and do not form connected moving parts. The first busbar 4, the second busbar 17 and the flexible connection 7 are connected. The flexible connection 7 can be a wire. The opening holding permanent magnet 12 has the function of maintaining the opening state. The opening coil 13 is used for opening. The opening energy storage circuit provides the opening current. The opening energy storage circuit includes an opening control thyristor 20, a closing control thyristor 21, an opening energy storage capacitor 22, a closing energy storage capacitor 23, a charging power supply 24, and an isolation transformer 25.

[0021] The present invention proposes a method for measuring the over-travel of a fast mechanical switch based on high-speed camera image processing. The high-speed camera 1-2 collects the image of the mechanical switch 1-1 and transmits it to the computer 1-3. The specific implementation steps of the present invention are as follows:

[0022] At the initial moment, the repulsive force disk 14 of the mechanical switch 1-1 and the opening coil 13 are in the closing position. Disc springs 18 are placed at the connection part between the insulator 9 and the upper pull rod 8. The magnetic force generated by the combined component of the closing holding permanent magnet 10 and the armature 11 keeps the moving parts of the repulsive force mechanism 16 in balance. The moving parts include the moving contact 3, the upper pull rod 8, the insulator 9, the armature 11, the repulsive force disk 14, and the lower pull rod 19. The object photographed by the high-speed camera 1-2 is the repulsive force disk 14 in the repulsive force mechanism 16. At this time, it is in the state of being photographed but not recorded, as shown in Figure 2.

[0023] When performing the opening operation of the mechanical switch 1-1, the opening control thyristor 20 controls the operation to cause the opening energy storage capacitor 22 to discharge to the opening coil 13 and generate a pulsed current, and the pulsed current generates eddy currents in the repulsion disk 14; the repulsion disk 14 generates a current opposite to that of the opening coil 13 under the influence of the eddy current effect, thereby generating an electromagnetic repulsion force, causing the repulsion disk 14 to drive the moving component connected thereto to move in the opening direction.

[0024] When the repulsion disk 14 continuously moves in the opening direction and the disc spring 8 finishes the over-travel and pulls the moving contact 3 to move, the mechanical switch 1-1 completes the over-travel during opening. At this time, it is recorded as the initial state when the static and dynamic contacts of the mechanical switch 1-1 are separated. At this time, the electrical connection is disconnected, and the edge of the line state change triggers the just-opened signal. The high-speed camera 1-2 receives the just-opened signal and triggers the buffer. The buffer point of the high-speed camera 1-2 is 1000 frame images before just-opening, including the opening signal triggering the diode to turn on and the moving image of the repulsion disk 14, with a total duration of 3000 frames.

[0025] Through the opening images of the mechanical switch 1-1 cached by the high-speed camera 1-2, calculate the displacement of the repulsion disk 14 during opening, that is, the total switch stroke, and then subtract the displacement during the over-travel time to obtain the opening distance of the mechanical switch 1-1. Therefore, the over-travel of the switch can be accurately measured by the method of the present invention.

[0026] A series branch of a light-emitting diode and a current-limiting resistor is installed at the gate of the thyristor in the opening control circuit of the mechanical switch 1-1, and the light emission is used to obtain the information of the moment when the opening instruction is issued. Opening means that the opening energy storage circuit is turned on when receiving the opening signal of the control system.

[0027] The above embodiments are only used to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the present invention.

Claims

1. A fast mechanical switch overtravel measurement method based on high-speed camera image processing, characterized in that: The steps include: Step 1: The high-speed camera is in a recording state but no image caching is performed. The recording object is a mechanical switch repulsion disk. The repulsion disk of the mechanical switch is in a closed position, i.e., an initial state of an opening operation, and the opening energy storage capacitor is charged. Step 2, using thyristor to control the opening operation, the opening energy storage capacitor is discharged, and the light-emitting diode lights up to indicate the opening control signal moment; Step 3, the opening coil generates a pulse current to generate an electromagnetic repulsive force on the repulsion disk; Step 4: When the mechanical switch is opened and the overtravel is completed, the two moving and static contacts of the mechanical switch are separated in the initial state. At this time, the electrical connection is disconnected, and the edge of the line state change triggers the just-opening signal, which is transmitted to the high-speed camera to achieve the high-speed camera cache condition for image cache; Step 5, by calculating the setting frame difference between the opening control signal moment when the light-emitting diode emits light and the buffer image of the high-speed camera just after the opening signal, the overtravel completion time of the mechanical switch is calculated to obtain the total stroke, opening distance and overtravel of the circuit breaker contact; In step 1, the opening process of the high-speed mechanical switch is as follows: at the initial moment, the repulsion disk and the excitation coil are in the closed position, disc springs are placed at the connection between the insulator and the upper pull rod, and the motion image of the repulsion disk is captured by a high-speed camera to obtain the total stroke of the switch. The compression amount of the disc spring is the overstroke, and the cache condition is that the high-speed camera obtains the just-opened signal of the mechanical switch; In step 2, a light-emitting diode and a current-limiting resistor series branch are installed at the gate of the thyristor of the mechanical switch opening control circuit. The light-emitting display is used to obtain the information of the time when the opening instruction is issued. Opening means that the opening energy storage circuit receives the opening signal of the control system and is turned on.

2. The method for measuring the overtravel of a fast mechanical switch based on high-speed camera image processing according to claim 1, characterized in that: The cache image setting described in step 4 is a process of setting the cache image to the first 1000 frames of the just-divided signal, with a total duration of 3000 frames.

3. The method for measuring the overtravel of a fast mechanical switch based on high-speed camera image processing according to claim 1, characterized in that: In step 5, the opening displacement of the repulsion disk, i.e., the total switch stroke, is calculated through the opening image of the mechanical switch cached by the high-speed camera, and then the displacement during the overtravel time is subtracted to obtain the opening distance of the mechanical switch.

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