Vacuum arc extinguish chamber contact surface ablation degree detection device and detection method for vacuum circuit breaker

Abstract

The invention discloses a vacuum arc extinguish chamber contact surface ablation degree detection device and method for a vacuum circuit breaker. The detection device comprises a high-voltage direct current source, a voltage divider, a field emission current measurement device, a stroke curve measurement device and an oscilloscope. The high-voltage direct-current source provides direct-current voltage for the vacuum circuit breaker; the voltage divider is used for measuring voltage waveforms at two ends of the contact; the field emission current measuring device is used for measuring field emission current generated in the closing process of the vacuum circuit breaker; the stroke curve measuring device is used for measuring the stroke curve of the moving contact of the vacuum arc-extinguishing chamber in the closing process of the vacuum circuit breaker; the field enhancement coefficient and the field effective area are calculated through the measuring device so as to represent the ablation degree of the surface of the contact of the arc extinguish chamber of the vacuum circuit breaker; according to the invention, nondestructive testing is realized, the measurement result can reflect the ablation degree of the vacuum arc to the surface of the contact of the vacuum arc-extinguishing chamber in the operation process of the vacuum circuit breaker, the method can be used for evaluating the operation condition, the breaking capacity and the service life of the vacuum circuit breaker, the installation is easy, the use is simple, and the detection efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of vacuum circuit breaker technology, specifically relating to a device and method for detecting the degree of ablation on the surface of the contacts of a vacuum interrupter in a vacuum circuit breaker. Background Technology

[0002] Vacuum circuit breakers are widely used in the 12kV-40.5kV medium-voltage power switchgear field. They offer advantages such as environmental friendliness, maintenance-free operation, and long service life. The vacuum interrupter is a crucial component of a vacuum circuit breaker, playing a decisive role in its performance. The vacuum interrupter uses the vacuum gap between the contacts as the arc-extinguishing medium. The condition of the contact surface closely affects the breaking performance, service life, withstand voltage, and current-carrying capacity of the vacuum interrupter. During operation, the ablation of the vacuum interrupter contact surface by the vacuum arc is unavoidable. This ablation damages the contact surface and can even cause welding, affecting the insulation strength and reducing the breaking capacity and service life of the vacuum interrupter. To improve the external insulation level of the vacuum interrupter, it is sealed within a solid-sealed pole in most vacuum circuit breakers. This design improves the insulation level and reduces the size of the vacuum circuit breaker; however, the vacuum interrupter cannot be removed or replaced from the circuit breaker.

[0003] The current method for measuring arc erosion on the contact surface involves dissecting the vacuum interrupter, removing the contacts, and scanning them with an electron microscope to observe the surface condition. This method completely destroys the interrupter. For vacuum circuit breakers with solid-sealed poles, the solid-sealed poles must be destroyed to remove the vacuum interrupter. This method is not suitable for testing the surface insulation strength of contacts in operating vacuum circuit breakers. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a device and method for detecting the ablation degree of the contact surface of a vacuum interrupter in a vacuum circuit breaker. This method enables non-destructive testing of the ablation degree of the contact surface in a vacuum circuit breaker without disassembling the vacuum circuit breaker or dissecting the vacuum interrupter, thus not affecting the use of the vacuum circuit breaker. The measurement results of this device can reflect the insulation strength of the vacuum interrupter contact surface and the degree of ablation of the contact surface by the vacuum arc.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A device for detecting the ablation degree of the contact surface of a vacuum interrupter for a vacuum circuit breaker includes: a high-voltage DC source, a voltage divider, a field emission current measuring device, a stroke curve measuring device, and an oscilloscope; The high-voltage DC source is connected to the input terminal of the vacuum circuit breaker under test, providing DC voltage to the vacuum circuit breaker. This high-voltage DC source is a low-power high-voltage DC source with a voltage level of 50kV or above, which can generate a sufficiently high amplitude field emission current to make the measurement more accurate. When the vacuum interrupter breaks down, the current flowing through the interrupter is less than 500mA, reducing the impact of the pre-breakdown arc on the contact surface and protecting the measurement branch. The voltage divider is connected in parallel across the high-voltage DC source and connected to an oscilloscope for measuring voltage waveforms. The field emission current measuring device is connected in series at the output terminal of the vacuum circuit breaker under test and grounded. The field emission current measuring device is connected to an oscilloscope and is used to measure the field emission current generated during the closing process of the vacuum circuit breaker. The field emission current measuring device includes a non-inductive resistor, a bidirectional transient voltage suppressor diode (TVS), and a gas discharge tube. The non-inductive resistor, the bidirectional transient voltage suppressor diode (TVS), and the gas discharge tube are connected in parallel. The voltage of the non-inductive resistor is measured by the oscilloscope. The field emission current value is characterized by the voltage value of the non-inductive resistor. The bidirectional transient voltage suppressor diode (TVS) and the gas discharge tube are protection devices. When the current exceeds the range, the protection device is turned on, allowing the current to flow through the protection device. A stroke curve measuring device is connected to the operating mechanism of the vacuum circuit breaker under test and to an oscilloscope. It is used to measure the stroke curve of the moving contact of the vacuum interrupter during the closing process of the vacuum circuit breaker. The device includes a sliding rheostat, a sliding rheostat mounting bracket, and a battery. The sliding rheostat is fixed to the operating mechanism of the vacuum circuit breaker via the mounting bracket. The moving end of the rheostat is connected to the moving contact rod of the vacuum interrupter. The battery supplies power to the rheostat, and the output terminal of the rheostat is connected to the oscilloscope. The stroke curve of the moving contact of the vacuum circuit breaker is characterized by the voltage change curve at the output terminal of the rheostat displayed on the oscilloscope.

[0006] The aforementioned device for detecting the ablation degree of vacuum interrupter contact surfaces in vacuum circuit breakers measures the field-induced emission current generated before the vacuum circuit breaker is pre-broken down by a DC voltage of a certain amplitude. This measurement is used to calculate the field-induced enhancement coefficient and effective field-induced emission area of ​​the vacuum interrupter contact surface, thus reflecting the degree of ablation. This invention enables non-destructive testing of the ablation degree of vacuum interrupter contact surfaces and is applicable to measuring vacuum circuit breakers in operation. The invention is easy to install, simple to use, and improves testing efficiency, making it beneficial for application in substations.

[0007] A method for detecting the degree of contact surface ablation using the aforementioned device for detecting the degree of contact surface ablation in a vacuum circuit breaker includes the following steps: S1: Install the high-voltage DC source, voltage divider, field emission current measuring device, stroke curve measuring device, and oscilloscope next to the vacuum circuit breaker under test as required above. S2: Charge the high-voltage DC source to the preset voltage amplitude and close the vacuum circuit breaker under test; measure the voltage across the vacuum circuit breaker under test using a voltage divider; measure the travel curve of the moving contact of the vacuum interrupter in the vacuum circuit breaker under test using a travel curve measuring device; measure the field emission current of the vacuum interrupter in the vacuum circuit breaker under test before pre-breakdown using a field emission current measuring device; all of the above measurements are acquired using an oscilloscope.

[0008] S3: From the start of the field emission current generation to the pre-breakdown time of the vacuum interrupter, take equal intervals. Record these points. The time and field-induced emission current value corresponding to each point. Simultaneously, take this... The value of the travel curve of the moving contact in the vacuum interrupter and the voltage value of the vacuum circuit breaker at each point and time are calculated to obtain... The corresponding contact opening distance of the vacuum interrupter at each point and the voltage value applied across the vacuum interrupter at this time.

[0009] S4: Selected Each field-induced emission current value Vacuum interrupter contact opening distance value Voltage value Substituting these values ​​into the FN formula, the field-induced enhancement coefficient on the surface of the vacuum interrupter contact in the vacuum circuit breaker is calculated. Effective area of ​​field emission on the contact surface and the multiplication factor of the ablation degree of the vacuum interrupter contact surface. The surface insulation strength of the vacuum interrupter contacts in a vacuum circuit breaker is determined by the field-induced enhancement coefficient. and the effective area of ​​field-induced launch and the multiplication factor of the ablation degree of the vacuum interrupter contact surface. These two quantities characterize [the data].

[0010] The FN formula can be expressed in two ways: Method 1:

[0011] Method 2:

[0012] In the formula, For field emission current, The DC voltage applied across the vacuum circuit breaker. Let be the work function corresponding to the contact material. This is the contact gap value. The field-induced enhancement coefficient of the contact surface is . The effective area of ​​the field emission on the contact surface; both of these expressions are applicable to this calculation method.

[0013] In actual testing, a multiplier factor for the ablation degree of the vacuum interrupter contact surface is introduced. K :

[0014] In the formula, For the first The multiplication factor of the ablation degree on the contact surface of the vacuum interrupter measured in this study. For the first The field-induced enhancement coefficient of the vacuum interrupter contact surface was measured in this study. The field-induced enhancement coefficient of the vacuum interrupter contact surface, measured for the first time before the vacuum circuit breaker is put into operation, serves as the benchmark value for testing.

[0015] Compared with the prior art, the present invention has the following advantages: This invention enables non-destructive testing of the ablation degree on the surface of the vacuum interrupter contacts during the operation of a vacuum circuit breaker. It does not require disassembling the vacuum circuit breaker or dissecting the vacuum interrupter, and does not affect the use of the vacuum circuit breaker. The measurement results can reflect the ablation degree of the vacuum arc on the surface of the vacuum interrupter contacts during the operation of the vacuum circuit breaker. It can be used to evaluate the operating status, breaking capacity and service life of the vacuum circuit breaker. It is easy to install, simple to use and improves the testing efficiency. Attached Figure Description

[0016] Figure 1 This is an electrical topology diagram of a device for detecting the degree of ablation on the surface of the contact of a vacuum interrupter in a vacuum circuit breaker, as described in this invention. Figure 2 This is an electrical topology diagram of the field emission current measuring device in the vacuum interrupter contact surface ablation degree detection device for vacuum circuit breakers according to the present invention; Figure 3 This is an electrical topology diagram of the stroke curve measuring device in the vacuum interrupter contact surface ablation degree detection device for vacuum circuit breakers according to the present invention; Figure 4 This is a schematic diagram of the DC voltage, field emission current, and moving contact travel curves according to an embodiment of the present invention.

[0017] Figure 5 This is a flowchart of the detection method of the present invention. Detailed Implementation

[0018] To further illustrate the technical solution and detection effect adopted in this invention, the technical solution of this invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] This invention provides a device for detecting the degree of ablation on the surface of the contacts of a vacuum interrupter for a vacuum circuit breaker.

[0020] The "degree of ablation" of the vacuum interrupter contact surface described in this invention is characterized by the field-induced enhancement coefficient, the effective area of ​​field emission, and the ablation multiplication coefficient of the contact surface, all obtained through measurement and calculation. These parameters reflect the degree of microscopic protrusions on the contact surface and the extent of ablation caused by the vacuum arc. Within a certain range, a larger field-induced enhancement coefficient indicates more microscopic protrusions on the contact surface and more severe ablation by the vacuum arc.

[0021] Figure 1 The diagram shown is an electrical topology diagram of a device for detecting the ablation degree of the contact surface of a vacuum interrupter in a vacuum circuit breaker according to the present invention, comprising: a high-voltage DC source 100, a voltage divider 200, a field emission current measuring device 400, a stroke curve measuring device 300, and an oscilloscope 600. Furthermore, the high-voltage DC source 100 is a low-power high-voltage DC source with a voltage level of 50kV or above, providing a DC voltage of 25kV to the vacuum circuit breaker under test. During the pre-breakdown process of the vacuum circuit breaker under test 500 during closing, the current flowing through the vacuum circuit breaker is less than 500mA, and it is connected to the incoming terminal of the vacuum circuit breaker under test 500.

[0022] Furthermore, the voltage divider 200 is connected in parallel across the high-voltage DC source 100 and connected to the oscilloscope 600 for measuring voltage waveforms.

[0023] Figure 2 The diagram shows the electrical topology of the field emission current measuring device 400 in the vacuum interrupter contact surface ablation detection device for a vacuum circuit breaker according to the present invention. It includes a non-inductive resistor 401, a bidirectional transient voltage suppressor diode (TVS) 402, and a gas discharge tube 403. The non-inductive resistor 401, TVS 402, and gas discharge tube 403 are connected in parallel. The voltage of the non-inductive resistor 401 is measured by an oscilloscope 600. The field emission current value is characterized by the voltage value of the non-inductive resistor 401. The TVS 402 and gas discharge tube 403 are protective devices. The field emission current measuring device 400 is connected in series with the output terminal of the vacuum circuit breaker 500 under test and grounded. The field emission current measuring device 400 is connected to the oscilloscope 600 and is used to measure the field emission current generated during the closing process of the vacuum circuit breaker 500.

[0024] Figure 3The diagram shows the electrical topology of the stroke curve measuring device 300 in the vacuum interrupter contact surface ablation detection device of the present invention, which includes a sliding rheostat 302, a sliding rheostat mounting bracket 301, and a battery 303. The sliding rheostat 302 is fixed to the operating mechanism of the vacuum circuit breaker 500 via the sliding rheostat mounting bracket 301. The moving end of the sliding rheostat 302 is connected to the moving contact pull rod of the vacuum interrupter. The battery 303 supplies power to the sliding rheostat 302. The output terminal of the sliding rheostat is connected to an oscilloscope 600. The stroke curve of the moving contact of the vacuum circuit breaker is characterized by the voltage change curve of the output terminal of the sliding rheostat displayed on the oscilloscope 600. The stroke curve measuring device 300 is connected to the operating mechanism of the vacuum circuit breaker 500 under test and to the oscilloscope 600, and is used to measure the stroke curve of the moving contact of the vacuum interrupter during the closing process of the vacuum circuit breaker 500.

[0025] Combination Figure 1 The electrical topology diagram of the detection device shown is illustrated. This invention also provides a working process for a device for detecting the degree of ablation on the surface of vacuum interrupter contacts in a vacuum circuit breaker, as follows: Figure 5 As shown, the detection method of the vacuum interrupter contact surface ablation degree detection device based on any one of the above includes: S1: Install the high voltage DC source 100, voltage divider 200, field emission current measuring device 400, stroke curve measuring device 300, and oscilloscope 600 next to the vacuum circuit breaker 500 under test as described above. S2: Charge the high-voltage DC source 100 to the preset voltage amplitude and close the vacuum circuit breaker 500 under test; measure the voltage waveform across the vacuum circuit breaker 500 under test using the voltage divider 200; measure the travel curve of the moving contact of the vacuum interrupter in the vacuum circuit breaker 500 under test using the travel curve measuring device 300; measure the field emission current before pre-breakdown during the closing process of the vacuum interrupter in the vacuum circuit breaker 500 under test using the field emission current measuring device 400; all of the above measurements are acquired by the oscilloscope 600. S3: From the start of the field emission current generation to the pre-breakdown time of the vacuum interrupter, take equal intervals. Record these points. The time and field-induced emission current value corresponding to each point. Simultaneously, take this... The values ​​of the vacuum interrupter moving contact travel curve and the vacuum circuit breaker voltage at each point and corresponding time were calculated to obtain... The contact opening distance of the vacuum interrupter corresponding to each point and the voltage value applied across the vacuum interrupter at this time; S4: Selected Each field-induced emission current value Vacuum interrupter contact opening distance value Voltage value Substituting these values ​​into the FN formula, the field-induced enhancement coefficient on the surface of the vacuum interrupter contact in the vacuum circuit breaker is calculated. Effective area of ​​field emission on the contact surface And the multiplication factor of the ablation degree on the surface of the vacuum interrupter contact. The degree of ablation on the contact surface of the vacuum interrupter in a vacuum circuit breaker is determined by the field-induced enhancement coefficient. and the effective area of ​​field-induced launch and the multiplication factor of the ablation degree of the vacuum interrupter contact surface. These three quantities characterize; The FN formula can be expressed in two ways: Method 1:

[0026] Method 2:

[0027] In the formula, For field emission current, The DC voltage applied across the vacuum circuit breaker. Let be the work function corresponding to the contact material. This is the contact gap value. The field-induced enhancement coefficient of the contact surface is . This represents the effective area of ​​the field-induced emission on the contact surface. Both of these expressions are applicable to this calculation method.

[0028] Figure 4 The diagram shows the measured DC voltage, field emission current, and moving contact travel curves of this embodiment, along with the selected... A measurement quantity.

[0029] The device for detecting the surface erosion of vacuum interrupter contacts in a vacuum circuit breaker, as described in this invention, can be used in substations to measure the degree of erosion on the surface of the vacuum interrupter contacts after a vacuum circuit breaker fails to interrupt or experiences a re-breakdown, in order to determine the cause of the fault or the condition of the circuit breaker. Alternatively, the degree of erosion on the contact surface can be measured at the time the vacuum circuit breaker leaves the factory as a reference value. After the vacuum circuit breaker is installed and put into operation in the substation, measurements are taken at certain intervals based on the number of interruptions, and the results are compared with the reference value. This serves to detect the surface condition of the vacuum interrupter contacts, predict interruption failures caused by contact erosion, and predict the service life of the vacuum interrupter.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vacuum interrupter contact surface erosion degree detection device for a vacuum circuit breaker, characterized by, The application relates to a device for measuring the field emission current and the travel curve of a vacuum circuit breaker, which comprises a high-voltage direct-current source (100), a voltage divider (200), a field emission current measuring device (400), a travel curve measuring device (300) and an oscilloscope (600). The high-voltage direct-current source (100) is connected to the incoming line end of the measured vacuum circuit breaker (500) and provides a direct-current voltage for the vacuum circuit breaker. The voltage divider (200) is connected in parallel to the high-voltage direct-current source (100) and is connected to the oscilloscope (600) and is used for measuring the voltage waveform. The field emission current measuring device (400) is connected in series to the outgoing line end of the measured vacuum circuit breaker (500) and is grounded, the field emission current measuring device (400) is connected to the oscilloscope (600) and is used for measuring the field emission current generated in the vacuum circuit breaker (500) during the closing process. The travel curve measuring device (300) is connected to the operating mechanism of the measured vacuum circuit breaker (500) and is connected to the oscilloscope (600) and is used for measuring the travel curve of the moving contact of the vacuum arc chamber during the closing process of the vacuum circuit breaker (500). The high-voltage direct-current source (100) is a low-power high-voltage direct-current source with a voltage level of 50kV or above, and the current flowing through the vacuum circuit breaker during the pre-breakdown of the closing process of the vacuum circuit breaker (500) is less than 500mA.

2. The device for detecting the degree of erosion of the surface of the contact of the vacuum interrupter according to claim 1, characterized in that: The field emission current measuring device (400) comprises a non-inductive resistor (401), a bidirectional transient voltage suppression diode TVS (402) and a gas discharge tube (403) connected in parallel, the voltage of the non-inductive resistor (401) is measured by the oscilloscope (600), the field emission current value is represented by the voltage value of the non-inductive resistor (401), and the bidirectional transient voltage suppression diode TVS (402) and the gas discharge tube (403) are protection devices.

3. The device for detecting the degree of erosion of the surface of the contact of the vacuum interrupter according to claim 1, characterized in that: The travel curve measuring device (300) for measuring the travel curve of the moving contact of the vacuum arc chamber comprises a slide rheostat (302), a slide rheostat fixing support (301) and a battery (303), the slide rheostat (302) is fixed beside the operating mechanism of the vacuum circuit breaker (500) through the slide rheostat fixing support (301), the moving end of the slide rheostat (302) is connected to the pull rod of the moving contact of the vacuum arc chamber, the battery (303) supplies power to the slide rheostat (302), the outgoing line end of the slide rheostat (302) is connected to the oscilloscope (600), and the travel curve of the moving contact of the vacuum circuit breaker is represented by the voltage change curve of the outgoing line end of the slide rheostat displayed by the oscilloscope (600).

4. The device for detecting the degree of erosion of the surface of the contact of the vacuum interrupter according to claim 1, characterized in that: The device comprises the following steps:

5. A contact surface erosion degree detection method using the vacuum interrupter contact surface erosion degree detection device according to any one of claims 1 to 4, characterized by, S1: installing the high-voltage direct-current source (100), the voltage divider (200), the field emission current measuring device (400), the travel curve measuring device (300) and the oscilloscope (600) beside the measured vacuum circuit breaker (500) according to requirements. ​ S2: the high voltage direct current source (100) is charged to a preset voltage amplitude, the measured vacuum circuit breaker (500) is closed, the voltage waveform between the measured vacuum circuit breaker (500) is measured through the voltage divider (200), the dynamic contact stroke curve of the vacuum arc-extinguishing chamber in the measured vacuum circuit breaker (500) is measured through the stroke curve measuring device (300), the field emission current before pre-breakdown in the vacuum arc-extinguishing chamber of the measured vacuum circuit breaker (500) is measured through the field emission current measuring device (400), and the measurement is collected through the oscilloscope (600); S3: From the start of the field emission current generation to the pre-breakdown time of the vacuum interrupter, take equal intervals. Record these points. The time and field-induced emission current value corresponding to each point; simultaneously, take these... The value of the travel curve of the moving contact in the vacuum interrupter and the voltage value of the vacuum circuit breaker at each point and time are calculated to obtain... The contact opening distance of the vacuum interrupter corresponding to each point and the voltage value applied across the vacuum interrupter at this time; S4: the selected field emission current value , the vacuum interrupter contact opening distance value , the voltage value are sequentially brought into the F-N formula, and the field emission enhancement coefficient of the vacuum interrupter contact surface in the vacuum circuit breaker is calculated , the effective area of the contact surface field emission , and the vacuum interrupter contact surface ablation degree multiplication coefficient ; the vacuum interrupter contact surface ablation degree in the vacuum circuit breaker is represented by the field emission enhancement coefficient , the effective area of the contact surface field emission , and the vacuum interrupter contact surface ablation degree multiplication coefficient .

6. The contact surface erosion degree detection method of the vacuum interrupter contact surface erosion degree detection device for vacuum circuit breakers according to claim 5, characterized by, The F-N formula has the following two expressions: Manner One: Method two: wherein, is the field emission current, is the DC voltage applied across the vacuum interrupter, is the work function of the contact material, is the contact opening distance, is the field enhancement factor of the contact surface, is the effective field emission area of the contact surface.

7. The contact surface erosion degree detection method of the vacuum interrupter contact surface erosion degree detection device for vacuum circuit breakers according to claim 5, characterized by: In the actual detection process, the vacuum interrupter contact surface ablation degree multiplication coefficient is introduced K : wherein is the degree of erosion of the vacuum interrupter contact surface for the nth is the degree of erosion of the vacuum interrupter contact surface for the nth is the degree of erosion of the vacuum interrupter contact surface for the nth is the field enhancement factor of the vacuum interrupter contact surface for the nth is the field enhancement factor of the vacuum interrupter contact surface for the first measurement before the vacuum circuit breaker is operated, which is used as a reference value for detection.

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