Test circuit and test method for measuring post-arc withstand voltage characteristic of vacuum switch

Abstract

The invention relates to the technical field of circuit withstand voltage testing, in particular to a test circuit and a test method for measuring the post-arc withstand voltage characteristic of a vacuum switch. The current generation branch circuit is connected to the first end of the vacuum switch to be tested and generates arcing current flowing through the vacuum switch to be tested. The commutation branch is connected in parallel to two ends of the tested vacuum switch, a second end of the tested vacuum switch is connected to the common connection point, the commutation branch is switched on after the tested vacuum switch is switched off, current commutation is realized, and transient recovery voltage is established at two ends; one end of the oscillation energy absorption branch is connected to the first end of the tested vacuum switch, and the other end is connected to the common connection point. According to the technical scheme, a simple topology can be constructed, a transient recovery voltage rising at a high speed is naturally generated by utilizing the reverse charging characteristic of the small-capacity commutation capacitor after current zero crossing, a post-arc breakdown test of the vacuum switch is realized without an additional heavy voltage circuit, and arcing and commutation actions can be controlled through a time sequence, so that the arcing time is accurately adjusted.

Description

Technical Field

[0001] This invention relates to the field of circuit withstand voltage testing technology, and in particular to a test circuit and test method for measuring the arc withstand voltage characteristics of a vacuum switch. Background Technology

[0002] Currently, most test methods for the post-arc withstand voltage characteristics of vacuum switches are based on power frequency or low-frequency oscillation circuits, which are difficult to realistically simulate the high-frequency, high di / dt transient stress environment during the actual breaking process of a DC circuit breaker. Existing high-frequency oscillation test circuits are often complex in structure, requiring multiple voltage superposition stages or additional post-arc high voltage application circuits, resulting in high system cost, high control difficulty, and inflexible parameter adjustment.

[0003] Existing methods have limited capabilities in simulating test conditions where multiple parameters such as different arcing times, different current drop rates, and different post-arc reverse voltages are synergistically affected. This makes it difficult to systematically study the influence of various factors on the post-arc dielectric recovery of vacuum switches, thus restricting the accurate selection and performance optimization of vacuum switches in DC interruption applications.

[0004] Therefore, there is a need for a test circuit and testing method that can construct a simple topology, utilize the reverse charging characteristics of a small-capacity commutation capacitor after the current crosses zero to naturally generate a rapidly rising transient recovery voltage, achieve post-arc breakdown testing of vacuum switches without the need for an external heavy-duty circuit, and precisely adjust the arcing time by controlling the arcing and commutation actions through timing control to meet the needs of the current environment. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is that: existing high-frequency oscillation test circuits are often complex in structure, requiring multiple voltage superpositions or additional post-arc high voltage application circuits, resulting in high system cost, difficulty in control, and inflexible parameter adjustment. Existing methods have limited ability to simulate test conditions where multiple parameters such as different arcing times, different current drop rates, and different post-arc reverse voltages are affected by synergistic effects.

[0006] The above-mentioned technical problems are solved by the following technical solution: This invention proposes a test circuit for measuring the arc withstand voltage characteristics of a vacuum switch, which includes, The current generating branch is connected to the first terminal of the vacuum switch under test, generating an arc current flowing through the vacuum switch under test; The commutation branch is connected in parallel across the vacuum switch under test. The second terminal of the vacuum switch under test is connected to the common connection point. The commutation branch is activated after the vacuum switch under test is opened, realizing current commutation and establishing transient recovery voltage across the two terminals. The oscillating energy absorption branch is connected at one end to the first terminal of the vacuum switch under test, and at the other end to the common connection point.

[0007] In a preferred embodiment of the test circuit for measuring the arc withstand voltage characteristics of a vacuum switch according to the present invention: A first LC oscillation unit and a first charging unit are provided in the current generating branch; The first LC oscillation unit includes a first capacitor and a first inductor connected in series; The first charging unit includes a first charging power supply, a first charging switch, and a first charging resistor; The positive terminal of the first charging power supply is connected to the high potential terminal of the first capacitor through the first charging switch and the first charging resistor connected in series, and the negative terminal is connected to the low potential terminal of the first capacitor. The first LC oscillation unit is connected to the main current path through the first control switch.

[0008] In a preferred embodiment of the test circuit for measuring the arc withstand voltage characteristics of a vacuum switch according to the present invention: A second LC oscillation unit and a second charging unit are provided in the commutation branch; The second LC oscillation unit includes a second capacitor and a second inductor connected in series; The second charging unit includes a second charging power supply, a second charging switch, and a second charging resistor. The positive terminal of the second charging power supply is connected to the high potential terminal of the second capacitor through the second charging switch and the second charging resistor connected in series, and the negative terminal is connected to the low potential terminal of the second capacitor. The second LC oscillation unit is connected to the main current path through the second control switch.

[0009] In a preferred embodiment of the test circuit for measuring the arc withstand voltage characteristics of a vacuum switch according to the present invention: A first discharge unit and a second discharge unit are respectively installed in the current generating branch and the converter branch; The first and second discharge units include a discharge switch and a discharge resistor.

[0010] In a preferred embodiment of the test circuit for measuring the arc withstand voltage characteristics of a vacuum switch according to the present invention: The oscillating energy-absorbing branch includes a third control switch and a series-connected energy-absorbing surge arrester; The capacitance of the second capacitor is less than that of the first capacitor.

[0011] A test method includes a test circuit for measuring the arc withstand voltage characteristics of a vacuum switch, and the following procedure: When the current generating branch 1 provides oscillating current to the closed vacuum switch under test, it controls the vacuum switch under test to open and start arcing. After the arcing of the vacuum switch under test continues for a set time, the commutation branch is activated, and the current is commutated from the current generating branch to the commutation branch, so that the two ends of the vacuum switch under test are subjected to transient recovery voltage. After the vacuum switch under test breaks down due to transient recovery voltage, it absorbs the remaining energy in the circuit through the oscillating energy absorption branch.

[0012] In a preferred embodiment of the testing method described in this invention: In the charging process before the converter branch is put into operation The first charging switch in the closed current generating branch charges the first capacitor to a first preset voltage through the first charging power supply and the first charging resistor; The second charging switch in the closed commutation branch charges the second capacitor to the second preset voltage through the second charging power supply and the second charging resistor. After charging is complete, disconnect the first charging switch and the second charging switch.

[0013] In a preferred embodiment of the testing method described in this invention: In the parameter adjustment steps, Adjust the power supply voltage for charging the second capacitor, select the inductance parameters of the commutation branch, and control the current drop rate before the current crosses zero and the reverse voltage characteristics of the vacuum switch under test after arc. Adjust the voltage of the second charging power supply, replace the second inductor with one having a different inductance value, and change the rate of change of current during the commutation process.

[0014] In a preferred embodiment of the testing method described in this invention: In the arc time control step, The vacuum switch under test is controlled to open before the oscillating current supplied by the current generating branch reaches its peak value. The second control switch is kept closed at a fixed set time, and the arcing time is adjusted by only changing the opening time of the vacuum switch under test.

[0015] The beneficial effects of this invention are as follows: Our technical solution can construct a simple topology, utilize the reverse charging characteristics of a small-capacity commutation capacitor after the current crosses zero, and naturally generate a rapidly rising transient recovery voltage. It can achieve the post-arc breakdown test of the vacuum switch without the need for an external heavy voltage circuit. Furthermore, it can precisely adjust the arcing time by controlling the arcing and commutation actions through timing control. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0017] Figure 1 The schematic diagram of the post-arc dielectric recovery test circuit of the present invention is shown.

[0018] Figure 2The graph shows the relationship between the pre-charge voltage of capacitor C2 and the rate of decrease of the current before zero under different L2 inductance values ​​in this invention.

[0019] Figure 3 The experimental sequence and characteristic waveforms of the dielectric recovery test after the fourth arc of the vacuum switch under test in this invention are shown.

[0020] Figure 4 Typical experimental waveforms from this invention are shown.

[0021] Figure 5 The curves showing the breakdown voltage versus arcing time under the condition of zero-precursor current drop rate of 900±50 kA / ms are illustrated.

[0022] Figure 6 The graph shows the breakdown voltage variation with the magnitude of the reverse voltage under two conditions: the zero-previous current drop rate is >600 kA / ms and 400~550 kA / ms. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0024] The terminology used in this invention refers to those general terms currently widely used in the art in consideration of the functionality of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new techniques. Furthermore, specific terms may be chosen independently, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terminology used in this specification should not be construed as simple names, but rather based on the meaning of the terms and the overall description of the invention.

[0025] Reference Figure 1 This embodiment provides a test circuit for measuring the post-arc withstand voltage characteristics of a vacuum switch. This circuit can be used to efficiently and accurately evaluate the post-arc dielectric recovery strength of a vacuum switch under high-frequency oscillation conditions. The circuit mainly includes three functional branches: current generation branch 1, commutation branch 2, and oscillation energy absorption branch 3. These three branches work together and are connected to the core test object—the vacuum switch under test 4—to simulate the key electrical stress conditions during the actual DC circuit breaker breaking process.

[0026] The function of current generating branch 1 is to generate a high-frequency, amplitude-controllable oscillating current to simulate the arcing current that the vacuum switch under test 4 needs to interrupt during the breaking process. The output terminal of current generating branch 1 is connected to the first terminal of the vacuum switch under test 4. Figure 1The upper end of the circuit. The internal components of the current generating branch 1 include a matching energy storage capacitor, a tuning inductor, a charging power supply, and corresponding control switches, used to generate a current waveform that meets the test requirements.

[0027] The function of converter branch 2 is to quickly start working after the vacuum switch under test 4 has been opened and a preset arcing time has elapsed. Converter branch 2 is connected in parallel across the two ends of the vacuum switch under test 4. The input end of converter branch 2 is connected to the first end of the vacuum switch under test 4, and the output end of converter branch 2 is connected to a common connection point.

[0028] The common connection point is also connected to the second terminal of the vacuum switch 4 under test. Figure 1 The lower end of the circuit. When the commutation branch 2 is engaged, it can force and quickly transfer the current flowing through the vacuum switch under test 4 to its own circuit, forcing the current of the vacuum switch under test 4 to cross zero and extinguish the arc. After the commutation branch 2 is engaged, by utilizing the fast reverse charging characteristic of the internal small-capacity capacitor, a transient recovery voltage TRV with an extremely high rise rate can be established across the vacuum switch under test 4, which is used to assess the arc insulation withstand capability of the vacuum switch under test 4.

[0029] The function of the oscillating energy absorption branch 3 is to absorb and protect energy. This branch is also connected in parallel across the two ends of the vacuum switch 4 under test. One end of the oscillating energy absorption branch 3 is connected to the first end of the vacuum switch 4 under test, and the other end of the oscillating energy absorption branch 3 is connected to the common connection point.

[0030] The oscillation energy absorption branch 3 mainly consists of a surge arrester and a control switch connected in series. When the vacuum switch 4 under test breaks down under the action of transient recovery voltage, the oscillation energy absorption branch 3 can quickly conduct, providing a discharge path for the subsequent surge current, and absorbing energy through the surge arrester, thereby limiting overvoltage and protecting other equipment in the test circuit from damage.

[0031] At the start of the test, current generating branch 1 operates, generating current that flows through the tested vacuum switch 4, which is in the closed state. Before the current reaches its peak value, the tested vacuum switch 4 opens, generating an electric arc. After a controlled arcing time, the trigger commutation branch 2 is activated, realizing current reversal and arc extinguishing, and subsequently a high-steep TRV is applied across the tested vacuum switch 4.

[0032] If the post-arc dielectric strength of the vacuum switch 4 under test is insufficient, it will break down under the action of TRV, and the current after breakdown will be absorbed by the oscillating energy absorption branch 3. Its post-arc withstand voltage characteristics can be evaluated by monitoring key parameters such as breakdown voltage.

[0033] This embodiment provides a clear experimental circuit architecture, with three branches having clearly defined functions and working collaboratively, providing a basic platform for efficiently and flexibly testing the post-arc performance of vacuum switches under high-frequency oscillations. This scheme generates a high-steepness TRV through the natural physical process of commutator branch 2, eliminating the need for a complex external high-voltage source, simplifying the system and reducing costs. Simultaneously, each branch can be controlled by an independent switch, and parameters such as arcing time and current drop rate are easily adjustable, exhibiting good operability and adaptability.

[0034] As one embodiment provided, such as Figure 1 , This embodiment more completely reveals the composition, collaborative working mechanism and overall workflow of the experimental circuit architecture.

[0035] The current generating branch 1 serves as the main energy source, simulating the fault current flowing through the vacuum switch 4 under test. The core of the current generating branch 1 is the first LC oscillation unit 11, which is composed of a first capacitor 111 and a first inductor 112 connected in series. The parameters of the first capacitor 111 and the first inductor 112 together determine the frequency and amplitude of the high-frequency oscillating current generated by the discharge circuit.

[0036] The first charging unit 12 provides energy to the first LC oscillation unit 11. The first charging unit 12 includes a first charging power supply 121, a first charging switch 122, and a first charging resistor 123. During the charging phase, the first charging switch 122 is closed, and the positive terminal of the first charging power supply 121 is connected to the high potential terminal of the first capacitor 111 through the first charging switch 122 and the first charging resistor 123; the negative terminal of the first charging power supply 121 is connected to the common connection point of the first capacitor 111 and the first inductor 112. This step can charge the first capacitor 111 to a preset voltage through the current limiting effect of the first charging resistor 123, thereby storing energy for the subsequent generation of arc current.

[0037] The entire current-generating branch 1 is connected to the main circuit via the first control switch 5. Only when the first control switch 5 is closed does the first capacitor 111, the first inductor 112, the vacuum switch under test 4 (which is in a closed state), and the third control switch 31 of the oscillation energy-absorbing branch 3 form a complete discharge circuit, generating an arcing current flowing through the vacuum switch. To ensure safety, a first discharge unit 13 is connected in parallel across the first capacitor 111. The first discharge unit 13 includes a discharge switch K2 and a discharge resistor R2 connected in series, used to safely release the residual charge of the first capacitor 111, i.e., C1, after the test or in an emergency.

[0038] The commutation branch 2 is responsible for forcing the current to zero after arcing and naturally generating a high-steep transient recovery voltage (TRV) for testing insulation. The core of the commutation branch 2 is the second LC oscillation unit 21, which is composed of a second capacitor 211 and a second inductor 212 connected in series.

[0039] In this scheme, the capacitance of the second capacitor 211 is much smaller than that of the first capacitor 111, which is the core physical basis for achieving rapid TRV establishment. The inductance value of the second inductor 212 is an adjustable parameter used to control the rate of change of current. The initial energy of the second LC oscillation unit 21 is provided by the second charging unit 22, which includes an adjustable voltage second charging power supply 221, a second charging switch 222, and a second charging resistor 223. By closing the second charging switch 222, the second charging power supply 221 can charge the second capacitor to the pre-charging voltage U2. The polarity and magnitude of the pre-charging voltage U2 are important variables for controlling the subsequent current zero-crossing characteristics and the initial reverse voltage.

[0040] The converter branch 2 is connected to the main circuit via the second control switch 6. The activation time is precisely controlled to achieve the setting of the arcing time and the forced transfer of current. Similarly, the second discharge unit 23 is connected in parallel across the second capacitor 211. The second discharge unit 23 includes a switch K4 and a resistor R3 for safe energy release.

[0041] The oscillating energy-absorbing branch 3 is the system's safety protection unit. It provides an energy discharge path when the tested vacuum switch 4 breaks down. The oscillating energy-absorbing branch 3 consists of an energy-absorbing surge arrester 32 and a third control switch 31 connected in series. The third control switch 31, i.e., k7, and the tested vacuum switch 4 open synchronously. In the initial closed state, the third control switch 31 provides a path for the current-generating branch 1. When the tested vacuum switch 4 opens, the third control switch 31 opens synchronously. When the tested vacuum switch 4 breaks down, the high-amplitude breakdown current is mainly discharged and absorbed through the energy-absorbing surge arrester 32, thereby effectively limiting overvoltage and protecting other parts of the circuit.

[0042] As one embodiment provided, such as Figures 1-6 , The testing method involved in this embodiment mainly includes the following stages: Circuit preparation and capacitor charging stage: Charge the energy storage elements of each branch to the preset voltage.

[0043] Arc current establishment and switch opening stage: Establish test current and control the vacuum switch to open and initiate arc at a specific time.

[0044] Current commutation and transient recovery voltage (TRV) application stage: The commutation branch is engaged, forcing the current to cross zero and establishing a rapidly rising TRV at the switch break.

[0045] Breakdown detection and energy absorption stage: Monitor whether the switch is broken down, and protect the circuit by the energy absorption branch after breakdown.

[0046] Data measurement and analysis phase: Acquire voltage and current waveforms, calculate key parameters, and evaluate post-arc withstand voltage level.

[0047] Step S1 is circuit initialization and capacitor charging. Before the test, it is necessary to ensure that the third control switch 31 of the vacuum switch 4 under test and the oscillation energy absorption branch 3 are in the closed state, and the first control switch 5 of the current generation branch 1 and the second control switch 6 of the commutation branch 2 are in the open state.

[0048] During the charging process of the first capacitor 111, the first charging switch 122 is closed, and the positive terminal of the first charging power supply 121 is connected to the high potential terminal of the first capacitor 111 through the first charging switch 122 and the first charging resistor 123; the negative terminal of the first charging power supply 121 is connected to the common connection point of the first capacitor 111 and the first inductor 112. This step can charge the first capacitor 111 to the preset voltage U1 through the current limiting effect of the first charging resistor 123. According to the typical parameters in Table 1, when C1=23 mF and L1=0.5 mH, an oscillating current with a half-cycle of about 10.6 ms and a peak value of about 15.6 kA can be generated.

[0049] When the second charging switch 222 is closed, the second charging power supply 221 can charge the second capacitor 211 to the pre-charging voltage U2. In this scheme, the value of the second capacitor 211 is selected as 22.5 μF / 120 kV, the value of the second inductor 212 is selected as 4 / 6 / 10 μH, the oscillation frequency is set between 10.6 and 16.0 kHz, and the voltage of the selected second charging power supply 221 is adjustable from 0 to 15 kV.

[0050] To control the arc current to be constant, it is necessary to ensure that the first capacitor 111 in the current generation branch 1 is precharged at a constant value, and that the parameters of C1 and L1 are constant. In addition, the capacitance of the second capacitor 211 remains unchanged, which can control the post-arc TRV rise rate to remain constant.

[0051] The variable parameters of the test circuit include the pre-charge voltage U2 of the second capacitor 211 and the inductance L2 of the commutation branch 2. Adjusting U2 and L2 controls the zero-previous current drop rate di / dt and the reverse voltage time. The curve relationship between the zero-previous current drop rate di / dt and the supply voltage U2 under different L2 values ​​can be derived, as follows: Figure 2 As shown.

[0052] Figure 2The relationship between the pre-charge voltage of capacitor C2 and the rate of decrease of the zero-precedent current is shown under different L2 inductance values. In addition, if it is necessary to control the arcing time, it is only necessary to keep the closing time of K6 unchanged and adjust the opening time of the vacuum switch.

[0053] By measuring the voltage across the vacuum switch 4 under test, the current flowing through the vacuum switch 4, and combining this with the opening sequence, the arcing time, the rate of decrease of the current before zero, the magnitude of the reverse voltage, the reverse voltage time, the rate of increase of the post-arc TRV, and the breakdown voltage can be obtained. Comparing the breakdown voltage can determine the post-arc dielectric recovery status of the vacuum switch. Figure 3 As shown, Figure 3 The test sequence and characteristic waveforms of the dielectric recovery test after the fourth arc of the vacuum switch under test are given.

[0054] The voltage across the vacuum switch 4 under test, the commutator branch 2, and the current waveform of the vacuum switch 4 under test can be measured by... Figure 4 The breakdown time and breakdown voltage can be obtained from the typical test waveform. Parameters such as the rate of decrease of the current before zero, the rate of increase of the voltage after arc, the magnitude of the reverse voltage, and the time can be calculated.

[0055] Step S2 involves establishing the arc current and opening the vacuum switch. First, the first control switch 5 is closed. At this time, the current generating branch 1 forms a discharge circuit: C1 positive terminal → L1 → K5 → the vacuum switch under test 4 closes → K7 closes → C1 negative terminal.

[0056] The current flowing through the tested vacuum switch 4 gradually increases according to the LC oscillation law. By monitoring the current waveform, a control signal is triggered before the oscillating current reaches its first peak value, causing the tested vacuum switch 4 and switch K7 to open synchronously. After the tested vacuum switch 4 opens, an electric arc is generated between the contacts, entering the arcing stage.

[0057] The control logic for the arcing time is as follows: keep the closing time of the second control switch K6 unchanged in the subsequent steps, and change the time interval from opening to closing of K6 by adjusting the opening time of the vacuum switch 4 under test and the third control switch K7, thereby achieving precise adjustment of the arcing time. As shown in Table 2, the arcing time was adjusted from 1.25 ms to 2.15 ms, which shows the test results after changing the arcing time.

[0058] By organizing the data, we obtained the breakdown voltage versus arcing time curve under the condition of zero-precession current drop rate of 900±50 kA / ms, as shown below. Figure 5 As shown.

[0059] It can be observed that after the vacuum switch oscillates at high frequency and crosses zero, the breakdown voltage first increases and then decreases with increasing arcing time. This is because as the arcing time increases, the opening gap increases, and the arcing energy also increases. However, the opening gap has a greater impact on dielectric recovery and is more conducive to dielectric recovery. When the arcing time exceeds 2.0 ms, the arcing energy at the break point has a greater impact on dielectric recovery and is not conducive to withstanding recovery overvoltage. The vacuum switch has a maximum breakdown voltage and a corresponding optimal arcing time. As shown in the figure, under the condition of a zero-precession current drop rate of 900±50 kA / ms, the maximum breakdown voltage is 66.6 kV, and the optimal arcing time is 1.98 ms.

[0060] Step S3 mainly involves current commutation and TRV application. After the set arcing time, the second control switch 6 is triggered to close. Commutation branch 2 starts working, and the second capacitor 211 discharges through the arc gap of the second inductor 212, the second control switch 6, and the vacuum switch under test 4. Since the oscillation frequency formed by the second inductor 212 and the second capacitor 21 is much higher than the main current frequency, the current flowing through the vacuum switch under test 4 is quickly commutated to commutation branch 2 and crosses zero, thus extinguishing the arc of the vacuum switch under test 4.

[0061] At this time, the second capacitor 211 is in a reverse voltage state, and the tested vacuum switch 4 experiences a brief post-arc reverse voltage. Subsequently, the current in the circuit begins to reverse charge the tiny second capacitor 211. Since the capacitance value of the second capacitor 211, C2, is much smaller than C1, the voltage Uc2 at the terminal of the second capacitor 211 rises rapidly, thereby establishing a transient recovery voltage with an extremely high rise rate across the tested vacuum switch 4.

[0062] Step S4 involves breakdown detection and energy absorption. As the TRV (Transient Voltage Value) increases, when the voltage across the tested vacuum switch 4 exceeds its current post-arc dielectric recovery strength, the tested vacuum switch 4 is re-broken down. After breakdown occurs, a high-frequency oscillating surge current is generated in the circuit. At this time, since switch K7 has already been synchronously tripped with the tested vacuum switch 4 in step S2, the main path of the breakdown current is: C2 → L2 → K6 → tested vacuum switch 4 → energy-absorbing surge arrester 32. The energy-absorbing surge arrester 32 quickly activates, clamping the overvoltage and absorbing most of the surge energy, protecting the test circuit.

[0063] When it is necessary to test the post-arc dielectric recovery characteristics of vacuum switches under different post-arc reverse voltages, the pre-charge voltage of the second capacitor 211 and the second inductor 212 of the commutation branch 2 are adjusted to ensure that the magnitude and duration of the applied reverse voltage are changed while the rate of decrease of the zero-previous current remains unchanged. Finally, the test results with the rate of decrease of the zero-previous current of 400~550 kA / ms and >600 kA / ms are obtained. The parameter settings and test results are shown below. The table below shows the test results of changing the post-arc reverse voltage parameter settings and changing the post-arc reverse voltage.

[0064] In this analysis, the arcing time, arcing current, and voltage rise rate remain constant. Since the ratio of reverse voltage magnitude to time remains constant, we can treat reverse voltage magnitude and reverse voltage time as variables. Using the average reverse voltage magnitude for analysis, and based on two data sets—one with a zero-precursor current drop rate >600 kA / ms and the other with a drop rate between 400 and 550 kA / ms—we have compiled the following curves showing the variation of breakdown voltage with post-arc reverse voltage magnitude within these two zero-precursor current drop rate ranges: Figure 6 As shown, Figure 6 The curve shows the breakdown voltage as a function of the post-arc reverse voltage.

[0065] The results show that, under both zero-precursor current drop rate conditions of >600 kA / ms and 400–550 kA / ms, increasing the post-arc reverse voltage significantly improves the breakdown voltage. However, under the same post-arc reverse voltage, the breakdown voltage is generally higher in the 400–550 kA / ms range than in the >600 kA / ms range. This indicates that under high-frequency oscillation conditions, applying reverse voltage is beneficial for post-arc dielectric recovery in vacuum switches, while a rapid current drop rate is detrimental.

[0066] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A test circuit for measuring the arc withstand voltage characteristics of a vacuum switch, characterized in that: include, The current generating branch (1) is connected to the first terminal of the vacuum switch (4) under test, generating an arc current flowing through the vacuum switch under test; The commutation branch (2) is connected in parallel across the two ends of the vacuum switch (4) under test. The second end of the vacuum switch (4) under test is connected to the common connection point. The commutation branch (2) is put into operation after the vacuum switch (4) under test is opened, so as to realize current commutation and establish transient recovery voltage at both ends. The oscillating energy absorption branch (3) is connected at one end to the first end of the vacuum switch (4) under test, and at the other end to the common connection point.

2. The test circuit for measuring the arc withstand voltage characteristics of a vacuum switch according to claim 1, characterized in that: A first LC oscillation unit (11) and a first charging unit (12) are provided in the current generating branch (1); The first LC oscillation unit (11) includes a first capacitor (111) and a first inductor (112) connected in series; The first charging unit (12) includes a first charging power supply (121), a first charging switch (122) and a first charging resistor (123). The positive terminal of the first charging power supply (121) is connected to the high potential end of the first capacitor (111) through the first charging switch (122) and the first charging resistor (123) connected in series, and the negative terminal is connected to the low potential end of the first capacitor (111). The first LC oscillation unit (11) is connected to the main current path through the first control switch (5).

3. The test circuit for measuring the arc withstand voltage characteristics of a vacuum switch according to claim 1, characterized in that: A second LC oscillation unit (21) and a second charging unit (22) are provided in the converter branch (2); The second LC oscillation unit (21) includes a second capacitor (211) and a second inductor (212) connected in series; The second charging unit (22) includes a second charging power supply (221), a second charging switch (222), and a second charging resistor (223). The positive terminal of the second charging power supply (221) is connected to the high potential end of the second capacitor (211) through the second charging switch (222) and the second charging resistor (223) connected in series, and the negative terminal is connected to the low potential end of the second capacitor (211). The second LC oscillation unit (21) is connected to the main current path through the second control switch (6).

4. The test circuit for measuring the arc withstand voltage characteristics of a vacuum switch according to any one of claims 1 to 3, characterized in that: The first discharge unit (13) and the second discharge unit (23) are respectively installed in the current generating branch (1) and the commutation branch (2); The first discharge unit (13) and the second discharge unit (23) include a discharge switch and a discharge resistor.

5. The test circuit for measuring the arc withstand voltage characteristics of a vacuum switch according to claim 4, characterized in that: The oscillating energy-absorbing branch (3) includes a third control switch (31) and a series-connected energy-absorbing surge arrester (32). The capacitance of the second capacitor (211) is less than that of the first capacitor (111).

6. A test method comprising the test circuit for measuring the arc withstand voltage characteristics of a vacuum switch as described in claim 5, characterized in that: It also includes the following processes: When the current generating branch (1) provides oscillating current to the closed vacuum switch (4), it controls the vacuum switch (4) to open and start arcing. After the arcing of the vacuum switch (4) under test continues for a set time, the commutation branch (2) is activated, and the current is commutated from the current generating branch (1) to the commutation branch (2), so that the two ends of the vacuum switch (4) under test are subjected to transient recovery voltage. After the vacuum switch under test (4) breaks down due to transient recovery voltage, it absorbs the remaining energy in the circuit through the oscillating energy absorption branch (3).

7. The test method according to claim 6, characterized in that: In the charging steps before engaging the converter branch (2), The first charging switch (122) in the closed current generating branch (1) charges the first capacitor (111) to the first preset voltage through the first charging power supply (121) and the first charging resistor (123); The second charging switch (222) in the closed commutation branch charges the second capacitor (211) to the second preset voltage through the second charging power supply (211) and the second charging resistor (223); After charging is complete, disconnect the first charging switch (122) and the second charging switch (222).

8. The test method according to claim 7, characterized in that: In the parameter adjustment steps, Adjust the power supply voltage for charging the second capacitor (211), select the inductance parameters of the commutation branch (2), and control the current drop rate before the current crosses zero and the reverse voltage characteristics of the vacuum switch (4) under test after the arc. Adjust the voltage value of the second charging power supply (221), replace the second inductor (212) with a different inductance value, and change the rate of change of current during the commutation process.

9. The test method according to claim 8, characterized in that: In the arc time control step, Control the vacuum switch under test (4) to open before the oscillating current provided by the current generating branch (1) reaches its peak value; Keep the second control switch (6) closed at the set fixed time, and only change the opening time of the vacuum switch (4) under test to achieve arcing time adjustment.

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