Post-arc insulation strength detection platform for contact gap of switch equipment and detection method of post-arc insulation strength detection platform

Abstract

The invention provides a platform and a method for detecting the post-arc insulation strength of a contact gap of switch equipment, and belongs to the technical field of electric appliance testing. The direct-current rectifying circuit and the pulse generating circuit are respectively connected to two ends of the switch cabinet; the switch control circuit is respectively connected with the direct-current rectifying circuit and the pulse generating circuit; the test electrode and the measuring circuit are connected with the switch cabinet; the test electrode is arranged in the switch cabinet; the switch cabinet is provided with a measuring circuit. Firstly, a direct-current arc is generated in a high-voltage breakdown mode; after forced arc quenching, pulse high voltage is rapidly applied to the two ends of the gap, and the post-arc withstand voltage value is measured. And then the power electronic switch is used for controlling the time interval between the arc extinguishing moment and the pressurization moment, namely the insulation recovery time is controlled. The detection platform constructed by the invention adopts a post-arc withstand voltage method to represent post-arc air post-arc electric strength characteristics so as to obtain post-arc air electric strength recovery time.

Description

Technical Field

[0001] The invention provides a post-arc insulation strength detection platform for contact gaps of switching equipment and a detection method thereof, belonging to the technical field of electrical appliance testing. Background Art

[0002] To address the problem of arc reignition across contact points in switchgear, measuring post-arc dielectric strength provides a direct basis for analyzing arc reignition. The post-arc dielectric strength between switchgear contacts determines whether the arc can reignite. If the dielectric strength recovery rate is consistently faster than the voltage recovery rate, the dielectric strength is sufficient and the arc will not reignite. If the dielectric strength recovery rate is slower than the voltage recovery rate, the gap will experience restrike, leading to arc reignition. After the spark path in a gas-gap switch is extinguished, the gap remains filled with a large amount of high-temperature gas and residual charged particles, preventing the dielectric strength between the switch contacts from recovering immediately. If the recovery of the gas dielectric strength is delayed after the circuit has released redundant power or eliminated residual voltage, the probability of restrike will increase significantly, potentially leading to malfunction of the switchgear and compromising the reliability and safety of the power grid. Therefore, it is necessary to test the post-arc dielectric strength of the switchgear contact gap. However, limited research has been conducted on the post-arc dielectric strength of switchgear contact gaps. Given the rapid recovery time of gas dielectric strength (typically tens to hundreds of milliseconds, or even microseconds), post-arc dielectric strength testing is difficult. Existing testing methods cannot meet the requirements for measuring the post-arc dielectric strength of switchgear. They can only obtain single-point or indirect data, resulting in limited data, making it difficult to generate time-reignition curves and imprecise measurements. The experimental setup is complex, and the testing cost is high.

[0003] Patent CN1661384A provides an insulation pulse dielectric strength tester. Based on a power supply and high-voltage switch module, this device uses a storage capacitor bank and a resistor network to generate bipolar high-voltage pulses to simulate the high-frequency pulses experienced by PWM variable-frequency motors. The test interface utilizes a high-voltage relay matrix and a multi-channel parallel architecture. Spring probes or clamping fixtures accommodate various wire diameters and structures. Insulation breakdown events are determined by current mutation thresholds, and breakdown time is recorded to quantify the material's lifespan.

[0004] This technology has the following technical disadvantages: short-term high-energy pulses may directly break down weak points in insulation, causing damage to the test equipment; the pulse rise time and amplitude are easily affected by distributed capacitance and inductance, resulting in waveform distortion, which makes the test results deviate greatly; current mutations may be triggered by non-breakdown phenomena such as corona discharge, but such phenomena may not necessarily cause breakdown, resulting in deviations in test results; the setting of the threshold for determining the amount of current mutation is unclear, and it lacks adaptability to multiple types of switching equipment. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of difficulty in measuring the post-arc dielectric strength of an arc and to provide a new test method and test platform for measuring the dielectric strength of contacts in switchgear equipment.

[0006] The post-arc dielectric strength testing platform for switchgear contact gaps constructed by this invention tests the dielectric strength of air after arc extinction and measures the post-arc dielectric strength recovery time. The platform uses the post-arc withstand voltage method to characterize post-arc dielectric strength.

[0007] The main functions of this platform are: 1. Using high-voltage breakdown to generate a DC arc; 2. After the arc is forced out, a pulsed high voltage can be quickly applied across the gap to measure the post-arc withstand voltage; 3. Using power electronic switches to control the time interval between arc extinction and voltage application, that is, to control the voltage recovery time. The protective high-voltage silicon stack serves to connect and isolate: (1) When the DC rectifier circuit continues current to the arc, the high-voltage silicon stack acts as a circuit connection (forward conduction); (2) When a pulsed high voltage is applied after the arc is extinguished, the high-voltage silicon stack acts as a reverse blocking pulse high voltage, thereby protecting the DC rectifier circuit, that is, isolation.

[0008] The specific technical solutions are:

[0009] A post-arc insulation strength testing platform for contact gaps of switchgear includes: a DC rectifier circuit and a pulse generator circuit respectively connected to both ends of a switch cabinet; and a switch control circuit respectively connected to the DC rectifier circuit and the pulse generator circuit;

[0010] The DC rectifier circuit uses the unidirectional conduction and rectification of the silicon stack to output DC current;

[0011] The pulse generating circuit is used to generate pulse high voltage to break down the gap between the test electrodes;

[0012] The switch control circuit is used to control the charging of the DC rectifier circuit and the charging and discharging of the pulse generating circuit;

[0013] The test electrodes are connected to the measuring circuit and the switch cabinet;

[0014] The test electrodes are arranged in the switch cabinet; the switch cabinet is equipped with a measuring circuit.

[0015] Furthermore, the DC rectifier circuit includes a rectifier silicon stack D1, a rectifier capacitor C2, and a control console connected in series to form a first circuit; wherein the rectifier silicon stack D1 and the rectifier capacitor C2 form a sub-circuit, and the sub-circuit is connected in parallel with the rectifier silicon stack D2;

[0016] The rectifier capacitor C2 acts as the second circuit and is connected in parallel with the first circuit to form a parallel circuit;

[0017] One end of the parallel circuit is connected to the protective silicon stack D3;

[0018] The other end of the parallel circuit is grounded, and is connected in series with a current limiting resistor R1 and a protective silicon stack D4;

[0019] The DC rectifier circuit stores the AC charging voltage on two rectifier capacitors respectively. In each cycle, the rectifier capacitor C2 charges the rectifier capacitor C1, so that the voltage of the rectifier capacitor C2 is continuously superimposed, stored, and then superimposed on the rectifier capacitor C1, and finally a DC current is output at both ends of the rectifier capacitor C1.

[0020] Furthermore, the pulse generating circuit includes a Marx generator, a rectifier transformer, a ZVS circuit, a single-phase full-wave rectifier bridge and a BK-50VA control transformer.

[0021] The 220V AC voltage is stepped down to 24V AC by a control transformer, then passes through a single-phase full-wave rectifier bridge to power the ZVS circuit. The rectifier transformer outputs a 20kV DC high voltage to charge the Marx generator. The Marx generator circuit ultimately generates a pulsed high voltage that breaks down the test electrode gap.

[0022] Furthermore, the switch control circuit includes two sets of IGBT switches, namely switch B1 and switch B2, as well as a main circuit board, a control box and a battery;

[0023] The switch B1 is installed on the input power side of the console, and it charges the DC rectifier circuit or forces the arc to be extinguished by turning on or off the power supply of the console.

[0024] Switch B2 is installed on the input power side of the pulse generating circuit to control the pulse generating circuit to achieve pulse breakdown and arc ignition and quickly apply secondary voltage after the arc.

[0025] The main circuit board and control box are powered by batteries.

[0026] Furthermore, the measurement circuit uses a weakly damped voltage divider with a voltage divider ratio of 642:1 to access the digital oscilloscope via a coaxial delay cable; a matching resistor and a filter capacitor are connected in parallel between the end of the coaxial delay cable and the ground wire.

[0027] Switchgear contact gap post-arc insulation strength test method:

[0028] Before testing, adjust the gap distance between the two detection electrodes in the switch cabinet and pre-test the pulse breakdown voltage value U1 of the air at the gap distance.

[0029] When starting the test, first turn on switch B1 to power the console and voltage regulator, slowly increase the voltage and match it with the adjusted current limiting resistor value so that the output capacity of the DC rectifier circuit reaches the required test parameters. At this time, DC voltage has been applied to both ends of the electrode to prepare for DC freewheeling.

[0030] Then, switch B2 is turned on to charge the Marx generator of the pulse generating circuit. After charging is completed, the pulse high voltage generated by the pulse circuit causes the electrode gap to break down, generating a transient arc. The transient arc is superimposed on the DC freewheeling current to form a steady-state high-current arc. The pulse breakdown arc is superimposed on the DC freewheeling current to generate a steady-state DC arc.

[0031] Finally, by automatically turning off switch B1 and automatically turning on switch B2, the arc is forcibly de-energized and extinguished. Turning on switch B2 re-energizes the pulse circuit and re-applies the high voltage pulse. During this process, an oscilloscope is used to record the post-arc withstand voltage value U2 and the duration of the post-arc voltage application. This completes the post-arc insulation withstand voltage test and determines the post-arc withstand voltage recovery characteristics.

[0032] The present invention can test the post-arc withstand voltage strength of switchgear with contacts, providing strong support for the research and performance of their arc interruption characteristics, facilitating the development and testing of switching equipment. The present invention is not limited to specific contact shapes and gaps and is applicable to switchgear of various voltage levels, encompassing a wide range of testing applications. Furthermore, the present invention can be used not only for switchgear but also in other applications requiring post-arc withstand voltage strength measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the detection platform of the present invention;

[0034] Figure 2 This is a schematic diagram of the charging process of the DC rectifier circuit of the present invention;

[0035] Figure 3 This is the pulse voltage waveform diagram of the present invention;

[0036] Figure 4 This is the button function and timing diagram of the present invention. DETAILED DESCRIPTION

[0037] The specific technical solutions of the present invention are described with reference to the accompanying drawings.

[0038] like Figure 1 As shown in the figure, the corresponding components of the switchgear contact gap post-arc insulation strength detection platform are as follows: DC rectification circuit (red line), pulse generation circuit (blue line), switch control circuit (green line), test electrode and measurement circuit (black line).

[0039] A post-arc insulation strength testing platform for contact gaps of switchgear includes: a DC rectifier circuit and a pulse generator circuit respectively connected to both ends of a switch cabinet; and a switch control circuit respectively connected to the DC rectifier circuit and the pulse generator circuit;

[0040] The DC rectifier circuit uses the unidirectional conduction and rectification of the silicon stack to output DC current;

[0041] The pulse generating circuit is used to generate pulse high voltage to break down the gap between the test electrodes;

[0042] The switch control circuit is used to control the charging of the DC rectifier circuit and the charging and discharging of the pulse generating circuit;

[0043] The test electrodes are connected to the measuring circuit and the switch cabinet;

[0044] The test electrodes are arranged in the switch cabinet; the switch cabinet is equipped with a measuring circuit.

[0045] The installation polarity of the protective high voltage silicon stack must be correct and should be strictly followed. Figure 1 shown.

[0046] Among them, the DC rectifier circuit includes: KZT-0.5kV control console, TYDA-380V inductive voltage regulator, two 0.5uF rectifier capacitors, two 3kV / 150A rectifier high-voltage silicon stacks, high-power current limiting resistors and two 225kV / 100A protective high-voltage silicon stacks.

[0047] Specifically, such as Figure 1 , including a rectifier silicon stack D1, a rectifier capacitor C2, and a control console connected in series to form a first circuit; the rectifier silicon stack D1 and the rectifier capacitor C2 form a sub-circuit, and the sub-circuit is connected in parallel with the rectifier silicon stack D2; the rectifier capacitor C2 serves as a second circuit, connected in parallel with the first circuit to form a parallel circuit; one end of the parallel circuit is connected to the protection silicon stack D3; the other end of the parallel circuit is grounded, and is connected in series with a current limiting resistor R1 and a protection silicon stack D4.

[0048] Figure 2 The charging process of a DC rectifier circuit is presented. The DC rectifier circuit utilizes the unidirectional conduction and rectification of the silicon stack to store the AC charging voltage on two rectifier capacitors. During each cycle, rectifier capacitor C2 charges rectifier capacitor C1, causing the voltage on rectifier capacitor C2 to be continuously superimposed, stored, and then added to rectifier capacitor C1, ultimately outputting a DC current across rectifier capacitor C1.

[0049] Among them, the pulse generating circuit: the pulse generating circuit includes a Marx generator, a rectifier transformer, a ZVS circuit, a single-phase full-wave rectifier bridge and a BK-50VA control transformer.

[0050] The 220V AC voltage is stepped down to 24V AC by the control transformer, and then passes through a single-phase full-wave rectifier bridge to power the ZVS circuit. The rectifier transformer outputs a 20kV DC high voltage to charge the Marx generator. The Marx generator circuit ultimately generates a pulsed high voltage that breaks down the electrode gap.

[0051] like Figure 3As shown. Considering the influence of residual charge during charging and discharging, the pre-charge time of the Marx generator needs to be calibrated in advance. Through experimental measurement, the pre-charge time of the Marx generator is approximately 1300ms±20ms, and the charging time is independent of the test electrode gap distance and has little dispersion. The Marx generator used in the present invention is a 20-stage CB80-2000pF / 30kV polystyrene film pulse capacitor C3 charged in parallel, with each stage charging resistor R2 having a value of 1MΩ and a series discharge resistor R3 having a value of 1kΩ. The resulting pulse voltage has a rising steepness of approximately 25kV / μs.

[0052] The switch control circuit utilizes an IGBT-based power electronic switch and its control circuit to independently control the charging and discharging of the DC rectifier circuit and the pulse generator circuit. It consists of two IGBT switches (hereinafter referred to as switches B1 and B2), a main circuit board, a control box, and a battery. Switch B1 is installed on the console's 380V input power supply side and serves to charge the DC rectifier circuit or forcefully extinguish the arc by turning the console's power supply on or off. Switch B2 is installed on the pulse generator circuit's 220V input power supply side and controls the pulse generator circuit to achieve pulse breakdown arc ignition and rapid application of a secondary voltage after the arc. Furthermore, to prevent false triggering of the IGBT switches due to strong electromagnetic interference during testing, the control circuit's drive lines utilize shielded cables, and the main circuit board and control box are powered by a 12V DC battery. The control box contains three control buttons and an emergency stop button: the "Manual 220V" button switches switch B2 on and off independently. The "Manual 380V" button switches switch B1 on and off independently. The "Auto Control" button automatically turns off switch B1 and turns on switch B2, with an adjustable time interval between the two. This button allows you to pre-set three time points: ΔT1, the time switch B2 turns on after pressing the "Auto Control" button; ΔT2, the time switch B1 turns off; and ΔT3, the time switch B2 turns off. Figure 4The function and timing diagram of the "Automatic Control" button are provided. Regarding the test electrodes and measurement circuit, the test electrodes are rod electrodes that can be installed horizontally or vertically with adjustable gap distance. Electrode materials include copper, carbon, and steel, with electrode diameters of 10 mm, 20 mm, and 30 mm, respectively. These electrodes can be used to study the effects of electrode diameter, installation method, gap distance, and electrode material on post-arc dielectric strength. Furthermore, the test electrodes can be placed inside the switchgear. The main measurement parameters are the initial gap breakdown voltage U1, the DC arc current I, and the post-arc breakdown voltage U2. The measurement circuit uses an FY-600kV weakly damped voltage divider with a voltage divider ratio of 642:1, connected to a DSO7104A digital oscilloscope via a coaxial time-delay cable. The oscilloscope has a sampling rate and bandwidth of 4 GS / s and 1 GHz, respectively, meeting the test requirements. In addition, to eliminate high-frequency oscillations superimposed on the pulse waveform due to wave refraction and reflection and gap breakdown, a 50Ω matching resistor and an 8nF filter capacitor were connected in parallel between the end of the coaxial delay cable and the ground wire. The capacitor should not be too large or too small. Too small will result in poor filtering effect, while too large may filter out the measured signal. This ensures that a clear and undistorted pulse breakdown voltage waveform can be acquired.

[0053] The post-arc insulation strength test method for switchgear contact gaps is as follows: Before testing, adjust the gap distance between the two electrodes in the switchgear and pre-test the air pulse breakdown voltage value U1 at this gap distance. To begin testing, first turn on switch B1 to power the control console and voltage regulator. Slowly increase the voltage and, in conjunction with the adjusted current-limiting resistor value, ensure that the output capacity of the DC rectifier circuit meets the required test parameters. At this point, DC voltage is applied across the electrodes, preparing for DC freewheeling. Then, manually turn on switch B2 to charge the Marx generator. After charging is complete, the pulsed high voltage generated by the pulse circuit causes the electrode gap to break down, generating a transient arc. This transient arc is then superimposed on the DC freewheeling current, forming a steady-state high-current arc. This process can be summarized as: pulse breakdown arcing superimposed on DC freewheeling current, resulting in a steady-state DC arc. Finally, press the automatic control button. This button automatically coordinates switches B1 and B2. The specific on / off timing and functions are automatically achieved using power electronic switch technology: 1. B1 is turned off, forcing the arc to be de-energized and extinguished; 2. B2 is turned on to power the pulse circuit and re-apply the high voltage pulse. During this process, an oscilloscope is used to record the post-arc withstand voltage value U2 and the duration of the post-arc voltage application. This completes the post-arc insulation withstand voltage test and determines the post-arc withstand voltage recovery characteristics.

[0054] In the present invention, high voltage silicon stacks (D3 and D4) are installed at the positive and negative output ends of the rectifier current. The high voltage silicon stack plays the role of reverse blocking pulse high voltage to protect the DC rectifier circuit, and the high voltage silicon stack plays the role of circuit connection (forward conduction). The rectifier circuit is free from the threat of high voltage (the installation method of the high voltage silicon stack must be consistent with the circuit Figure 1 To).

[0055] The control circuit of the present invention starts from the low-voltage side power supply of the pulse generating circuit and the sorting circuit, completely cuts off the arc power supply, forces the arc to extinguish, and uses power electronic switching technology to control the secondary pulse application time, test the electrical recovery characteristics, and realize the relationship curve between the electrical strength (withstand voltage) and time after the test arc.

[0056] The method of the present invention is not limited by contact gap distance and is applicable to switchgear of various voltage levels (from low voltage to high voltage), covering a wide range of testing. Furthermore, the method and principle of the present invention are applicable not only to switchgear but also to other situations requiring gas dielectric strength testing.

Claims

1. The post-arc insulation strength testing platform for contact gap of switchgear is characterized by: include: The DC rectifier circuit and the pulse generating circuit are connected to both ends of the switch cabinet respectively, and the switch control circuit is connected to the DC rectifier circuit and the pulse generating circuit respectively; The DC rectifier circuit uses the unidirectional conduction and rectification of the silicon stack to output DC current; The pulse generating circuit is used to generate pulse high voltage to break down the gap between the test electrodes; The switch control circuit is used to control the charging of the DC rectifier circuit and the charging and discharging of the pulse generating circuit; The test electrodes are connected to the measuring circuit and the switch cabinet; The test electrodes are arranged in the switch cabinet; the switch cabinet is equipped with a measuring circuit.

2. The switchgear contact gap post-arc insulation strength testing platform according to claim 1, characterized in that: The DC rectifier circuit includes a rectifier silicon stack D1, a rectifier capacitor C2, and a control console connected in series to form a first circuit; wherein the rectifier silicon stack D1 and the rectifier capacitor C2 form a sub-circuit, and the sub-circuit is connected in parallel with the rectifier silicon stack D2; The rectifier capacitor C2 acts as the second circuit and is connected in parallel with the first circuit to form a parallel circuit; One end of the parallel circuit is connected to the protective silicon stack D3; The other end of the parallel circuit is grounded, and is connected in series with a current limiting resistor R1 and a protective silicon stack D4; The DC rectifier circuit stores the AC charging voltage on two rectifier capacitors respectively. In each cycle, the rectifier capacitor C2 charges the rectifier capacitor C1, so that the voltage of the rectifier capacitor C2 is continuously superimposed, stored, and then superimposed on the rectifier capacitor C1, and finally a DC current is output at both ends of the rectifier capacitor C1.

3. The switchgear contact gap post-arc insulation strength testing platform according to claim 1, characterized in that: The pulse generating circuit includes a Marx generator, a rectifier transformer, a ZVS circuit, a single-phase full-wave rectifier bridge and a control transformer; The 220V AC voltage is stepped down to 24V AC voltage by the control transformer, and then passes through the single-phase full-wave rectifier bridge to power the ZVS circuit; the rectifier transformer outputs 20kV DC high voltage to charge the Marx generator, and the Marx generator circuit eventually forms a pulse high voltage to cause the test electrode gap to break down.

4. The switchgear contact gap post-arc insulation strength testing platform according to claim 1, characterized in that: The switch control circuit includes two sets of IGBT switches, namely switch B1 and switch B2, as well as a main circuit board, a control box and a battery; Switch B1 is installed on the input power side of the console. It charges the DC rectifier circuit or extinguishes the arc by turning on or off the power supply of the console. Switch B2 is installed on the input power side of the pulse generating circuit to control the pulse generating circuit to achieve pulse breakdown arc ignition and rapid application of secondary voltage after arcing; The main circuit board and control box are powered by batteries.

5. The switchgear contact gap post-arc insulation strength testing platform according to claim 1, characterized in that: The measurement circuit uses a weakly damped voltage divider with a voltage divider ratio of 642:1 to access the digital oscilloscope via a coaxial delay cable; a matching resistor and a filter capacitor are connected in parallel between the end of the coaxial delay cable and the ground wire.

6. A method for testing the post-arc insulation strength of the contact gap of a switchgear, characterized in that: The post-arc insulation strength testing platform for contact gap of a switchgear according to any one of claims 1 to 5 comprises the following steps: Before the test, adjust the gap distance between the two test electrodes in the switch cabinet and pre-test the pulse breakdown voltage value U1 of the air at the gap distance; When starting the test, first turn on switch B1 to power the console and voltage regulator, slowly increase the voltage and match the adjusted current limiting resistor value so that the output capacity of the DC rectifier circuit reaches the required test parameters. At this time, DC voltage has been applied to both ends of the electrode, preparing for DC freewheeling. Then, switch B2 is turned on to charge the Marx generator of the pulse generating circuit. After charging is completed, the pulse high voltage generated by the pulse circuit causes the electrode gap to break down and generate a transient arc. The transient arc is superimposed on the DC freewheeling current to form a steady-state high-current arc. The pulse breakdown arc is superimposed on the DC freewheeling current to generate a steady-state DC arc. Finally, by automatically turning off switch B1 and automatically turning on switch B2, turning off B1 forces the arc to be de-energized and extinguished; turning on B2 supplies power to the pulse circuit and applying the pulse high voltage again; during this process, an oscilloscope is used to record the post-arc withstand voltage value U2 and the time of applying the voltage after the arc, thus completing the post-arc insulation withstand voltage test and obtaining the post-arc withstand voltage recovery.

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