A long continuous current discharge simulation device with independently controllable current magnitude and duration

Abstract

The invention discloses a long continuous current discharge simulation device with independently controllable current magnitude and duration, mainly comprising a high-voltage arc starting unit (1) and a continuous discharge unit (2), and also comprising a capacitance control system (3), a charging voltage control system (4), a time-delay circuit breaking system (5) and control software connected to the continuous discharge unit (2). The high-voltage arc starting unit (1) of the device can ignite an arc in an instant (tens of microseconds), and then the continuous discharge unit (2) can maintain the arc for a long time (arc current of 100 to 300 amperes, duration of 100 to 500 milliseconds). The capacitance control system (3) and the charging voltage control system (4) of the device can control the discharge current magnitude; the time-delay circuit breaking system (5) can control the discharge duration. The invention can independently control the current magnitude and duration in simulating long continuous current discharge, and is used to carry out research on lightning ignition of forest combustibles.

Description

Technical Field

[0001] The invention belongs to the technical field of fire safety, and in particular relates to a long continuous current discharge simulation device with independently controllable current magnitude and duration. Background Art

[0002] Lightning strikes are an important natural cause of forest fires, and forest fires caused by lightning strikes are called "lightning fires." Although the number of lightning fires is less than that of man-made fires, the burned area and economic losses caused are often very large, so lightning fires have received widespread attention.

[0003] There are two basic forms of lightning discharge in nature: pulse impact current discharge and long continuous current discharge. The peak current of pulse impact current discharge is large (about tens to hundreds of kiloamperes), but the duration is extremely short (about hundreds of microseconds), and it is usually unable to ignite forest combustibles. Long continuous current discharge is close to direct current discharge, with a lower current amplitude (about hundreds of amperes), but a longer duration (more than 40 milliseconds), which can transmit a large amount of charge and release a large amount of heat. It is generally considered to be the main discharge form that ignites forest combustibles.

[0004] At present, the lightning discharge simulation devices on the market are mainly impulse voltage or impulse current generating devices, which mainly simulate the pulse impulse current discharge in lightning strikes. They are usually used to carry out impulse voltage tests on power overhead lines, aircraft composite materials, etc. under the action of lightning shock waves to detect the safety performance of these equipment or materials. Although this type of discharge simulation device has a high voltage / current level (amplitude can reach tens or hundreds of kilovolts / kiloamperes), the duration is only tens of microseconds, which cannot simulate the long continuous current discharge in lightning strikes.

[0005] The existing simulation device for long continuous current discharge uses high-voltage pulse discharge to start the arc, and then a large-capacity capacitor bank maintains the discharge for a long time (tens of milliseconds) to simulate the long continuous current discharge in lightning strikes. However, this test device can only change the initial voltage of the capacitor bank, and cannot independently control the discharge current size and duration. The initial voltage of the capacitor bank depends on the parameters of the discharge device and cannot directly represent the parameters of actual lightning.

[0006] Therefore, in order to further study the ignition of forest lightning fires and explore the effects of lightning current size and duration on lightning fires, it is very important to develop a long continuous current discharge simulation device with independently controllable current size and duration. This discharge simulation device is not only suitable for experimental research on forest lightning fires, but also for research on power lines, power equipment, aircraft, wooden buildings, etc. that are impacted by long continuous current discharges. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a long continuous current discharge simulation device with independently controllable current magnitude and duration, which provides an experimental basis for studying the ignition problem of forest lightning fires.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] A long continuous current discharge simulation device with independently controllable current magnitude and duration, comprising a high-voltage arc starting unit, a continuous discharge unit, a capacitance control system, a charging voltage control system and a time-delayed circuit breaking system; the capacitance control system, the charging voltage control system and the time-delayed circuit breaking system are connected to the continuous discharge unit;

[0010] The high-voltage arc starting unit includes an impulse voltage generator;

[0011] The continuous discharge unit includes a capacitor group and a DC charging device for charging the capacitor group; the capacitor group is composed of a plurality of sub-capacitor groups connected in parallel;

[0012] The capacitance control system comprises a selection switch and a plurality of on-off switches a, wherein the selection switch is connected to each on-off switch a to control the on-off of each on-off switch a; the number of the on-off switches a is equal to the number of the sub-capacitor groups in the continuous discharge unit, and the on-off switches a are connected to the parallel branch where the sub-capacitor groups are located;

[0013] The charging voltage control system includes a voltage sensor, a voltage comparison microprocessor, and an on-off switch b; the voltage sensor is connected to both ends of the capacitor group in the continuous discharge unit, and the on-off switch b is connected between the capacitor group and the DC charging device;

[0014] The voltage sensor and the on-off switch b are both connected to a voltage comparison microprocessor;

[0015] The time-delay circuit-breaking system comprises an electric signal sensor, a time-delay control microprocessor, and an on-off switch C. The electric signal sensor and the on-off switch C are both connected in a continuous discharge unit and are both connected to the time-delay control microprocessor.

[0016] Furthermore, two needle-shaped electrodes are arranged on the same vertical axis, and the fuel sample to be tested is placed between the two electrodes; the high-voltage arm of the impulse voltage generator is connected to the upper electrode, and the grounding end and the lower electrode are simultaneously connected to the grounding grid of the test room; one end of the capacitor group of the continuous discharge unit is connected to the upper electrode through an inductor, and the other end and the lower electrode are simultaneously connected to the grounding grid.

[0017] Furthermore, the on-off switch a, the on-off switch b and the on-off switch c are all DC contactors.

[0018] Furthermore, when the discharge simulation device is working, the high-voltage arc starting unit first instantly breaks through the gap between the electrodes to ignite the arc, and then the continuous discharge unit continuously supplies power to maintain the arc for a long time to simulate the long continuous current discharge in a lightning strike.

[0019] Beneficial effects:

[0020] The discharge simulation device of the present invention can obtain long continuous current discharge of different current magnitudes by presetting different capacitances and charging voltages of capacitor groups, and establish a corresponding relationship between the discharge current magnitude, capacitance and charging voltage, and then independently control the discharge current magnitude by controlling the capacitance and charging voltage of the capacitor group; and control the duration of the discharge by presetting different delay times. The discharge simulation device can simulate discharge according to typical parameters (current magnitude and duration) of actual lightning, and the parameter control is convenient and accurate, providing an experimental basis for the study of forest lightning fires. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The main components and principle diagram of the long continuous current discharge simulation device with independently controllable current magnitude and duration of the present invention;

[0022] Figure 2 The circuit diagram of the long continuous current discharge simulation device with independently controllable current magnitude and duration of the present invention;

[0023] Figure 3 This is an example diagram of the discharge waveform of the long continuous current discharge simulation device with independently controllable current magnitude and duration of the present invention.

[0024] Among them, 1. high-voltage arc starting unit; 2. continuous discharge unit; 3. capacitor capacity control system; 4. charging voltage control system; 5. delayed circuit breaking system; 6. impulse voltage generator; 7. high-voltage arm; 8. grounding terminal; 9. capacitor group; 10. sub-capacitor group; 11. DC charging device; 12. inductor; 13. electrode; 14. grounding grid; 15. selection switch; 16. on-off switch a; 17. voltage sensor; 18. voltage comparison microprocessor; 19. on-off switch b; 20. electrical signal sensor; 21. delay control microprocessor; 22. on-off switch c; 23. voltage dividing resistor; 24. voltage measuring probe b. DETAILED DESCRIPTION

[0025] The following describes in detail the embodiments of the present invention. Figure 1 )、Circuit Diagram (Attached Figure 2 ) and waveform example diagram (attached Figure 3 It should be noted that the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, rather than to limit the present invention.

[0026] In the description of the present invention, it should be noted that specific physical quantity values ​​such as "peak value of about 40 kV", "rated voltage of 400 V", "capacitance of 0.2 Farad", "diameter of 4 mm", "electrode spacing of 10 mm" are preferred parameters based on the present embodiment, which are only for the purpose of clearly describing the present invention, rather than indicating or implying that the physical quantities involved can only be these values, and therefore should not be understood as limitations on the present invention.

[0027] In the description of the present invention, it should be noted that terms such as "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" indicate directions or positional relationships based on the orientations or positional relationships shown in the accompanying drawings of this example, and are only for the purpose of clearly describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be installed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0028] In the description of the present invention, unless otherwise specified, it should be noted that the terms "connect", "connected", "access", "connected" and the like should be understood in a broad sense. For example, in some contexts, they can be understood as the direct connection of multiple components or devices or the connection through an intermediate medium. For some electrical components, they can be understood as being connected to the input end or the output end of the electrical component according to the physical function of the connected object. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0029] In the description of the present invention, unless otherwise specified, it should be noted that when the same term is used to express devices with different positions or functions, and when they need to be distinguished, they are distinguished by adding lowercase English letters after the term. For example, "power-on switches" are used in many places in the discharge simulation device, and their connection positions and functions are different. They are distinguished by "power-on switch a", "power-on switch b", "power-on switch c"... instead of indicating or implying different devices, and therefore should not be understood as a limitation to the present invention.

[0030] The present invention provides a long continuous current discharge simulation device with independently controllable current magnitude and duration. Figure 1 and 2 As shown, the discharge simulation device mainly includes a high-voltage arc starting unit 1, a continuous discharge unit 2, a capacitance control system 3, a charging voltage control system 4, a time-delay circuit breaking system 5 and control software. The high-voltage arc starting unit 1 and the continuous discharge unit 2 are both connected to the electrode 13. The capacitance control system 3, the charging voltage control system 4 and the time-delay circuit breaking system 5 are all connected to the continuous discharge unit 2.

[0031] The main body of the high-voltage arc starting unit 1 is an impulse voltage generator 6, which can generate extremely short high-voltage pulses, the extremely short time is tens of microseconds, and the peak value of the high-voltage pulse is tens of kilovolts, preferably about 40 kilovolts. The continuous discharge unit 2 includes a capacitor group 9 and a DC charging device 11 for charging the capacitor group 9. The capacitor group 9 is composed of 5 sub-capacitor groups 10 in parallel. Two needle-shaped electrodes 13 are arranged on the same vertical axis, and the fuel sample to be tested is placed between the two electrodes 13. The high-voltage arm 7 of the impulse voltage generator 6 is connected to the upper electrode 13, and the grounding terminal 8 and the lower electrode 13 are simultaneously connected to the grounding grid 14 of the test room. One end of the capacitor group 9 of the continuous discharge unit 2 is connected to the upper electrode 13 through a large inductor 12, and the other end and the lower electrode 13 are simultaneously connected to the grounding grid 14. When the discharge simulation device is working, the high-voltage arc starting unit 1 first instantly breaks through the gap of the electrode 13 to ignite the arc, and then the continuous discharge unit 2 continuously supplies power to maintain the arc for a long time. The arc current is 100 to 300 amperes and the duration is 100 to 500 milliseconds to simulate the long continuous current discharge in a lightning strike. The rated voltage of the DC charging device 11 is 400 volts. The capacitance of the sub-capacitor group 10 is 0.2 farads and the rated voltage is 400 volts. The electrode 13 is a graphite electrode with a diameter of 4 mm and an electrode spacing of 10 mm. The inductance value of the inductor 12 is 1.7 millihenries.

[0032] The capacitance control system 3 includes a selection switch 15 and a plurality of on-off switches a 16. In the present embodiment, preferably, the selection switch 15 and the on-off switch a 16 are respectively a 5-position rotary switch and 5 DC contactors a. The 5 positions of the 5-position rotary switch correspond to the access to 1, 2, 3, 4 and 5 DC contactors a, respectively, and the 5 DC contactors a are respectively connected to the parallel branches of the 5 sub-capacitor groups 10 of the continuous discharge unit 2. By rotating the 5-position rotary switch to change the position, the number of DC contactors a in the closed state can be changed, thereby changing the number of sub-capacitor groups 10 connected to the capacitor group 9, and then changing the capacitance of the capacitor group 9. The capacitance corresponding to the 5 positions of the 5-position rotary switch is 0.2, 0.4, 0.6, 0.8 and 1.0 Farad, respectively.

[0033] The charging voltage control system 4 includes a voltage sensor 17, a voltage comparison microprocessor 18, an on-off switch b 19 and a control software. In this embodiment, preferably, the voltage sensor 17 is a pair of voltage measuring probes a connected to the two terminals of the capacitor group 9, and the signal output terminal of the voltage measuring probe a is connected to the voltage comparison microprocessor 18; the on-off switch b 19 is a DC contactor b, which is connected in the connection between the DC charging device 11 and the capacitor group 9, and the control end of the DC contactor b is connected to the voltage comparison microprocessor 18. During the charging process of the capacitor group 9, the voltage value of the capacitor group 9 is collected in real time by the voltage sensor 17 and transmitted to the voltage comparison microprocessor 18. The voltage comparison microprocessor 18 can compare the voltage of the capacitor group 9 collected by the voltage measurement probe a with the reference voltage preset by the control software. When the voltage of the capacitor group reaches the preset reference voltage, the charging is stopped by disconnecting the DC contactor b. At this time, the voltage at both ends of the capacitor group 9 is the preset reference voltage, that is, the charging voltage.

[0034] The time-delay circuit breaker system 5 includes an electric signal sensor 20, a time-delay control microprocessor 21, an on-off switch c 22 and control software. In this embodiment, preferably, the electric signal sensor 20 is a voltage-dividing resistor 23 connected in series in the circuit of the continuous discharge unit 2 and a voltage measuring probe b 24 connected at both ends of the voltage-dividing resistor, and the signal output end of the voltage measuring probe b 24 is connected to the time-delay control microprocessor 21; the on-off switch c 22 is a high-current DC contactor connected in the circuit of the continuous discharge unit 2. When the discharge simulation device is running, the delay time (i.e., the discharge duration) is preset by the control software. Once the long continuous current discharge starts, the electric signal sensor 20 detects the electric signal and triggers the time-delay control microprocessor 21 to start timing. When the counted time reaches the delay time preset by the control software, the discharge circuit is cut off by disconnecting the high-current DC contactor to stop the discharge. At this time, the actual discharge duration is the preset delay time, i.e., the discharge duration. The rated current of the on-off switch c22 is 400 amperes.

[0035] The discharge simulation device of the present invention can obtain long continuous current discharge with different current magnitudes by presetting different capacitances and charging voltages of the capacitor group 9, and establish a corresponding relationship between the discharge current magnitude, capacitance and charging voltage, and then independently control the discharge current magnitude by controlling the capacitance and charging voltage of the capacitor group 9; and control the duration of discharge by presetting different delay times. Figure 3 This embodiment provides a waveform example diagram of a capacitor with a capacitance of 1.0 Farad (the corresponding selection switch 15 is in the 5th gear), a charging voltage of 300 volts and a discharge duration of 200 milliseconds, respectively.

[0036] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A long continuous current discharge simulation device with independently controllable current magnitude and duration, Features: The invention comprises a high-voltage arc starting unit (1), a continuous discharge unit (2), a capacitance control system (3), a charging voltage control system (4) and a time-delay circuit breaking system (5); the high-voltage arc starting unit (1) and the continuous discharge unit (2) are both connected to an electrode (13); the capacitance control system (3), the charging voltage control system (4) and the time-delay circuit breaking system (5) are connected to the continuous discharge unit (2); The high-voltage arc starting unit (1) comprises an impulse voltage generator (6); The continuous discharge unit (2) comprises a capacitor group (9) and a DC charging device (11) for charging the capacitor group (9); The capacitor group (9) is composed of a plurality of sub-capacitor groups (10) connected in parallel; The capacitance control system (3) comprises a selection switch (15) and a plurality of on-off switches a (16); the selection switch (15) is connected to each on-off switch a (16) to control the on-off of each on-off switch a (16); the number of the on-off switches a (16) is equal to the number of the sub-capacitor groups (10) in the continuous discharge unit (2); the on-off switches a (16) are connected to the parallel branches where the sub-capacitor groups (10) are located; The charging voltage control system (4) comprises a voltage sensor (17), a voltage comparison microprocessor (18), and an on-off switch b (19); the voltage sensor (17) is connected to both ends of the capacitor group (9) in the continuous discharge unit (2), and the on-off switch b (19) is connected between the capacitor group (9) and the DC charging device (11); The voltage sensor (17) and the on-off switch b (19) are both connected to a voltage comparison microprocessor (18); The time-delay circuit-breaking system (5) comprises an electrical signal sensor (20), a time-delay control microprocessor (21), and an on-off switch c (22); the electrical signal sensor (20) and the on-off switch c (22) are both connected to the continuous discharge unit (2) and are both connected to the time-delay control microprocessor (21).

2. The long continuous current discharge simulation device with independently controllable current magnitude and duration according to claim 1, Features: Two electrodes (13) are arranged on the same vertical axis, and a fuel sample to be tested is placed between the two electrodes (13); a high voltage arm (7) of the impulse voltage generator (6) is connected to the upper electrode (13), and a grounding end (8) and the lower electrode (13) are simultaneously connected to a grounding grid (14) in a test room; one end of a capacitor group (9) of the continuous discharge unit (2) is connected to the upper electrode (13) via an inductor (12), and the other end and the lower electrode (13) are simultaneously connected to the grounding grid (14).

3. The long continuous current discharge simulation device with independently controllable current magnitude and duration according to claim 1, Features: The on-off switch a (16), the on-off switch b (19) and the on-off switch c (22) are all DC contactors.

4. The long continuous current discharge simulation device with independently controllable current magnitude and duration according to claim 2, Features: When the discharge simulation device is working, the high-voltage arc starting unit (1) first instantly breaks through the gap between the electrodes (13) to ignite the arc, and then the continuous discharge unit (2) continuously supplies power to maintain the arc for a long time to simulate the long continuous current discharge caused by a lightning strike.

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