A method for locating the self-discharge position of LTD large-scale multi-branch gas switch

Abstract

A method for locating the self-discharge position of a large-scale multi-branch gas switch in an LTD (Large-Scale Tolerancing) system is disclosed. Each branch switch housing integrates a B-dot probe. The output of the B-dot probe is fed through a unidirectional diode to a node between equal-length segmented series coaxial cables. The method monitors the pulse signals at both ends of the series coaxial cables to accurately locate the branch where self-discharge occurs. When a gas switch discharges, the signal waveforms acquired at the two ends of the series coaxial cables are similar and exhibit a certain time delay. Signal processing identifies the pulse start positions at both ends of the cable, determining the transmission delay of the two signals. The time delay difference is equal to an odd or even multiple of the electrical length of the segmented cable between two adjacent B-dot probes. The difference in the number of current probes between the self-discharge switch signal source and the two ends of the series cable is then calculated, thus locating the discharging gas switch.

Description

Technical Field

[0001] The invention belongs to the technical field of pulse power and proposes a method for detecting and locating abnormal self-discharge of a multi-channel gas switch. Background Art

[0002] Gas switches are core components in large pulse power devices, such as linear transformer drivers (LTDs). Reducing the self-discharge of gas switches in LTDs with a large number of gas switches is of great significance to ensure the stable operation of the equipment.

[0003] With the advancement of technology, the stability of a single gas switch has been greatly improved, and its self-discharge probability can be as low as 10 -5Order of magnitude. However, large-scale LTD devices contain tens of thousands to hundreds of thousands of fast-discharge branches. During the experimental operation, some gas switches will inevitably self-discharge, thus affecting the operation of large-scale LTD devices. In addition, during the assembly, commissioning, and maintenance of LTD single-stage, components, and branches, it is necessary to monitor the occurrence of self-discharge to troubleshoot or improve the working characteristics of the LTD device. Therefore, quickly locating the location of self-discharge in LTD devices with a large number of gas switches is conducive to quickly identifying the main branch gas switches with abnormal performance and replacing, adjusting, or repairing the gas switches in time. Previous methods for monitoring the self-discharge of branch switches in LTD mainly include two categories: optical signals and electrical signals generated by switch discharge. The optical signal generated by the self-discharge of the switch can be used to identify the gas switch that has self-discharged by optical fiber monitoring. However, when the gas switch self-discharges, the width of the optical signal pulse can reach tens of microseconds, and the time resolution is poor, making it difficult to locate the location of the gas switch that has self-discharged. At the same time, since the insulating shell of the gas switch has a certain degree of light transmittance when the gas switch self-discharges, it also interferes with the self-discharge switch positioning method based on the optical signal generated by the switch discharge, resulting in inaccurate positioning or ineffective operation. Compared with the method based on optical signals, the method using the electrical signal output by the B-dot probe integrated on the outer insulating shell of the switch can directly monitor the discharge moment of each branch switch, thereby accurately identifying the switch that self-discharges. It has been successfully applied to the single-stage 1MA FLTD module with gas insulation, separate column return, and plug-in branch developed by Xi'an Jiaotong University and the West China Nuclear Research Institute. However, in the current monitoring method based on the electrical signal generated by the switch discharge, the electrical signal output by the B-dot probe integrated on each LTD branch needs to be recorded using a channel of a measuring and recording device, which requires more measurement channels, resulting in high cost of the monitoring system and difficulty in engineering implementation. In addition, a voltage probe is arranged on the inner conductor of the LTD secondary water transmission line to detect the transmission delay of the branch discharge in the circumferential direction of the water line to locate the position of the discharge branch. This method can only be applied when the inner cylinder of the secondary water line is in the atmospheric environment. It cannot be used when the inner cylinder of the LTD secondary water line is filled with deionized water. In addition, since the diameter of the LTD secondary inner cylinder is smaller than the outer diameter of the LTD module, the arc length of the secondary inner cylinder corresponding to the branch is short, and it is not easy to accurately locate the position of the self-discharge branch.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention integrates a B-dot probe in each branch switch housing, and proposes to feed a large number of B-dot probe output signals in parallel into the same coaxial cable core wire connection node connected in segmented series through unidirectional conducting diodes, and monitor the signal delay time at both ends of the cable to accurately locate the self-discharge branch position.

[0006] The present invention is implemented by the following technical scheme. The method for locating the self-discharge position of a multi-branch gas switch comprises the following steps:

[0007] Integrate B-dot probe on gas switch;

[0008] Several cables of the same length are connected in series in sequence. A three-way cable connector is used at the connection point to connect the current probes on several gas switches in sequence. The ends of the series-connected cables are connected to the two measurement channels of the waveform recording device through extension cables.

[0009] A diode is inserted between the cable core and the B-dot probe output as an isolation device, and the B-dot coil and the diode are arranged on a printed circuit board PCB;

[0010] When one of the gas switches discharges, the voltage signal induced by the B-dot propagates along the cable to both ends and is eventually collected by the two measurement channels at the end. The waveforms of the signals collected by the two channels are basically the same and there is a certain time delay.

[0011] After the two waveforms are processed and the delay difference of the extended cables at both ends is compensated, the pulse starting position is automatically identified according to the arrival time, and the transmission delay of the two signals is obtained. If the total number of probes is an odd number, the delay is equal to an even number of times the cable propagation delay between two adjacent current probes, otherwise it is an odd number of times.

[0012] In the described method, due to the unidirectional conduction characteristic of the diode, the induced voltage generated in the coil of the B-dot probe is rectified into a unipolar pulse and transmitted losslessly to the cable; if the gas switch at the current position is not actuated, when the signal generated at other positions is propagated to the current B-dot probe, the diode at the current position is reversely cut off, which is equivalent to an open circuit, and does not affect the transmission of the output signal of the B-dot probe of the self-discharge switch in two directions.

[0013] Method for locating the self-discharge position of a multi-branch switch:

[0014] LTD has N parallel discharge branches. The B-dot signal integrated in the switch housing is connected to the three-way joints between the segmented cables of equal length in parallel through diodes according to the position. The single electrical length of the segmented cable is τ. Assuming that the branch position of the random self-discharge switch is X branches away from the cable CH1 (the position is unknown), the branch position of the random self-discharge switch is (NX) branches away from the cable CH2. The time for the B-dot signal at the self-discharge branch position to be transmitted to the coaxial cable CH1 and CH2 ends is:

[0015] T1=X.τ (1)

[0016] T2=(N-X+1)·τ (2)

[0017] Use cables of the same length to connect the pulse signals of CH1 and CH2 to the two channels of the oscilloscope (if the extended cable lengths are inconsistent, the delay difference needs to be compensated). Through the oscilloscope, it can be obtained that the delay of the two pulse signals measured by CH1 and CH2 at both ends of the cable is T2-T1; that is, through equations (2)-(1), X can be obtained:

[0018] X=(N-(T2-T1) / τ) / 2 (3)

[0019] The rounded-off value of formula (3) is the position of the self-discharge branch.

[0020] Compared with the prior art, the present invention has the following advantages: simple structure and easy implementation, greatly reducing the number of oscilloscope channels required for locating the branch self-discharge current, and reducing the detection cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0022] In the attached picture:

[0023] Figure 1 This is a schematic diagram of the connection principle of the B-dot signal feed cables of 46 branch switches according to an embodiment of the present invention;

[0024] Figure 2 The structure diagram of the front and back sides of a PCB board including a B-dot coil and a diode according to an embodiment of the present invention, wherein the diode is soldered on the pads at the positions indicated by the two arrows;

[0025] Figure 3 A schematic diagram of a B-dot probe arrangement installed on a switch housing according to an embodiment of the present invention;

[0026] Figure 4 It is a schematic diagram of the principle of a single B-dot coil feeding cable according to an embodiment of the present invention;

[0027] Figure 5 It is a schematic diagram of the original waveform of the two signals at the middle and end of the embodiment of the present invention, the waveform after filtering, and the waveform starting position detected by the time window energy ratio;

[0028] Figure 6 This is a schematic diagram of the relationship between the terminal signal delay difference and the difference in the number of nodes experienced by the transmission when the B-dots at 46 positions generate signals respectively in an embodiment of the present invention.

[0029] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0030] The following will refer to the attached Figures 1 to 6 Specific embodiments of the present invention are described in more detail. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0031] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0032] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0033] For better understanding, in one embodiment, Figures 1 to 6 As shown, the abnormal self-discharge detection method of a multi-channel gas switch includes the following steps:

[0034] Integrate B-dot probe on gas switch;

[0035] Several cables of the same length are connected in series. A tee connector is used at the connection point to connect the current probes on several gas switches in sequence. The ends of the series-connected cables are connected to the two measurement channels of the oscilloscope respectively.

[0036] A diode is connected between the cable and the current probe as an isolation device, and the current probe and the diode are arranged on a printed circuit board PCB;

[0037] When one of the gas switches discharges, the voltage signal propagates along the cable to both ends and is eventually collected by the two channels of the oscilloscope. The waveforms of the signals collected by the two channels are the same and there is a certain time delay.

[0038] After signal processing, the two waveforms are used to identify the pulse start positions of each other using the time window energy ratio method to obtain the transmission delay of the two signals. If the total number of probes is an odd number, the delay is equal to an even number of times the cable propagation delay between two adjacent current probes, otherwise it is an odd number of times. The difference in the number of current probes between the signal source and the two ends of the cable is calculated to locate the specific position of the gas switch of the discharge.

[0039] In a preferred embodiment of the method, due to the unidirectional conduction characteristics of the diode, only the positive or negative half-cycle voltage (the polarity depends on the direction of the arrangement of the B-dot induction coil and the diode) of the induced voltage generated in the coil of the B-dot probe is transmitted to the cable almost losslessly; if the gas switch at the current position is not operated, when the signal generated at other positions is propagated to the current B-dot probe, the diode at the current position is reversely cut off, which is basically equivalent to an open circuit.

[0040] In one embodiment, two measurement channels are used to locate the self-discharge switches in 46 gas switches; several sections of 0.5 m RG316 cables are connected in sequence, the signal transmission delay in the cable is 5 ns / m, and a three-way connector is used at the connection to sequentially connect several B-dot probes installed on the gas switch, and the ends of the serially connected cables are respectively connected to two measurement channels of an oscilloscope, and the oscilloscope input impedance is set to 50Ω matching; a fast recovery diode (FRD) is connected between the cable and the B-dot probe as an isolation device, and the B-dot probe and the diode are arranged on a printed circuit board (PCB) to reduce the influence of stray inductance and ensure the consistency of the probe;

[0041] When one of the switches discharges, the voltage signal propagates along the serial cable to both ends and is eventually collected by the two channels of the oscilloscope. The waveforms of the two signals are basically the same, and there is a certain delay. After the two signals are processed, the time window energy ratio method is used to identify the start position of each pulse, and the transmission delay of the two signals is obtained. The delay is equal to an odd number of the cable propagation delay between two adjacent current probes. The difference in the number of current probes between the signal source and the two ends of the cable is calculated to locate the specific position of the discharged gas switch.

[0042] In one embodiment, see Figure 1 In the embodiment, the B-dot probes on 46 gas switches are connected in sequence with 0.5m long cables, and the two ends are connected to the two measurement channels of the oscilloscope respectively, and the oscilloscope input impedance is matched; please refer to Figure 2 The B-dot and diode series branch PCB board used in the present invention has a length of 4.2cm and a width of 2cm; please refer to Figure 3 , the B-dot used in the present invention is directly integrated into the gas switch housing; please refer to Figure 4 The present invention connects a fast recovery diode (FRD) in series with the traditional B-dot coil. Due to the unidirectional conduction characteristics of the diode, only the voltage of the positive or negative half cycle (depending on the direction of the B-dot induction coil and the diode) is transmitted to the cable almost losslessly; if the gas switch at the current position does not operate, when the signal generated at other positions is transmitted to the current B-dot probe, the diode at the current position is reversely cut off, which is basically equivalent to an open circuit.

[0043] See also Figure 5 In the embodiment, the voltage waveforms measured at both ends of the cable are basically the same, and the amplitudes are slightly different due to different transmission distances. Due to the presence of the diode, the negative half cycle of the oscillating voltage output by the B-dot is basically cut off, and at the same time, the positive voltage causes the diode in the B-dot branch that is not the signal source to be reversely cut off, and the signal is transmitted almost losslessly in the cable; the time window energy ratio method is used to automatically identify the starting position of the waveform; please refer to Figure 6 The time delay identified by the waveform difference is linearly related to the difference in the number of B-dot nodes that the signal generated by the discharge switch position passes through when propagating to both ends of the cable.

[0044] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A method for detecting abnormal self-discharge position of a multi-branch gas switch in a single-stage or component LTD, characterized in that: Integrate B-dot probe on the gas switch housing of each LTD branch; Several cables of the same length are connected in sequence, and the B-dot probes are connected in sequence using a three-way connector at the connection point. The first and second ends of the series-connected cables are connected to the two measurement channels of the waveform recording device through extension cables. Connect a diode between the cable core and the output end of the B-dot probe as an isolation device for the multi-channel B-dot probe; When a branch gas switch self-discharges, the attenuated oscillation voltage signal output by the B-dot probe integrated in the shell of the branch gas switch is rectified by the diode into a unipolar signal, fed into the cable core, propagated to both ends along the series coaxial cable, and finally collected by the two channels of the waveform recording device. The signal waveforms collected by the two channels are similar and there is a certain time delay; After signal processing, the two waveforms are used to identify their respective pulse starting positions based on the arrival time method, and the transmission delay of the two signals is obtained. After compensating for the delay difference of the extended cables at both ends, the transmission delay is equal to an integer multiple of the cable propagation delay between two adjacent B-dot probes. The difference in the number of B-dot probes between the signal source and the two ends of the cable is calculated, thereby locating the specific position of the discharge gas switch.

2. The method according to claim 1, characterized in that The B-dot probe and the series diode are arranged on a printed circuit board PCB.

3. The method according to claim 1, characterized in that Due to the unidirectional conduction characteristics of the diode, the induced voltage generated in the coil of the B-dot probe is rectified into a unipolar pulse and transmitted losslessly to the cable; if the gas switch at the current position is not activated, when the signal generated at other positions is transmitted to the current B-dot probe, the diode at the current position is reversely cut off, which is equivalent to an open circuit and does not affect the transmission of the output signal of the B-dot probe of the self-discharge switch in both directions.

4. The method according to claim 1, characterized in that In order to avoid signal reflection at the end of the cable and affect signal recognition, a parallel matching resistor is connected at the end of the series cable.

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