CN115902536A - Photomultiplier-based insulator fluid flow propagation speed measuring device and method - Google Patents
Photomultiplier-based insulator fluid flow propagation speed measuring device and method Download PDFInfo
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- CN115902536A CN115902536A CN202211341869.3A CN202211341869A CN115902536A CN 115902536 A CN115902536 A CN 115902536A CN 202211341869 A CN202211341869 A CN 202211341869A CN 115902536 A CN115902536 A CN 115902536A
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Abstract
The invention discloses a photomultiplier-based device and method for measuring the propagation speed of insulator fluid flow. The invention designs the insulator streamer propagation speed measuring device based on the photomultiplier, so that when the device is applied, standard lightning impulse voltage output by a high-voltage pulse generator is applied to a high-voltage electrode of a metal testing unit through a sleeve, the high-voltage electrode of the metal testing unit generates creeping discharge on the surface of an insulator sample through a metal needle and generates streamer and optical signals, the optical signals are collected, amplified and converted into electric signals through optical fibers by the photomultiplier, and a signal collector analyzes the electric signals to obtain total streamer time so that a user can determine the streamer propagation speed according to the total creepage distance and the total streamer time fixed by the device, thereby accurately collecting the optical signals generated when the creeping discharge occurs on the surface of the insulator sample by applying the insulator streamer propagation speed measuring device based on the photomultiplier and realizing the measurement of the streamer propagation speed.
Description
Technical Field
The invention relates to the technical field of electrical insulation, in particular to a photomultiplier-based device and a photomultiplier-based method for measuring the propagation speed of insulator fluid flow.
Background
Sulfur hexafluoride (SF 6) gas is the most commonly used insulating medium for Gas Insulated Switchgear (GIS) in the power industry, but due to its high Global Warming Potential (GWP), environmentally friendly insulating gas is increasingly used. C 4 F 7 N/CO 2 /O 2 The mixed gas has the insulation strength similar to that of SF6 gas and has a lower GWP value, and is considered to be a high-quality substitute gas.
Besides the insulating gas itself, the solid spacer layer supporting the conductor is one of the important points that must be considered in the design process of the GIS device, and therefore, it is necessary to study the process of the arc development along the gas-solid interface. The junction of the metal electrode, the solid insulator and the gas-solid interface is considered as the weakest link of the electrical insulation of the GIS, and creeping discharge is most likely to occur at the junction. At present, the research on the development process of the gas-solid interface creeping discharge mostly focuses on using SF6 as an insulating medium, especially for environment-friendly insulating gas, especially C 4 F 7 N/CO 2 /O 2 The mixed gas is less involved and most of these studies focus on the magnitude of its flashover voltage rather than its development, lacking relevant studies on the effect of its tangential electric field on the streaming arc.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides the device and the method for measuring the propagation speed of the insulator streamer based on the photomultiplier tube, and the device and the method can be used for accurately collecting optical signals generated when creeping discharge occurs on the surface of an insulator sample by applying the device for measuring the propagation speed of the insulator streamer based on the photomultiplier tube, so that the propagation speed of the streamer is measured.
In order to solve the above technical problems, in a first aspect, an embodiment of the present invention provides a photomultiplier-based insulator streamer propagation velocity measurement apparatus, including a high-voltage pulse generator, a voltage divider, a bushing, a metal test unit, a photomultiplier, and a signal collector;
the metal testing unit is placed in a metal tank filled with insulating gas, an insulator sample is placed between a high-voltage electrode and a grounding electrode of the metal testing unit, a metal needle is placed on the high-voltage electrode of the metal testing unit, and the tip of the metal needle is in contact with the surface of the insulator sample;
the output of high voltage pulse generator respectively with the input of voltage divider with the sheathed tube input is connected, sheathed tube output with metal test unit's high-voltage electrode is connected, photomultiplier's input passes through the optic fibre and aims at the most advanced position of metal needle, the output of voltage divider with photomultiplier's output respectively with signal collector's input is connected, high voltage pulse generator's earthing terminal the earthing terminal of voltage divider with metal test unit's telluric electricity field all grounds.
Further, the insulating gas includes C 4 F 7 N/CO 2 /O 2 Mixing the gas.
Further, the high-voltage pulse generator comprises a Marx generator, and the signal collector comprises a digital oscilloscope.
Further, the insulator sample is a cylinder made of alumina-filled epoxy.
Further, the high voltage electrode and the ground electrode of the metal test unit are both made of aluminum, and the metal needle is made of tungsten.
In a second aspect, an embodiment of the present invention provides a method for measuring propagation speed of insulator streamer based on a photomultiplier, which is applied to the apparatus for measuring propagation speed of insulator streamer based on a photomultiplier as described above, and the method includes:
positioning the insulator sample to obtain a total creepage distance, and filling the insulating gas in the metal tank;
the standard lightning impulse voltage with the positive polarity and the standard lightning impulse voltage with the negative polarity output by the high-voltage pulse generator are increased successively according to a preset voltage increment until flashover occurs, and the test is repeatedly carried out until the accumulated flashover times reach the preset flashover times;
converting optical signals generated at the tip position of the metal needle when flashover occurs each time into electric signals through the photomultiplier tube to obtain all the electric signals, and generating photoelectric signal waveforms according to all the electric signals through the signal collector;
and determining total flow time under positive polarity and negative polarity according to the waveform of the photoelectric signal, and respectively calculating average flow velocity under positive polarity and negative polarity according to the total creepage distance and the total flow time under positive polarity and negative polarity to obtain flow propagation velocity.
Further, the positioning of the insulator sample to obtain the total creepage distance specifically comprises:
and determining the relative position of the tip of the metal needle and the grounding electrode of the metal testing unit, and recording the distance between the tip of the metal needle and the grounding electrode of the metal testing unit as the total creepage distance.
Further, the filling of the insulating gas in the metal can specifically includes:
filling 0.75Mpa of C into the metal tank 4 F 7 N/CO 2 /O 2 And (4) mixing the gases.
Further, the step of increasing the standard lightning impulse voltage of the positive polarity and the standard lightning impulse voltage of the negative polarity output by the high-voltage pulse generator successively according to the preset voltage increment respectively until flashover occurs, and the step of repeatedly performing the test until the accumulated flashover frequency reaches the preset flashover frequency specifically comprises the steps of:
and after the standard lightning impulse voltage with the positive polarity or the negative polarity output by the high-voltage pulse generator is increased every time, waiting for preset time and then performing the next action.
Further, the average streamer speed in the positive polarity = the total creepage distance/total streamer time in the positive polarity, and the average streamer speed in the negative polarity = the total creepage distance/average streamer speed in the negative polarity.
Compared with the prior art, the embodiment of the invention has the following beneficial effects:
by designing the insulator streamer propagation speed measuring device based on the photomultiplier, when the device is applied, standard lightning impulse voltage output by a high-voltage pulse generator is applied to a high-voltage electrode of a metal testing unit through a sleeve, creeping discharge occurs on the surface of an insulator sample by the high-voltage electrode of the metal testing unit through a metal needle, streamer and optical signals are generated, the optical signals are collected, amplified and converted into electric signals through optical fibers by the photomultiplier, and a signal collector analyzes the electric signals to obtain total streamer time so that a user can determine the streamer propagation speed according to the total creepage distance and the total streamer time fixed by the device.
Further, by filling C in the metal can 4 F 7 N/CO 2 /O 2 The mixed gas is used for discharge test, which is favorable for helping research C 4 F 7 N/CO 2 /O 2 Mixed gas carrier ionization and deionization processes to facilitate understanding of C 4 F 7 N/CO 2 /O 2 Dielectric properties of the gas mixture supporting it as SF 6 Alternative to gas.
Drawings
Fig. 1 is a schematic structural diagram of a photomultiplier-based device for measuring propagation velocity of an insulator fluid stream according to a first embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an exemplary metal test cell in a first embodiment of the present invention;
fig. 3 is a schematic flow chart of a method for measuring propagation velocity of an insulator streamer based on a photomultiplier according to a second embodiment of the present invention;
wherein, the reference numbers in the description attached figures 1-2 are as follows:
1: a high voltage pulse generator; 2: a voltage divider; 3: a sleeve; 4: a metal test unit; 41: a high voltage electrode; 42: a metal needle; 43: a ground electrode; 5: a photomultiplier tube; 6: a signal collector; 7: an insulator sample.
Detailed Description
The technical solutions in the present invention will be described clearly and completely with reference to the drawings in the present invention, and it should be apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that, the step numbers in the text are only for convenience of explanation of the specific embodiments, and do not serve to limit the execution sequence of the steps. The method provided by the embodiment can be executed by the relevant terminal device, and the following description takes a processor as an execution subject as an example.
As shown in fig. 1, a first embodiment provides a photomultiplier-based insulator fluid flow propagation speed measuring device, which includes a high-voltage pulse generator 1, a voltage divider 2, a bushing 3, a metal testing unit 4, a photomultiplier 5, and a signal collector 6; the metal testing unit 4 is placed in a metal can filled with insulating gas, an insulator sample 7 is placed between a high-voltage electrode 41 and a grounding electrode 43 of the metal testing unit 4, a metal needle 42 is placed on the high-voltage electrode 41 of the metal testing unit 4, and the tip of the metal needle 42 is in contact with the surface of the insulator sample 7; the output end of the high-voltage pulse generator 1 is respectively connected with the input end of the voltage divider 2 and the input end of the sleeve 3, the output end of the sleeve 3 is connected with the high-voltage electrode 41 of the metal testing unit 4, the input end of the photomultiplier 5 is aligned to the tip position of the metal needle 42 through an optical fiber, the output end of the voltage divider 2 and the output end of the photomultiplier 5 are respectively connected with the input end of the signal collector 6, and the grounding end of the high-voltage pulse generator 1, the grounding end of the voltage divider 2 and the grounding electrode 43 of the metal testing unit 4 are all grounded.
Exemplarily, the insulator sample 7 is placed between the high voltage electrode 41 and the ground electrode 43 of the metal test unit 4, a hole is drilled on the high voltage electrode 41 of the metal test unit 4 to place the metal needle 42 having a controlled tip radius, and the tip of the metal needle 42 is brought into contact with the surface of the insulator sample 7, wherein the schematic structural diagram of the metal test unit 4 is shown in fig. 2; and connecting the output end of the high voltage pulse generator 1 with the input end of the voltage divider 2, connecting the output end of the voltage divider 2 with the input end of the signal collector 6, grounding the grounding ends of the high voltage pulse generator and the voltage divider 2, connecting the output end of the high voltage pulse generator 1 with the input end of the voltage divider 2 in parallel, outputting standard lightning impulse voltage by the high voltage pulse generator 1, measuring the standard lightning impulse voltage after voltage division by the voltage divider 2, collecting the electric signal output by the voltage divider 2 by the signal collector 6, connecting the output end of the high voltage pulse generator 1 with the input end of the bushing 3, connecting the output end of the bushing 3 with the high voltage electrode 41 of the metal test unit 4, grounding the grounding electrode 43 of the metal test unit 4, applying the standard lightning impulse voltage output by the high voltage pulse generator 1 to the high voltage electrode 41 of the metal test unit 4 by the bushing 3, the metal needle 42 is connected with the high-voltage electrode 41 of the metal test unit 4 and the surface of the insulator sample 7, surface discharge can be promoted on the surface of the insulator sample 7 due to the tip effect, a flow stream and an optical signal are generated, the surface discharge can be generated on the surface of the insulator sample 7 through the metal needle 42 by the high-voltage electrode 41 of the metal test unit 4, the flow stream and the optical signal are generated, the input end of the photomultiplier 5 is aligned to the tip position of the metal needle 42 through an optical fiber, the output end of the photomultiplier 5 is connected with the input end of the signal collector 6, the optical fiber faces the tip of the metal needle 42, the optical activity of the tip position of the metal needle 42 is observed through the open end of an optical fiber, such as a broad-spectrum optical fiber (180-1200 nm), so that only the optical signal attached to the tip of the metal needle 42 is detected, the optical signal is collected through the optical fiber by the photomultiplier 5, the optical signal is amplified and converted into an electric signal, the electric signal output by the photomultiplier 5 is collected by the signal collector 6, and the design of the device for measuring the propagation speed of the insulator stream based on the photomultiplier 5 is completed.
Wherein, the output end of the photomultiplier 5 is provided with an electric attenuator inside, which can avoid signal saturation and enhance signal accuracy.
In this embodiment, by designing the photomultiplier-based insulator streamer propagation velocity measurement apparatus, when applying the apparatus, a standard lightning impulse voltage output by the high-voltage pulse generator 1 is applied to the high-voltage electrode 41 of the metal test unit 4 through the bushing 3, the high-voltage electrode 41 of the metal test unit 4 generates creeping discharge on the surface of the insulator sample 7 through the metal pin 42, and generates streamer and optical signals, the optical signals are collected, amplified and converted into electrical signals by the photomultiplier 5 through the optical fiber, and the signal collector 6 analyzes the electrical signals to obtain the total streamer time, so that a user determines the streamer propagation velocity according to the total creepage distance and the total streamer time fixed by the apparatus, thereby being capable of applying the photomultiplier-based insulator streamer propagation velocity measurement apparatus, accurately collecting the optical signals generated when creeping discharge occurs on the surface of the insulator sample 7, and realizing measurement of the streamer propagation velocity.
In a preferred embodiment, the insulating gas comprises C 4 F 7 N/CO 2 /O 2 And (4) mixing the gases.
This example was carried out by filling a metal can with C 4 F 7 N/CO 2 /O 2 The mixed gas is used for discharge test, which is favorable for helping research C 4 F 7 N/CO 2 /O 2 Mixed gas carrier ionization and deionization processes to facilitate understanding of C 4 F 7 N/CO 2 /O 2 Dielectric properties of the gas mixture supporting it as SF 6 Alternative to gas.
In a preferred embodiment, the high voltage pulse generator 1 comprises a Marx generator and the signal collector 6 comprises a digital oscilloscope.
It is understood that a Marx Generator (Marx Generator) is a high voltage device that generates high voltage pulses from a low voltage dc power source, charges in parallel through a capacitor, and discharges in series, and can simulate the lightning and over-voltage operation.
Marx generator, which can provide standard lightning impulse voltage (1.2/50 mus) of positive and negative polarity as defined by IEC 60060-1.
In the embodiment, the Marx generator is used as the high-voltage pulse generator 1, the Marx generator can be used for applying the standard lightning impulse voltage with positive polarity and negative polarity to the high-voltage electrode 41 of the metal testing unit 4, the accuracy of the discharge test is improved, and the digital oscilloscope is used as the signal collector 6, so that the visual photoelectric signal waveform can be obtained, and the signal analysis efficiency is improved.
In a preferred embodiment, the insulator sample 7 is a cylinder made of alumina filled epoxy.
As an example, the insulator sample 7 is a cylinder made of alumina-filled epoxy resin and molded to have the same surface state as the GIS pad at both ends in contact with the electrodes.
In a preferred embodiment, insulator sample 7 is 65mm in length and 25mm in diameter.
In the preferred embodiment, the spacing between the tip of the metal needle 42 and the ground electrode 43 of the metal test element 4 is 50mm.
It will be appreciated that the spacing between the tip of the metal pin 42 and the ground electrode 43 of the metal test element 4 is the total creepage distance.
In the preferred embodiment, the high voltage electrode 41 and the ground electrode 43 of the metal test unit 4 are both made of aluminum, and the metal needle 42 is made of tungsten.
As an example, a metal needle 42 is placed on the high voltage electrode 41 of the metal test unit 4, preferably made of tungsten, because it has a high melting temperature (3422 ℃), degradation due to partial discharge before breakdown can be avoided.
In the preferred embodiment, the tip radius of the metal needle 42 is 250 μm.
A second embodiment provides a method for measuring propagation speed of insulator streamer based on photomultiplier tube, which is applied to the apparatus for measuring propagation speed of insulator streamer based on photomultiplier tube according to the first embodiment, and the method includes steps S1 to S4:
s1, positioning an insulator sample 7, acquiring a total creepage distance, and filling insulating gas in a metal tank;
s2, the standard lightning impulse voltages with positive polarity and negative polarity output by the high-voltage pulse generator 1 are gradually increased according to the preset voltage increment until flashover occurs, and the test is repeatedly carried out until the accumulated flashover times reach the preset flashover times;
s3, converting optical signals generated at the tip position of the metal needle 42 when flashover occurs each time into electric signals through the photomultiplier 5 to obtain all the electric signals, and generating photoelectric signal waveforms according to all the electric signals through the signal collector 6;
and S4, determining total flow time under the positive polarity and the negative polarity according to the waveform of the photoelectric signal, and respectively calculating average flow velocity under the positive polarity and the negative polarity according to the total creepage distance and the total flow time under the positive polarity and the negative polarity to obtain the flow propagation velocity.
Illustratively, in step S1, the insulator sample 7 is positioned in a photomultiplier-based insulator streamer propagation velocity measuring apparatus, a total creepage distance is acquired, and an insulating gas such as C is filled in the metal can 4 F 7 N/CO 2 /O 2 And (4) mixing the gases.
In step S2, under a preset test condition, the high-voltage pulse generator 1 is controlled to output the standard lightning impulse voltage, the standard lightning impulse voltage with the positive polarity and the standard lightning impulse voltage with the negative polarity output by the high-voltage pulse generator 1 are respectively and successively increased according to a preset voltage increment until flashover occurs, and the test is repeated until the accumulated flashover frequency reaches the preset flashover frequency.
For example, the first positive standard lightning impulse voltage applied by the high voltage pulse generator to the high voltage electrode 41 of the metal test unit 4 is 20kV (negative standard lightning impulse voltage is-20 kV). The standard lightning impulse voltage is successively increased to 25kV, 30kV, 35kV until flashover occurs according to a preset voltage increment, such as 5kV. A waiting time of one minute is maintained after each pulse application. After the first flashover, additional pulses are applied at the same voltage value to obtain a predetermined number of flashovers, such as at least three, on the insulator sample 7. This allows additional data to be collected under the same gas conditions even if the surface conditions of the insulator sample 7 were changed.
In the test process, in order to avoid the influence of flashover on surface traces of the insulator sample 7, the insulator sample 7 is replaced for each test condition. After the flashover, the erosion of the tip radius of the metal needle 42 is observed and the metal needle 42 is replaced if necessary.
In step S3, the photo-signal generated at the tip position of the metal needle 42 each time a flashover occurs is converted into an electrical signal by the photomultiplier 5, and all the electrical signals are obtained, so that a photo-signal waveform is generated from all the electrical signals by the signal collector 6.
It will be appreciated that the instant of the peak of the photomultiplier tube 5 matches the onset of the voltage drop. This event corresponds to a flashover, i.e. the establishment of a conductive path between the electrodes, resulting in a loss of electrical insulation in the gas and a voltage drop to zero. During a flashover, the photomultiplier 5 measurement signal can be broken down into four distinct phases:
(1) The signal remains around 0: there is no optical activity around the tip of the metal needle 42;
(2) The signal is not zero and starts to rise: measuring optical activity around the tip of the metal needle 42; the discharge of the color ribbon occurs and diffuses;
(3) A steep slope appears on the signal: establishing a conductive channel; the current is increased rapidly, the temperature of the gas in the metal tank is increased, and the luminous luminosity is increased;
(4) The luminosity starts to decrease: the circuit discharges through a short circuit caused by an arc channel, and the circulating energy slowly decreases until extinction.
The photomultiplier tube 5 measurement signal is used to compare the streamer propagation velocity at which flashover occurs under various test conditions. For this purpose, the delay between the first occurrence of the signal and the peak is measured, matching the continuous application of the phases (2) and (3) described above. It corresponds to the time between the start of the streaming activity around the tip of the metal pin 42 and the fully established conducting channel, i.e. the total streaming time, when the stream reaches the ground electrode 43 on the other side of the insulator sample 7. And finally, combining the total creepage distance to determine the propagation speed of the stream.
In step S4, total streaming time in the positive polarity and the negative polarity is determined according to the waveform of the photoelectric signal, and average streaming speed in the positive polarity and the negative polarity is calculated according to the total creepage distance and the total streaming time in the positive polarity and the negative polarity, respectively, to obtain the streaming propagation speed.
In the embodiment, by applying the insulator streamer propagation velocity measuring device based on the photomultiplier, a standard lightning impulse voltage output by the high-voltage pulse generator 1 is applied to the high-voltage electrode 41 of the metal testing unit 4 through the sleeve 3, the high-voltage electrode 41 of the metal testing unit 4 generates creeping discharge on the surface of the insulator sample 7 through the metal needle 42, and generates streamer and optical signals, the optical signals are collected, amplified and converted into electrical signals through the optical fiber by the photomultiplier 5, and the signal collector 6 analyzes the electrical signals to obtain the total streamer time, so that a user can determine the streamer propagation velocity according to the total creepage distance and the total streamer time fixed by the device, thereby being capable of accurately collecting the optical signals generated when creeping discharge occurs on the surface of the insulator sample 7 by applying the insulator streamer propagation velocity measuring device based on the photomultiplier 5, and realizing measurement of the streamer propagation velocity.
In a preferred embodiment, the positioning of the insulator sample 7 to obtain the total creepage distance specifically includes: the relative position of the tip of the metal needle 42 and the ground electrode 43 of the metal test unit 4 is determined, and the distance between the tip of the metal needle 42 and the ground electrode 43 of the metal test unit 4 is recorded as the total creepage distance.
As an example, in the insulator fluid propagation velocity measuring apparatus based on the photomultiplier 5, the insulator sample 7 is installed, the surface of the insulator sample 7 is brought into contact with the tip of the metal pin 42, the relative position of the tip of the metal pin 42 and the ground electrode 43 of the metal test unit 4 is determined, and the distance between the tip of the metal pin 42 and the ground electrode 43 of the metal test unit 4 is recorded as the total creepage distance.
In a preferred embodiment, the filling of the insulating gas in the metal can is specifically: in metal cansC filled at 0.75MPa 4 F 7 N/CO 2 /O 2 And (4) mixing the gases.
In this example, a metal can was filled with 0.75MPa of C 4 F 7 N/CO 2 /O 2 The mixed gas is used for discharge test, which is favorable for helping research C 4 F 7 N/CO 2 /O 2 Mixed gas carrier ionization and deionization processes facilitating understanding of C 4 F 7 N/CO 2 /O 2 Dielectric properties of the gas mixture supporting it as SF 6 Alternative to gas.
In a preferred embodiment, the successively increasing the standard lightning impulse voltage with positive polarity and the standard lightning impulse voltage with negative polarity output by the high-voltage pulse generator 1 according to the preset voltage increment respectively until flashover occurs, and repeatedly performing the test until the accumulated flashover frequency reaches the preset flashover frequency specifically includes: after the standard lightning impulse voltage with positive polarity or negative polarity output by the high-voltage pulse generator 1 is increased every time, waiting for the preset time and then performing the next action.
As an example, after each time the standard lightning surge voltage of positive polarity or negative polarity output from the high voltage pulse generator 1 is increased, a preset time, for example, one minute, is waited, and then the next action is performed.
This embodiment is favorable to improving the experimental accuracy of discharging through setting up latency.
In a preferred embodiment, the average streamer speed at positive polarity = total creepage distance/total streamer time at positive polarity, and the average streamer speed at negative polarity = total creepage distance/average streamer speed at negative polarity.
As an example, in order to more clearly illustrate the method for measuring the propagation velocity of insulator streamer based on the photomultiplier according to the second embodiment, the high voltage pulse generator 1, the metal test unit 4, the signal collector 6, and the like are connected according to the circuit connection manner shown in fig. 1, the distance between the tip of the fixed metal pin 42 and the ground electrode 43 of the metal test unit 4 is 50mm, and the metal can is filled with 0.75Mpa C 4 F 7 N/CO 2 /O 2 Mixing the gas.
Then, by gradually and slowly raising the output voltage of the high voltage pulse generator 1, the standard lightning impulse voltage of positive polarity and negative polarity is applied to the high voltage electrode 41 of the metal test unit 4 until finally the flashover occurs. After each pulse application, the operation is repeated for about 1 minute until more than three flashovers are accumulated, and the flashover voltage and the waveform of the photoelectric signal measured by the photomultiplier 5 and collected by the signal collector 6 are recorded.
Based on the measured waveform of the photoelectric signal, according to the rising and falling rule of the voltage waveform, respectively finding a time period with signal characteristics from the stage (1) to the stage (4), wherein the stage (2) and the stage (3) represent time corresponding to the development and flashover process of the streamer, the time and total time for completely establishing a conductive channel for streamer activity, namely total streamer time, the total creepage distance is the distance between the tip of the fixed metal needle 42 and the grounding electrode 43 of the metal test unit 4 and is 50mm, and the average streamer speed under the positive and negative polarities can be estimated by dividing the total streamer time under the positive and negative polarities respectively.
The experiment shows that the flashover voltage under positive polarity is 84KV, and the average streamer speed is 2.4 multiplied by 10 5 m/s, flashover voltage under negative polarity is-105 KV, and average streamer speed is 1.35 × 10 5 m/s。
From the experimental results, it is found that, in the positive polarity, the electrons are collected by the high voltage electrode 41, and the positive space charge of the head of the stream advances along the solid surface toward the ground electrode 43. In gas, electrons which have an effect on the propagation of the flow are mainly generated by photoionization of surrounding gas molecules, and for a gas-solid interface, a solid surface can be an additional photoelectron source, so that the development of the flow is promoted, and the propagation speed of the flow is accelerated.
On the other hand, when the tip of the metal pin 42 is a negative electrode, electrons useful for the propagation of discharge are directly emitted from the high voltage electrode 41, however, the trap on the surface of the insulator sample 7 captures part of the electrons during the development of discharge, slowing down the development of the electrons, and meanwhile, the accumulation of negative charges can also reduce the further enhancement of the electric field around the tip of the metal pin 42. The influence of the electric field on the development of the discharge is also reduced. The above structure can prove the negative electrodeThe velocity of flow propagation is lower in the sexual regime than in the positive regime. At the same time for study C 4 F 7 N/CO 2 /O 2 The mixed gas photoionization process and the deionization process provide theoretical support for explaining C 4 F 7 N/CO 2 /O 2 The dielectric properties of the mixed gas provide a reliable method.
In summary, the embodiment of the present invention has the following advantages:
by designing the insulator streamer propagation velocity measuring device based on the photomultiplier, when the device is applied, standard lightning impulse voltage output by the high-voltage pulse generator 1 is applied to the high-voltage electrode 41 of the metal testing unit 4 through the sleeve 3, the high-voltage electrode 41 of the metal testing unit 4 generates creeping discharge on the surface of the insulator sample 7 through the metal needle 42 and generates streamer and optical signals, the optical signals are collected, amplified and converted into electric signals through the optical fiber by the photomultiplier 5, and the signal collector 6 analyzes the electric signals to obtain total streamer time so that a user can determine the streamer propagation velocity according to the total creepage distance and the total streamer time fixed by the device, thereby being capable of applying the insulator streamer propagation velocity measuring device based on the photomultiplier to accurately collect the optical signals generated when the creeping discharge occurs on the surface of the insulator sample 7 and realizing the measurement of the streamer propagation velocity.
Further, a metal can was filled with C 4 F 7 N/CO 2 /O 2 The mixed gas is used for discharge test, which is favorable for helping research C 4 F 7 N/CO 2 /O 2 Mixed gas carrier ionization and deionization processes facilitating understanding of C 4 F 7 N/CO 2 /O 2 Dielectric properties of the gas mixture supporting it as SF 6 Alternative to gas.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
It will be understood by those skilled in the art that all or part of the processes of the above embodiments may be implemented by hardware related to instructions of a computer program, and the computer program may be stored in a computer readable storage medium, and when executed, may include the processes of the above embodiments. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
Claims (10)
1. An insulator flow propagation speed measuring device based on a photomultiplier is characterized by comprising a high-voltage pulse generator, a voltage divider, a sleeve, a metal testing unit, the photomultiplier and a signal collector;
the metal testing unit is placed in a metal tank filled with insulating gas, an insulator sample is placed between a high-voltage electrode and a grounding electrode of the metal testing unit, a metal needle is placed on the high-voltage electrode of the metal testing unit, and the tip of the metal needle is in contact with the surface of the insulator sample;
the output of high voltage pulse generator respectively with the input of voltage divider with the sheathed tube input is connected, sheathed tube output with metal test unit's high-voltage electrode is connected, photomultiplier's input passes through the optic fibre and aims at the most advanced position of metal needle, the output of voltage divider with photomultiplier's output respectively with signal collector's input is connected, high voltage pulse generator's earthing terminal the earthing terminal of voltage divider with metal test unit's telluric electricity field all grounds.
2. The photomultiplier-based insulator streamer propagation velocity measurement device of claim 1, wherein the insulating gas comprises C 4 F 7 N/CO 2 /O 2 And (4) mixing the gases.
3. The photomultiplier-based insulator streamer propagation velocity measurement device of claim 1, wherein the high voltage pulse generator comprises a Marx generator and the signal collector comprises a digital oscilloscope.
4. The photomultiplier-based insulator flood propagation velocity measuring apparatus according to claim 1, wherein said insulator sample is a cylinder made of alumina-filled epoxy.
5. The photomultiplier-based insulator streamer propagation velocity measurement device of claim 1, wherein the high voltage electrode and the ground electrode of the metallic test cell are both made of aluminum and the metallic pin is made of tungsten.
6. A photomultiplier-based insulator streamer propagation speed measurement method, characterized by being applied to a photomultiplier-based insulator streamer propagation speed measurement device according to any one of claims 1 to 5, the method comprising:
positioning the insulator sample to obtain a total creepage distance, and filling the insulating gas in the metal tank;
the standard lightning impulse voltage with the positive polarity and the standard lightning impulse voltage with the negative polarity output by the high-voltage pulse generator are increased successively according to a preset voltage increment until flashover occurs, and the test is repeatedly carried out until the accumulated flashover times reach the preset flashover times;
converting optical signals generated at the tip position of the metal needle when flashover occurs each time into electric signals through the photomultiplier tube to obtain all the electric signals, and generating photoelectric signal waveforms according to all the electric signals through the signal collector;
and determining total flow time under positive polarity and negative polarity according to the waveform of the photoelectric signal, and respectively calculating average flow velocity under positive polarity and negative polarity according to the total creepage distance and the total flow time under positive polarity and negative polarity to obtain flow propagation velocity.
7. The method for measuring the propagation velocity of the insulator streamer based on the photomultiplier as claimed in claim 6, wherein the step of positioning the insulator sample to obtain the total creepage distance comprises the steps of:
and determining the relative position of the tip of the metal needle and the grounding electrode of the metal test unit, and recording the distance between the tip of the metal needle and the grounding electrode of the metal test unit as the total creepage distance.
8. The method for measuring the propagation velocity of insulator fluid based on a photomultiplier according to claim 6, wherein the insulating gas is filled in the metal tank, specifically:
filling 0.75Mpa of C into the metal tank 4 F 7 N/CO 2 /O 2 Mixing the gas.
9. The method for measuring the propagation velocity of the insulator slip stream based on the photomultiplier according to claim 6, wherein the step of increasing the standard lightning impulse voltage of the positive polarity and the standard lightning impulse voltage of the negative polarity output by the high voltage pulse generator according to the preset voltage increment until the flashover occurs and the step of repeating the test until the accumulated flashover times reach the preset flashover times comprises the steps of:
and after the standard lightning impulse voltage with the positive polarity or the negative polarity output by the high-voltage pulse generator is increased every time, waiting for preset time and then performing the next action.
10. The photomultiplier-based insulator streamer propagation velocity measurement apparatus of claim 6, wherein the average streamer velocity in the positive polarity = the total creepage distance/total streamer time in the positive polarity, and the average streamer velocity in the negative polarity = the total creepage distance/average streamer velocity in the negative polarity.
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