Extra-high voltage alternating current line voltage corona discharge detection and analysis method

Abstract

The invention relates to the technical field of extra-high voltage alternating current line voltage detection, in particular to an extra-high voltage alternating current line voltage corona discharge detection and analysis method. Based on the dielectric theory and the voltage division principle, the voltage of the extra-high voltage alternating current circuit is measured, the corona discharge phase can be obtained in an auxiliary mode, and the corona discharge reason can be judged. Based on the principle of electromagnetic induction, corona discharge is indirectly measured by measuring corona discharge induced voltage, the space charge condition generated by discharge can be judged, the corona discharge degree can be evaluated, and the discharge intensity can be evaluated by combining the charge induced voltage and the line voltage which are measured synchronously.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high voltage alternating current (UHV) line voltage detection, and in particular to a method for detecting and analyzing corona discharge of an UHV AC line voltage. Background Art

[0002] When ultra-high voltage transmission lines are energized, some towers, particularly tension towers, are susceptible to corona discharge or creeping discharge. Continuous corona discharge on transmission lines consumes energy, causing energy loss along the line. Furthermore, the discharge triggers ionized chemical reactions in the surrounding air, generating products such as ozone and nitrogen oxides, which can corrode the transmission line conductors and insulation, reducing their lifespan. Furthermore, corona discharge generates high-frequency electromagnetic pulses. Because these pulses fall within the radio frequency range, they can interfere with signal transmission, such as radio communications, and affect the operation of related monitoring equipment. Furthermore, under AC voltage, charged particles generated by corona discharges move around metal conductors, forming air jets (ionic winds). These reactions, combined with the generation of harmful substances such as ozone, can pose a risk to human health.

[0003] Therefore, it is necessary to measure the corona discharge of UHV transmission lines, analyze the corona discharge characteristics of UHV transmission lines in combination with the voltage of UHV transmission lines, obtain the corona discharge voltage, and propose line structure optimization design schemes or maintenance strategies based on this.

[0004] The current status of related technology research is: 1) Line corona discharge measurement method The spatial field strength caused by continuous corona discharge changes little, and when the electrodes are far apart, it is difficult to measure using the traditional pulse current method of partial discharge measurement. At present, most of the methods for detecting corona discharge in transmission lines are audible noise, ultraviolet detection, infrared detection, and ultrasonic detection. However, these methods can only roughly determine the severity of the discharge, but it is difficult to make a more accurate study of the discharge amount on the surface of the insulator or at the connection point.

[0005] The audible noise detection method uses the hissing sound produced by discharge during line inspection to determine whether corona discharge is present. This method can only detect the presence of partial discharge when the discharge is strong and there is no interference, and cannot accurately determine the extent and characteristics of the discharge.

[0006] The infrared detection method detects the thermal radiation band signal during corona discharge based on the principle of photoelectric technology and converts the signal into a visual image. However, its sensitivity is poor. When the line is overloaded or fails, corona discharge cannot be detected through thermal imaging.

[0007] The ultraviolet detection method can determine whether there is continuous corona discharge by quantifying the number of photons, but the measurement accuracy depends on the precision of dedicated instruments, is expensive, and is affected by the measurement distance. The measured continuous corona discharge voltage has a large error. Figure 1 This is the schematic diagram of the UV detection method, which consists of a lens system, filters, light sensors, a control and analysis system, and an image display system. The visible light lens captures a visible image of the corona target, while the filter removes light waves outside the solar blind zone. The UV lens creates an ultraviolet image of the light waves removed by the filter. The light sensor performs photoelectric conversion on the corona image. The control and analysis system analyzes the light intensity and controls the entire detection system. The image display system fuses and displays the two types of image information. The combined imaging information is analyzed to determine the specific discharge situation of the target.

[0008] like Figure 2 As shown in Figure 1, the ultrasonic detection method detects partial discharge through three steps: acoustic-to-electrical signal conversion, electrical signal amplification, and signal display. However, the ultrasonic detection method is susceptible to electromagnetic interference, has low detection sensitivity, and cannot perform quantitative analysis and detection.

[0009] In summary, existing corona discharge detection methods are difficult to determine the severity of corona discharge and obtain accurate continuous corona discharge voltage. At the same time, they are unable to analyze the situation of charged particles in space.

[0010] 2) Line voltage measurement method In order to analyze the characteristics and causes of corona discharge in UHV transmission lines, it is necessary to synchronously measure the voltage waveform of the UHV transmission lines. Existing methods mainly include: ① Capacitor voltage transformer (CVT). Figure 3 This is the electrical structure of a CVT. The capacitive voltage divider consists of a high-voltage arm capacitor CH and a low-voltage arm capacitor CL connected in series. The electromagnetic unit comprises an intermediate transformer T, a compensating reactor L, and a damper D. Z represents the secondary load. The line voltage Us is stepped down by the capacitive voltage divider and fed into the electromagnetic unit. After the compensating reactor's "compensation" function, it is fed into the intermediate transformer, where it undergoes a secondary step-down process before being output.

[0011] CVTs, when measuring line voltage, suffer from poor transient characteristics. Furthermore, in line arrester applications, the arrester and CVT may be far apart, or there may be no CVT nearby, making it difficult to obtain the line voltage nearby. Even if a voltage signal can be obtained, the long-distance signal transmission process is subject to electromagnetic interference, making it difficult to accurately calculate the arrester's resistive current.

[0012] ②External partial pressure method like Figure 4As shown, the method of adding a capacitive sensor outside the existing capacitive device (sleeve) is the same as the high-voltage voltage divider, and the geometric capacitance of the capacitive device is equivalent to the high-voltage capacitor, and the additional capacitance is equivalent to the low-voltage capacitor, and the two are connected in series to form a capacitive voltage divider, and the external impedance voltage of the capacitive device is measured and the line voltage is calculated. This method also has the problem of no available capacitive device in the direct surrounding, and because the capacitive device itself has a certain resistance, the voltage phase difference will be introduced.

[0013] In summary, there is no convenient ultra-high voltage transmission line voltage waveform synchronous measurement method. SUMMARY

[0014] The present application aims at the problem that the existing ultra-high voltage transmission line voltage waveform measurement cannot guarantee accuracy and is easy to introduce voltage phase difference, and proposes an ultra-high voltage AC line voltage corona discharge detection analysis method; based on dielectric theory and voltage division principle, the ultra-high voltage AC circuit voltage is measured, and the corona discharge phase, the judgment of corona discharge reason and the like are obtained; based on electromagnetic induction principle, the corona discharge is indirectly measured by measuring the corona discharge induced voltage, the space charge condition of the discharge is judged, the degree of corona discharge is evaluated, and the evaluation of the discharge intensity is realized by combining the synchronous measured charge induced voltage and line voltage.

[0015] The specific implementation content of the present application is as follows: An ultra-high voltage AC line voltage corona discharge detection analysis method, specifically comprising the following steps: Step S1: The unmanned aerial vehicle carrying a metal induction plate, a detection circuit and a shielding box is horizontally lifted and hovered from below the ultra-high voltage line, and an electric field numerical model is established according to electromagnetic field theory; Step S2: The obtained transmission conductor voltage is taken as an initial condition, a simulation model is established according to the electric field numerical model, the stray capacitance of the air between the ultra-high voltage line and the metal induction plate is calculated, and the line voltage on the metal induction plate is obtained; Step S3: The charged transmission conductor is taken as an initial condition, a simulation model is established according to the electric field numerical model, the charge induced voltage is calculated, and the proportional relationship between the discharge space charge and the charge induced voltage of the metal induction plate is obtained according to the set discharge space charge value in the simulation and the calculated charge induced voltage value; Step S4: According to the measured charge induced voltage, the space charge amount generated by the corona discharge is obtained, and the corona discharge intensity is judged according to the space charge amount, and the corona discharge characteristics of the ultra-high voltage line are analyzed.

[0016] In order to better realize the present application, further, the step S1 specifically comprises the following steps: Step S11: Raise the UAV equipped with the metal sensing plate, detection circuit, and shielding box from the bottom of the UHV line and hover horizontally; wherein the distance between the metal sensing plate and the UHV line is equal, and the distance between the metal sensing plate and the UHV line is greater than the maximum distance between the UHV line and the metal sensing plate for air to break down; Step S12: Correlating charge and potential based on space charge density, relative dielectric constant, and dielectric constant of free space, and establishing a potential numerical model; Step S13: Calculate the electric field numerical model and the electric displacement numerical model according to the electric potential numerical model.

[0017] In order to better implement the present invention, further, the specific operations of step S12 are: Where ρ is the space charge density, is the dielectric constant of free space, is the relative dielectric constant, V is the electric potential, represents the gradient; The specific operations of step S13 are: Where E is the electric field strength, is the dielectric constant of free space, is the relative dielectric constant, D is the electric displacement, V is the electric potential, Represents the gradient.

[0018] In order to better implement the present invention, further, step S2 specifically includes the following steps: Step S21: Using the obtained transmission line voltage as the initial condition, the electric field intensity on the surface of the metal induction plate and the potential difference between the line and the plate are calculated according to the electric potential numerical model, the electric field numerical model, and the electric displacement numerical model; Step S22: Calculate the total charge based on the surface strength of the metal sensing plate, the dielectric constant of free space, and the area of ​​the metal sensing plate; Step S23: Calculate the stray capacitance of the air between the UHV line and the metal induction plate based on the potential difference between the line plates and the total charge; Step S24: Calculate the line divided voltage on the metal sensing plate according to the stray capacitance, the capacitance of the detection circuit in the shielding box at the lower end of the metal sensing plate, and the obtained line voltage.

[0019] In order to better implement the present invention, further, the specific operations of step S21 are: Where σ is the charge density, is the dielectric constant of free space.

[0020] The method for detecting and analyzing corona discharge in an ultra-high voltage AC line according to claim 5, wherein the specific operation of step S22 is: in, E n is the normal component of the electric field, s is the area of ​​the induction plate, Q 1 is the total charge.

[0021] In order to better implement the present invention, further, the specific operations of step S23 are: in, Q 1 is the total charge, and △V is the potential difference between the wires and plates.

[0022] In order to better implement the present invention, further, the specific operations of step S24 are: in, U is the line voltage, U 1' is the line divided voltage on the metal sensing plate, C1 is the stray capacitance of the air between the UHV line and the metal sensing plate, and C2 is the main capacitance of the detection circuit in the shielding box at the lower end of the metal sensing plate.

[0023] In order to better implement the present invention, further, step S3 specifically includes the following steps: Step S31: Taking the transmission wire as the initial condition with a charge, the electric field intensity on the surface of the metal induction plate is calculated according to the electric potential numerical model, the electric field numerical model, and the electric displacement numerical model; Step S32: Calculating the charge of the metal sensing plate according to the surface strength of the metal sensing plate, the dielectric constant of free space, and the area of ​​the metal sensing plate; Step S33: Calculating the charge induced voltage according to the charge amount of the metal sensing plate and the capacitance of the detection circuit in the shielding box at the lower end of the metal sensing plate.

[0024] Step S34: according to the discharge space charge value set in the simulation and the charge induced voltage value obtained by calculation, a proportional relationship between the discharge space charge and the charge induced voltage of the metal induction plate is obtained.

[0025] In order to better implement the present invention, the specific operation of step S4 is further as follows: analyzing the generation and dissipation of single-cycle space charge based on the charge induced voltage distortion; if the charge induced voltage and the UHV line divider voltage have obvious bulges within the set period, the space charge generated by corona discharge is formed and dissipated, and based on whether the charge induced voltage is higher or lower than the zero value horizontal line, it is judged whether there is a continuous space charge around the UHV line.

[0026] The present invention has the following beneficial effects: (1) In terms of voltage equivalence, the present invention is based on electromagnetic field theory and uses finite element simulation methods to directly establish large models such as circuits and plates to analyze capacitance, without the need for equivalence and to reduce errors. It is also applicable to the derivation of capacitance when the metal induction plate is not a complete plate. It is further combined with the simultaneously measured charge induced voltage and circuit voltage to evaluate the severity of discharge.

[0027] (2) The present invention derives the air stray capacitance based on electromagnetic field theory and proposes a line voltage measurement method based on voltage division, which can obtain the line voltage locally at the corona discharge location. This solves the problem in the existing technology that the CVT method and the external voltage division method are not convenient for measuring the corona discharge location to obtain the ultra-high voltage line voltage, and the voltage waveform phase may be inaccurate.

[0028] (3) The line voltage measurement method proposed in the present invention is a non-contact measurement method, which can solve the problem of safety risks in the prior art when CVT and other directly connected lines introduce line voltage.

[0029] (4) The present invention proposes a method for measuring charge induced voltage in combination with a line voltage measurement induction plate; proposes a transmission line corona discharge detection and analysis method based on charge induced voltage, which has the characteristics of high sensitivity, non-contact measurement at a long distance, low cost, and anti-interference. It solves the problems in existing line corona discharge detection technologies, such as the low sensitivity of infrared detection methods under conditions such as line heating, the limited detection distance of ultraviolet detection methods, and the significant influence of electromagnetic interference on ultrasonic detection methods, which are limited in application under conditions of ultra-high voltage transmission lines.

[0030] (5) The corona discharge measurement and analysis method based on charge induced voltage of the present invention does not require complex signal processing and is simple and practical to operate, thereby solving the problems of complex signal processing and application of detection technologies such as ultraviolet detection method and ultrasonic detection method.

[0031] (6) The present invention proposes a line voltage and charge induced voltage measurement method based on electromagnetic field theory, which takes into account the influence of ground potential on the symmetry of the electric field. It can be applied to the line voltage analysis of asymmetric electric fields and non-standard induction plates, and solves the problem that the existing line voltage measurement and charge induced voltage measurement methods are not applicable to UAV measurement schemes.

[0032] (7) The present invention combines the discharge pulse waveform, charge induced voltage and line voltage waveform to specifically analyze the discharge strength, discharge phase, discharge cause, and charge distribution in the space near the line. This solves the problem of the existing technology that is unable to analyze and determine the degree of corona discharge and discharge phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1The existing ultraviolet detection method principle diagram.

[0034] Figure 2 The existing ultrasonic wave detection flow chart.

[0035] Figure 3 The existing CVT electrical structure diagram.

[0036] Figure 4 The existing sleeve end frequency voltage sensor schematic diagram.

[0037] Figure 5 The detection device overall structure and principle diagram provided by the present application.

[0038] Figure 6 The metal sensing plate and detection circuit schematic diagram provided by the present application.

[0039] Figure 7 The shielding box structure diagram provided by the present application.

[0040] Figure 8 The detection device circuit principle diagram provided by the present application.

[0041] Figure 9 The line-plate-ground finite element simulation model structure schematic diagram provided by the present application.

[0042] Figure 10 The line-plate-ground finite element simulation model finite element mesh division structure schematic diagram provided by the present application.

[0043] Figure 11 The 750kV potential and electric field strength simulation result diagram provided by the present application.

[0044] Figure 12 The electric field strength and potential simulation result diagram provided by the present application under the condition of Q0=1μC.

[0045] Figure 13 The induced voltage schematic diagram provided by the present application.

[0046] Figure 14 The full cycle discharge pulse signal schematic diagram provided by the present application.

[0047] Figure 15 The single discharge pulse signal schematic diagram provided by the present application.

[0048] Figure 16 The detection position schematic diagram provided by the present application.

[0049] Figure 17 The detection method schematic diagram provided by the present application.

[0050] Figure 18A detection result diagram provided by the embodiment of the present application.

[0051] 1, unmanned aerial vehicle, 2, metal induction plate, 3, shielding box, 31, upper cover plate, 32, lower cover plate, 33, front cover plate, 34, rear cover plate, 4, detection circuit, 5, signal acquisition device, 6, unmanned aerial vehicle rotor hole, 7, first bolt hole, 8, second bolt hole, 9, cable hole, 10, third bolt hole, 11, fourth bolt hole, 12, fifth bolt hole, 13, sixth bolt hole, 14, seventh bolt hole, 15, eighth bolt hole. DETAILED DESCRIPTION

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. It should be understood that the described embodiments are only a part of the embodiments of the present application, not all the embodiments, and therefore should not be regarded as limiting the scope of protection. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0053] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "provided", "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0054] Embodiment 1 The present embodiment proposes a method for detecting and analyzing voltage corona discharge of an ultra-high voltage AC line, which specifically includes the following steps: A method for detecting and analyzing voltage corona discharge of an ultra-high voltage AC line, which specifically includes the following steps: Step S1: The unmanned aerial vehicle 1 carrying the metal induction plate 2, the detection circuit 4 and the shielding box 3 is horizontally lifted and hovered from below the ultra-high voltage line, and an electric field numerical model is established according to electromagnetic field theory; The step S1 specifically includes the following steps: Step S11: The unmanned aerial vehicle 1 carrying the metal induction plate 2, the detection circuit 4 and the shielding box 3 is horizontally lifted and hovered from below the ultra-high voltage line; wherein the distance from the plane of the metal induction plate 2 to the ultra-high voltage line is equal, and the distance from the metal induction plate 2 to the ultra-high voltage line is greater than the maximum distance of air breakdown between the ultra-high voltage line and the metal induction plate 2; Step S12: Correlating charge and potential based on space charge density, relative dielectric constant, and dielectric constant of free space, and establishing a potential numerical model; The specific operations of step S12 are: Where ρ is the space charge density, is the dielectric constant of free space, is the relative dielectric constant, V is the electric potential, represents the gradient; Step S13: Calculate the electric field numerical model and the electric displacement numerical model according to the electric potential numerical model.

[0055] The specific operations of step S13 are: Where E is the electric field strength, is the dielectric constant of free space, is the relative dielectric constant, D is the electric displacement, V is the electric potential, Represents the gradient.

[0056] Step S2: Using the obtained transmission line voltage as the initial condition, a simulation model is established based on the electric field numerical model to calculate the stray capacitance of the air between the UHV line and the metal induction plate 2, and obtain the line divided voltage on the metal induction plate 2; The step S2 specifically includes the following steps: Step S21: Using the obtained transmission line voltage as the initial condition, the electric field intensity on the surface of the metal induction plate 2 and the potential difference between the line and the plate are calculated according to the electric potential numerical model, the electric field numerical model, and the electric displacement numerical model; The specific operations of step S21 are: Where σ is the charge density, is the dielectric constant of free space.

[0057] Step S22: Calculate the total charge based on the surface strength of the metal sensing plate 2, the dielectric constant of free space, and the area of ​​the metal sensing plate; The specific operations of step S22 are: in, E n is the normal component of the electric field, s is the area of ​​the sensing plate, and Q1 is the total charge.

[0058] Step S23: Calculate the stray capacitance of the air between the UHV line and the metal induction plate 2 based on the potential difference between the line and the plate and the total charge; The specific operations of step S23 are: Where Q1 is the total charge and △V is the potential difference between the wires and plates.

[0059] Step S24: Calculate the line divided voltage on the metal sensing plate 2 according to the stray capacitance, the main capacitance of the detection circuit 4 in the shielding box 3 at the lower end of the metal sensing plate 2, and the obtained line voltage.

[0060] The specific operations of step S24 are: Where U is the line voltage, U 1' is the line divided voltage on the metal sensing plate 2, C1 is the stray capacitance of the air between the UHV line and the metal sensing plate 2, and C2 is the main capacitance of the detection circuit 4 in the shielding box 3 at the lower end of the metal sensing plate 2.

[0061] Step S3: Taking the transmission line as the initial condition with charge, a simulation model is established according to the electric field numerical model to calculate the charge induced voltage; The step S3 specifically includes the following steps: Step S31: Taking the transmission wire as the initial condition with a charge, the electric field intensity on the surface of the metal induction plate 2 is calculated according to the electric potential numerical model, the electric field numerical model, and the electric displacement numerical model; Step S32: Calculate the charge of the metal sensing plate according to the surface strength of the metal sensing plate 2, the dielectric constant of free space, and the area of ​​the metal sensing plate; Step S33: Calculate the charge induced voltage according to the charge amount of the metal sensing plate and the main body capacitance of the detection circuit 4 in the shielding box 3 at the lower end of the metal sensing plate 2.

[0062] Step S34: according to the discharge space charge value set in the simulation and the charge induced voltage value obtained by calculation, a proportional relationship between the discharge space charge and the charge induced voltage of the metal induction plate is obtained.

[0063] Step S4: obtaining the amount of space charge generated by corona discharge according to the charge induced voltage, judging the intensity of corona discharge according to the amount of space charge, and analyzing the corona discharge characteristics of the UHV line.

[0064] The specific operation of step S4 is as follows: analyzing the generation and dissipation of single-cycle space charge based on the charge-induced voltage distortion; if the charge-induced voltage and the UHV line voltage divider have obvious bulges within the set period, the space charge generated by corona discharge is formed and dissipated, and judging whether there is persistent space charge around the UHV line based on whether the charge-induced voltage is above or below the zero-value horizontal line.

[0065] Working principle: Based on the dielectric theory and the voltage division principle, the voltage of the ultra-high voltage alternating current circuit is measured, and the corona discharge phase and the reason for the corona discharge are obtained; based on the electromagnetic induction principle, the corona discharge is indirectly measured by measuring the induced voltage of the corona discharge, and the space charge generated by the discharge is judged, the degree of corona discharge is evaluated, and the evaluation of the discharge intensity is realized by combining the synchronous measured charge induction voltage and the line voltage.

[0066] Embodiment 2: Based on the above embodiment 1, as shown in Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 A specific embodiment is used to explain the structure of the detection device of the unmanned aerial vehicle 1 equipped with the metal induction plate 2, the detection circuit 4 and the shielding box 3 in detail.

[0067] As shown in Figure 5 , the detection device includes an unmanned aerial vehicle 1, a metal induction plate 2, a shielding box 3, a detection circuit 4, and a signal acquisition device 5. The unmanned aerial vehicle 1 is arranged above the metal induction plate 2 and is fixedly connected with the metal induction plate 2. The shielding box 3 is arranged below the metal induction plate 2 and is fixedly connected with the metal induction plate 2. The detection circuit 4 and the signal acquisition device 5 are arranged in the shielding box 3, one end of the detection circuit 4 is connected with the metal induction plate 2, and the other end is connected with the signal acquisition device 5. The signal acquisition device 5 acquires a signal waveform, and judges the space charge characteristics of the transmission line corona discharge according to the signal waveform.

[0068] The detection device is composed of an unmanned aerial vehicle 1, a metal induction plate 2, a detection circuit 4, a shielding box 3, a signal transmission line cable, and a signal acquisition device 5. The unmanned aerial vehicle 1 is a load-bearing kg, hoverable unmanned aerial vehicle. In this embodiment, the metal induction plate 2, the detection circuit 4, the shielding box 3 and the signal acquisition device 5 are lifted to the vicinity of the measured ultra-high voltage line by the unmanned aerial vehicle 1, the signal waveform is acquired by the signal acquisition device 5, and the space charge characteristics of the transmission line corona discharge are judged according to the signal waveform, the surface induction charge of the metal induction plate 2 is more accurately obtained, the device is simple to operate, the instrument parameter requirement is low, the cost is low, and it is suitable for line detection.

[0069] As shown in Figure 6 , the metal induction plate 2 is provided with an unmanned aerial vehicle rotor hole 6. The propeller of the unmanned aerial vehicle 1 is arranged in the unmanned aerial vehicle rotor hole 6, and the diameter of the unmanned aerial vehicle rotor hole 6 is greater than the diameter of the rotation of the propeller of the unmanned aerial vehicle 1. The present embodiment proposes a structural method combining the metal induction plate 2 and the anti-collision protection structure of the unmanned aerial vehicle 1 by arranging the unmanned aerial vehicle rotor hole 6, and solves the problem that the whole plate of the metal induction plate 2 affects the flight of the wing unmanned aerial vehicle 1. The metal induction plate 2 in the present embodiment is an aluminum plate with a thickness of 1 mm and a length of dozens of centimeters, which plays a role of charge induction on one hand and a role of the anti-collision protection ring of the propeller of the unmanned aerial vehicle 1 on the other hand; the conditioning circuit and the unmanned aerial vehicle control circuit are arranged below the metal induction plate 2, that is, the metal induction plate 2 simultaneously plays a role of the protection cover above the circuit.

[0070] As shown in Figure 7 The shielding box 3 includes an upper cover plate 31 and a lower cover plate 32. The upper cover plate 31 is provided with a first bolt hole 7, and the metal induction plate 2 is connected through the first bolt hole 7. The lower cover plate 32 is provided with a second bolt hole 8, and the detection circuit 4 is fixedly arranged in the shielding box 3 through the second bolt hole 8.

[0071] The lower cover plate 32 is further provided with a cable hole 9. The cable hole 9 is arranged at the center of the lower cover plate 32, and the detection circuit 4 is connected with the signal acquisition device 5 through the cable hole 9.

[0072] The shielding box 3 further includes a front cover plate 33 and a rear cover plate 34. The front cover plate 33 is provided with a third bolt hole 10, the front end of the upper cover plate 31 is provided with a fifth bolt hole 12, and the front end of the lower cover plate 32 is provided with a sixth bolt hole 13. The front cover plate 33 is connected through the third bolt hole 10, the fifth bolt hole 12 and the sixth bolt hole 13. The rear cover plate 34 is provided with a fourth bolt hole 11, the rear end of the upper cover plate 31 is provided with a seventh bolt hole 14, and the front end of the lower cover plate 32 is provided with an eighth bolt hole 15. The rear cover plate 34 is connected through the fourth bolt hole 11, the seventh bolt hole 14 and the eighth bolt hole 15.

[0073] In the present embodiment, the shielding box 3 of the detection circuit and the control circuit selects a split type aluminum shell with high conductivity as a shielding material, and the thickness is 1 mm. The shielding box 3 is coated with an insulating material on the whole outer layer. The metal induction plate 2 is arranged above the shielding box 3, and the shielding box 3 is used as a support.

[0074] The front and back structures of the shielding box 3 are as shown in Figure 7As shown, the large holes on the front and back are first screw holes 7 for securing the shielding box 3 to the metal sensing plate 2. The four smaller holes on the back are second screw holes 8 for securing the circuit board for the detection circuit 4. The four smaller holes on the front and back are screw holes for the shielding box's airtight cover. Use screws through the large holes to secure the upper cover 31, metal sensing plate 2, and lower cover 32 together. Use insulating studs to secure the detection circuit 4 to the center of the shielding box 3. Finally, use screws through the four smaller holes at the bottom to secure the airtight cover to the bottom of the shielding box, sealing the entire box.

[0075] The metal sensing plate 2 is connected to the detection circuit 4 through a wire passing through the first bolt hole 7; the middle hole of the lower cover 32 is the coaxial cable outlet, i.e. the cable hole 9, which ensures that the circuit board transmits the signal to the signal acquisition device 5 through the coaxial cable after receiving the signal, and is closed with a cover at the front and back.

[0076] like Figure 8 As shown, the detection circuit 4 includes a capacitor C2, a resistor R1, a resistor R2, and a resistor R3; One end of the resistor R2 is connected to the metal sensing plate 2, and the other end is connected to the signal acquisition device 5 through a cable; One end of the capacitor C2 is connected between the metal sensing plate 2 and the resistor R2, and the other end is connected between the resistor R1 and the resistor R3; One end of the resistor R3 is connected between the resistor R1 and the capacitor C2, and the other end is connected to the signal acquisition device 5 through a cable; One end of the resistor R1 is connected between the capacitor C2 and the resistor R3 , and the other end is connected to the ground terminal of the signal acquisition device 5 through a cable.

[0077] In this embodiment, the detection circuit 4 is housed within the shielding box 3 and comprises a circuit consisting of capacitors and matching resistors. The signal transmission line is a three-core coaxial cable, comprising a ground wire, a transmission line for the first signal acquisition unit, and a transmission line for the second signal acquisition unit. The signal acquisition device 5 is a RIGOL high-sampling-rate oscilloscope, which can be substituted with other sampling devices.

[0078] During measurement, a drone 1 is used to lift the metal sensing plate 2, detection circuit 4, and shielding box 3 to a horizontal distance of several meters near the UHV line under test. When a corona discharge occurs on the line, the signal acquisition device 5 captures: the line voltage divider + charge-induced voltage U1, a low-frequency signal acquired at a sampling rate of over 100 Msa / s; and the discharge pulse signal U2, a high-frequency signal acquired at a sampling rate of over 1 Gsa / s. Based on the signal waveforms captured by the signal acquisition device 5, such as on an oscilloscope, the characteristics of the corona discharge on the transmission line and the space charge near the line are analyzed and determined.

[0079] In this embodiment, the metal sensing plate 2 is combined with the anti-collision protection structure of the UAV 1 and constitutes a part of the shielding structure. The shielding structure serves both to support the metal sensing plate 2 and to provide shielding.

[0080] In the measuring device, the metal sensing plate 2 and the detection circuit 4 are passive sensing devices; the metal sensing plate 2 and the shielding shell are integrated, and a lightweight design is adopted while ensuring the effect. The shielding shell of the detection circuit 4 can ensure that signal acquisition is not interfered with by electromagnetic fields.

[0081] A drone (1) serves as a lifting device, raising and lowering a metal sensing plate (2) and a detection circuit (4) beneath the power lines. The device is positioned at a distance greater than the air insulation breakdown distance from the UHV transmission lines, ensuring no impact on the lines and safe operation. The device boasts a simple structure, low cost, and short detection times. It requires no complex signal processing and is easy to operate.

[0082] The rest of this embodiment is the same as that of the above-mentioned embodiment 1, and therefore will not be described in detail.

[0083] Example 3: This embodiment is based on any one of the above embodiments 1 to 2. Figure 9 、 Figure 10 、 Figure 11 、 Figure 12 、 Figure 13 、 Figure 14 As shown, a specific embodiment is described in detail.

[0084] Step S1: Line voltage measurement.

[0085] During measurement, the drone 1 is raised and hovered horizontally from below the line, with the distance between the metal sensing plate 2 and the UHV line being equal. The distance between the metal sensing plate 2 and the UHV line is greater than the maximum distance that the air between the UHV line and the metal sensing plate can penetrate. According to dielectric theory, there is stray capacitance in the air between the UHV line and the metal sensing plate 2. C 1. The main body of the detection circuit 4 under the metal sensing plate 2 is a capacitor C 2. Due to the capacitor voltage division of the UHV transmission line AC voltage, a line induced voltage proportional to the line voltage will be generated on the metal induction plate 2.

[0086] To obtain the stray capacitance C 1. According to electromagnetic field theory, establish the electric field numerical model, connect the electric potential and charge, electric potential V Satisfies Poisson's equation: (1) in is the dielectric constant of free space, is the relative permittivity, and ρ is the space charge density. The electric field and electric displacement are calculated according toV The gradient of is obtained: (2) (3) Take the above equation as the control equation, as Figure 9 、 Figure 10 As shown, the electric potential and electric field strength at various locations can be obtained through finite element simulation calculations in a wire-plate-ground simulation model of real structure size.

[0087] like Figure 11 As shown, the transmission line voltage V As the initial condition, based on the simulation calculation of equations (1) to (3), the normal electric field strength on the surface of the line or metal induction plate 2 can be obtained. E n 。

[0088] Furthermore, the electric field strength E n The surface charge density σ is calculated as: (4) The total charge is the area of ​​the circuit or metal induction plate s The surface integral of : (5) Solving for capacitance C 1, the known line voltage is set as the initial condition. Based on the relationship between equations (1) to (3), the potential difference △V between the line and the plate can be obtained; based on equations (4) to (5), the charge of the line and the charge of the metal induction plate 2 can be calculated, and the charge difference between the line and the plate △ Q .

[0089] Final stray capacitance C 1: (6) The line voltage is U , then the circuit divided voltage on the metal sensing plate 2 is U 1' is equal to: (7) Step S2: Obtain the charge induced voltage and the set circuit discharge space charge Q 0 relationship.

[0090] When no corona discharge occurs in the line, the charge is basically confined to the inside of the conductor, and there is no space charge. However, when corona discharge occurs, the space charge in the space near the line can generate 2 induced charges on the metal induction plate due to the induction principle.

[0091] Study on the charge induced voltage and the set line discharge space charge Q 0 relationship, specifically: like Figure 12 As shown, the transmission wire carries charge Q 0 is the initial condition. Based on the simulation calculation of equations (1) to (3), the electric field intensity on the surface of the metal induction plate 2 can be obtained. E n 。

[0092] Then, based on the simulation calculation of formula (4) to formula (5), the induced charge of the metal induction plate 2 can be obtained: Q 2.

[0093] The induction board is connected to the conditioning circuit, and the resistance under the power frequency voltage R 1 is much smaller than C 2 capacitive reactance, then the charge induced voltage U 1” means: (8) Right now U 1” is determined by Q 2, with Q 0 is positively correlated with the size of the discharge space charge. Q 0 and metal induction plate charge induced voltage U The ratio of 1" is Q 0 / U 1".

[0094] Based on the above theory, the size of the sensing plate, the distance from the circuit, and the sampling capacitor can be analyzed and designed.

[0095] because U 1" depends on the amount of space charge Q 0, and the amount of space charge generated by corona discharge can measure the intensity of corona discharge. Therefore, according to U 1” can analyze the corona discharge characteristics of the line.

[0096] because U 1" combined with line voltage divider U 1', forming line divided voltage + charge induced voltage signal U 1 is measured by the signal acquisition device, so it needs to be extracted U 1". Figure 13 As shown, the signal acquisition device measures the induced voltage U 1. The line voltage is divided by the line voltage generated on the sensing plate U 1 ’ It can be measured at a location without corona discharge nearby, or the waveform amplitude can be calculated according to formula (7) and then the sine waveform can be reconstructed. Subtracting the two, the charge induced voltage is obtained. U 1".

[0097] Step S3: Discharge pulse measurement.

[0098] like Figure 14 、 Figure 15 As shown in Figure 1, if corona discharge further develops into streamer discharge, during a single streamer discharge, the short-term space charge changes rapidly and is accompanied by charge migration. This generates induced charge on the metal electrode surface, which in turn forms a pulse current in the measurement circuit. The frequency range of the discharge pulse signal is approximately 3 MHz to 30 MHz. Taking the lowest frequency f = 3 MHz, the maximum capacitive reactance of C2, X, is calculated. c1 max =5.3 Ω. Then the resistance value of the measurement circuit is R1=100 Ω>>X c1 max The generated pulse voltage basically acts on R1, and the discharge pulse signal U2 can be measured on R1. Combined with the line voltage divider U1', the characteristics of the streamer discharge phase can be analyzed.

[0099] Working Principle: This embodiment combines a sensing plate with a drone's anti-collision structure, utilizing stray air capacitance to form a voltage divider circuit and measure the power-frequency voltage of an ultra-high voltage line. The design utilizes theoretical derivation and finite element simulation to analyze and design the sensing plate's dimensions, distance from the line, and sampling capacitance. This overcomes the errors caused by existing methods for calculating equivalent stray air capacitance when obtaining line voltage, as well as the problem that capacitance derivation only works when the sensing plate is a solid flat plate.

[0100] The above line voltage measurement method is used to measure the effect at the position where no corona discharge occurs. Figure 14 Line divided voltage U 1'.

[0101] Under actual working conditions, measurement was achieved at a distance of about 10m from the vertical position of the line, that is, the line voltage was obtained locally at the corona discharge position, achieving the effect of non-contact measurement at a relatively long distance.

[0102] It solves the problem that the aforementioned CVT method and external voltage division method are not convenient for measuring the corona discharge position to obtain the ultra-high voltage line voltage, and the voltage waveform phase may be inaccurate. It also solves the problem that CVT and other methods directly connect to the line and introduce line voltage, which poses a safety risk.

[0103] A method for detecting and analyzing corona discharge in transmission lines based on induced charge voltage is proposed. A method for further analyzing the intensity, discharge phase, and whether persistent space charge is generated of corona discharge and streamer discharge is also proposed.

[0104] The effect was achieved by actual measurement at the location where corona discharge occurred, such as Figure 13 Charge induced voltage U 1”, Figure 14 Discharge pulse signal U 2nd, etc. Figure 15 forFigure 14 Medium discharge pulse signal U 2 single discharge pulse amplification value. Figure 13 As shown, according to the charge induced voltage U 1" distortion can be used to analyze the generation and dissipation of single-cycle space charge. Red charge induced voltage U 1", corresponding to the black line divided voltage U There are obvious bulges at 30°~90° and 210°~270° of the 1' sinusoidal cycle, reflecting the formation and dissipation of space charge generated by corona discharge, and its size reflects the strength of the discharge; according to whether the average value of the charge induced voltage is higher or lower than the zero value horizontal line, it can be judged whether there is a continuous space charge around the line. If the charge induced voltage is higher than the zero value horizontal line, it means that positive polarity space charge has accumulated around the line and persists, thus generating induced voltage waveform displacement. Figure 14 As shown, according to U 2. Whether there is a discharge pulse and its polarity. Determine whether there is a strong streamer discharge and its polarity. Corona discharge does not produce a clear discharge pulse. Discharge pulses are mainly caused by localized discharge at the tips of lines, insulators, hardware, etc., or by localized electric field concentration caused by contamination or ice along the insulator surface. This can be used as a basis for analyzing whether there is a phenomenon such as electric field concentration.

[0105] Under actual working conditions, measurements were achieved at a distance of about 8m from the horizontal position of the line. The charge induced voltage and discharge pulse measurement sensitivity were high and the anti-interference performance was good. According to the description of the technical solution, the sensor is mainly composed of an induction plate, a shielding box and a relatively simple passive detection circuit, and has low cost.

[0106] The invention solves the problems that the aforementioned infrared detection method has low sensitivity under conditions such as line heating, the ultraviolet detection method is limited by the detection distance, and the ultrasonic detection method is significantly affected by electromagnetic interference, which limits its application under conditions of ultra-high voltage transmission lines; solves the problem that the ultraviolet imaging method, which is a more accurate existing measurement technology, relies on the accuracy of special instruments and is expensive; solves the problem that the existing technology cannot analyze and determine the degree of corona discharge, discharge phase, etc.

[0107] The rest of this embodiment is the same as any of the above-mentioned embodiments 1 and 2, and thus will not be described in detail.

[0108] Example 4: This embodiment is based on any one of the above embodiments 1 to 3. Figure 16 、 Figure 17 As shown, take the 750kV line and the distance between the drone's lifting induction plate and the line as an example. Figure 9In the finite element simulation model shown, the line voltage is set to 750 kV, the distance between the induction plate and the line is 8 m, the electromagnetic field simulation is carried out, and the electric field intensity and potential simulation results are as shown in Figure 10 .

[0109] Based on formulas (4) to (6), according to simulation calculation, the line-plate capacitance C 1=37.631 pF. Considering the line voltage division voltage U 1' in the measurable range of the oscilloscope (0~20V), according to formula (7), C 2, take 1.5 pF capacitance.

[0110] Taking the line charge 1 pC and the unmanned aerial vehicle lifting the induction plate distance from the line distance 8 m as an example. In Figure 9 the finite element simulation model shown, the line charge amount Q 0=1 pC, the distance between the induction plate and the line is 8 m, the electromagnetic field simulation is carried out, and the electric field intensity and potential simulation results are as shown in Figure 11 .

[0111] Based on formulas (4) to (5), according to simulation calculation, the induction charge of the metal induction plate 2 can be obtained Q 2=0.0041 pC, U 1”=2.73 mV. Then Q 0 / U 1”=3.66×10 -10 .

[0112] Further, the measured and calculated U 1” can be calculated. The line charge amount Q 0. For example, the measured and calculated charge induction voltage U 1”=10 mV, the actual space charge amount Q 0=3.66 pC.

[0113] Using the unmanned aerial vehicle to lift the induction plate under the outside line, the distance between the induction plate and the line is 8 m, and the detection position is directly opposite, combined with the signal processing and acquisition device, the induction voltage and the discharge pulse are detected and analyzed. The signal acquisition unit collects U 1, U 2 signal, for example, the induction voltage signal U 1, the discharge signal U 2 are collected by using a sampling rate of 1 Gsa / s. The sampling resolution is 12 bit.

[0114] The detected induction voltage signal U 1 (green) is compared and subtracted with the line voltage division voltage U 1 ’ (black), and the charge induction voltage U 1” (red).

[0115] The discharge pulse signal (blue) is filtered and processed.

[0116] According to the analysis of the induced voltage waveform: the detected induced voltage waveform is less distorted than the sine wave. It can be judged that the induced voltage is basically composed of the line voltage U1', and the charge-induced voltage U1" is close to 0, and the corona discharge phenomenon is not obvious in the period; the overall induced voltage waveform moves slightly to the positive half cycle, that is, there is a small amount of charge near the line, and the overall electrical property is positive According to the analysis of the discharge waveform: negative polarity discharge pulses are detected on the negative half axis of the sinusoidal voltage, that is, there is streamer discharge, and the detection position may exist a region with concentrated electric field strength.

[0117] Finally, it can be concluded that the corona discharge is weak, the corona discharge is not obvious in the period, and a small amount of positive space charge accumulates. There is streamer discharge.

[0118] The embodiment proposes a line voltage and charge-induced voltage measurement method based on electromagnetic field theory, considers the influence of ground potential on the symmetry of the electric field, and can be applied to the analysis of line voltage of asymmetric electric field and non-standard induction plate, solving the problem that the existing line voltage measurement and charge-induced voltage measurement method is not applicable in the unmanned aerial vehicle measurement scheme. The method of synchronously detecting the power frequency voltage and discharge charge-induced voltage of the transmission line by the induction plate is used to analyze the characteristics of the line corona discharge by combining the line voltage and the charge-induced voltage, and the discharge pulse signal.

[0119] The other parts of the embodiment are the same as any one of the above-mentioned embodiments 1-3, and will not be repeated here.

[0120] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification or equivalent change based on the technical essence of the present application to the above embodiment falls within the protection scope of the present application.

Claims

1. A method for detecting and analyzing corona discharge of ultra-high voltage AC line voltage, characterized in that: The specific steps include: Step S1: The drone (1) equipped with the metal sensing plate (2), the detection circuit (4), and the shielding box (3) is lifted and hovered horizontally from below the UHV line, and an electric field numerical model is established according to electromagnetic field theory; Step S2: using the obtained transmission line voltage as an initial condition, establishing a simulation model based on the electric field numerical model, calculating the stray capacitance of the air between the UHV line and the metal induction plate (2), and obtaining the line divided voltage on the metal induction plate (2); Step S3: Taking the charge on the transmission line as an initial condition, a simulation model is established based on the electric field numerical model, and the charge induced voltage is calculated. Based on the discharge space charge value set in the simulation and the calculated charge induced voltage value, the proportional relationship between the discharge space charge and the charge induced voltage of the metal induction plate is obtained; Step S4: obtaining the amount of space charge generated by corona discharge according to the measured charge induced voltage, judging the intensity of corona discharge according to the amount of space charge, and analyzing the corona discharge characteristics of the UHV line.

2. The method for detecting and analyzing corona discharge of a UHV AC line voltage according to claim 1, wherein: The step S1 specifically includes the following steps: Step S11: The drone (1) equipped with the metal sensing plate (2), the detection circuit (4), and the shielding box (3) is lifted and hovered horizontally from below the ultra-high voltage line; wherein the distance between the plane of the metal sensing plate (2) and the ultra-high voltage line is equal, and the distance between the metal sensing plate (2) and the ultra-high voltage line is greater than the maximum distance at which the air between the ultra-high voltage line and the metal sensing plate (2) breaks down; Step S12: Correlating charge and potential based on space charge density, relative dielectric constant, and dielectric constant of free space, and establishing a potential numerical model; Step S13: Calculate the electric field numerical model and the electric displacement numerical model according to the electric potential numerical model.

3. The method for detecting and analyzing corona discharge of a UHV AC line voltage according to claim 2, wherein: The specific operations of step S12 are: Where ρ is the space charge density, is the dielectric constant of free space, is the relative dielectric constant, V is the electric potential, represents the gradient; The specific operations of step S13 are: Where E is the electric field strength, is the dielectric constant of free space, is the relative dielectric constant, D is the electric displacement, V is the electric potential, Represents the gradient.

4. The method for detecting and analyzing corona discharge of an ultra-high voltage AC line voltage according to claim 3, wherein: The step S2 specifically includes the following steps: Step S21: using the obtained transmission line voltage as the initial condition, the electric field intensity on the surface of the metal induction plate (2) and the potential difference between the line and the plate are calculated according to the electric potential numerical model, the electric field numerical model and the electric displacement numerical model; Step S22: Calculate the total charge according to the surface strength of the metal sensing plate (2), the dielectric constant of free space, and the area of ​​the metal sensing plate; Step S23: Calculate the stray capacitance of the air between the UHV line and the metal induction plate (2) based on the potential difference between the line and the plate and the total charge; Step S24: Calculate the line divided voltage on the metal sensing plate (2) based on the stray capacitance, the main capacitance of the detection circuit (4) in the shielding box (3) at the lower end of the metal sensing plate (2), and the obtained line voltage.

5. The method for detecting and analyzing corona discharge of ultra-high voltage AC line voltage according to claim 4, characterized in that: The specific operations of step S21 are: Where σ is the charge density, is the dielectric constant of free space.

6. The method for detecting and analyzing corona discharge of an ultra-high voltage AC line voltage according to claim 5, characterized in that: The specific operations of step S22 are: in, E n is the normal component of the electric field, s is the area of ​​the sensing plate, and Q1 is the total charge.

7. The method for detecting and analyzing corona discharge of an ultra-high voltage AC line voltage according to claim 6, characterized in that: The specific operations of step S23 are: Where Q1 is the total charge and △V is the potential difference between the wires and plates.

8. The method for detecting and analyzing corona discharge of an ultra-high voltage AC line voltage according to claim 7, characterized in that: The specific operations of step S24 are: in, U is the line voltage, U 1' is the line divided voltage on the metal sensing plate (2), C1 is the stray capacitance of the air between the UHV line and the metal sensing plate, and C2 is the main capacitance of the detection circuit (4) in the shielding box (3) at the lower end of the metal sensing plate (2).

9. The method for detecting and analyzing corona discharge of ultra-high voltage AC line voltage according to claim 3, characterized in that: The step S3 specifically includes the following steps: Step S31: Taking the transmission line as the initial condition with a charge, the electric field intensity on the surface of the metal induction plate (2) is calculated according to the electric potential numerical model, the electric field numerical model, and the electric displacement numerical model; Step S32: Calculate the charge of the metal sensing plate according to the surface strength of the metal sensing plate (2), the dielectric constant of free space, and the area of ​​the metal sensing plate; Step S33: Calculate the charge induced voltage based on the charge of the metal sensing plate and the capacitance of the detection circuit in the shielding box at the lower end of the metal sensing plate (2); Step S34: according to the discharge space charge value set in the simulation and the charge induced voltage value obtained by calculation, a proportional relationship between the discharge space charge and the charge induced voltage of the metal induction plate is obtained.

10. The method for detecting and analyzing corona discharge of ultra-high voltage AC line voltage according to claim 3, characterized in that: The specific operation of step S4 is as follows: analyzing the generation and dissipation of single-cycle space charge based on the charge-induced voltage distortion; if the charge-induced voltage and the UHV line voltage divider have obvious bulges within the set period, the space charge generated by corona discharge is formed and dissipated, and judging whether there is persistent space charge around the UHV line based on whether the charge-induced voltage is above or below the zero-value horizontal line.

Images