Non-contact high voltage measuring device with self-checking capability and measuring method thereof

Abstract

The application discloses a non-contact high-voltage measuring device with self-checking capability and a measuring method thereof. The device comprises an electric field sensing device, a signal conditioning circuit and a received signal processing device. The core of the electric field sensing device is two measuring electrode plates and a shielding electrode plate. The two measuring electrode plates are placed inside the shielding electrode plate and symmetrically distributed relative to the measured wire. Electrical insulation is realized between each electrode plate through insulating elastic material. The signal conditioning circuit is used to sample the voltage signals on the two measuring electrode plates capable of representing the electric field intensity and to amplify and filter the voltage signals. The received signal processing device is used to process and output the sampled voltage signals and to judge the correctness of the measurement data. The electric field sensing device of the application can effectively improve the accuracy of the measuring device and make the measuring device have self-checking capability, thereby improving the reliability of the measurement.

Description

Technical Field

[0001] This invention belongs to the fields of electrical engineering, measurement and control technology and instruments, and specifically relates to a non-contact high voltage measuring device with self-testing capability and its measuring method. Background Technology

[0002] With the continuous development and improvement of power systems and the continuous increase in voltage levels, the difficulty of voltage measurement is also increasing. Traditional voltage measurement methods are often contact measurements, which require a direct electrical connection between the voltage measuring instrument and the conductor under test. This requires breaking the surface insulation layer of the conductor before voltage measurement. However, the higher the voltage level, the easier it is to cause short circuits and other power system faults by breaking the conductor insulation layer, which can cause greater damage to the power system. Therefore, non-contact voltage measurement research has become the main research direction.

[0003] The principle of non-contact voltage measurement is now very mature. The common non-contact voltage measurement sensor is the non-contact differential voltage sensor. This sensor can suppress common-mode interference to a certain extent. However, this type of voltage sensor cannot judge the accuracy of the measurement data on its own. In addition, differential voltage sensors often cannot meet the measurement accuracy requirements in applications where high voltage measurement accuracy is required. Therefore, this non-contact high voltage measurement device is developed based on the goal of achieving self-testing function while having high measurement accuracy. Summary of the Invention

[0004] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a non-contact high voltage measuring device and its measuring method with self-testing capability. The electric field sensing device of this invention is a concentric cylindrical structure composed of two measuring electrode plates and a shielding electrode plate, which enables the device to have self-testing capability while ensuring the accuracy of the measurement data.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The present invention provides a non-contact high voltage measuring device with self-testing capability, including an electric field sensing device, a signal conditioning circuit, and a receiving signal processing device;

[0007] The electric field sensing device includes two measuring electrode plates and one shielding electrode plate; the two measuring electrode plates are placed inside the shielding electrode plate and are symmetrically distributed relative to the conductor to be measured, and the two measuring electrode plates and the shielding electrode plate respectively constitute two input signals of the signal conditioning circuit;

[0008] The signal conditioning circuit has two paths, which are used to condition the analog voltage signals acquired from the two measuring electrode plates respectively. Each signal conditioning circuit includes a first-stage amplifier circuit, a voltage follower, a second-stage amplifier circuit, and a filter circuit. The input of the first-stage amplifier circuit is the analog voltage signal on the measuring electrode plate, and the output of the first-stage amplifier circuit is connected to the input of the voltage follower. The output of the voltage follower is connected to the input of the second-stage amplifier circuit, and the output of the second-stage amplifier circuit is connected to the input of the filter circuit.

[0009] The receiving signal processing device includes a dual-input signal acquisition circuit, a dual-channel analog-to-digital converter circuit, and a digital signal processing circuit. The dual-input signal acquisition circuit is connected to the outputs of two filter circuits in the signal conditioning circuit. The output of the dual-input signal acquisition circuit is connected to the input of the dual-channel analog-to-digital converter circuit. The output of the dual-channel analog-to-digital converter circuit is connected to the input of the digital signal processing circuit.

[0010] Preferably, the electric field sensing device further includes an insulating elastic filler between the various electrode plates for electrical insulation and fixation, and a material constituting the electrode plates, the material including a substrate and copper foil;

[0011] The shielding electrode plate is shaped like a common hollow cylinder with a thin wall on the first side surface. The copper foil is plated on the inner or outer side wall of the thin wall on the first side surface. The thickness of the thin wall on the first side surface is greater than 0.1 mm. The radius of the shielding electrode plate must ensure that the internal electric field strength is less than the breakdown strength of the insulating elastic filler to prevent the insulating elastic filler from being broken down.

[0012] The two measuring electrode plates are identical in shape and are both formed by a thin wall on the second side surface of a common hollow arc-shaped cylinder. The copper foil is plated on the inner or outer wall of the thin wall on the second side surface. The angle of the thin wall on the second side surface is between 10° and 30°, and the thickness of the thin wall on the second side surface is the same as the thickness of the shielding electrode plate. The measuring electrode plate and the shielding electrode plate are coaxial in space. The two measuring electrode plates are placed inside the shielding electrode plate, and the length of the shielding electrode plate along the axial direction is three times or more than that of the measuring electrode plate. A through hole is left at the central axis of each electrode plate to accommodate the wire to be measured.

[0013] Preferably, the radius of the measuring electrode plate is determined by the voltage level to be measured. When the high-voltage measuring device is working normally, the shielding electrode plate is grounded, and the conductor to be measured will generate an electric field inside the shielding electrode plate. Under the action of the electric field, the two measuring electrode plates will generate voltage changes. When the voltage level is large, the two measuring electrode plates should be close to the shielding electrode plate to achieve indirect voltage reduction, provided that the electric field strength is less than the breakdown strength of the insulating elastic filler. When the voltage level is small, the two measuring electrode plates should be close to the conductor to be measured to increase the voltage ratio, provided that the electric field strength is less than the breakdown strength of the insulating elastic filler.

[0014] Preferably, the signal conditioning circuit comprises two independent conditioning circuits; the first-stage amplifier circuit is a variable capacitor connected in parallel with the coupling capacitor between the measuring electrode plate and the shielding electrode plate, which serves as both a sampling circuit and a first-stage amplifier circuit, with a gain of less than 1; the gain of the second-stage amplifier circuit is adjusted according to the range of the voltage to be measured; the filtering circuit filters the voltage amplified by the second-stage amplifier circuit to remove high-frequency harmonics and improve the quality of the sampled voltage signal.

[0015] Preferably, the dual-input signal acquisition circuit samples the two analog voltage signals after passing through the signal conditioning circuit. The two analog voltage signals are then converted into two digital voltage signals by a dual-channel analog-to-digital converter circuit. Finally, the two digital voltage signals are processed by a digital signal processing circuit, the core of which is a microprocessor.

[0016] Another aspect of the present invention provides a measurement method for a non-contact high-voltage measuring device with self-testing capability, applied to the aforementioned non-contact high-voltage measuring device with self-testing capability, comprising the following steps:

[0017] When the non-contact high voltage measuring device with self-testing capability is working normally, it calculates the coupling capacitance value between the wire under test and the two measuring electrode plates and the coupling capacitance value between the two measuring electrode plates and the shielding electrode plate, and calculates the two analog voltage signals on the two measuring electrode plates.

[0018] The two analog voltage signals on the two measuring electrodes are amplified and filtered by the signal conditioning circuit to obtain the amplified two analog voltage signals.

[0019] The amplified analog voltage signals are converted into two digital voltage signals by a dual-channel analog-to-digital converter circuit. Finally, the digital signal processing circuit performs inversion calculations on the two digital voltage signals to obtain the voltage value to be measured, and compares the two digital voltage signals to ensure the reliability of the data.

[0020] Preferably, the calculation of the coupling capacitance between the conductor under test and the two measuring electrode plates, and the coupling capacitance between the two measuring electrode plates and the shielding electrode plate, specifically involves:

[0021] Assuming the two measuring electrode plates are strictly symmetrically distributed relative to the conductor under test, the formula for calculating the coupling capacitance between the conductor under test and the two measuring electrode plates is as follows:

[0022] ;

[0023] in, C This represents the coupling capacitance between the conductor under test and the measuring plate. ε The dielectric constant of the insulating elastic filler is L To measure the axial length of the electrode plate, θ To measure the angle of the electrode plates, R 1 represents the radius of the cylinder where the measuring electrode plate is located. r Let be the radius of the conductor to be measured;

[0024] The formula for calculating the coupling capacitance between the two measuring electrode plates and the shielding electrode plate is as follows:

[0025] ;

[0026] in, C 0 represents the coupling capacitance between the measuring electrode and the shielding electrode. ε The dielectric constant of the insulating elastic filler is L To measure the axial length of the electrode plate, θ To measure the angle of the electrode plates, R 2 represents the radius of the shielding electrode plate. R 1 represents the radius of the cylinder where the measuring electrode plate is located;

[0027] The calculation involves two analog voltage signals on the two measuring electrode plates. U The formula for 0 is:

[0028] ;

[0029] in, U This represents the voltage value on the conductor to be tested.

[0030] Preferably, when a slight displacement of the test lead causes the two measuring electrode plates to be non-strictly symmetrically distributed relative to the test lead, the coupling capacitance between the two measuring electrode plates and the shielding electrode plate remains constant. C 0, but the capacitance between the test lead and the two measuring electrode plates changes slightly due to the change in distance. The formula for calculating the coupling capacitance between the test lead and the two measuring electrode plates is:

[0031] ;

[0032] in, C 01 and C 02 These represent the coupling capacitance values ​​between the measuring electrode plates and the test lead when the two measuring electrode plates are not strictly symmetrically distributed relative to the test lead. r 1 and r 2 represents the average distance between the conductor to be tested and the two measuring electrode plates. d The diameter of the circular position where the electrode plate is located is measured, and it is a fixed value.

[0033] Preferably, the amplified two analog voltage signals U The formula for calculating 1 is:

[0034] ;

[0035] in, k This represents the amplification factor of the signal conditioning circuit.

[0036] Preferably, the specific steps for comparing the two digital voltage signals to ensure data reliability are as follows:

[0037] When the electrode plate is working normally, slight movement of the test lead will cause the two measured voltage values ​​to be not exactly the same. At this time, after receiving the two digital voltage signals, the digital signal processing circuit first compares the two digital voltage signals, that is, sets a threshold for the difference between the two digital voltage signals. The size of the threshold depends on the level of the voltage to be measured. If the difference between the two acquired digital voltage signals is less than the set threshold, the measured voltage value is still reliable; otherwise, if the difference between the two acquired digital voltage signals is greater than the set threshold, the measured data will be judged to be abnormal.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] 1. The core of the device of the present invention lies in the two measuring electrode plates and one shielding electrode plate in the electric field induction device. In order to improve the accuracy of the emission electric field generated by the conductor under test, both the measuring electrode plate and the shielding electrode plate are cylindrical or semi-cylindrical in shape to ensure that the voltage on the electrode plate is equal everywhere rather than due to electrostatic induction, thereby improving the accuracy of the measurement data. There are two electrodes in the electric field induction device for measurement. This structural design enables the voltage measurement device to have the ability of data self-detection.

[0040] 2. The two measuring electrode plates are symmetrically distributed relative to the conductor under test. Therefore, the voltage data collected from the two measuring electrode plates are close during actual measurement. If one of the two measuring electrode plates malfunctions or the corresponding processing circuit malfunctions, the measurement result will change. If the voltage signals obtained from the two measurements differ significantly, the microprocessor in the digital signal processing circuit can determine that the measurement data is abnormal, thus enabling the voltage measuring device to have self-detection capabilities. At the same time, the electric field induction device also has a shielding electrode plate. The length of the shielding electrode plate along the axial direction is much greater than the axial length of the measuring electrode plate, which can weaken the edge effect of the electrode capacitor itself and improve the accuracy of voltage measurement. In addition, there are two signal conditioning circuits in this voltage measuring device, which improves the reliability of the measuring device operation. The receiving signal processing circuit contains a microprocessor, which mainly processes the digital voltage signal after analog-to-digital conversion and compares the voltage values ​​to achieve the purpose of voltage measurement. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is an overall block diagram of a non-contact high voltage measuring device with self-testing capability according to an embodiment of the present invention;

[0043] Figure 2 This is a three-dimensional structural diagram of the electric field sensing device in a non-contact high voltage measuring device with self-testing capability according to an embodiment of the present invention.

[0044] Figure 3 This is a topology diagram of the signal conditioning circuit in a non-contact high-voltage measuring device with self-testing capability according to an embodiment of the present invention;

[0045] Figure 4 This is a connection diagram of the electric field sensing device and the signal conditioning circuit in a non-contact high voltage measuring device with self-testing capability according to an embodiment of the present invention.

[0046] Explanation of reference numerals: 100, electric field induction device; 200, signal conditioning circuit; 300, receiving signal processing device;

[0047] 1. Outer surface of the shielding electrode plate; 2. Insulating elastic filler; 3. Air gap; 4. Inner surface of the shielding electrode plate; 5. Measuring electrode plate. Detailed Implementation

[0048] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort are within the scope of protection of the present application.

[0049] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0050] Please see Figure 1 In one embodiment of this application, a non-contact high voltage measuring device with self-testing capability is provided, including an electric field sensing device 100, a signal conditioning circuit 200, and a receiving signal processing device 300; the electric field sensing device 100 is connected to the signal conditioning circuit 200, and the signal conditioning circuit 200 is signal-connected to the receiving signal processing device 300.

[0051] For further details, please refer to Figure 2 The electric field sensing device 100 includes two measuring electrode plates 5 and one shielding electrode plate. The shielding electrode plate is cylindrical and includes an outer surface 1 and an inner surface 4. The two measuring electrode plates 5 are placed on the inner surface 4 of the shielding electrode plate and are symmetrically distributed relative to the wire to be measured. The two measuring electrode plates and the shielding electrode plate respectively constitute two input signals of the signal conditioning circuit. An air gap 3 for placing the wire to be measured is provided at the center of the electric field sensing device.

[0052] For further details, please refer to the following: Figure 2The electric field sensing device 100 further includes an insulating elastic filler 2 for electrical insulation and fixation between the various electrode plates, and a material constituting the electrode plates. The insulating elastic filler 2 is epoxy resin or silicone rubber. The material includes a substrate and copper foil. The substrate of the shielding electrode plate is a thin wall formed by a common hollow cylinder on the first side surface. Copper foil is plated on the inner or outer side wall of the thin wall. To improve the stability and service life of the device, in this embodiment, the copper foil is plated on the inner side of the substrate. To ensure uniform distribution of the dielectric of the coupling capacitance between the electrode plates, the material of the substrate can be consistent with the insulating elastic filler, and the thickness of the thin wall can be greater than 0.1 mm. However, the radius of the shielding electrode plate must ensure that the internal electric field strength is less than the breakdown strength of the insulating elastic filler to prevent the insulating elastic filler from being broken down.

[0053] Furthermore, the two measuring electrode plates are identical in shape and are both thin-walled second side surfaces formed by ordinary hollow arc-shaped cylinders. The measuring electrode plates also include a substrate and surface copper foil. The substrate should be consistent with the shielding electrode plate. The copper foil can also be plated on the inner or outer side of the thin wall. The angle of the thin wall on the arc-shaped cylinder side surface is in the range of 10° to 30°, and the thickness of the thin wall is consistent with the thickness of the shielding electrode plate. The positions of the two measuring electrode plates are symmetrical with respect to the central axis, thereby ensuring that the voltages on the two measuring electrode plates are similar. In addition, the measuring electrode plates and the shielding electrode plate are coaxial in spatial position. The two measuring electrode plates are placed inside the shielding electrode plate, and the length of the shielding electrode plate along the axial direction is three times or more than that of the measuring electrode plate. A through-hole is left at the central axis of each electrode plate to accommodate the wire to be measured.

[0054] Furthermore, the radius of the two measuring electrode plates is determined by the level of the voltage to be measured. During normal operation, the shielding electrode plate of this non-contact voltage measuring device is grounded, meaning its potential is zero. The charged conductor at the central axis generates a radiating electric field inside the cylindrical shielding electrode plate. The two measuring electrode plates will experience potential changes under the influence of this electric field. The sum of the voltage across the coupling capacitance between the conductor to be measured and the measuring electrode plate and the voltage across the coupling capacitance between the measuring electrode plate and the shielding electrode plate equals the voltage of the conductor to be measured. When the voltage level of the conductor to be measured is high, the measuring electrode plate should be as close as possible to the shielding electrode plate, ensuring the electric field strength is less than the breakdown strength of the elastic insulating filler material. This increases the coupling capacitance between the conductor to be measured and the measuring electrode plate to indirectly reduce the voltage. When the voltage level of the conductor to be measured is low, the measuring electrode plate should be as close as possible to the conductor to be measured, ensuring the electric field strength is less than the breakdown strength of the insulating filler material, to increase the voltage ratio.

[0055] Please see Figure 3The signal conditioning circuit 200 has two paths, one for conditioning the signals acquired from the two measuring electrode plates.

[0056] The analog voltage signal is used; each signal conditioning circuit includes a first-stage amplifier circuit, a voltage follower, a second-stage amplifier circuit, and a filter circuit; wherein, the input of the first-stage amplifier circuit is the voltage signal on the measuring electrode plate, the output of the first-stage amplifier circuit is connected to the input of the voltage follower, the output of the voltage follower is connected to the input of the second-stage amplifier circuit, and the output of the second-stage amplifier circuit is connected to the input of the filter circuit.

[0057] For further details, please refer to Figure 4 In normal operation, the non-contact high-voltage measuring device with self-testing capability first processes the two voltage signals measured from the two measuring electrode plates through a signal conditioning circuit. This signal conditioning circuit includes two independent conditioning circuits, each used to condition the voltage signals acquired from the two measuring electrode plates. In sequence, each signal conditioning circuit includes a first-stage amplifier circuit, a voltage follower, a second-stage amplifier circuit, and a filter circuit. The first-stage amplifier circuit is a variable capacitor connected in parallel with the coupling capacitor between the measuring electrode plate and the shielding electrode plate. This variable capacitor serves as both the sampling circuit and the first-stage amplifier circuit. It is worth noting that the first-stage amplifier circuit is essentially only used for voltage reduction; that is, its amplification factor is less than 1. The amplification factor of the second-stage amplifier circuit is adjustable, and the specific amplification factor should be determined based on the range of the voltage to be measured and the input requirements of the filter circuit. The filter circuit filters the voltage to remove high-frequency harmonics and improve the quality of the sampled voltage signal. Furthermore, the bandwidth of the filter circuit can be determined based on the required voltage frequency.

[0058] The receiving signal processing device 300 includes a dual-input signal acquisition circuit, a dual-channel analog-to-digital converter circuit, and a digital signal processing circuit. The two inputs of the signal acquisition circuit are connected to the outputs of the two filter circuits in the signal conditioning circuit, and the output is connected to the input of the dual-channel analog-to-digital converter circuit. The output of the dual-channel analog-to-digital converter circuit is connected to the input of the digital signal processing circuit.

[0059] Furthermore, the dual-channel input of the signal acquisition circuit samples two analog voltage signals after being filtered by the signal conditioning circuit. The two analog voltage signals are then converted into two digital voltage signals by the dual-channel analog-to-digital converter circuit. Finally, the digital voltage signals are processed by the digital signal processing circuit. The core of the digital signal processing circuit is a microprocessor. The microprocessor can not only calculate the value of the voltage to be measured by inverting the digital voltage signal, but also judge the accuracy of the measurement data based on the difference between the two digital voltage signals.

[0060] Specifically, the conductor under test is cylindrical, so the electric field generated by the voltage under test in the electric field induction device is distributed divergently around the conductor. Therefore, to ensure the measurement accuracy of the device, the measuring electrode plate and the shielding electrode plate no longer use the traditional parallel plate structure, but instead adopt a cylindrical or arc-shaped side wall structure. The coupling capacitance between the conductor under test and the measuring electrode plate and the coupling capacitance between the measuring electrode plate and the shielding electrode plate can be accurately calculated using formulas. At the same time, this electrode plate structure can achieve accurate measurement of the electric field strength, ensuring that the potential change generated on the measuring electrode plate is strictly consistent. Due to the symmetrical structure of the two measuring electrode plates, the position of the conductor under test... The slight movement of the conductor will not affect the measurement results of this device. Thanks to the thin-walled structure of the cylindrical or arc-shaped sides of the two measuring electrode plates, the slight movement of the conductor under test has little effect on the capacitance value between the conductor under test and the measuring motor plate. At the same time, the radius of the annulus where the two measuring electrode plates are located is fixed. Therefore, by combining the values ​​of the two measuring electrode plates, the voltage value under test can still be accurately measured. In addition, the design of the electric field measuring device structure can effectively reduce the edge effect of the coupling capacitor. The length of the shielding electrode plate along the axial direction is more than three times the axial length of the two measuring electrode plates, which can effectively reduce the edge effect between the plates, thereby ensuring the measurement accuracy of the voltage measuring device.

[0061] In this embodiment of the invention, the two measuring electrode plates do not form a differential structure, but rather enable the non-contact high-voltage measuring device to perform data self-checks. Using two measuring electrode plates to measure the voltage value under test can effectively improve the reliability of the measurement data of the measuring device. After receiving the two digital voltage signals, the digital signal processing circuit compares the two digital voltage signals. Theoretically, the voltage values ​​measured from the two measuring electrode plates are the same. However, considering the non-strict symmetry of the electric field induction device, the two measurement signals are not exactly the same. Therefore, a threshold is set for the difference between the two digital voltage signals. The size of the threshold depends on the range of the voltage under test. When the difference between the two collected digital voltage signals is greater than the set threshold, the measurement data is considered abnormal. By self-checking the two sampled data, the measurement accuracy of the measuring device can be effectively improved, and the reliability of the measurement data can be judged at the same time.

[0062] In another embodiment of this application, a non-contact high voltage measurement method with self-testing capability is provided, comprising the following steps:

[0063] S1. When the non-contact high voltage measuring device with self-testing capability is working normally, it calculates the coupling capacitance value between the wire under test and the two measuring electrode plates and the coupling capacitance value between the two measuring electrode plates and the shielding electrode plate, and calculates the two analog voltage signals on the two measuring electrode plates.

[0064] Furthermore, the calculation of the coupling capacitance between the conductor under test and the two measuring electrode plates, and the coupling capacitance between the two measuring electrode plates and the shielding electrode plate, specifically involves:

[0065] S11. Assuming the two measuring electrode plates are strictly symmetrically distributed relative to the conductor under test, the formula for calculating the coupling capacitance between the conductor under test and the two measuring electrode plates is:

[0066] ;

[0067] in, C This represents the coupling capacitance between the conductor under test and the measuring plate. ε The dielectric constant of the insulating elastic filler is L To measure the axial length of the electrode plate, θ To measure the angle of the electrode plates, R 1 represents the radius of the cylinder where the measuring electrode plate is located. r Let be the radius of the conductor to be measured.

[0068] S12, The formula for calculating the coupling capacitance between the two measuring electrode plates and the shielding electrode plate is as follows:

[0069] ;

[0070] in, C 0 represents the coupling capacitance between the measuring electrode and the shielding electrode. ε The dielectric constant of the insulating elastic filler is L To measure the axial length of the electrode plate, θ To measure the angle of the electrode plates, R 2 represents the radius of the shielding electrode plate. R 1 represents the radius of the cylindrical position where the measuring electrode plate is located.

[0071] S13, The calculation of the two analog voltage signals on the two measuring electrode plates. U The formula for 0 is:

[0072] ;

[0073] in, U This represents the voltage value on the conductor to be tested.

[0074] S14. When a slight displacement of the lead under test results in a non-strictly symmetrical distribution of the two measuring electrode plates relative to the lead under test, the coupling capacitance between the two measuring electrode plates and the shielding electrode plate remains unchanged. C 0, but the capacitance between the test lead and the two measuring electrode plates changes slightly due to the change in distance. The formula for calculating the coupling capacitance between the test lead and the two measuring electrode plates is:

[0075] ;

[0076] in, C 01 and C 02 These represent the coupling capacitance values ​​between the measuring electrode plates and the test lead when the two measuring electrode plates are not strictly symmetrically distributed relative to the test lead. r 1 and r 2 represents the average distance between the conductor to be tested and the two measuring electrode plates. d The diameter of the circular position where the electrode plate is located is measured, and it is a fixed value.

[0077] S2. The two analog voltage signals obtained from the measuring electrode plate are amplified and filtered by the signal conditioning circuit to obtain the amplified two analog voltage signals.

[0078] The amplified two analog voltage signals U The formula for calculating 1 is:

[0079] ;

[0080] in, k This represents the amplification factor of the signal conditioning circuit.

[0081] S3. The amplified two analog voltage signals are converted into two digital voltage signals through an analog-to-digital converter circuit; finally, by...

[0082] The digital signal processing circuit performs inversion calculations on the two digital voltage signals to obtain the voltage value to be measured, and also compares the two voltage signals to ensure the reliability of the data.

[0083] Specifically, the steps for comparing the two digital voltage signals to ensure data reliability are as follows: When the electrode plate is working normally, slight movement of the wire under test will cause the two measured voltage values ​​to be not exactly the same. At this time, after receiving the two digital voltage signals, the digital signal processing circuit first compares the two digital voltage signals, that is, sets a threshold for the difference between the two digital voltage signals. The size of the threshold depends on the level of the voltage under test. If the difference between the two acquired digital voltage signals is less than the set threshold, the measured voltage value is still reliable. Otherwise, if the difference between the two acquired digital voltage signals is greater than the set threshold, the measured data will be judged to be abnormal.

[0084] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A non-contact high-voltage measuring device with self-testing capability, characterized in that, It includes an electric field sensing device, a signal conditioning circuit, and a receiving signal processing device; The electric field sensing device includes two measuring electrode plates and one shielding electrode plate; the two measuring electrode plates are placed inside the shielding electrode plate and are symmetrically distributed relative to the conductor to be measured, and the two measuring electrode plates and the shielding electrode plate respectively constitute two input signals of the signal conditioning circuit; the measuring electrode plates and the shielding electrode plate adopt a cylindrical or arc-shaped side wall structure. The signal conditioning circuit has two paths, which are used to condition the analog voltage signals acquired from the two measuring electrode plates respectively. Each signal conditioning circuit includes a first-stage amplifier circuit, a voltage follower, a second-stage amplifier circuit, and a filter circuit. The input of the first-stage amplifier circuit is the analog voltage signal on the measuring electrode plate, and the output of the first-stage amplifier circuit is connected to the input of the voltage follower. The output of the voltage follower is connected to the input of the second-stage amplifier circuit, and the output of the second-stage amplifier circuit is connected to the input of the filter circuit. The receiving signal processing device includes a dual-input signal acquisition circuit, a dual-channel analog-to-digital converter circuit, and a digital signal processing circuit. The dual-input signal acquisition circuit is connected to the outputs of two filter circuits in the signal conditioning circuit. The output of the dual-input signal acquisition circuit is connected to the input of the dual-channel analog-to-digital converter circuit. The output of the dual-channel analog-to-digital converter circuit is connected to the input of the digital signal processing circuit. The radius of the measuring electrode plate is determined by the voltage level to be measured. When the high-voltage measuring device is working normally, the shielding electrode plate is grounded, and the conductor to be measured will generate an electric field inside the shielding electrode plate. Under the action of the electric field, the two measuring electrode plates will produce voltage changes. When the voltage level is large, the two measuring electrode plates should be close to the shielding electrode plate to achieve indirect voltage reduction, provided that the electric field strength is less than the breakdown strength of the insulating elastic filler. When the voltage level is small, the two measuring electrode plates should be close to the conductor to be measured to increase the voltage ratio, provided that the electric field strength is less than the breakdown strength of the insulating elastic filler. The insulating elastic filler is used for electrical insulation and fixation and is set between each electrode plate.

2. The non-contact high-voltage measuring device with self-testing capability according to claim 1, characterized in that, The electric field sensing device also includes an insulating elastic filler between the various electrode plates for electrical insulation and fixation, and materials constituting the electrode plates, the materials including a substrate and copper foil; The shielding electrode plate is shaped like a common hollow cylinder with a thin wall on the first side surface. The copper foil is plated on the inner or outer side wall of the thin wall on the first side surface. The thickness of the thin wall on the first side surface is greater than 0.1 mm. The radius of the shielding electrode plate must ensure that the internal electric field strength is less than the breakdown strength of the insulating elastic filler to prevent the insulating elastic filler from being broken down. The two measuring electrode plates are identical in shape and are both formed by a thin wall on the second side surface of a common hollow arc-shaped cylinder. The copper foil is plated on the inner or outer wall of the thin wall on the second side surface. The angle of the thin wall on the second side surface is between 10° and 30°, and the thickness of the thin wall on the second side surface is the same as the thickness of the shielding electrode plate. The measuring electrode plate and the shielding electrode plate are coaxial in space. The two measuring electrode plates are placed inside the shielding electrode plate, and the length of the shielding electrode plate along the axial direction is three times or more than that of the measuring electrode plate. A through hole is left at the central axis of each electrode plate to accommodate the wire to be measured.

3. A non-contact high-voltage measuring device with self-testing capability according to claim 1, characterized in that, The signal conditioning circuit consists of two independent conditioning circuits. The first-stage amplifier circuit is a variable capacitor connected in parallel with the coupling capacitor between the measuring electrode plate and the shielding electrode plate. This variable capacitor serves as both a sampling circuit and a first-stage amplifier circuit, and the amplification factor of the first-stage amplifier circuit is less than 1. The amplification factor of the second-stage amplifier circuit is adjusted according to the range of the voltage to be measured. The filtering circuit filters the voltage amplified by the second-stage amplifier circuit to remove high-frequency harmonics and improve the quality of the sampled voltage signal.

4. A non-contact high-voltage measuring device with self-testing capability according to claim 1, characterized in that, The dual-input signal acquisition circuit samples the two analog voltage signals after passing through the signal conditioning circuit. The two analog voltage signals are then converted into two digital voltage signals by the dual-channel analog-to-digital converter circuit. Finally, the two digital voltage signals are processed by the digital signal processing circuit, the core of which is a microprocessor.

5. A measurement method for a non-contact high-voltage measuring device with self-testing capability according to any one of claims 1-4, characterized in that, Includes the following steps: When the non-contact high voltage measuring device with self-testing capability is working normally, it calculates the coupling capacitance value between the wire under test and the two measuring electrode plates and the coupling capacitance value between the two measuring electrode plates and the shielding electrode plate, and calculates the two analog voltage signals on the two measuring electrode plates. The two analog voltage signals on the two measuring electrodes are amplified and filtered by the signal conditioning circuit to obtain the amplified two analog voltage signals. The amplified analog voltage signals are converted into two digital voltage signals by a dual-channel analog-to-digital converter circuit. Finally, the digital signal processing circuit performs inversion calculations on the two digital voltage signals to obtain the voltage value to be measured, and compares the two digital voltage signals to ensure the reliability of the data.

6. The measurement method according to claim 5, characterized in that, The calculation of the coupling capacitance between the conductor under test and the two measuring electrode plates, and the coupling capacitance between the two measuring electrode plates and the shielding electrode plate, specifically involves: Assuming the two measuring electrode plates are strictly symmetrically distributed relative to the conductor under test, the formula for calculating the coupling capacitance between the conductor under test and the two measuring electrode plates is as follows: ； Where C is the coupling capacitance between the conductor under test and the measuring electrode plate, ε is the dielectric constant of the insulating elastic filler, L is the axial length of the measuring electrode plate, θ is the angle of the measuring electrode plate, R1 is the radius of the cylindrical position where the measuring electrode plate is located, and r is the radius of the conductor under test. The formula for calculating the coupling capacitance between the two measuring electrode plates and the shielding electrode plate is as follows: ； Where C0 is the coupling capacitance between the measuring electrode plate and the shielding electrode plate, ε is the dielectric constant of the insulating elastic filler, L is the axial length of the measuring electrode plate, θ is the angle of the measuring electrode plate, R2 is the radius of the shielding electrode plate, and R1 is the radius of the cylindrical position where the measuring electrode plate is located. The formula for calculating the two analog voltage signals U0 on the two measuring electrode plates is as follows: ； Where U is the voltage value on the conductor to be tested.

7. The measurement method according to claim 5, characterized in that, Also includes: When the test lead undergoes a slight displacement, resulting in a non-strictly symmetrical distribution of the two measuring electrode plates relative to the test lead, the coupling capacitance between the two measuring electrode plates and the shielding electrode plate remains C0. However, the capacitance between the test lead and the two measuring electrode plates changes slightly due to the change in distance. The formula for calculating the coupling capacitance between the test lead and the two measuring electrode plates is as follows: ； Among them, C 01 and C 02 The values ​​represent the coupling capacitance between the measuring electrode plates and the conductor under test when the two measuring electrode plates are not strictly symmetrically distributed relative to the conductor under test. ε is the dielectric constant of the insulating elastic filler, L is the axial length of the measuring electrode plate, θ is the angle of the measuring electrode plate, r1 and r2 are the average distances between the conductor under test and the two measuring electrode plates, respectively, d is the diameter of the circular position where the measuring electrode plates are located and is a fixed value, and r is the radius of the conductor under test.

8. The measurement method according to claim 7, characterized in that, The formula for calculating the amplified two analog voltage signals U1 is as follows: ； Where k is the amplification factor of the signal conditioning circuit, U0 is the two analog voltage signals on the two measuring electrode plates, C0 is the coupling capacitance between the measuring electrode plate and the shielding electrode plate, and U is the voltage value on the wire to be tested.

9. The measurement method according to claim 5, characterized in that, The specific steps for comparing the two digital voltage signals to ensure data reliability are as follows: When the electrode plate is working normally, the slight movement of the wire under test will cause the two measured voltage values ​​to be not exactly the same. At this time, after receiving the two digital voltage signals, the digital signal processing circuit first compares the two digital voltage signals, that is, sets a threshold for the difference between the two digital voltage signals. The size of the threshold depends on the level of the voltage under test. If the difference between the two acquired digital voltage signals is less than the set threshold, the measured voltage value is still reliable; otherwise, if the difference between the two acquired digital voltage signals is greater than the set threshold, the measured data will be judged to be abnormal.

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