High-voltage non-contact measurement method and system for online partial discharge monitoring of high-voltage equipment

Abstract

The invention relates to the technical field of high-voltage measurement, and discloses a high-voltage non-contact measurement method and system for online partial discharge monitoring of high-voltage equipment, and the method comprises the steps: arranging a fixed capacitance probe near the high-voltage equipment, enabling the capacitance coupling between the capacitance probe and the high-voltage equipment to be stable and not to be interfered by the outside, and enabling the capacitance probe to be connected with the high-voltage equipment; the capacitance probe measures a voltage signal on the high-voltage equipment in real time; performing data processing on the voltage signal measured by the capacitance probe in real time, and calculating and calibrating the voltage ratio of the capacitance probe by combining the impedance of the high-voltage equipment and the capacitance probe; when the voltage of the high-voltage equipment, the voltage measured by the capacitance probe, the time, the angular frequency, the total capacitance, the input total resistance and the standard uncertainty measured by the coupling capacitance all meet preset conditions, the final voltage value of the high-voltage equipment is calculated according to the voltage ratio; and analyzing the final voltage value to realize partial discharge monitoring of the high-voltage equipment. According to the invention, the real-time accurate monitoring of the partial discharge condition of the high-voltage equipment can be realized, the safety is high, the operation is convenient, and the cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage measurement, and in particular to a non-contact high-voltage measurement method and system for on-line partial discharge monitoring of high-voltage equipment. Background Art

[0002] As a key device in the power system, the operating state of a power transformer is directly related to the stability and safety of the entire power system. Partial discharge is one of the early signs of insulation aging and faults in power transformers. Therefore, detecting partial discharge in power transformers is an important means of preventive maintenance. Measuring the instantaneous voltage during the operation of a transformer is a method for detecting partial discharge activities in the power transformer. Accurately measuring the instantaneous voltage during the operation of the transformer can analyze the relationship between partial discharge activities and the operating voltage of the equipment, and achieve preventive maintenance of the power transformer.

[0003] Currently, mature methods for detecting partial discharge in power transformers usually measure the real-time voltage of the transformer through contact measurement tools such as voltage transformers. A voltage transformer is a traditional voltage measurement tool that needs to be electrically connected to a high-voltage device. It converts the high-voltage signal into a low-voltage signal through the principle of electromagnetic induction and transmits it to the monitoring system. The monitoring system processes the collected low-voltage signal and calculates the actual voltage value on the high-voltage side to achieve the purpose of high-voltage measurement.

[0004] However, contact measurement devices usually need to be electrically connected to high-voltage devices, which not only makes the installation complex but also may interfere with the normal operation of the devices. When using contact measurement devices for measurement, the measurement personnel and equipment face relatively high electrical safety risks. In case of an accident, it may lead to casualties and equipment damage. At the same time, the maintenance and calibration of the equipment also require professional technical personnel to operate, increasing the maintenance cost. In addition, contact measurement devices usually have difficulty in achieving real-time and continuous monitoring of high-voltage devices. During the operation of the devices, fault phenomena such as partial discharge may occur instantaneously, and contact measurement devices cannot capture these key information in time, so preventive maintenance of power transformers cannot be achieved. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a non-contact high-voltage measurement method and system for on-line partial discharge monitoring of high-voltage devices, which can achieve real-time and accurate monitoring of the partial discharge situation of high-voltage devices, and has high safety, convenient operation and low cost.

[0006] To solve the above technical problem, the present invention provides a non-contact high-voltage measurement method for on-line partial discharge monitoring of high-voltage devices, including:

[0007] A fixed capacitance probe is set near the high-voltage equipment. The capacitance coupling between the capacitance probe and the high-voltage equipment is stable and not affected by external interference. The capacitance probe measures the voltage signal on the high-voltage equipment in real time;

[0008] Data processing is performed on the voltage signal measured by the capacitance probe in real time. Combining the impedance of the high-voltage equipment and the capacitance probe, the voltage ratio of the capacitance probe is calculated and calibrated. The voltage ratio is the proportional relationship between the voltage measured by the capacitance probe and the actual voltage of the high-voltage equipment;

[0009] When the voltage of the high-voltage equipment, the voltage measured by the capacitance probe, time, angular frequency, total capacitance, standard uncertainty of the input total resistance, and coupling capacitance measurement all meet the preset conditions, the final voltage value of the high-voltage equipment measured in real time is obtained according to the voltage ratio and the voltage signal after data processing;

[0010] Analyze the final voltage value of the high-voltage equipment measured in real time to realize the partial discharge monitoring of the high-voltage equipment.

[0011] Furthermore, the capacitance probe is a single-pole capacitance probe, which is composed of a receiving element made of a copper rod. The copper rod is wrapped with a housing, and one end of the copper rod is equipped with a coaxial connector.

[0012] Furthermore, the data processing of the voltage signal measured by the capacitance probe in real time includes:

[0013] The voltage signal collected by the capacitance probe in real time is amplified by a signal conditioning unit. A diode is set at the input end of the signal conditioning unit, and the amplified voltage signal is converted into a digital signal by a signal acquisition card;

[0014] The digital signal is subjected to multiple filtering processes, and each filtering is average filtering, wavelet filtering, or Butterworth low-pass filtering.

[0015] Furthermore, the calculation method of the voltage ratio is:

[0016] Let Z1 represent the impedance of the electrical component connected in series with the high-voltage equipment, and Z2 represent the impedance of the electrical component connected in series with the capacitance probe. The calculation formula of the voltage ratio is:

[0017]

[0018] where j is the imaginary part, ω is the angular frequency, C1 is the coupling capacitance, R S is the input total resistance, and C2 is the total capacitance.

[0019] Furthermore, the calculation method of the standard uncertainty of the high-voltage equipment voltage measurement is:

[0020] Denote the high-voltage equipment voltage as U1, and the modulus formula of U1 is:

[0021]

[0022] The combined standard uncertainty formula is used to calculate the standard uncertainty of the voltage measurement of the high-voltage equipment as follows:

[0023]

[0024] where U1 is the voltage of the high-voltage equipment, u(U1) represents the standard uncertainty of the voltage measurement of the high-voltage equipment, C1 is the coupling capacitor, u(C1) is the standard uncertainty of the coupling capacitor measurement, C2 is the total capacitance, u(C2) is the standard uncertainty of the total capacitance measurement, ω is the angular frequency, u(ω) is the standard uncertainty of the angular frequency measurement, and R S is the total input resistance, and u(R S ) is the standard uncertainty of the total input resistance measurement. U2 is the voltage measured by the capacitance probe, and u(U2) represents the standard uncertainty of the voltage measurement of the capacitance probe.

[0025] Furthermore, the calculation method for the standard uncertainty of the voltage measurement of the capacitance probe is as follows:

[0026] The expanded uncertainty of the voltage measurement of the high-voltage equipment is calculated as:

[0027] U(U1) = k·u(U1)

[0028] where U(U1) is the expanded uncertainty of the voltage measurement of the high-voltage equipment, k is the coverage factor, and u(U1) represents the standard uncertainty of the voltage measurement of the high-voltage equipment;

[0029] The limit error of the voltage measured by the capacitance probe recorded in the average mode is:

[0030] E U = ±(0.03·V MEAS )

[0031] where E U is the limit error of the voltage measured by the capacitance probe, and V MEAS is the voltage value measured by the signal acquisition card;

[0032] The standard uncertainty of the voltage measurement of the capacitance probe is:

[0033]

[0034] where u(U2) represents the standard uncertainty of the voltage measurement of the capacitance probe.

[0035] Furthermore, the calculation method for the standard uncertainty of the time measurement is as follows:

[0036] Calculate the limit error E of time T is:

[0037] E T = ±(0.2·S i + 0.05·W i + 10 -4 ·T MEAS ), where E T is the limit error of time, S i is the sampling interval, W i is the waveform interval, T MEAS is the measured value of time;

[0038] Considering the limit error of time measurement and the error caused by the resolution of time measurement, the standard uncertainty of time measurement is:

[0039]

[0040] where u(T) is the standard uncertainty of time measurement, and d is the error caused by the resolution of time measurement.

[0041] Furthermore, the calculation method of the standard uncertainty of the total capacitance measurement is:

[0042] The total capacitance includes the capacitance of the capacitance probe, the capacitance of the coaxial cable, and the input capacitance of the analog input. The limit errors of the capacitance of the capacitance probe and the coaxial cable are:

[0043] E C = ±(0.006·C MEAS + 5·LSD),

[0044] where E C is the limit error of the capacitance of the capacitance probe and the coaxial cable, C MEAS is the measured capacitance value, and LSD is the least significant digit within the given measurement range;

[0045] Calculate the standard uncertainty of the total capacitance measurement as:

[0046]

[0047] where u(C2) is the standard uncertainty of the total capacitance measurement.

[0048] Furthermore, the calculation method of the standard uncertainty of the coupling capacitance measurement is:

[0049] Calculate the modulus value of the coupling capacitance as:

[0050]

[0051] Among them, U2 is the voltage measured by the capacitive probe, C2 is the total capacitance, U1 is the voltage of the high-voltage equipment, j is the imaginary part, ω is the angular frequency, and R S is the total input resistance;

[0052] The standard uncertainty of the coupling capacitance measurement is calculated using the combined standard uncertainty formula as follows:

[0053]

[0054] Among them, u(C1) is the standard uncertainty of the coupling capacitance measurement, C1 is the coupling capacitance, u(C1) is the standard uncertainty of the coupling capacitance measurement, u(C2) is the standard uncertainty of the total capacitance measurement, u(ω) is the standard uncertainty of the angular frequency measurement, u(R S ) is the standard uncertainty of the total input resistance measurement, and u(U2) represents the standard uncertainty of the voltage measurement by the capacitive probe.

[0055] The present invention also provides a high-voltage non-contact measurement system for on-line partial discharge monitoring of high-voltage equipment, including:

[0056] A capacitive probe is arranged near the high-voltage equipment. The capacitive coupling between the capacitive probe and the high-voltage equipment is stable and not affected by external interference. The capacitive probe measures the voltage signal on the high-voltage equipment in real time;

[0057] A voltage signal processing module is used to process the voltage signal measured by the capacitive probe in real time;

[0058] A voltage ratio processing module is used to calculate and calibrate the voltage ratio of the capacitive probe by combining the impedances of the high-voltage equipment and the capacitive probe. The voltage ratio is the proportional relationship between the voltage measured by the capacitive probe and the actual voltage of the high-voltage equipment;

[0059] A high-voltage equipment voltage value calculation module is used to determine whether the voltage of the high-voltage equipment, the voltage measured by the capacitive probe, time, angular frequency, total capacitance, total input resistance, and the standard uncertainty of the coupling capacitance measurement meet the preset conditions, and when the preset conditions are met, obtain the final voltage value of the high-voltage equipment measured in real time according to the voltage ratio and the voltage signal after data processing;

[0060] A partial discharge monitoring module is used to analyze the final voltage value of the high-voltage equipment measured in real time to achieve on-line partial discharge monitoring of the high-voltage equipment.

[0061] The above technical solution of the present invention has the following beneficial effects compared with the prior art:

[0062] The present invention is based on the principle of capacitive coupling. The induced voltage is measured through a capacitive probe, which is simply installed and does not interfere with the normal operation of high-voltage equipment. By amplifying, filtering, and calibrating the voltage signal at the output end of the capacitive probe, the partial discharge monitoring of high-voltage equipment is realized. The voltage value of high-voltage equipment can be indirectly obtained in real time, effectively reducing the monitoring and maintenance costs. At the same time, the present invention establishes a voltage calculation model according to the circuit parameters of the measurement system and the coupling characteristics of the capacitive probe. The model takes into account the influence of factors such as the coupling capacitance between the capacitive probe and the high-voltage equipment, other capacitance and resistance parameters in the measurement system, and the signal frequency on the voltage measurement result, and can accurately judge the existence of partial discharge phenomena, thereby accurately judging the operating state and potential fault risks of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to make the content of the present invention easier to be clearly understood, the following further describes the present invention in detail according to the specific embodiments of the present invention and in combination with the drawings, where:

[0064] Figure 1 It is a flowchart of the method in the preferred embodiment of the present invention.

[0065] Figure 2 It is a framework structure diagram of the system in the preferred embodiment of the present invention.

[0066] Figure 3 It is a schematic diagram of the model of the capacitive probe in the preferred embodiment of the present invention.

[0067] Description of the reference numerals in the drawings: 1, outer shell; 2, copper rod; 3, connector. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0068] The following further describes the present invention in combination with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and can implement it, but the embodiments cited do not limit the present invention.

[0069] Embodiment 1

[0070] Referring to Figure 1 、 Figure 2 As shown, the present invention discloses a non-contact high-voltage measurement method for on-line partial discharge monitoring of high-voltage equipment, including the following steps:

[0071] S1: Use a capacitive probe to collect the voltage signal on the high-voltage device. Set a fixed capacitive probe near the high-voltage device. The capacitive coupling between the capacitive probe and the high-voltage device is stable and not affected by external interference. The capacitive probe measures the voltage signal on the high-voltage device in real time. When setting a fixed capacitive probe near the high-voltage device, place the capacitive probe on the insulating support structure or pipeline near the transformer to ensure stable capacitive coupling between the probe and the high-voltage device and not affected by external interference. Place the capacitive probe at an appropriate position relative to the high-voltage device so that it can sense the voltage signal on the high-voltage device. Use magnetic adsorption or other fixing methods to firmly install the capacitive probe at the selected position to ensure that the probe will not shift or loosen during the measurement process, thus ensuring the stability of the measurement. In this embodiment, the high-voltage device is a power transformer, and the present invention can also be applied to other high-voltage devices.

[0072] As Figure 3 shown is the schematic diagram of the model of the capacitive probe in this embodiment. Figure 3 In (a) is the front view of the capacitive probe. Figure 3 In (b) is the cross-sectional view of the capacitive probe. The capacitive probe is a monopole capacitive probe, which consists of a receiving element made of a copper rod 2 with a length of 20 cm and a diameter of 2 mm. The copper rod 2 is wrapped with a housing 1. One end of the copper rod is equipped with a coaxial connector 3. In this embodiment, it is equipped with a coaxial BNC connector and a waterproof polyethylene housing. The capacitance value of this probe measured by an LCR bridge is 2.2 pF. Compared with a disc-shaped probe, this monopole probe has a lower degree of capacitive coupling with the measured high-voltage object, can be installed closer to the energized device, and will not have problems due to the digital device connected to the output end exceeding the limit value. And the monopole probe has a more compact structure, which is convenient to ensure the sealing of the housing, so as to maintain good working performance under different weather conditions. In laboratory tests, the capacitance value of the monopole probe is less affected by humidity. Its active part surrounded by air makes the capacitance value change only about 0.012% in the range of relative humidity from 25% to 75%. While for the disc-shaped probe, since its active part is filled with a solid medium, its parameters will change significantly when contacting a humid environment, resulting in a change in the voltage ratio of the measurement system, and further leading to an increase in measurement error. In addition, it is more difficult for the disc-shaped probe to prevent moisture intrusion. Due to its large size and structural characteristics, it is more difficult to protect. Therefore, the present invention selects to use a monopole probe.

[0073] S2: Process the voltage signal measured by the capacitive probe in real time.

[0074] S2-1: Amplify and digitize the signal output from the capacitive probe (signal conditioning and data acquisition unit). Amplify the voltage signal collected in real time by the capacitive probe through the signal conditioning unit. A diode is set at the input end of the signal conditioning unit, and the amplified voltage signal is converted into a digital signal through the signal acquisition card. The capacitive probe is a component with extremely low current efficiency. Connecting it to a data acquisition card with an input impedance of 1 MΩ will cause a significant reduction in the signal amplitude. Therefore, amplification processing needs to be carried out through the signal conditioning circuit. First, amplify the signal output from the capacitive probe. Connect the output end of the capacitive probe to the signal conditioning unit, which includes a voltage follower based on the AD549 operational amplifier. This amplifier has an input impedance of 10 15 Ω and a low offset voltage of up to 0.5 mV, which can effectively amplify the weak voltage signal induced by the capacitive probe and reduce signal attenuation. In addition, this operational amplifier can safely drive a 4000 pF capacitor at unity gain, which allows the use of a long coaxial cable without adverse effects such as parasitic oscillation or signal attenuation. To protect the circuit from overvoltage, a BAV20 type protection diode is used at the input end of the voltage follower.

[0075] The conditioned voltage signal is sampled by the analog-to-digital converter of the signal acquisition card and then transmitted to the industrial computer in digital form through a universal serial bus cable. The present invention uses a DrDAQ signal acquisition card produced by Pico Technology. Connect the output end of the signal conditioning unit to the DrDAQ signal acquisition card. Its sampling frequency in block mode is 1 MS / s, and the sampling frequency in fast USB stream mode is 100 kS / s, with a resolution of 8 bits. The input resistance of this acquisition card is 1 MΩ, and the input capacitance is 17 pF, which can convert the conditioned voltage signal into a digital signal and transmit it to the subsequent processing unit.

[0076] S2-2: Perform multiple filtering processes on the digital signal. In order to remove high-frequency noise and interference signals in the signal, multi-stage filtering is designed. Each filtering can be average filtering, wavelet filtering, Butterworth low-pass filtering, etc. First, remove the random noise in the signal through average filtering; secondly, use wavelet filtering to remove the high-frequency interference in the signal; finally, remove the high-order harmonics and transient interference in the signal through Butterworth low-pass filtering. The collected digital signal is processed through each stage of filtering in turn to remove the interference signal and extract the pure voltage signal. The signal after filtering processing can more accurately reflect the actual voltage change on the high-voltage equipment.

[0077] The digital signal filtering processing module works under the control of an application program developed in the NI LabVIEW environment. The main panel of the user interface provides functions related to data acquisition, digital signal processing, calibration, and the display of voltage values and voltage waveforms. An important function of the program is a special three-stage sequential filter, which allows voltage measurements to be made using a capacitive probe even in the presence of strong electromagnetic interference, such as corona discharge, lightning discharge, and substation switch operations. At each stage of the sequential filter, the user can select an average filter, a wavelet filter, or a Butterworth low-pass filter. The standard setting of the program is two-stage filtering. First, the signal is averaged over at least 2 and at most 128 voltage cycles, and then a second-order Butterworth low-pass filter is used to remove high-order harmonics and transient interference from the signal. In cases where the signal noise is large or the signal-to-noise ratio is low, the filtering efficiency can be improved by applying a wavelet denoising function in the first stage of the sequential filter. By default, the sym8 wavelet is used to perform five-level wavelet decomposition on the signal, and then the soft thresholding technique is used to denoise the signal at each level.

[0078] S3: Calculate and calibrate the voltage ratio of the capacitive probe by combining the impedance calculations of the high-voltage equipment and the capacitive probe. The voltage ratio is the proportional relationship between the voltage measured by the capacitive probe and the actual voltage of the high-voltage equipment.

[0079] The calculation method of the voltage ratio is as follows:

[0080] Let Z1 represent the impedance of the electrical component in series with the high-voltage equipment, and Z2 represent the impedance of the electrical component in series with the capacitive probe. Then the calculation formula for the voltage ratio is:

[0081]

[0082] Simplify the above formula to obtain the final calculation formula for the voltage ratio:

[0083]

[0084] where j is the imaginary part, ω is the angular frequency, C1 is the coupling capacitor, and R S is the total input resistance of the system (including the resistances of various parts such as the capacitive probe, high-voltage equipment, and signal acquisition card), and C2 is the total capacitance of the system (including the capacitance C p of the capacitive probe, the capacitance C c of the coaxial cable, and the input capacitance C s of the analog input, that is, C2 = C p + C c + C s ).

[0085] The accuracy of measuring high voltage using a capacitive probe mainly depends on the precision of the voltage ratio. Therefore, in order to ensure the accuracy of the measurement results, the voltage ratio is also calibrated in this embodiment. The calculated voltage value is compared with the instantaneous voltage value obtained through the substation SCADA system or a standard voltage source to calibrate and determine the voltage ratio of the measurement system. The reference voltage is input into the voltage calculation model, and the model parameters are adjusted to make the calculated voltage value consistent with the reference voltage, thus completing the calibration process. In this embodiment, it works under the control of an application program developed in the NI LabVIEW environment. This program can monitor voltage changes at regular time intervals and perform calibration quickly. The calibration process includes determining the value of the coupling capacitor C1 and the voltage ratio v of the measurement system. To this end, the instantaneous voltage value U1 read from the substation SCADA system or an analog voltmeter installed in the substation control room is input into the program. During calibration, the substation staff usually inform the voltage value U1 by phone.

[0086] S4: When the standard uncertainties of the high-voltage equipment voltage, the voltage measured by the capacitive probe, time, angular frequency, the total capacitance of the system, the input total resistance, and the coupling capacitance measurement all meet the preset conditions, the final voltage value of the high-voltage equipment measured in real time is obtained based on the voltage ratio and the voltage signal after data processing.

[0087] Under laboratory conditions, a standard voltage source or a traditional reference high-voltage measurement method can be used to determine the voltage ratio of the capacitive probe measurement system. Under substation site conditions, the value of the voltage ratio is estimated based on the instantaneous voltage value recorded by the substation SCADA system. In this case, the accuracy of determining the voltage ratio will depend on the measurement uncertainty introduced by the voltage transformer used in the substation and the parameters of the measurement system. Therefore, in this embodiment, evaluating the measurement uncertainty requires considering multiple factors, including the standard uncertainties of the high-voltage equipment voltage, the voltage measured by the capacitive probe, time, angular frequency, coupling capacitance, input total resistance, and total capacitance measurement.

[0088] S4-1: The calculation method for the standard uncertainty of the high-voltage equipment voltage measurement is as follows:

[0089] Denote the high-voltage equipment voltage as U1, and the modulus formula of U1 is:

[0090]

[0091] It can be seen that the voltage U1 depends on U2, ω, R S , C1 and C2. These parameters are independent of each other. Therefore, the standard uncertainty of the high-voltage equipment voltage measurement can be calculated using the combined standard uncertainty formula as:

[0092]

[0093] Among them, each derivative is the result of differentiating the above equation with respect to the given quantity. U1 is the voltage of the high-voltage equipment, u(U1) represents the standard uncertainty of the high-voltage equipment voltage measurement, C1 is the coupling capacitance, u(C1) is the standard uncertainty of the coupling capacitance measurement, C2 is the total capacitance of the system, u(C2) is the standard uncertainty of the total capacitance measurement of the system, ω is the angular frequency, u(ω) is the standard uncertainty of the angular frequency measurement, and R S is the total input resistance of the system, and u(R S ) is the standard uncertainty of the total input resistance measurement of the system. U2 is the voltage measured by the capacitive probe, and u(U2) represents the standard uncertainty of the voltage measurement by the capacitive probe.

[0094] S4-2: The calculation method for the standard uncertainty of the voltage measurement by the capacitive probe is as follows:

[0095] The expanded uncertainty of the high-voltage equipment voltage measurement is calculated as:

[0096] U(U1) = k·u(U1)

[0097] Among them, U(U1) is the expanded uncertainty of the high-voltage equipment voltage measurement, k is the coverage factor. For a 95% confidence level, k = 2. u(U1) represents the standard uncertainty of the high-voltage equipment voltage measurement;

[0098] In the partial discharge monitoring system, the DrDAQ signal acquisition card is used to measure the voltage. According to the technical specifications, the accuracy of the voltage measurement is ±3% of the measured value. The limit error of the voltage measured by the capacitive probe recorded in at least sixteen waveform averaging modes is:

[0099] E U = ±(0.03·V MEAS )

[0100] Among them, E U is the limit error of the voltage measured by the capacitive probe, and V MEAS is the voltage value measured by the signal acquisition card;

[0101] Assuming that the error is uniformly distributed and the influence of the voltage measurement resolution can be ignored, the standard uncertainty of the voltage measurement by the capacitive probe is:

[0102]

[0103] Among them, u(U2) represents the standard uncertainty of the voltage measurement by the capacitive probe.

[0104] S4-3: The calculation method for the standard uncertainty of the time measurement is as follows:

[0105] According to the formula ω = 2π / T, the only factor determining the uncertainty of the parameter ω is the measurement of time T. The time measurement is also carried out using a DrDAQ signal acquisition card. According to what is provided by the manufacturer in the technical specifications, the limit error E of calculating time is T as follows:

[0106] E T = ±(0.2·S i + 0.05·W i + 10 -4 ·T MEAS ), where E T is the limit error of time, S i is the sampling interval, which depends on the sampling frequency, W i is the waveform interval, which depends on the recording length, T MEAS is the measured value of time;

[0107] Considering the limit error E T of time measurement and the error caused by the resolution of time measurement, the standard uncertainty of time measurement is:

[0108]

[0109] where u(T) is the standard uncertainty of time measurement, and d is the error caused by the resolution of time measurement.

[0110] S4-4: The calculation method for the standard uncertainty of the angular frequency measurement is as follows:

[0111] After calculating the differential of ω = 2π / T and considering the standard uncertainty of time measurement, the standard uncertainty of angular frequency measurement can be calculated using the following formula:

[0112]

[0113] where u(ω) is the standard uncertainty of angular frequency measurement, and T is time.

[0114] S4-5: The calculation method for the standard uncertainty of the total capacitance measurement of the system is as follows:

[0115] The total capacitance C2 of the system includes the capacitance probe capacitance C p , the coaxial cable capacitance C c , and the input capacitance C s of the analog input. The first two capacitances are measured together using an LCR bridge of model ESCORT ELC-3131D. The limit error of the capacitance probe capacitance and the coaxial cable capacitance is:

[0116] E C = ±(0.006·C MEAS + 5·LSD),

[0117] Among them, E C is the limit error of the capacitance of the capacitive probe and the coaxial cable, C MEAS is the capacitance value measured using an LCR bridge, and LSD is the least significant digit within the given measurement range;

[0118] According to the data of the DrDAQ card provided by the manufacturer, the input capacitance C s of the signal acquisition channel is 17 ± 3 pF. After considering these two parameters and assuming that the errors are uniformly distributed, the standard uncertainty of the total capacitance measurement of the system can be calculated as:

[0119]

[0120] Among them, u(C2) is the standard uncertainty of the total capacitance measurement of the system.

[0121] S4-6: The calculation method of the standard uncertainty of the input total resistance measurement is as follows:

[0122] According to the technical specifications of the signal acquisition card used, the input resistance of the analog channel is 1 ± 0.5% MΩ. Therefore, the standard uncertainty of the input total resistance measurement can be estimated using the following formula:

[0123]

[0124] Among them, R S is the input total resistance of the system, and u(R S ) is the standard uncertainty of the input total resistance measurement of the system.

[0125] S4-7: The calculation method of the standard uncertainty of the coupling capacitance measurement is as follows:

[0126] Each component in the measurement chain except the coupling capacitance C1 is determined in the laboratory, and the value of the coupling capacitance C1 is determined through the probe calibration procedure after the partial discharge monitoring system is installed in the substation. In order to estimate the value of the coupling capacitance C1, a proportional measurement is carried out, and the modulus value of the coupling capacitance is calculated based on these measurement results as:

[0127]

[0128] Among them, U2 is the voltage measured by the capacitive probe, C2 is the total capacitance of the system, U1 is the voltage of the high-voltage equipment, j is the imaginary part, ω is the angular frequency, and R S is the input total resistance of the system;

[0129] The standard uncertainty of the coupling capacitance measurement is calculated using the combined standard uncertainty formula as:

[0130]

[0131] where \(u(C_1)\) is the standard uncertainty of the measurement of the coupling capacitance, \(C_1\) is the coupling capacitance, \(u(C_1)\) is the standard uncertainty of the measurement of the coupling capacitance, \(u(C_2)\) is the standard uncertainty of the measurement of the total capacitance of the system, \(u(\omega)\) is the standard uncertainty of the measurement of the angular frequency, and \(u(R S ) is the standard uncertainty of the measurement of the total input resistance of the system, and \(u(U_2)\) represents the standard uncertainty of the measurement of the voltage measured by the capacitance probe.

[0132] S4 - 8: For an on - line partial discharge monitoring system, when the ranges of the standard uncertainties of the voltage of the high - voltage equipment, the voltage measured by the capacitance probe, time, angular frequency, the total capacitance of the system, the total input resistance, and the coupling capacitance are from 1% to 5%, it is an acceptable level. Therefore, when the ranges of all the standard uncertainties are from 1% to 5%, the final voltage value of the high - voltage equipment obtained according to the voltage ratio and the processed voltage signal is:

[0133] \(U'=v\times U\), where \(v\) is the voltage ratio, \(U'\) is the final voltage value of the high - voltage equipment obtained by calculation, and \(U\) is the processed voltage signal measured by the capacitance probe.

[0134] S5: Analyze the final voltage value of the high - voltage equipment measured in real - time to achieve the partial discharge monitoring of the high - voltage equipment.

[0135] In this embodiment, the voltage signal after amplification, filtering, and calibration is transmitted to the industrial computer of the partial discharge monitoring system through the USB 2.0 interface to achieve real - time data transmission and sharing. Start the partial discharge monitoring system and at the same time turn on the non - contact high - voltage measurement device. The monitoring system synchronously records the acoustic emission signal generated by the partial discharge and the voltage signal on the high - voltage equipment. By analyzing the relationship between the two, the association between the partial discharge phenomenon and the voltage is evaluated, so as to more accurately judge the operating state and potential fault risk of the high - voltage equipment. The monitoring results are presented in the form of charts or data reports to provide an intuitive reference basis for the operation and maintenance personnel of the power system. After the proposed solution of the present invention is applied in practice, the capacitance probe can be placed at different positions to meet the standard uncertainty of the measurement, which also proves the application feasibility of the proposed solution of the present invention.

[0136] Embodiment 2

[0137] The present invention also discloses a non - contact high - voltage measurement system for on - line partial discharge monitoring of high - voltage equipment, including:

[0138] A capacitance probe is arranged near the high - voltage equipment. The capacitance coupling between the capacitance probe and the high - voltage equipment is stable and not affected by external interference. The capacitance probe measures the voltage signal on the high - voltage equipment in real - time;

[0139] A voltage signal processing module for processing the voltage signals measured in real time by the capacitance probe;

[0140] A voltage ratio processing module for calculating and calibrating the voltage ratio of the capacitance probe by combining the impedances of the high-voltage equipment and the capacitance probe, where the voltage ratio is the proportional relationship between the voltage measured by the capacitance probe and the actual voltage of the high-voltage equipment;

[0141] A high-voltage equipment voltage value calculation module for determining whether the high-voltage equipment voltage, the voltage measured by the capacitance probe, time, angular frequency, the total capacitance of the system, the input total resistance, and the standard uncertainty of the coupling capacitance measurement meet the preset conditions, and obtaining the final voltage value of the high-voltage equipment measured in real time based on the voltage ratio and the voltage signal processed through data when the preset conditions are met;

[0142] A partial discharge monitoring module for analyzing the final voltage value of the high-voltage equipment measured in real time to achieve partial discharge monitoring of the high-voltage equipment. This module is integrated into the PD tracker system, which has eight analog channels, each equipped with an independent analog-to-digital converter, and a maximum sampling frequency of 20MS / s. This system also adapts to work with high-frequency current transformers, UHF antennas, and active dielectric windows. The signal conditioning electronic circuit and the signal acquisition card are placed in a separate compact enclosure with dimensions of 6×6×4 cm. The power supply and data transmission between the signal acquisition card and the industrial computer are carried out through USB2.0, and the data transmission rate can reach 60MB / s.

[0143] The present invention first applies the capacitance probe to the partial discharge monitoring system of high-voltage equipment such as power transformers, and proposes a brand-new non-contact high-voltage measurement method. This method not only avoids the safety risks brought by electrical connections but also ensures the safety of measurement personnel and equipment. At the same time, non-contact measurement does not interfere with the electric field distribution of the object to be measured, ensuring the accuracy and reliability of the measurement. By using the capacitance probe, the present invention makes the portable partial discharge monitoring system completely independent of the SCADA system and equipment of the substation. Without the need for complex communication protocol adaptation and additional infrastructure construction, it reduces the installation cost and time, and improves the flexibility and adaptability of the system. The present invention can achieve high-precision high-voltage measurement in a strong electromagnetic interference environment through precise voltage ratio calibration and effective digital filtering and noise reduction techniques. The measurement uncertainty is controlled within the range of 1% to 5%, meeting the requirements of partial discharge monitoring for voltage measurement accuracy. In addition, the non-contact measurement method does not require the transformer to be shut down for installation and commissioning, greatly reducing the installation time and cost of the monitoring system, and improving the economy and practicality of the system.

[0144] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0145] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices produce means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0146] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing devices to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0147] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, such that a series of operation steps are executed on the computer or other programmable devices to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable devices provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0148] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A high voltage non-contact measurement method for online partial discharge monitoring of high voltage equipment, characterized in that: include: A fixed capacitance probe is arranged near the high-voltage equipment, the capacitance coupling between the capacitance probe and the high-voltage equipment is stable and not subject to external interference, and the capacitance probe measures the voltage signal on the high-voltage equipment in real time; Performing data processing on the voltage signal measured in real time by the capacitance probe, calculating and calibrating the voltage ratio of the capacitance probe in combination with the impedance of the high-voltage device and the capacitance probe, wherein the voltage ratio is the proportional relationship between the voltage measured by the capacitance probe and the actual voltage of the high-voltage device; When the standard uncertainties of the voltage of the high-voltage equipment, the voltage measured by the capacitance probe, time, angular frequency, total capacitance, total input resistance and coupling capacitance measurement all meet the preset conditions, the final voltage value of the high-voltage equipment measured in real time is obtained according to the voltage ratio and the voltage signal after data processing; Analyze the final voltage value of the high-voltage equipment measured in real time to realize partial discharge monitoring of the high-voltage equipment.

2. The high-voltage non-contact measurement method for online partial discharge monitoring of high-voltage equipment according to claim 1 is characterized in that: The capacitance probe is a monopolar capacitance probe, which is composed of a receiving element made of a copper rod. The copper rod is wrapped with a shell, and one end of the copper rod is equipped with a coaxial connector.

3. The high-voltage non-contact measurement method for online partial discharge monitoring of high-voltage equipment according to claim 1 is characterized in that: The voltage signal measured by the capacitance probe in real time is processed, including: Amplifying the voltage signal collected in real time by the capacitance probe through a signal conditioning unit, setting a diode at the input end of the signal conditioning unit, and converting the amplified voltage signal into a digital signal through a signal acquisition card; The digital signal is filtered multiple times, and each filtering is average filtering, wavelet filtering or Butterworth low-pass filtering.

4. The high-voltage non-contact measurement method for online partial discharge monitoring of high-voltage equipment according to claim 1 is characterized in that: The voltage ratio is calculated as follows: Z1 represents the impedance of the electrical component connected in series with the high-voltage device, and Z2 represents the impedance of the electrical component connected in series with the capacitance probe. The voltage ratio is calculated as: Where j is the imaginary part, ω is the angular frequency, C1 is the coupling capacitor, R S is the total input resistance, and C2 is the total capacitance.

5. The high-voltage non-contact measurement method for online partial discharge monitoring of high-voltage equipment according to claim 1 is characterized in that: The calculation method of the standard uncertainty of the voltage measurement of the high-voltage equipment is: Let the voltage of the high-voltage equipment be U1, and the modulus formula of U1 is: The standard uncertainty of the voltage measurement of the high-voltage equipment is calculated using the synthetic standard uncertainty formula: Where U1 is the voltage of the high-voltage equipment, u(U1) represents the standard uncertainty of the voltage measurement of the high-voltage equipment, C1 is the coupling capacitance, u(C1) is the standard uncertainty of the coupling capacitance measurement, C2 is the total capacitance, u(C2) is the standard uncertainty of the total capacitance measurement, ω is the angular frequency, u(ω) is the standard uncertainty of the angular frequency measurement, R S is the total input resistance, u(R S ) is the standard uncertainty of the input total resistance measurement, U2 is the voltage measured by the capacitance probe, and u(U2) represents the standard uncertainty of the voltage measurement measured by the capacitance probe.

6. The high-voltage non-contact measurement method for online partial discharge monitoring of high-voltage equipment according to claim 3 is characterized in that: The standard uncertainty of the voltage measurement measured by the capacitance probe is calculated as follows: Calculate the expanded uncertainty of voltage measurement of high-voltage equipment as: U(U1)=k·u(U1) Among them, U(U1) is the expanded uncertainty of the voltage measurement of the high-voltage equipment, k is the coverage factor, and u(U1) represents the standard uncertainty of the voltage measurement of the high-voltage equipment; The limit error of the voltage measured by a capacitance probe recorded in average mode is: E U =±(0.03 V MEAS ) Among them, E U is the limit error of the voltage measured by the capacitance probe, V MEAS is the voltage value measured by the signal acquisition card; The standard uncertainty of the voltage measurement measured by a capacitance probe is: Where u(U2) represents the standard uncertainty of the voltage measurement measured by the capacitance probe.

7. The high-voltage non-contact measurement method for online partial discharge monitoring of high-voltage equipment according to claim 1 is characterized in that: The calculation method of the standard uncertainty of the time measurement is: The limit error of calculation time E T for: HAVE BEEN T =±(0.2·Si+0.05·W i +10 -4 ·T MEAS ), Among them, E T is the time limit error, S i is the sampling interval, W i is the waveform interval, T MEAS is a measurement of time; Considering the limit error of time measurement and the error caused by the resolution of time measurement, the standard uncertainty of time measurement is: Where u(T) is the standard uncertainty of time measurement and d is the error caused by the resolution of time measurement.

8. The high-voltage non-contact measurement method for online partial discharge monitoring of high-voltage equipment according to claim 1 is characterized in that: The standard uncertainty of the total capacitance measurement is calculated as: The total capacitance includes the capacitance of the capacitance probe, the capacitance of the coaxial cable and the input capacitance of the analog input. The limit error of the capacitance of the capacitance probe and the capacitance of the coaxial cable is: AND C =±(0.006·C MEAS +5 LSD), Among them, E C is the limit error of the capacitance probe capacitance and the coaxial cable capacitance, C MEAS is the measured capacitance value, LSD is the least significant digit within the given measurement range; Calculate the standard uncertainty of the total capacitance measurement as: Where u(C2) is the standard uncertainty of the total capacitance measurement.

9. The high-voltage non-contact measurement method for online partial discharge monitoring of high-voltage equipment according to any one of claims 1 to 8, characterized in that: The calculation method of the standard uncertainty of the coupling capacitance measurement is: The modulus of the coupling capacitor is calculated as: Among them, U2 is the voltage measured by the capacitance probe, C2 is the total capacitance, U1 is the voltage of the high-voltage device, j is the imaginary part, ω is the angular frequency, R S is the total input resistance; The standard uncertainty of coupling capacitance measurement is calculated using the combined standard uncertainty formula: Where u(C1) is the standard uncertainty of the coupling capacitance measurement, C1 is the coupling capacitance, u(C1) is the standard uncertainty of the coupling capacitance measurement, u(C2) is the standard uncertainty of the total capacitance measurement, u(ω) is the standard uncertainty of the angular frequency measurement, and u(R S ) is the standard uncertainty of the input total resistance measurement, and u(U2) represents the standard uncertainty of the voltage measurement measured by the capacitance probe.

10. A high voltage non-contact measurement system for online partial discharge monitoring of high voltage equipment, characterized in that: include: A capacitance probe is arranged near the high-voltage equipment. The capacitance coupling between the capacitance probe and the high-voltage equipment is stable and not subject to external interference. The capacitance probe measures the voltage signal on the high-voltage equipment in real time. A voltage signal processing module, used for performing data processing on the voltage signal measured in real time by the capacitance probe; A voltage ratio processing module, used to calculate and calibrate the voltage ratio of the capacitance probe in combination with the impedance of the high-voltage device and the capacitance probe, wherein the voltage ratio is a proportional relationship between the voltage measured by the capacitance probe and the actual voltage of the high-voltage device; The high-voltage equipment voltage value calculation module is used to determine whether the standard uncertainty of the high-voltage equipment voltage, the voltage measured by the capacitance probe, time, angular frequency, total capacitance, total input resistance and coupling capacitance measurement meets the preset conditions, and obtain the final voltage value of the high-voltage equipment measured in real time according to the voltage ratio and the voltage signal after data processing when the preset conditions are met; The partial discharge monitoring module is used to analyze the final voltage value of the high-voltage equipment measured in real time to realize partial discharge monitoring of the high-voltage equipment.

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