Single-ended grounding self-calibration voltage measuring device and method

Abstract

The invention discloses a single-ended grounding self-calibration voltage measuring device and method, and the device comprises a sensing probe and a shielding box, the sensor probe comprises a sensing layer and a grounding layer, the shielding box is internally provided with a voltage collection circuit, a capacitor switching module and a data transmission module, the sensor probe and the shielding box are designed in an integrated manner, and the voltage collection circuit is connected with the capacitor switching module. And the inductive probe is electrically connected to the voltage processing circuit. The to-be-measured voltage is obtained in a self-calibration solution mode, the method is not influenced by the environment, the method is suitable for various measurement scenes, the interference of space and interphase stray electric fields on the sensor is solved, and the measurement precision is high.

Description

Technical Field

[0001] The present invention relates to a single-ended grounded self-calibrating voltage measurement device and method, belonging to the technical field of intelligent power distribution network power technology. Background Art

[0002] In the power system, voltage is the most important evaluation parameter, and its accurate measurement is of great significance for the effective evaluation of key network nodes and electrical equipment of the line, electric energy metering, fault prediction, etc. At present, in the power transmission and transformation system on the high-voltage side, the measurement of most power equipment and important nodes of the power transmission and transformation network mainly relies on voltage and current transformers. However, their bandwidth is narrow, and at the same time, due to their high insulation requirements, the transformers are large in volume and high in quality, which makes it difficult to widely install them distributively on power transmission and distribution lines with limited space. In the field of low-voltage power distribution and utilization, the measurement of voltage and current mainly relies on traditional multimeters. Multimeters need to strip the insulation layer for contact measurement, which has problems such as inconvenient measurement and threatening the safety of operators. In addition, they also have the disadvantage of only being able to measure power frequency signals. With the application of new energy and a large number of power electronics technologies, higher requirements are put forward for the real-time online monitoring of the grid operation status. Voltage and current measurement devices are required to have characteristics such as wide frequency band, miniaturization, and portable distribution devices.

[0003] The current electric field coupling type voltage measurement technology is applicable to the measurement of mutually separated single-phase wires and is not applicable to the measurement of cables with ground wires and neutral wires. When there are neutral wires and ground wires in addition to the live wire in the measured cable, the measurement model will change. At the same time, the sensor gain will change due to changes in the measurement object or the measurement environment, and the measurement results are inaccurate and the accuracy is difficult to guarantee due to factors such as interphase coupling and interference electric fields. Therefore, it is imperative and of great significance to develop a sensor that is easy to install and can accurately measure voltage. Summary of the Invention

[0004] The purpose of the present invention is to overcome and solve the problems in existing voltage measurement, and provide a non-contact voltage measurement device with strong anti-interference ability, capable of self-calibration, and high measurement accuracy.

[0005] The present invention is realized through the following technical solutions. By using a coaxial probe and placing the signal processing module in a shielding box, it can effectively shield the interference of external stray electric fields on the measured voltage signal. The problem of uncertain structural capacitance and coupling capacitance is solved by switching capacitors, and self-calibration is achieved through remote control.

[0006] To achieve the above object, the technical solution of the present invention is: a single-ended grounded self-calibrating voltage measurement device, including a voltage sensor probe (1), a shielding box (2) and a signal processing circuit (3). The sensor probe is connected to the shielding box, and the signal processing circuit (3) is placed in the shielding box (2). The signal processing circuit (3) includes a capacitance switching circuit, a single-chip microcomputer processing circuit, a communication module and a power supply module.

[0007] The sensor probe (1) is an open-and-close structure in a coaxial shape. The sensor probe (1) includes an induction electrode plate (101), a grounding electrode plate (102), an open-and-close buckle (104), an open-and-close hinge (105) and an insulating medium (103). An insulating medium is provided between the induction electrode plate (101) and the grounding electrode plate (102).

[0008] The induction electrode plate (101) and the grounding electrode plate (102) are electrically connected to the signal processing circuit (3).

[0009] The grounding electrode plate (102) wraps the induction electrode plate (101).

[0010] The capacitance switching circuit includes, but is not limited to, relay switch control.

[0011] The signal processing circuit (3) is fixed to the bottom of the shielding box using non-conductive materials.

[0012] The above voltage sensor probe is composed of an induction electrode, a grounding electrode, a connecting hinge and an open-and-close buckle. A coupling capacitance is formed between the induction electrode and the measurement signal. At the same time, there is a structural capacitance in the sensor probe itself. A sampling resistor is connected at the back end, and a voltage sampling signal is obtained through the capacitance voltage division principle. The above shielding box is to reduce electromagnetic interference and protect the signal processing circuit from the external environment. The above capacitance switching module obtains different voltage signals by switching different capacitor groups, and obtains the coupling capacitance and the structural capacitance of the sensor itself through calibration fitting and solution under a standard environment. Under actual measurement conditions, the structural capacitance is not affected by the environment, while the coupling capacitance will change with the measurement environment. By determining the structural capacitance, the voltage to be measured is solved. The above signal processing and transmission module transmits the voltage sampling signal to the metering chip, and the metering chip calculates voltage, current, phase and frequency, converts the analog signal into a digital signal and transmits the voltage value to an external reading display through remote transmission. The above power supply module supplies power to the signal processing circuit.

[0013] In the above, in order to reduce the structural capacitance between the induction electrode and the grounding electrode and increase the measurement accuracy of the sensor, the intermediate insulating medium can adopt a hollow design.

[0014] The present invention provides a single-ended grounded self-calibrated voltage measuring device, which is characterized in that the voltage measuring device adopts electric field coupling capacitor voltage division technology, combined with A / D conversion, computer hardware, wireless transmission and other technologies, converts high voltage into low voltage signal through capacitor voltage division, filters and amplifies the sampled signal, and obtains a standard digital signal through built-in algorithm processing and transmits it to an external reading device. The present invention solves the problem that the sensor gain of the electric field coupling voltage measuring device cannot be determined due to the uncertainty of the coupling capacitor, so that the voltage to be measured cannot be accurately reconstructed. At the same time, the present invention has good anti-interference performance, is easy to install, has strong scene adaptability, can realize automatic calibration of the measurement signal, and is smaller in size, safer, and has higher measurement accuracy than traditional voltage transformers.

[0015] Specifically, the present invention provides a single-ended grounded self-calibrated voltage measuring device, comprising a voltage sensor probe, a shielding box, a capacitor switching calibration module, a signal processing and transmission module, and a power supply module. The shielding box has built-in modules necessary for signal processing and transmission, such as capacitor switching calibration, A / D conversion, and power supply. The sensor probe comprises an induction plate and a grounding plate, which are respectively connected to the input end of the voltage sampling. The voltage sampling is connected to the signal processing module. The power supply is built into the shielding box to provide ± voltage signals for single-chip signal sampling and processing. The signal transmission is connected to the signal processing module to transmit the obtained standard digital signal to an external display.

[0016] Preferably, the voltage sensor probe obtains the relationship between the sensor length and the inner and outer radii and the structural capacitance and coupling capacitance through simulation, analyzes their influence on the measurement and calibration accuracy, and obtains the structural parameters. In the present invention, the length L of the sensor probe is set to 6 cm, the outer radius R1 is set to 1.8 cm, and the inner radius R2 is set to 0.8 cm.

[0017] Preferably, the sensor probe adopts an opening and closing design, with one end connected by a connecting hinge and the other end using an opening and closing buckle connection structure. The upper end of the opening and closing buckle is provided with a guide groove and the lower end is provided with a contact terminal, which can achieve quick connection and disconnection and facilitate installation in practical applications.

[0018] Preferably, the switching capacitors C1, C2, and C3 are connected to the sampling resistor and controlled by a relay switch, which can improve the response speed of the switch. Compared with a mechanical switch, the switch has less wear and tear and higher stability and reliability.

[0019] Preferably, the signal processing includes a filtering proportional amplifier circuit to amplify the collected weak voltage signal and improve the signal-to-noise ratio of the signal.

[0020] Preferably, STM32 is used as the main control chip for signal processing, and a half-duplex, low-power RS-485 transceiver (MAX3485E) is used to achieve signal transmission.

[0021] Preferably, in order to reduce the volume and weight, the power supply module uses a ±12V lithium battery to supply power to each active device of the sensor.

[0022] Another object of the present invention is to provide a single-ended grounded self-calibrating voltage measurement method. The sensor probe output is obtained through a standard voltage source, and the accurate structural capacitance value is calculated. After the voltage measurement device is installed on the line to be measured, by switching three different capacitance values respectively, three different voltage outputs are obtained, the collected data is recorded and stored, the collected data is fitted and calculated to obtain the voltage of the line to be measured, and the voltage waveform is reconstructed based on the real-time voltage output.

[0023] The present invention has the following advantages:

[0024] 1. Compared with the traditional power transformer, the single-ended contact self-calibrating voltage measurement device has a simple insulation structure through spatial electric field measurement, does not need to be electrically connected to the wire to be measured, and is convenient for maintenance.

[0025] 2. Compared with the traditional power transformer, it is small in volume, light in weight, low in manufacturing cost, and has an open-close structure, which is convenient for installation.

[0026] 3. The voltage to be measured is obtained through self-calibration solution, which is not affected by the environment and is applicable to various measurement scenarios.

[0027] 4. It solves the interference of spatial and phase-interphase stray electric fields to the sensor, and has high measurement accuracy.

[0028] 5. It is suitable for data acquisition, detection, line loss analysis and other distribution automation management in intelligent distribution power systems. Description of the Drawings

[0029] Figure 1 It is a structural schematic diagram of a single-ended grounded self-calibrating voltage measurement device;

[0030] Figure 2 It is a circuit topology schematic diagram of a single-ended grounded self-calibrating voltage measurement device;

[0031] Figure 3 It is an implementation step diagram of the calibration process of a single-ended grounded self-calibrating voltage measurement device;

[0032] Figure 4 It is a working block diagram of a single-ended grounded self-calibrating voltage measurement device;

[0033] In the figure, the components represented by each label are as follows:

[0034] In the figure, 1 is the sensor probe, 2 is the shielding box, 3 is the signal processing circuit, 101 is the induction electrode plate, 102 is the grounding electrode plate, 103 is the insulating medium, 104 is the opening and closing buckle, 105 is the opening and closing hinge, 106 is the contact terminal of the opening and closing buckle, 201 is the connecting wire between the induction electrode plate and the signal processing circuit, and 202 is the grounding wire. Specific implementation manner

[0035] Next, a specific implementation manner of the present invention will be described in detail in conjunction with the drawings and embodiments. The protection scope of the present invention includes but is not limited to the following:

[0036] As Figure 1 shown, the present invention provides a single-ended contact voltage measurement device with shielding, which is a structure that can be opened from the side. The signal processing circuit 3 is a backend signal acquisition, processing, and transmission module. 101 is the induction electrode plate, and 102 is the grounding electrode, both of which are circular arc surfaces. Moreover, the area of the grounding electrode is larger than the area facing the induction electrode to improve the shielding effect. The insulating medium 103 is used to increase the measurement accuracy of the sensor. It is hollowed out and replaced with air. The opening and closing buckle 104 and the contact terminal 106 of the opening and closing buckle facilitate the installation of the sensor.

[0037] A single-ended grounded self-calibrating voltage measurement device includes a voltage sensor probe 1, a shielding box 2, and a signal processing circuit 3. The sensor probe is connected to the shielding box. The signal processing circuit 3 is placed inside the shielding box 2. The signal processing circuit 3 includes a capacitor switching circuit, a single-chip microcomputer processing circuit, a communication module, and a power supply module.

[0038] The sensor probe 1 is a coaxial-shaped opening and closing structure. The sensor probe 1 includes an induction electrode plate 101, a grounding electrode plate 102, an opening and closing buckle 104, an opening and closing hinge 105, and an insulating medium 103. An insulating medium is provided between the induction electrode plate 101 and the grounding electrode plate 102.

[0039] The induction electrode plate 101 and the grounding electrode plate 102 are electrically connected to the signal processing circuit 3.

[0040] The grounding electrode plate 102 wraps the induction electrode plate 101.

[0041] The capacitor switching circuit includes but is not limited to relay switch control.

[0042] The signal processing circuit 3 is fixed at the bottom of the shielding box using non-conductive materials.

[0043] As Figure 2 shown, C p is the coupling capacitor between the wire to be measured and the induction electrode plate, C sis the structural capacitance between the sensor induction electrode plate and the grounding electrode plate, C b1 , C b2 , C b3 is the lumped capacitance C bn incorporated during the calibration process. The relay switches Sn respectively control whether the capacitance C bn is incorporated into the circuit. R m is the sampling resistor, and the operational amplifier OP represents the backend signal processing and transmission part. In this example, the calibration method and process will be mainly described. When the sensor is in self-integration, the transfer function can be expressed as:

[0044]

[0045] In this example, with the same standard voltage and no interference experiment, let the switches S1, S2, and S3 be closed respectively to obtain three different outputs V o1 , V o2 , V o3 The following expressions can be obtained:

[0046] V o1 C p -V L C p +V o1 C s +C b1 =0 (2)

[0047] V o2 C p -V L C p +V o2 C s +C b2 =0 (3)

[0048] V o3 C p -V L C p +V o3 C s +C b3 =0 (4)

[0049] In the formula, only C p and C s are unknown. By using methods such as Newton's method and iterative root finding, but not limited to these two methods, a set of determined values of C p and C s can be obtained. By changing the experimental line voltage, multiple sets of determined values of C p and C s can be obtained. By taking the average value, the calculation error can be reduced to obtain the structural capacitance Cs under the experimental conditions. In actual measurement, the voltage V L to be measured is unknown, and the coupling capacitance Cp Unknown and varying with different measurement conditions, but the structural capacitance is generally constant. Similarly, the voltage to be measured and the coupling capacitance value under different measurement environments can be obtained.

[0050] As Figure 3 shown, under experimental conditions, the output of the sensor probe is obtained through a standard voltage source, and the accurate structural capacitance value C s is obtained. After installing the voltage measurement device on the line to be measured, by switching three groups of different capacitance values respectively, three different voltage outputs are obtained, and the collected data (marked as V o1 , V o2 , V o3 ) are recorded and stored. The voltage of the wire line to be measured is calculated by fitting the collected data according to formulas (2), (3), and (4), and the voltage waveform can be reconstructed based on the real-time voltage output.

[0051] As Figure 4 shown, the single-ended contact self-calibrating voltage measurement device includes the acquisition and sampling of voltage signals, filtering and amplifying the signals, the single-chip microcomputer samples the analog signals, and obtains standard digital signals through the built-in A / D conversion. The wireless transmission module transmits the obtained digital signals to an external display.

[0052] Finally, it should be noted that: The present invention has the advantages of simple structure, convenient operation, strong anti-interference, etc., and can effectively solve the interference of the spatial and phase-interphase stray electric fields on the capacitive coupling sensor. The present invention is not limited to the above embodiments, and various changes and modifications are within the protection scope of the present invention.

Claims

1. A single-ended grounded self-calibrated voltage measurement device, comprising a voltage sensor probe (1), a shielding box (2) and a signal processing circuit (3), wherein the sensor probe is connected to the shielding box, the signal processing circuit (3) is placed in the shielding box (2), and the signal processing circuit (3) comprises a capacitor switching circuit, a single-chip processing circuit, a communication module and a power module.

2. A single-ended grounding self-calibration voltage measurement device according to claim 1, characterized in that: The sensor probe (1) is a coaxial opening and closing structure, comprising an induction plate (101), a grounding plate (102), an opening and closing buckle (104), an opening and closing hinge (105) and an insulating medium (103), wherein an insulating medium is provided between the induction plate (101) and the grounding plate (102).

3. A single-ended grounding self-calibration voltage measurement device according to claim 2, characterized in that: The induction electrode (101) and the grounding electrode (102) are electrically connected to the signal processing circuit (3).

4. A single-ended grounding self-calibration voltage measurement device according to claim 3, characterized in that: The grounding electrode plate (102) wraps the sensing electrode plate (101).

5. A single-ended grounded self-calibrated voltage measuring device according to claim 1, characterized in that: The capacitor switching circuit includes but is not limited to relay switch control.

6. A single-ended grounded self-calibrated voltage measuring device according to claim 1, characterized in that: The signal processing circuit (3) is fixed to the bottom of the shielding box using non-conductive material.

7. A single-ended grounding self-calibration voltage measurement method, using the single-ended grounding self-calibration voltage measurement device according to any one of claims 1 to 6, characterized in that: The sensor probe output is obtained through a standard voltage source, and the accurate structural capacitance value is calculated. After the voltage measuring device is installed on the line to be tested, three groups of different capacitance values ​​are switched on and off respectively to obtain three groups of different voltage outputs. The collected data are recorded and stored, and the collected data are fitted and calculated to obtain the voltage of the conductor line to be tested, and the voltage waveform is reconstructed based on the real-time voltage output.

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