Non-contact voltage measuring device and measuring method suitable for power distribution network

Abstract

The invention discloses a non-contact voltage measuring device and measuring method suitable for a power distribution network, and relates to the technical field of power distribution network voltage measurement, and the technical scheme is characterized in that the non-contact voltage measuring device comprises a double-probe structure, a front-end circuit and a signal processing circuit; the double-probe structure comprises an upper probe, a lower probe and a shielding cover; the front-end circuit comprises a differential amplification module, a harmonic source and two OP transimpedance operational amplifiers; the input end of the signal processing circuit is electrically connected with the output end of the differential amplification module. According to the invention, a shielding case is added on the outer sides of an upper probe, a lower probe and a leading-out wire of the sensor, then two OP transimpedance operational amplifiers of the same model and a differential amplification module are adopted in a front-end circuit, and a harmonic source is connected to the positive polarity ends of the two OP transimpedance operational amplifiers and is connected with the shielding case, so that the coupling effect between the environment and the internal probes is effectively avoided; the problem that a non-contact voltage measurement device cannot adapt to the measurement working condition of coupling capacitance change between measurement devices caused by the distribution network environment is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage measurement of distribution network, and more specifically, to a non-contact voltage measurement device and a measurement method suitable for distribution network. Background Art

[0002] Under the goal of carbon neutrality, the future power grid will be characterized by a high proportion of renewable energy and a high proportion of power electronic equipment connected to the grid. This will lead to more complex wide-band, multi-modal signals in the distribution network area, and there is an urgent need to propose highly reliable voltage sensors that can be widely deployed.

[0003] At present, traditional contact voltage sensors are sparsely deployed in power systems due to their large size, heavy weight, high cost, and inconvenient installation. They cannot meet the urgent needs of increasingly complex power grids for massive data. Non-contact voltage sensors do not directly contact the wires, and their insulation is simple. They can achieve lightweight and miniaturization of voltage sensors, which makes up for the shortcomings of contact voltage sensors. However, existing non-contact voltage sensors do not have effective measurement methods that adapt to environmental changes, and cannot be widely deployed in complex and diverse distribution network environments.

[0004] Therefore, how to research and design a non-contact voltage measurement device and measurement method suitable for distribution network that can overcome the above-mentioned defects is a problem that we urgently need to solve. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the purpose of the present invention is to provide a non-contact voltage measurement device and a measurement method suitable for a distribution network. A shielding cover is added to the upper and lower double probes of the sensor and the outer side of the lead wire, and then two OP transimpedance amplifiers and differential amplifier modules of the same model are used in the front-end circuit, and a harmonic source is connected to the positive polarity end of the two OP transimpedance amplifiers and connected to the shielding cover, which effectively avoids the coupling effect between the environment and the internal probe.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] In a first aspect, a non-contact voltage measurement device suitable for a power distribution network is provided, comprising a dual-probe structure, a front-end circuit and a signal processing circuit;

[0008] The dual-probe structure comprises an upper probe, a lower probe and a shielding cover; the shielding cover wraps the upper probe, the lower probe and their lead wires, and insulating materials with different relative dielectric constants are filled between the upper probe and the circuit, and between the lower probe and the circuit.

[0009] The front-end circuit includes a differential amplifier module, a harmonic source and two OP transimpedance amplifiers; the input ends of the two OP transimpedance amplifiers are respectively connected to the upper probe and the lower probe, and the output ends of the two OP transimpedance amplifiers are connected to the differential amplifier module; the harmonic source is connected to the positive polarity input ends of the two OP transimpedance amplifiers, and the positive polarity input ends of the two OP transimpedance amplifiers are electrically connected to the shielding cover;

[0010] The input end of the signal processing circuit is electrically connected to the output end of the differential amplifier module;

[0011] Among them, the signal processing circuit uses the DFT method to process the differential signal output by the front-end circuit to obtain the voltage component and the harmonic source voltage, and solves the voltage component, the harmonic source voltage and the sensor output-input relationship under the harmonic frequency in parallel to obtain the difference in coupling capacitance between the upper probe and the lower probe to the line, and substitutes the difference in coupling capacitance into the sensor input-output relationship under the fundamental frequency, and obtains the voltage amplitude of the measured line by taking the amplitude value.

[0012] Furthermore, the upper probe and the lower probe are bonded together by epoxy resin.

[0013] Further, the OP transimpedance amplifier includes an operational amplifier, a feedback capacitor and a feedback resistor;

[0014] After the feedback capacitor and the feedback resistor are connected in parallel, one end of the feedback capacitor is connected to the output end of the operational amplifier, and the other end is connected to the negative input end of the operational amplifier;

[0015] Furthermore, the negative polarity input terminal of the operational amplifier is connected to the corresponding upper probe or lower probe, and the positive polarity input terminal is connected to the shielding cover.

[0016] In a second aspect, a non-contact voltage measurement method applicable to a power distribution network is provided, wherein the method uses a non-contact voltage measurement device applicable to a power distribution network as described in any one of the first aspects to measure a power line, comprising the following steps:

[0017] The voltage component and harmonic source voltage are obtained by processing the differential signal output by the front-end circuit using the DFT method;

[0018] The difference in coupling capacitance between the upper probe and the lower probe to the circuit can be obtained by solving the relationship between the sensor output and input at the combined voltage component, harmonic source voltage and harmonic frequency.

[0019] Substitute the difference in coupling capacitance into the sensor input-output relationship at the fundamental frequency, and obtain the voltage amplitude of the measured line by taking the amplitude.

[0020] Furthermore, the process of using the DFT method to process the differential signal output by the front-end circuit to obtain the voltage component and the harmonic source voltage is specifically as follows:

[0021] The differential module output voltage signal and the harmonic source voltage signal are sampled to obtain a differential voltage sequence and a harmonic source voltage sequence respectively;

[0022] The DFT method is used to operate the differential voltage sequence and the harmonic source voltage sequence to obtain the voltage component output by the differential module and the harmonic source voltage respectively.

[0023] Furthermore, the voltage component output by the differential module includes a voltage component output at a harmonic angular frequency and a voltage component output at a fundamental frequency.

[0024] Furthermore, the sensor input-output relational expression represents the relationship between the output voltage phasor of the differential module and the voltage phasor of the power line to be measured.

[0025] Furthermore, the sensor input-output relationship is obtained by analyzing the harmonic source path of the front-end circuit and the fundamental wave path of the power line to be measured respectively using the superposition theorem based on the differential input structure of the front-end circuit.

[0026] Furthermore, the expression for solving the difference between the coupling capacitance of the upper probe and the lower probe to the line is specifically:

[0027]

[0028] Among them, C x2 -C x1 Indicates the difference in coupling capacitance between the upper probe and the lower probe to the line; C Z is the feedback capacitor of the OP transimpedance amplifier; R Z is the feedback resistor of the OP transimpedance amplifier; ω1 represents the harmonic angular frequency; Represents the voltage component output by the differential module at the harmonic angular frequency; Represents the harmonic source voltage output by the differential module at the harmonic angular frequency.

[0029] ω0 and ω1 are the fundamental angular frequency and harmonic angular frequency respectively. is the voltage phasor output by the differential amplifier module, is the voltage phasor of the measured power line;

[0030] Furthermore, the calculation expression of the measured line voltage amplitude is specifically:

[0031]

[0032] in, Indicates the voltage amplitude of the measured line at the fundamental frequency; ω0 indicates the fundamental angular frequency; ω1 indicates the harmonic angular frequency; C Z is the feedback capacitor of the OP transimpedance amplifier; R ZIt is the feedback resistor of OP transimpedance amplifier; Represents the voltage component output by the differential module at the harmonic angular frequency; Represents the voltage component output by the differential module at the fundamental frequency; Represents the harmonic source voltage output by the differential module at the harmonic angular frequency.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention first adds a shielding cover to the upper and lower dual probes of the sensor and the outer side of the lead wire, and then uses two OP transimpedance amplifiers and differential amplifier modules of the same model in the front-end circuit, and connects the harmonic source to the positive polarity ends of the two OP transimpedance amplifiers and connects them to the shielding cover, which effectively avoids the coupling effect between the environment and the internal probe, and solves the measurement working condition problem that the non-contact voltage measurement device cannot adapt to the distribution network environment and causes the change of the coupling capacitance between the measurement devices;

[0035] 2. The present invention uses the DFT method in the signal processing circuit to obtain the fundamental component and harmonic component of the voltage output signal of the differential module. The difference in coupling capacitance between the upper and lower probes and the circuit to be measured can be solved by using the harmonic components and the known harmonic sources, so that the non-contact voltage measurement method can be adapted to power lines with different wire diameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0037] Figure 1 is a connection principle diagram of the non-contact voltage measurement device in Embodiment 1 of the present invention;

[0038] Figure 2 It is a schematic diagram of an equivalent circuit model in Example 2 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0040] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it can be directly or indirectly connected to the other component.

[0041] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0042] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0043] Embodiment 1: A non-contact voltage measurement device suitable for a power distribution network, such as Figure 1 As shown, it includes a dual-probe structure, a front-end circuit and a signal processing circuit.

[0044] The dual-probe structure includes an upper probe, a lower probe and a shielding cover; the shielding cover wraps the upper probe, the lower probe and their lead wires to prevent the copper electrode from forming stray capacitance with the surrounding environment, and insulating materials with different relative dielectric constants are filled between the upper probe and the line, and between the lower probe and the line.

[0045] The front-end circuit includes a differential amplifier module, a harmonic source and two OP transimpedance amplifiers; the input ends of the two OP transimpedance amplifiers are connected to the upper probe and the lower probe respectively, and the output ends of the two OP transimpedance amplifiers are connected to the differential amplifier module; the harmonic source U S The positive input terminals of the two OP transimpedance operational amplifiers are connected, and the positive input terminals of the two OP transimpedance operational amplifiers are electrically connected to the shielding cover.

[0046] The front-end circuit uses two OP transimpedance amplifiers of the same model, whose input terminals are connected to the upper and lower probes respectively. They have the same input capacitance C. in The output terminals of the two OP transimpedance amplifiers are connected to the differential amplifier module, and the influence of the input capacitor is eliminated by using the differential circuit structure. In addition, the 1kHz harmonic source is connected to the positive input terminals of the two OP transimpedance amplifiers, and the positive input terminals are electrically connected to the shielding cover, so that the differential signal output by the differential module contains fundamental and harmonic components.

[0047] The input end of the signal processing circuit is electrically connected to the output end of the differential amplifier module. The signal processing circuit uses the DFT method to process the differential signal output by the front-end circuit to obtain the voltage component and the harmonic source voltage, and solves the voltage component, the harmonic source voltage and the sensor output-input relationship under the harmonic frequency in parallel to obtain the difference in coupling capacitance between the upper probe and the lower probe to the line, and substitutes the difference in coupling capacitance into the sensor input-output relationship under the fundamental frequency, and obtains the voltage amplitude of the measured line by taking the amplitude value.

[0048] In addition, the upper probe and the lower probe can be bonded together by epoxy resin.

[0049] In addition, the OP transimpedance operational amplifier includes an operational amplifier (such as A1 and A2), a feedback capacitor and a feedback resistor; after the feedback capacitor is connected in parallel with the feedback resistor, one end is connected to the output end of the operational amplifier, and the other end is connected to the negative input end of the operational amplifier; and the negative input end of the operational amplifier is connected to the corresponding upper probe or lower probe, and the positive input end is connected to the shielding cover.

[0050] Embodiment 2: A non-contact voltage measurement method applicable to a power distribution network, wherein the method uses a non-contact voltage measurement device applicable to a power distribution network as described in Embodiment 1 to measure power lines.

[0051] Before measurement, the present invention needs to combine the dual probe structure, the front-end circuit, the coupling capacitance formed between the power line and the ground to obtain an equivalent circuit model of the non-contact voltage measurement method, such as Figure 2 As shown; based on the differential input structure of the front-end circuit, the harmonic source path of the front-end circuit and the fundamental wave path of the power line to be measured are analyzed respectively by using the superposition theorem, and the sensor output and input relationship under the fundamental wave and harmonic wave containing the coupling capacitor parameters are obtained respectively.

[0052] Specifically, the superposition theorem is used to analyze the harmonic source path of the front-end circuit and the fundamental wave path of the power line to be measured, and the fundamental wave component of the relationship between the output voltage phasor of the differential module and the voltage phasor of the power line to be measured is obtained. And harmonic components

[0053]

[0054] In the formula, (C x2 -C x1 ) is the difference in coupling capacitance between the upper and lower probes to the power line, C Z is the feedback capacitor of the OP transimpedance amplifier, R Z is the feedback resistor of the OP transimpedance amplifier, ω0 and ω1 correspond to the fundamental angular frequency and the harmonic angular frequency respectively. is the voltage phasor output by the differential amplifier module, is the voltage phasor of the measured power line.

[0055] When the fundamental wave component and harmonic wave component are known, the signal processing circuit first performs a sampling operation at a sampling frequency of The differential module outputs voltage signals u d And the harmonic source voltage signal u s Sampling is performed to obtain a differential voltage sequence u containing N items. d (n) and the harmonic source voltage sequence u s (n). And use DFT to calculate the voltage sequence u d (n),u s (n) is calculated to obtain the differential module output voltage components at the angular frequency ω1 And the harmonic source voltage The specific expression is:

[0056]

[0057]

[0058] Similarly, the differential module output voltage signal u is obtained using DFT d The voltage component at the angular frequency ω0

[0059] Then, the harmonic components of the differential signal are combined Harmonic source voltage The sensor output-input relationship (2) at the harmonic frequency is solved to obtain the difference in coupling capacitance between the upper and lower probes and the power line. The specific expression is:

[0060]

[0061] Next, the differential module voltage output component at the fundamental frequency Substituting the difference in coupling capacitance between the upper and lower probes and the power line into the input-output relationship at the fundamental frequency, we can get:

[0062]

[0063] And taking the amplitude of the above formula, we can get the voltage amplitude of the measured line, the expression is:

[0064]

[0065] Working principle: The present invention first adds a shielding cover to the upper and lower dual probes and the outer side of the lead-out wires of the sensor, and then adopts two OP transimpedance amplifiers and differential amplifier modules of the same model in the front-end circuit, and connects the harmonic source to the positive polarity ends of the two OP transimpedance amplifiers and connects them to the shielding cover, which effectively avoids the coupling effect between the environment and the internal probe, and solves the measurement condition problem that the non-contact voltage measurement device cannot adapt to the distribution network environment and causes the coupling capacitance between the measurement devices to change.

[0066] In addition, the present invention uses the DFT method in the signal processing circuit to obtain the fundamental component and harmonic component of the differential module voltage output signal. The difference in coupling capacitance between the upper and lower probes and the line to be measured can be solved using the harmonic components and known harmonic sources, so that the non-contact voltage measurement method can be adapted to power lines with different wire diameters.

[0067] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A non-contact voltage measuring device suitable for a power distribution network, characterized in that: It includes a dual-probe structure, a front-end circuit and a signal processing circuit; The dual-probe structure comprises an upper probe, a lower probe and a shielding cover; the shielding cover wraps the upper probe, the lower probe and their lead wires, and insulating materials with different relative dielectric constants are filled between the upper probe and the circuit, and between the lower probe and the circuit. The front-end circuit includes a differential amplifier module, a harmonic source and two OP transimpedance amplifiers; the input ends of the two OP transimpedance amplifiers are respectively connected to the upper probe and the lower probe, and the output ends of the two OP transimpedance amplifiers are connected to the differential amplifier module; the harmonic source is connected to the positive polarity input ends of the two OP transimpedance amplifiers, and the positive polarity input ends of the two OP transimpedance amplifiers are electrically connected to the shielding cover; The input end of the signal processing circuit is electrically connected to the output end of the differential amplifier module; Among them, the signal processing circuit uses the DFT method to process the differential signal output by the front-end circuit to obtain the voltage component and the harmonic source voltage, and solves the voltage component, the harmonic source voltage and the sensor output-input relationship under the harmonic frequency in parallel to obtain the difference in coupling capacitance between the upper probe and the lower probe to the line, and substitutes the difference in coupling capacitance into the sensor input-output relationship under the fundamental frequency, and obtains the voltage amplitude of the measured line by taking the amplitude value.

2. A non-contact voltage measuring device suitable for a power distribution network according to claim 1, characterized in that: The upper probe and the lower probe are bonded together by epoxy resin.

3. A non-contact voltage measuring device suitable for a power distribution network according to claim 1, characterized in that: The OP transimpedance amplifier comprises an operational amplifier, a feedback capacitor and a feedback resistor; After the feedback capacitor and the feedback resistor are connected in parallel, one end of the feedback capacitor is connected to the output end of the operational amplifier, and the other end is connected to the negative input end of the operational amplifier; Furthermore, the negative polarity input terminal of the operational amplifier is connected to the corresponding upper probe or lower probe, and the positive polarity input terminal is connected to the shielding cover.

4. A non-contact voltage measurement method suitable for a distribution network, characterized in that: The method uses a non-contact voltage measuring device applicable to a power distribution network as described in any one of claims 1 to 3 to measure a power line, comprising the following steps: The voltage component and harmonic source voltage are obtained by processing the differential signal output by the front-end circuit using the DFT method; The difference in coupling capacitance between the upper probe and the lower probe to the circuit can be obtained by solving the relationship between the sensor output and input at the combined voltage component, harmonic source voltage and harmonic frequency. Substitute the difference in coupling capacitance into the sensor input-output relationship at the fundamental frequency, and obtain the voltage amplitude of the measured line by taking the amplitude.

5. The non-contact voltage measurement method applicable to a power distribution network according to claim 1, characterized in that: The process of using the DFT method to process the differential signal output by the front-end circuit to obtain the voltage component and the harmonic source voltage is specifically as follows: The differential module output voltage signal and the harmonic source voltage signal are sampled to obtain a differential voltage sequence and a harmonic source voltage sequence respectively; The DFT method is used to operate the differential voltage sequence and the harmonic source voltage sequence to obtain the voltage component output by the differential module and the harmonic source voltage respectively.

6. The non-contact voltage measurement method applicable to a power distribution network according to claim 1, characterized in that: The voltage component output by the differential module includes a voltage component output at a harmonic angular frequency and a voltage component output at a fundamental frequency.

7. The non-contact voltage measurement method applicable to a power distribution network according to claim 1, characterized in that: The sensor input-output relational expression represents the relation between the output voltage phasor of the differential module and the voltage phasor of the power line to be measured.

8. The non-contact voltage measurement method applicable to a power distribution network according to claim 7, characterized in that: The sensor input-output relationship is obtained by analyzing the harmonic source path of the front-end circuit and the fundamental wave path of the power line to be measured respectively using the superposition theorem on the basis of the differential input structure of the front-end circuit.

9. The non-contact voltage measurement method applicable to a power distribution network according to claim 1, characterized in that: The specific solution expression for the difference between the coupling capacitance of the upper probe and the lower probe to the line is: Among them, C x2 -C x1 Indicates the difference in coupling capacitance between the upper probe and the lower probe to the line; C Z is the feedback capacitor of the OP transimpedance amplifier; R Z is the feedback resistor of the OP transimpedance amplifier; ω1 represents the harmonic angular frequency; Represents the voltage component output by the differential module at the harmonic angular frequency; Represents the harmonic source voltage output by the differential module at the harmonic angular frequency. ω0 and ω1 are the fundamental angular frequency and harmonic angular frequency respectively. is the voltage phasor output by the differential amplifier module, is the voltage phasor of the measured power line.

10. The non-contact voltage measurement method applicable to a power distribution network according to claim 1, characterized in that: The calculation expression of the measured line voltage amplitude is specifically: in, Indicates the voltage amplitude of the measured line at the fundamental frequency; ω0 indicates the fundamental angular frequency; ω1 indicates the harmonic angular frequency; C Z is the feedback capacitor of the OP transimpedance amplifier; R Z It is the feedback resistor of the OP transimpedance amplifier; Represents the voltage component output by the differential module at the harmonic angular frequency; Represents the voltage component output by the differential module at the fundamental frequency; Represents the harmonic source voltage output by the differential module at the harmonic angular frequency.

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