TWI822099B - Current measurement system and method - Google Patents

Abstract

A current measurement system is suitable for being installed on a flying vehicle. The system includes a magnetic field sensor array, a geometric measurement system and a digital signal processing module. The magnetic field sensor array is used for sensing the magnetic field component at the position of the flying vehicle to generate a magnetic field signal. The geometrical measurement system includes a distance sensor and an inertial measurement unit for measuring a spatial geometrical data of a target to be measured. The digital signal processing module processes the magnetic field signal to generate a digital magnetic field data, and calculates the three-phase current provided by the object to be measured according to the magnetic field data and the spatial geometric data.

Description

Current measurement system and method

The present invention relates to a current measurement system and method, and in particular to a system and method for measuring current and current distortion using an unmanned aerial vehicle.

As economic growth and the proportion of renewable energy increase year by year, in order to solve energy transmission problems, overhead transmission lines in countries around the world will cover wider and more complex areas. This will lead to a more complex operating environment of the power grid, a higher probability of failure, a greater difficulty in detection, and a wider impact after a failure. This makes the need for overhead line condition monitoring technology increasingly urgent.

In the power transmission system, the grid structure is relatively simple, so the overhead line current status monitoring and evaluation can be completed based on the current sensing device in the substation. At the distribution network level, most of the overhead lines adopt branch circuits after leaving the substation. Although various countries have actively promoted distribution automation technology in recent years, the power grid structure between urban and rural areas is complex, the ring network has many contacts, and most suburban and rural distribution lines are powered by radial distribution networks. Therefore, the current data collected at distribution substations (Including internal measurement devices in substations and sensing devices installed for distribution automation) will not be able to meet the current state assessment needs of distribution line sites. This situation results in on-site power quality testing and equipment maintenance staff often lacking accurate and timely power information. Therefore, developing an on-site measurement technology for power transmission and distribution overhead lines is one of the current development priorities of global power measurement technology.

Because of the above problems, new current measurement technology should be easy to install on site, lightweight, without physical contact, capable of measuring current waveforms, and without the assistance of power plant personnel.

The current related non-contact current measurement technology is mainly designed based on magnetic field sensing, and can be divided into two types: short-range and long-range measurement.

The non-contact and short-range current measurement method reduces the risk of high-voltage electric shock to some extent. For low-voltage systems, non-contact proximity technology is more likely to allow live wire installation. However, in high-voltage systems, general power personnel still recommend power-off installation or live-wire installation with sufficient insulation protection.

Non-contact long-distance current measurement method is a new sensing concept similar to wireless sensor network (WSN). Under the structure of the sensing network, multiple sensors are placed on the ground to measure the spatial synthetic magnetic field at different locations. Finally, the coupling matrix obtained after calibration is used to infer the three-phase current values of the overhead lines (real three-phase current waveform). However, with the sensing method placed on the ground, the magnetic field signal is too small and the overall error in current measurement is too large.

On the other hand, drone flight technology is becoming increasingly mature, and in response to the construction and development of smart grids, more and more power companies are introducing drones for inspection of transmission lines, such as Hydro-Québec’s wire corrosion technology, Darling Geomatics’ 3D mapping geographic information, ULC Robotics' image line inspection, Cyberhawk Innovations Limited's image line inspection, wind turbine inspection, and many other companies focus on temperature inspection of power transmission lines.

One object of the present invention is to provide a current measurement system and method, which is installation-free, lightweight, has no physical contact, can measure current waveforms remotely, and does not require the assistance of power plant personnel.

In order to achieve the above object, the present invention provides a current measurement system suitable for installation on an aircraft. The system includes a magnetic field sensor array, a geometric measurement system and a digital signal processing module. The magnetic field sensor array is used to sense the magnetic field component at the location of the aircraft to generate a magnetic field signal. The geometric measurement system includes a distance sensor and an inertial measurement unit for measuring spatial geometric data of a target to be measured. The digital signal processing module processes the magnetic field signal to generate a digital magnetic field data, and calculates the three-phase current provided by the target to be measured based on the magnetic field data and the spatial geometry data.

In one embodiment, the target to be measured is an overhead line which includes a first conductor, a second conductor and a third conductor respectively carrying three-phase currents, wherein the second conductor is located between the first conductor and the third conductor. between wires. The spatial geometric data includes the vertical distance from the flying vehicle to the first wire, the vertical distance from the flying vehicle to the second wire, the vertical distance from the flying vehicle to the third wire, the vertical distance between the first wire and the The horizontal distance between the second conductive lines, and the horizontal distance between the second conductive line and the third conductive line.

In one embodiment, the multi-axis magnetic field sensor array includes a plurality of multi-axis magnetic field sensors arranged in a vertical array.

In one embodiment, the digital signal processing module is an embedded system, and the embedded system is used to calculate the spatial geometry data and the three-phase current.

In one embodiment, the aforementioned system further includes a current analysis platform, which is connected to the embedded system through wireless communication.

On the other hand, the present invention provides a current measurement method, which includes: installing the aforementioned current measurement system on a drone, and operating the drone to fly directly below the target to be measured to measure the target to be measured. Measure the three-phase current of the target.

In one embodiment, the target to be measured is an overhead line, and the method further includes: using the current measurement system to measure the current distortion degree of the overhead line.

In one embodiment, the aforementioned method further includes: providing a matrix operation relationship between the spatial geometry data, the magnetic field data and the current value in the digital signal processing module to calculate the three-phase current.

In one embodiment, the aforementioned method further includes: selecting a data representation method of the three-phase current through the current analysis platform.

In one embodiment, the aforementioned method further includes: integrating an analog signal processing circuit into the magnetic field sensor array to remove a high-frequency interference from the magnetic field signal, wherein the high-frequency interference is caused by the UAV. produce.

Aiming at the detection of overhead line current, the present invention is designed to use a drone as a vehicle, and install a vertical multi-axis magnetic field sensor array on the drone, so that the overhead line current measurement can be carried out. The drone is equipped with a distance sensor, which allows the drone to fly directly under any phase conductor of the overhead line, which can improve the accuracy of the current algorithm of this invention. In addition, the drone is equipped with GPS global time and positioning, which allows the measured current data to be marked with global time and location information. The UAV design includes an aerial photography device, and the operator can wirelessly remotely control the UAV to conduct current measurements on overhead lines over a wide range of paths.

The aforementioned and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. Directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only used to refer to the directions of the accompanying drawings. Therefore, these directional terms are only used to illustrate and not to limit the present invention.

Figure 1 shows a current measurement system 100 according to an embodiment of the present invention. The current measurement system 100 uses the drone 110 as its vehicle to measure the current of overhead lines. Its structure includes: (a) magnetic field sensor array 120; (b) geometric measurement system 140; (c) Embedded system 160; and (d) aerial photography device 180. The breakdown is as follows:

(a) Magnetic field sensor array 120

The magnetic field sensor array 120 includes a multi-axis magnetic field sensor 122, such as a two-axis (x-axis and y-axis in the horizontal plane) magnetic field sensor or a three-axis (x-axis and y-axis in the horizontal plane, and vertical axis z) magnetic field sensor. The detector is used to sense the magnetic field component at the location of the drone 110 in space and generate a magnetic field signal. In one embodiment, the magnetic field sensor array 120 may be a vertical multi-axis magnetic field sensor array as shown in FIG. 2 , which includes at least three multi-axis magnetic field sensors S ₁ , S ₂ , S ₃ , S ₄ ,...S _n are arranged vertically into a vertical array, and then installed on the UAV 110 . The multi-axis magnetic field sensor (S ₁ ~S _n ) in Figure 2 is used to sense the magnetic field components in the X ₁ ~X _n direction, Y ₁ ~Y _n direction and Z ₁ ~Z _n direction respectively; each two The distance between adjacent multi-axis magnetic field sensors (S ₁ ~S _n ) in the vertical direction is d.

In addition, the magnetic field sensor array 120 also includes an analog signal processing circuit 124 for matching the multi-axis magnetic field sensor 122 . The analog signal processing circuit 124 basically includes an amplifier circuit and a low-pass filter circuit. The amplifier circuit can amplify the sensed magnetic field signal; and the low-pass filter circuit is used to filter out the magnetic field signal in the high-frequency band. In other words, the present invention can use the analog signal processing circuit 124 to remove the high-frequency interference generated by the drone 110 from the magnetic field signal.

(b) Geometric measurement system 140

The geometric measurement system 140 includes a distance sensor 142 and an inertial measurement unit 144 for measuring spatial geometric data of an object to be measured. As shown in Figure 2, in this embodiment, the target to be measured is an air line 200. The overhead line 200 includes three conductors 20a, 20b and 20c respectively having three-phase voltages _Va , _Vb and _Vc and transmitting three-phase currents _Ia , _Ib and _Ic , wherein the conductor 20b is located between the conductors 20a and 20c. First, the drone 110 flies below the overhead line 200 and uses the distance sensor 142 to measure a vertical distance H in a direction perpendicular to the horizontal plane. When measuring the vertical distance H, if the drone 110 is controlled directly under any phase conductor of the overhead line 200, the vertical distance H measured by the distance sensor 142 will be the smallest; if the drone 110 is not any phase conductor directly below the distance sensor 142, the vertical distance H measured by the distance sensor 142 in the sky will be infinitely long. In fact, the distance measurement limit Hmax of the distance sensor 142 may occur. As shown in Figure 3B, the distance measurement limit Hmax Hmax is approximately 34 meters. Then, the inertial measurement unit 144 is used to ensure that the drone 110 flies horizontally and records a horizontal flight distance D. At this time, the distance sensor 142 and the inertial measurement unit 144 simultaneously record the vertical distance H and the horizontal flight distance D, and the distribution diagram of FIG. 3B can be obtained, so the spatial geometric data related to the overhead line 200 can be calculated.

Referring to FIGS. 3A and 3B simultaneously, the triangular relationship formed by the conductors 20a, 20b, and 20c in FIG. 3A is similar to the triangular relationship formed by the three troughs 20A, 20B, and 20C of the curve in FIG. 3B. _The spatial geometric data shown in Figure 3B includes Ha, _Hb , _Hc , _Dab , and _Dbc . H _a is the vertical distance from the drone 110 to the wire 20 a, H _b is the vertical distance from the drone 110 to the wire 20 b, H _c is the vertical distance from the drone 110 to the wire 20 c, D _ab is the distance between the wire 20 a and the wire 20 b. The horizontal distance, D _bc, is the horizontal distance between the conductor 20b and the conductor 20c. At this time, the UAV 110 can choose to fly stationary at a vertical distance _Ha , _Hb or _Hc below any wire 20a, 20b or 20c, measure the magnetic field of the space with the magnetic field sensor array 120, and use the UAV The position of 110 is given by an air line geometric matrix. .

(c) Embedded Systems 160

This embodiment uses the embedded system 160 to digitally sample the magnetic field signal. Specifically, the digitized magnetic field data can be obtained through a sampling circuit and an analog-to-digital converter. . Then, perform magnetic field data Signal processing can include (1) Fourier Transform, which only retains the fundamental frequency of power and the magnetic field in harmonic order, and (2) low-pass filtering. On the other hand, the embedded system 160 receives the sensing data related to the spatial geometry of the overhead line 200 obtained by the geometric measurement system 140, and performs the overhead line geometry calculation based on the stationary position of the drone 110 flying in the air to obtain the overhead line. geometric matrix . Then, the embedded system 160 performs three-phase current calculation .

Fourier Transform can calculate the magnetic field values corresponding to the fundamental frequency of electric power and each harmonic order. Before performing Fourier transform, the operator can pre-select the power fundamental frequency and the required harmonic order through the current analysis platform 300. For example: the power fundamental frequency is generally 50 Hz or 60 Hz; when the selected power fundamental frequency is 50 Hz and When the harmonic order is n, n magnetic field values will be obtained, the corresponding frequencies of which are 1 to n times 50 Hz. Incidentally, during the Fourier transform, only the fundamental frequency of electricity and its harmonic frequencies are retained, which can also filter out the low-frequency electromagnetic field interference generated by the operation of the drone itself. Then, a current distortion value is calculated based on these magnetic field values via the embedded system 160 .

The embedded system 160 can transmit the three-phase current calculation results or current distortion values to a current analysis platform 130 through wireless communication. The operator can select the data representation method of the three-phase current calculation results through the current analysis platform 130, including: (1) current waveform (in this representation method, the magnetic field data does not require Fourier transform for signal processing), (2) current fundamental wave and The harmonic value (expressed as effective value), (3) current total harmonic distortion rate, (4) single current harmonic distortion rate, etc. are displayed on the operator's current analysis platform 130 .

The current distortion formula is as follows:

Current total harmonic distortion (THD) (%) I ₁ : Current fundamental wave; I _n : Current harmonics

Single current harmonic subdistortion (%)

In addition, the embedded system 160 also includes a GPS (Global Positioning System) receiver 162, which can receive global time and positioning data returned by the GPS. This global time and positioning data will also be marked on the three-phase current calculation results or current distortion values. , and are transmitted back to the operator's current analysis platform 130 together.

Accordingly, the current measurement system 100 of the present invention can provide a digital signal processing module equivalent to the embedded system 160, and place a matrix operation relationship between spatial geometry data, magnetic field data and current values into the digital In the signal processing module, it is used to calculate the three-phase current. This digital signal processing module can process magnetic field signals to generate digitized magnetic field data, and perform overhead line spatial geometry calculations to generate spatial geometry data; then, based on the magnetic field data and spatial geometry data, calculate the location of the target to be measured. Three-phase current provided. At the same time, the current measurement system 100 can also be used to measure the current distortion degree of the overhead line 200 .

(d) Aerial photography device 180

The field to be measured usually occupies a large area, so the drone 110 in this embodiment includes an aerial photography device 180 . The images captured by the aerial photography device 180 are also transmitted back to the operator's current analysis platform 130 via wireless communication of the embedded system 160 . In this way, the operator can remotely control the drone 110 in real time through wireless communication through the current analysis platform 130 to perform current measurement on a wide range of paths.

In summary, the present invention aims at detecting the current of each phase of the overhead line. It is designed to use a drone as a vehicle. A vertical multi-axis magnetic field sensor array is installed on the drone, which can measure the current of each phase of the overhead line. Test. The UAV is equipped with an overhead line geometric measurement system (including: distance sensor, inertial measurement unit). The distance sensor allows the UAV to fly directly under any phase conductor of the overhead line and measure The distance between the conductor and the drone; and the distance sensor combined with the inertial measurement unit (including: gyroscope, accelerometer) can measure the distance between the conductors, so the entire overhead line geometry can be calculated. The measured overhead line geometry is used as the coupling matrix of the current algorithm of the present invention. The magnetic field measured by the vertical multi-axis magnetic field sensor array can be used to calculate the three-phase current through the coupling matrix. In addition, the drone is equipped with GPS global time and positioning, which can mark the measured current data of each phase of the overhead line with time and location information to conduct large-scale overhead line current measurement.

The invention has the following advantages:

1. The present invention does not require installation when used for on-site measurement, and can measure the power quality of the target to be measured at a long distance.

2. Large-scale on-site measurement of power quality.

3. Accurately measure the current waveform, current frequency, and current harmonic components of any phase conductor of the overhead line.

4. When measuring current, it can shield the drone's own high-frequency electromagnetic field interference.

Based on the drone as the vehicle and non-contact sensing as the basis, the present invention designs a novel long-distance overhead line current measurement method and system, which can be used to accurately measure the current waveform of any phase conductor of the overhead line. Current frequency and current harmonic components. With the help of the remote control function of the drone, large-scale on-site power quality measurements can be safely realized. Coupled with GPS global time and positioning, the measurement location and absolute time of current distortion can be completely recorded.

Accordingly, the present invention has different technical features from the conventional technology, and it is difficult for a person with ordinary knowledge in the field to easily associate the concept of the present invention with the conventional technology. Therefore, the present invention should be novel and progressive.

However, the above are only preferred embodiments of the present invention, and should not be used to limit the scope of the present invention. That is, simple equivalent changes and modifications may be made based on the patent scope of the present invention and the description of the invention. All are still within the scope of the patent of this invention. In addition, any embodiment or patentable scope of the present invention does not need to achieve all the purposes, advantages or features disclosed in the present invention. In addition, the abstract section and title are only used to assist in searching patent documents and are not intended to limit the scope of the invention.

100:Current measurement system 100:Current measurement system 110:UAV 120:Magnetic field sensor array 122:Multi-axis magnetic field sensor 124:Analog signal processing circuit 130:Current analysis platform 140:Geometric measurement system 142: Distance sensor 144: Inertial measurement unit 160: Embedded system 162: GPS receiver 180: Aerial photography device 200: Overhead wires 20A, 20B, 20C: Wave troughs 20a, 20b, 20c: Wire D: Horizontal flight distance D _ab , D _bc : horizontal distance between wires d: separation distance between adjacent multi-axis magnetic field sensors H: vertical distance Ha, H _b , H _c : vertical _distance from drone to wire Hmax: ranging limit Values I _a , I _b , I _c : three-phase current S ₁ ~S _n : multi-axis magnetic field sensor V _a , V _b , V _c : three-phase voltage X ₁ ~X _n , Y ₁ ~Y _n , Z ₁ ~ _Zn : direction

Figure 1 is a schematic diagram of a current measurement system according to an embodiment of the present invention.

Figure 2 is a schematic diagram of an overhead line geometry measurement system according to an embodiment of the present invention.

3A and 3B are schematic diagrams of an overhead line geometry measurement system and its measurement results according to an embodiment of the present invention.

100:Current measurement system

110: Drone

120:Magnetic field sensor array

122:Multi-axis magnetic field sensor

124: Analog signal processing circuit

130:Current analysis platform

140:Geometric measurement system

142: Distance sensor

144:Inertial Measurement Unit

160:Embedded systems

162:GPS receiver

180:Aerial shooting device

Claims (10)

A current measurement system suitable for installation on an aircraft. The system includes: a magnetic field sensor array for sensing the magnetic field component at the location of the aircraft to generate a magnetic field signal; a geometric measurement The system includes a distance sensor and an inertial measurement unit for measuring spatial geometric data of a target to be measured; and a digital signal processing module for processing the magnetic field signal to generate a digitized magnetic field. data, and calculate the three-phase current provided by the target to be measured based on the magnetic field data and the spatial geometry data. The system according to claim 1, wherein the target to be measured is an overhead line which includes a first conductor, a second conductor and a third conductor respectively transmitting three-phase current, wherein the second conductor is located on the first conductor and the third wire, the spatial geometric data includes the vertical distance from the flying vehicle to the first wire, the vertical distance from the flying vehicle to the second wire, the vertical distance from the flying vehicle to the third wire distance, the horizontal distance between the first conductor and the second conductor, and the horizontal distance between the second conductor and the third conductor. The system of claim 1 further includes a multi-axis magnetic field sensor array, which includes a plurality of multi-axis magnetic field sensors arranged in a vertical array. The system according to claim 1, wherein the digital signal processing module is an embedded system, and the embedded system is used to calculate the spatial geometric data and the three-phase current. The system of claim 4 further includes a current analysis platform connected to the embedded system through wireless communication. A current measurement method, including: installing the current measurement system as described in any one of claims 1 to 5 on a drone, operating the drone to fly directly below the target to be measured, to measure The three-phase current of the target to be measured. The method of claim 6, wherein the target to be measured is an overhead line, and the method further includes: using the current measurement system to measure the current distortion degree of the overhead line. The method described in claim 6 further includes: providing a matrix operation relationship between the spatial geometry data, the magnetic field data and the current value in the digital signal processing module to calculate the three-phase current. The method of claim 6, wherein the current measurement system is the one described in claim 5, and the method further includes: selecting a data representation method of the three-phase current through the current analysis platform. The method of claim 6 further includes: integrating an analog signal processing circuit into the magnetic field sensor array to remove a high-frequency interference from the magnetic field signal, wherein the high-frequency interference is caused by the unmanned aerial vehicle. machine is generated.

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