Overhead line current accurate measurement system and method based on MEMS sensor array

Abstract

The application discloses an overhead line current accurate measurement system and method based on a MEMS sensor array, which comprises three-phase line devices located on an overhead line; the A-phase line device comprises three TMR sensors, one MEMS sensor and one data processing module, the B-phase and C-phase line devices each comprise one MEMS sensor; all the TMR sensors and the MEMS sensors are located on the same vertical plane of the overhead line; on the vertical plane, the three TMR sensors are arranged on concentric circles of the A-phase line, and the sensors TMR a , TMR b and TMR c are located on the perpendicular line of the center connecting line of the BC-phase line; the data processing module of the A-phase line device calculates the three-phase current of the overhead line according to the measurement data of each sensor and the mutual position relationship between the phase lines in the static state. The application realizes the accurate detection of the three-phase current of the overhead line by using the TMR.

Description

Technical Field

[0001] This invention belongs to the field of current measurement technology, specifically relating to a precise measurement system and method for overhead line current based on a MEMS sensor array. Background Technology

[0002] With the rapid development of my country's power system, power technology is gradually moving towards automation, convenience, and maintenance-free operation. The requirements for current detection in various power monitoring, protection, and metering devices within the power system are increasing, and more accurate and convenient current signal measurement methods are needed to more accurately assess the power grid status.

[0003] Traditionally, TMR current sensors are used to measure copper busbar current. In this case, both the copper busbar and the TMR current sensor are fixed, so the decoupling equation of the TMR current sensor remains unchanged. To better monitor the power grid's operating status and protect its safe and stable operation, TMR current sensors can be used for overhead line current detection. Similarly, decoupling is used to eliminate magnetic field interference between phases, enabling the measurement of three-phase current.

[0004] However, the key challenge lies in the fact that overhead lines can vibrate irregularly in real-world environments, causing changes in the relative positions of each phase. This results in changes in the parameters of the decoupling equation of the TMR current sensor, inevitably leading to errors in the obtained three-phase current and affecting the monitoring of the power grid's operating status. Summary of the Invention

[0005] This invention provides a system and method for accurate measurement of overhead line current based on a MEMS sensor array, enabling accurate detection of the current in each phase of an overhead line using a TMR current sensor.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] A precise measurement system for overhead line current based on a MEMS sensor array, comprising a three-phase line device located on the overhead line;

[0008] The A-phase line device includes three TMR current sensors, one MEMS sensor, and one data processing module; the B-phase line device and the C-phase line device each include one MEMS sensor; and each phase line device includes a near-field communication unit for mutual data transmission.

[0009] All TMR current sensors and MEMS sensors are located on the same vertical plane of the overhead line.

[0010] On the vertical plane, the center O of phase A line A Located at the center O of phase B line BCenter O of C phase line C Connecting segment O B O C The midpoint;

[0011] On the vertical plane, three TMR current sensors are arranged on concentric circles of the A-phase line, and one of them is a TMR current sensor. a Located at connecting segment O B O C On the vertical line, there are two other TMR current sensors. b TMR c All are located at connecting segment O B O C They are located on the side closest to the B-phase overhead line and the C-phase overhead line, respectively;

[0012] The B-phase and C-phase line devices transmit the acceleration measured by their respective MEMS sensors to the A-phase line device via a near-field communication unit. The data processing module of the A-phase line device calculates the three-phase current of the overhead line based on the measurement data of each sensor and the relative positional relationship between each phase line when it is stationary.

[0013] Furthermore, each phase line unit also includes an energy storage management unit for providing operating power to its respective line unit.

[0014] Furthermore, the A-phase line device also includes a 4G communication unit for transmitting the calculated three-phase current back to the main station.

[0015] Furthermore, the data processing module calculates the three-phase current using the following expression:

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024] ,

[0025] In the formula, These are the currents for phases A, B, and C, respectively. TMR a TMR b TMR c The measured magnetic field strength, All are intermediate variables;

[0026] For TMR a TMR b TMR c The radius of the concentric circles, This is the original set distance between the middle A-phase line and the B / C-phase lines on both sides of the overhead line when it is stationary. These are the horizontal and vertical displacement distances of phase A line, respectively. These are the horizontal and vertical displacement distances of phase B line, respectively. These are the horizontal and vertical displacement distances of phase C, respectively. The horizontal and vertical displacement distances of each phase are calculated from the horizontal and vertical accelerations measured by the MEMS sensors on their respective line devices.

[0027] Furthermore, the horizontal and vertical accelerations measured by the MEMS sensors are used to calculate the horizontal and vertical displacement distances of the line in question, specifically:

[0028]

[0029]

[0030] In the formula, These represent the initial positions of the conductor in the horizontal and vertical directions, respectively. Let be the initial velocities of the conductors in the horizontal and vertical directions, respectively, and ensure that the three-phase conductors are in a stable, stationary state when the sensors are installed, i.e., satisfying: , , , ; These represent the lines at the [number]th [position]. Each division time Horizontal and vertical acceleration; For the first Each time interval is divided into segments.

[0031] A method for accurately measuring overhead line current based on a MEMS sensor array is provided, applied to the aforementioned system for accurately measuring overhead line current based on a MEMS sensor array. The method for accurately measuring overhead line current includes:

[0032] The three TMR current sensors and MEMS sensors in the A-phase line device transmit their measured magnetic field data and acceleration data to the data processing module.

[0033] The MEMS sensors in the B-phase and C-phase line devices transmit their measured acceleration data to the data processing module of the A-phase line device via the near-field communication unit.

[0034] The data processing module of the A-phase line device calculates the three-phase current of the overhead line based on all received magnetic field data and acceleration data, combined with the mutual positional relationship set between each phase line in the static state.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) This invention effectively solves the problem of error in the measurement of current by the TMR current sensor array when the overhead line gallops, and meets the need for real-time accurate monitoring of the current when the overhead line gallops. The current detection has high reliability and accuracy.

[0037] (2) The present invention performs dynamic array-type measurement of overhead line current, which can more accurately monitor the power grid operation status and maintain the safe and stable operation of the power grid;

[0038] (3) The method of the present invention not only effectively solves the problem of accurate detection of overhead line current by TMR current sensor, but also provides data for abnormal galloping monitoring of transmission line by acceleration MEMS sensor. It can achieve dual monitoring purpose with a single installation, and the dual data fusion monitoring has higher reliability and reduces the false judgment rate of line fault.

[0039] (4) This invention does not require disconnecting the line for invasive measurement and can be installed while energized, thus avoiding the safety risks that may be caused by changing the line once. Attached Figure Description

[0040] Figure 1 This is a diagram showing the locations of the three TMR current sensors in the measurement system described in this application embodiment on a three-phase overhead line;

[0041] Figure 2 This is a schematic diagram showing the current direction and the magnetic field direction of each phase line in the measurement system described in the embodiments of this application;

[0042] Figure 3 It is a coordinate system established with the center of the cross-section of each phase line as the origin;

[0043] Figure 4 These are the spatial coordinates of the overhead line after displacement in the embodiments of this application. Detailed Implementation

[0044] The embodiments of the present invention will be described in detail below. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operation processes to further explain the technical solutions of the present invention.

[0045] Example 1

[0046] This embodiment provides a precise overhead line current measurement system based on a MEMS sensor array, comprising a three-phase line device located on an overhead line; the A-phase line device includes one energy storage management unit, three TMR current sensors, one MEMS sensor, one near-field communication unit, one data processing module, and one 4G communication unit; the B-phase line device includes one energy storage management unit, one MEMS sensor, and one near-field communication unit; the C-phase line device includes one energy storage management unit, one MEMS sensor, and one near-field communication unit. The MEMS sensor in this invention is used to measure acceleration.

[0047] like Figure 1 As shown, all TMR current sensors and MEMS sensors are located on the same vertical plane of the overhead line; on this vertical plane, the center O of phase A is... A Located at the center O of phase B line B Center O of C phase line C Connecting segment O B O C The midpoint; and on the vertical plane, three TMR current sensors are arranged on concentric circles of the A-phase line, and one of the TMR current sensors is a TMR a Located at connecting segment O B O C On the vertical line, there are two other TMR current sensors. b TMR c All are located at connecting segment O B O C They are located on the side closest to the B-phase overhead line and the C-phase overhead line, respectively.

[0048] The B-phase and C-phase line devices transmit the acceleration measured by their respective MEMS sensors to the A-phase line device via a near-field communication unit. The data processing module of the A-phase line device calculates the three-phase current of the overhead line based on the measurement data of each sensor and the relative positional relationship between each phase line when it is stationary.

[0049] The 4G communication unit in the A-phase line device is used to ultimately transmit the calculated three-phase current of the overhead line back to the main station.

[0050] The following is a detailed derivation of the expression for calculating the three-phase current of the overhead line by the data processing module.

[0051] 1. Construct the TMR measurement array decoupling equation for a three-phase overhead line in a static state (i.e., in a fixed position).

[0052] For a three-phase overhead line, phases A, B, and C are placed parallel to each other at equal intervals. The distance between the center point of phase A and the center points of phases B and C is L. Consider the line connecting the center points of phases A, B, and C as the x-axis. With the center point of phase A as the origin, draw the perpendicular line to the x-axis, which is the y-axis. Then the coordinates of the center points of phases A, B, and C are O... A (0,0), O B (-L, 0), O C (L, 0), TMR a TMR b TMR c The three TMR sensors are placed at coordinates (0, d), (-d, 0), and (d, 0) respectively, with the magnetic field sensing direction of all three sensors perpendicularly upwards. Figure 1 As shown.

[0053] Assume that at a certain point in time, the direction of the current in the three-phase line is as follows: Figure 2 As shown (A / C phases exit the paper, B phase enters the paper), according to Ampere's law, the directions of the magnetic fields generated by the three-phase currents at the three TMR sensors can be obtained respectively.

[0054] Based on the vector sum of the magnetic field strengths, the expression for the coupled magnetic field can be obtained as follows:

[0055]

[0056] in, , , They are TMR a TMR b TMR c The strength of the coupled magnetic field can be obtained from the output value of the TMR sensor and is a known quantity; , , (X=A / B / C) represent the X-phase lines at the TMR. a TMR b TMR c The magnetic field strength generated at the location can be A, B, or C.

[0057] For the magnetic field generated by the A-phase current, due to its TMR a The direction of the magnetic field strength generated at that location is the same as that of TMR. a If the magnetic field sensitivity direction is perpendicular, then the A-phase current in the TMR a There is no output value at this location, i.e. Therefore, according to the Biot-Savart law, the magnetic field strength generated by the A-phase current at the three TMR sensors is:

[0058]

[0059] For the magnetic field generated by the B-phase current, the magnetic field strength generated by the B-phase current at the three TMR sensors can be obtained by the Biot-Savart law:

[0060]

[0061] Similarly, the magnetic field strength generated by the C-phase current at the three TMR sensors can be obtained as follows:

[0062]

[0063] In summary, we can conclude that:

[0064]

[0065] in , , Since L and d are known quantities that can be measured by the sensor, they can be solved from the results. , , This achieves decoupling and enables the measurement of current in three-phase fixed-position overhead lines.

[0066] 2. Correct the dynamic position of the three-phase overhead line based on MEMS sensors.

[0067] The galloping of overhead power lines is a gradual, nonlinear process. Initially, the conductor remains stable. Under the influence of external factors, the conductor will oscillate within a small range. Due to the accumulation of wind energy and the negative damping of the air, the amplitude will gradually increase, forming an elliptical trajectory. Finally, under the influence of system damping, it will gradually stabilize.

[0068] Taking the center of the cross-section of the overhead line conductor as the origin, the direction parallel to the ground is the x-axis (horizontal direction), and the direction perpendicular to the ground is the y-axis (vertical direction), such as... Figure 3 As shown.

[0069] Conductor galloping is an irregular motion that can occur at any moment; therefore, triaxial acceleration data acquired by accelerometer MEMS sensors is needed to analyze the real-time displacement of the conductor. The x and y axes are as follows: Figure 3 Once set, the z-axis represents the direction of the current in the conductor. When the line vibrates, the displacement mainly occurs in the xy plane, so the influence of the z-axis direction can be ignored.

[0070] In the xy plane, the irregular displacement of the line can be decomposed into the sum of displacement vectors in the horizontal and vertical directions. Therefore, the displacements in the x and y directions can be solved separately.

[0071] Based on the measurement results from the MEMS sensor, write the displacement function of the wire in the x-axis direction. for:

[0072]

[0073] in, This represents the initial velocity of the line in the x-axis direction; This represents the initial position of the line along the x-axis; a x This represents the horizontal acceleration measured by the MEMS sensor.

[0074] Similarly, the displacement function in the y-axis direction for:

[0075]

[0076] in, This represents the initial velocity of the line in the y-axis direction; The horizontal acceleration output by the accelerometer; The initial position of the line in the y-axis direction; a y This represents the vertical acceleration measured by the MEMS sensor.

[0077] The velocity and displacement functions mentioned above are continuous functions. The acceleration signals collected by the accelerometer are all analog quantities. However, after the analog quantity is converted into a digital quantity, it becomes discrete. By using differentiation, time can be divided into several small time intervals. During these time intervals, the acceleration changes very little. The acceleration can be regarded as a constant value. Then, by using the constant value of this time interval, a portion of the acceleration can be calculated. Summing these values ​​gives the velocity at any given time.

[0078] Taking the x-axis, i.e. the horizontal direction, as an example, a time interval [0, t] is divided into several times: t0, t1, ..., t n The velocities at each time point are v0, v1, ..., v n Then we can obtain n equal time intervals: , … During the time period [t] i-1 ,t i [Uptake Time] Then we can get:

[0079] i=1,2,…,n

[0080] in, for The velocity over a time interval. From this, we can obtain the velocity at any time along the x-axis. speed for:

[0081]

[0082] Then at any time along the x-axis displacement for:

[0083]

[0084] Similarly, we can obtain any time along the y-axis. displacement for:

[0085]

[0086] During actual sensor installation, it is ensured that the three-phase conductors are in a stable and stationary state, such as... Figure 1 As shown, the center point of the cross-section of each phase line is its own displacement coordinate system ( Figure 3 The origin of the displacement formula is the initial velocity in the above displacement formula. , and initial position , It can be set to 0.

[0087] The frequency of overhead power line oscillation is between 0.1Hz and 3Hz. The sampling frequency of the acceleration MEMS sensor is set to f. s If the Hz is constant, then the sampling period is f. s -1 Based on the acceleration value output by the MEMS acceleration sensor, the position of the three-phase line at any given time can be calculated using the displacement formula. Now, let's assume the position of the three-phase line at a certain moment is as follows: Figure 4 As shown.

[0088] Figure 4 In the middle, s xa s ya These represent the horizontal and vertical displacement distances of phase A line, respectively. xb s yb These represent the horizontal and vertical displacement distances of phase B line, respectively. xc s yc These represent the horizontal and vertical displacement distances of phase C line, respectively.

[0089] At this point, the coordinates of the three-phase lines A, B, and C can be obtained as follows (s xa s ya ), (-L+s xb syb (L+s) xc s yc ); TMR a TMR b TMR c The coordinates are (-d+s) xa s ya ), (s xa d+s ya ), (d+s xa s ya Therefore, the displacement obtained by using the acceleration value output by the acceleration MEMS sensor can help correct the real-time coordinate position of each circuit and the TMR current sensor, and thus correct the magnetic field strength formula of the three TMR current sensors.

[0090] After the correction, the relative positions of the A-phase line and the three TMR current sensors remain unchanged, so the magnetic field strength generated at the three TMR current sensors remains unchanged.

[0091]

[0092] After correction, the magnetic field strength generated by the B-phase line at the three TMR current sensors is:

[0093]

[0094] After correction, the magnetic field strength generated by the C-phase line at the three TMR current sensors is:

[0095]

[0096] In summary, the corrected expression for the magnetic field strength can be obtained as follows:

[0097]

[0098] make: ,

[0099] ,

[0100] ,

[0101] ,

[0102] ,

[0103] ,

[0104] ,

[0105] ,

[0106] The above expression can then be represented as:

[0107]

[0108] The three-phase current decoupling matrix is ​​then:

[0109]

[0110] In summary, by using a TMR current sensor and an accelerometer MEMS sensor, three-phase current detection was achieved when an overhead line was galloping.

[0111] Example 2

[0112] This embodiment provides a method for accurate measurement of overhead line current based on a MEMS sensor array, applied to the accurate measurement system for overhead line current based on a MEMS sensor array described in Embodiment 1. The method for accurate measurement of overhead line current includes:

[0113] The three TMR current sensors and MEMS sensors in the A-phase line device transmit their measured magnetic field data and acceleration data to the data processing module.

[0114] The MEMS sensors in the B-phase and C-phase line devices transmit their measured acceleration data to the data processing module of the A-phase line device via the near-field communication unit.

[0115] The data processing module of the A-phase line device calculates the three-phase current of the overhead line based on all received magnetic field data and acceleration data, combined with the mutual positional relationship set between each phase line in the static state.

[0116] The expression and derivation process for calculating the three-phase current of the overhead line are the same as in Example 1, and will not be repeated in this example.

[0117] The above embodiments are preferred embodiments of this application. Those skilled in the art can make various changes or improvements based on them. Without departing from the overall concept of this application, these changes or improvements should fall within the scope of protection claimed in this application.

Claims

1. A precise measurement system for overhead line current based on a MEMS sensor array, characterized in that, This includes three-phase line equipment located on overhead lines; The A-phase line device includes three TMR current sensors, one MEMS sensor, and one data processing module; the B-phase line device and the C-phase line device each include one MEMS sensor; and each phase line device includes a near-field communication unit for mutual data transmission. All TMR current sensors and MEMS sensors are located on the same vertical plane of the overhead line. On the vertical plane, the center O of phase A line A Located at the center O of phase B line B Center O of C phase line C Connecting segment O B O C The midpoint; On the vertical plane, three TMR current sensors are arranged on concentric circles of the A-phase line, and one of them is a TMR current sensor. a Located at connecting segment O B O C On the vertical line, there are two other TMR current sensors. b TMR c All are located at connecting segment O B O C They are located on the side closest to the B-phase overhead line and the C-phase overhead line, respectively; The B-phase and C-phase line devices transmit the acceleration measured by their respective MEMS sensors to the A-phase line device through the near-field communication unit; the data processing module of the A-phase line device calculates the three-phase current of the overhead line based on the measurement data of each sensor and the relative positional relationship between each phase line when it is stationary. The expression for calculating the three-phase current by the data processing module is as follows: ； ； ； ； ； ； ； ； ； In the formula, These are the currents for phases A, B, and C, respectively. TMR a TMR b TMR c The measured magnetic field strength, All are intermediate variables; For TMR a TMR b TMR c The radius of the concentric circles, This is the original set distance between the middle A-phase line and the B / C-phase lines on both sides of the overhead line when it is stationary. These are the horizontal and vertical displacement distances of phase A line, respectively. These are the horizontal and vertical displacement distances of phase B line, respectively. These are the horizontal and vertical displacement distances of phase C, respectively. The horizontal and vertical displacement distances of each phase are calculated from the horizontal and vertical accelerations measured by the MEMS sensors on their respective line devices. Specifically: ； ； In the formula, These represent the initial positions of the conductor in the horizontal and vertical directions, respectively. Let be the initial velocities of the conductors in the horizontal and vertical directions, respectively, and ensure that the three-phase conductors are in a stable, stationary state when the sensors are installed, i.e., satisfying: , , , ; These represent the lines at the [number]th ... Each division time Horizontal and vertical acceleration; For the first Each time interval is divided into segments.

2. The overhead line current precision measurement system based on MEMS sensor array according to claim 1, characterized in that, Each phase line unit also includes an energy storage management unit for providing operating power to its respective line unit.

3. The overhead line current precision measurement system based on MEMS sensor array according to claim 1, characterized in that, The A-phase line device also includes a 4G communication unit, which is used to transmit the calculated three-phase current back to the main station.

4. A method for accurate measurement of overhead line current based on a MEMS sensor array, characterized in that, The overhead line current precision measurement method, applied to the MEMS sensor array-based overhead line current precision measurement system according to any one of claims 1-3, comprises: The three TMR current sensors and MEMS sensors in the A-phase line device transmit their measured magnetic field data and acceleration data to the data processing module. The MEMS sensors in the B-phase and C-phase line devices transmit their measured acceleration data to the data processing module of the A-phase line device via the near-field communication unit. The data processing module of the A-phase line device calculates the three-phase current of the overhead line based on all received magnetic field data and acceleration data, combined with the mutual positional relationship set between each phase line in the static state. The expression for calculating the three-phase current by the data processing module is as follows: ； ； ； ； ； ； ； ； ； In the formula, These are the currents for phases A, B, and C, respectively. TMR a TMR b TMR c The measured magnetic field strength, All are intermediate variables; For TMR a TMR b TMR c The radius of the concentric circles, This is the original set distance between the middle A-phase line and the B / C-phase lines on both sides of the overhead line when it is stationary. These are the horizontal and vertical displacement distances of phase A line, respectively. These are the horizontal and vertical displacement distances of phase B line, respectively. These are the horizontal and vertical displacement distances of phase C, respectively. The horizontal and vertical displacement distances of each phase are calculated from the horizontal and vertical accelerations measured by the MEMS sensors on their respective line devices. Specifically: ； ； In the formula, These represent the initial positions of the conductor in the horizontal and vertical directions, respectively. Let be the initial velocities of the conductors in the horizontal and vertical directions, respectively, and ensure that the three-phase conductors are in a stable, stationary state when the sensors are installed, i.e., satisfying: , , , ; These represent the lines at the [number]th ... Each division time Horizontal and vertical acceleration; For the first Each time interval is divided into segments.

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