System and method for accurately measuring current of overhead line based on MEMS sensor array

Abstract

The invention discloses an overhead line current accurate measurement system and method based on an MEMS sensor array. The system comprises a three-phase line device located on an overhead line. The A-phase line device comprises three TMR sensors, one MEMS sensor and one data processing module, and the B-phase line device and the C-phase line device respectively 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 the concentric circle of the A-phase line, the sensor TMRa is located on the vertical line of the center connecting line of the BC-phase line, and the sensors TMRb and TMRc are both located on the center connecting line of the BC-phase line; and 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 relation set when each phase line is in a static state. According to the invention, accurate detection of each phase current of the overhead line by using the TMR is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of current measurement, and in particular relates to a system and method for accurately measuring overhead line current based on a MEMS sensor array. Background Art

[0002] With the rapid development of my country's power system, power technology is gradually moving towards automation, convenience and maintenance-free. The current detection requirements for various power monitoring equipment, protection equipment and metering equipment in the power system are increasing day by day. More accurate and convenient current signal measurement methods can help to more accurately evaluate the state of the power grid.

[0003] The traditional use scenario of TMR current sensor is generally used to measure copper busbar current. In this case, the copper busbar position and TMR current sensor position are fixed, so the decoupling equation of TMR current sensor remains unchanged. In order to better monitor the operation status of the power grid and protect the safe and stable operation of the power grid, TMR current sensor can be used for current detection of overhead lines. Similarly, decoupling is used to eliminate the magnetic field interference between phases to achieve three-phase current measurement.

[0004] However, the key difficulty lies in the fact that overhead lines will dance irregularly in actual environments, and the relative positions of each phase will change, causing the parameters in the decoupling equation of the TMR current sensor to change. The obtained three-phase current will inevitably produce errors, affecting the monitoring of the power grid operation status. Summary of the invention

[0005] The present invention provides an overhead line current accurate measurement system and method based on a MEMS sensor array, which realizes accurate detection of each phase current of the overhead line by using a TMR current sensor.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] An overhead line current precision measurement system based on a MEMS sensor array includes 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, and 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 the A phase line A Located at the center of phase B line O BWith C phase line center O C Connect line segment O B O C The midpoint of

[0011] 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 TMR a Located on the connecting line segment O B O C On the vertical line, the other two TMR current sensors TMR b 、TMR c Both are located on the connecting line segment O B O C and are located on the side close to the B-phase overhead line and the C-phase overhead line respectively;

[0012] The B-phase line device and the C-phase line device send 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 position relationship set between each phase line when in a static state.

[0013] Furthermore, each phase line device also includes an energy storage management unit for providing working power for the respective line device.

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

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

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024] ,

[0025] In the formula, The currents of phase A, phase B, and phase C are respectively, TMR a 、TMR b 、TMR c The measured magnetic field strength, All are intermediate variables;

[0026] TMR a 、TMR b 、TMR c The radius of the concentric circle, It is the original set distance between the middle A-phase line and the B / C-phase lines on both sides of the overhead line in the static state; are the horizontal displacement distance and vertical displacement distance of phase A line respectively, are the horizontal displacement distance and vertical displacement distance of phase B line respectively, They are the horizontal displacement distance and vertical displacement distance of the C phase line respectively. The horizontal displacement distance and vertical displacement distance of each phase line are calculated by the acceleration in the horizontal direction and the vertical direction measured by the MEMS sensors on the respective line devices.

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

[0028]

[0029]

[0030] In the formula, are the initial positions of the conductor in the horizontal and vertical directions, are the initial velocities of the conductor in the horizontal and vertical directions respectively, and the sensor is installed to ensure that the three-phase conductor is in a stable static state, that is, it satisfies: , , , ; Respectively represent the lines in The dividing moment Horizontal and vertical accelerations; For the A divided time interval.

[0031] A method for accurately measuring overhead line current based on a MEMS sensor array is applied to the above-mentioned 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 the magnetic field data and acceleration data measured by each to the data processing module;

[0033] The MEMS sensors in the B-phase line device and the C-phase line device send the acceleration data measured by each of them to the data processing module of the A-phase line device through 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 the received magnetic field data and acceleration data and the relative position relationship set between the phase lines when they are in a static state.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

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

[0037] (2) The present invention performs dynamic array measurement of overhead line current, which can more accurately monitor the operation status of the power grid 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 using TMR current sensors to accurately detect current in overhead lines, but also the acceleration MEMS sensor can provide data for abnormal vibration monitoring of transmission lines, and can achieve dual monitoring purposes with a single installation. In addition, the dual data fusion monitoring has higher reliability and reduces the misjudgment rate of line faults.

[0039] (4) The present invention does not need to disconnect the line for invasive measurement and can be installed under power, thus avoiding the safety risks that may be caused by changing the primary line. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a position diagram of three TMR current sensors in a three-phase overhead line in a measurement system according to an embodiment of the present application;

[0041] Figure 2 is a schematic diagram of the current direction of each phase circuit and the direction of the generated magnetic field in the measurement system according to the embodiment of the present 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 It is the spatial coordinate after the overhead line is displaced in the embodiment of the present application. DETAILED DESCRIPTION

[0044] The following is a detailed description of an embodiment of the present invention. This embodiment is based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process to further explain the technical solution of the present invention.

[0045] Example 1

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

[0047] like Figure 1 As shown in the figure, 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 the A phase line A Located at the center of phase B line O B With C phase line center O C Connect line segment O B O C 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 TMR a Located on the connecting line segment O B O C On the vertical line, the other two TMR current sensors TMR b 、TMR c Both are located on the connecting line segment O B O C and are located on one side close to the B-phase overhead line and the C-phase overhead line respectively.

[0048] The B-phase line device and the C-phase line device send 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 position relationship set between each phase line when in a static state.

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

[0050] The following specifically derives the expression for calculating the three-phase current of the overhead line by the data processing module.

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

[0052] For three-phase overhead lines, the A, B, and C three-phase lines are placed in parallel at equal distances, and the distance between the center point of the A phase line and the center points of the B and C two-phase lines is L; the line connecting the center points of the A, B, and C three-phase lines is regarded as the x-axis, and the center point of the A phase line is taken as the origin, and the perpendicular line to the x-axis is drawn, which is the y-axis. Then the coordinates of the center points of the A, B, and C three-phase lines are O and A (0,0),O B (-L, 0), O C (L, 0), TMR a 、TMR b 、TMR c They are placed at coordinate points (0, d), (-d, 0), and (d, 0), respectively, and the magnetic field sensitivity directions of the three TMR sensors are all vertically upward. Figure 1 shown.

[0053] Assume that at a certain time point, the current direction of the three-phase line is as follows: Figure 2 As shown (A / C phases radiate out of the paper, and B phase radiates into 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.

[0054] According to the vector sum of magnetic field strength, the coupled magnetic field expression can be obtained as:

[0055]

[0056] in, , , TMR a 、TMR b 、TMR c The coupling magnetic field strength can be output by the TMR sensor and is a known quantity; , , (X=A / B / C) are the X phase lines in TMR a 、TMR b 、TMR c The magnetic field strength generated at, X can be A, B, C.

[0057] For the magnetic field generated by phase A current, due to its TMR a The direction of the magnetic field strength generated at the location is related to TMR a The magnetic field sensitive direction is perpendicular to the A phase current in TMR. a There is no output value, that is 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 Biot-Savart law shows that the magnetic field strength generated by the B-phase current at the three TMR sensors is:

[0060]

[0061] Similarly, the magnetic field strength generated by the C-phase current at the three TMR sensors is:

[0062]

[0063] In summary, we can get:

[0064]

[0065] in , , is the quantity that can be measured by the sensor. L and d are determined as known quantities during installation, so we can solve , , , realize decoupling and complete the measurement of three-phase fixed position overhead line current.

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

[0067] The dancing of overhead lines is a nonlinear process that is gradually formed. In the initial state, the conductor remains stable. Under the influence of external factors, the conductor will swing in a small range. Due to the accumulation of wind energy and the influence of negative air damping, the amplitude will gradually increase, forming an elliptical motion trajectory, and finally gradually stabilize under the influence of system damping.

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

[0069] Wire galloping is an irregular movement that may occur at any time, so it is necessary to obtain three-axis acceleration data from the acceleration MEMS sensor to analyze the real-time displacement of the line. Figure 3 After setting, the z-axis is the direction of the conductor current. When the line dances, the displacement generated is mainly on 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, so the displacement in the x and y directions can be solved separately.

[0071] Write the displacement function of the wire in the x-axis direction according to the measurement results of the MEMS sensor for:

[0072]

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

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

[0075]

[0076] in, Indicates the initial velocity of the line in the y-axis direction; It is the horizontal acceleration output by the acceleration sensor; is the initial position of the line in the y-axis direction; a y Represents the vertical acceleration measured by the MEMS sensor.

[0077] The above velocity function and displacement function are both continuous functions. The acceleration signals collected by the acceleration sensor are all analog quantities, but they are discrete after being converted into digital quantities. Differentiation can be used to divide time into several small time periods. During this time period, the acceleration changes very little. The acceleration can be regarded as a constant. The partial acceleration can be calculated using the constant value of this time period, and the sum is the velocity at any time.

[0078] Taking the x-axis (horizontal direction) as an example, a time period [0, t] is divided into several equal moments: t0, t1, ..., t n The speeds at each moment are v0, v1, ..., v n , then we can get n equal time intervals: , , …, In the time period [t i-1 ,t i ]Upload time , we can get:

[0079] ; i = 1, 2, …, n

[0080] in, for The speed of the time period. From this, we can get the speed at any time in the x-axis direction. Speed for:

[0081]

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

[0083]

[0084] Similarly, we can get the value of Displacement for:

[0085]

[0086] When installing the sensor, it is necessary to ensure that the three-phase conductors are in a stable and static state. Figure 1 As shown, the center point of the cross section of each phase line is its own displacement coordinate system ( Figure 3 ), so the initial velocity in the above displacement formula is , and initial position , Can be set to 0.

[0087] The frequency of overhead line vibration is between 0.1Hz and 3Hz. The sampling frequency of the acceleration MEMS sensor is set to f s Hz, then the sampling period is f s -1 s, according to the acceleration value output by the acceleration MEMS sensor, the position of the three-phase line at any time can be calculated by the displacement formula. Now assume that the position of the three-phase line at a certain moment is as follows: Figure 4 shown.

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

[0089] At this time, the coordinates of the three-phase lines A, B, and C are (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 the acceleration value output by the acceleration MEMS sensor can help correct the real-time coordinate position of each line and TMR current sensor, and then correct the magnetic field strength formula of the three TMR current sensors.

[0090] After the correction, the positions of the A-phase line and the three TMR current sensors remain unchanged, so the magnetic field strengths generated at the three TMR current sensors remain 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 of magnetic field intensity is:

[0097]

[0098] make: ,

[0099] ,

[0100] ,

[0101] ,

[0102] ,

[0103] ,

[0104] ,

[0105] ,

[0106] Then the above expression can be expressed as:

[0107]

[0108] Then the three-phase current decoupling matrix is:

[0109]

[0110] In summary, by using TMR current sensors and acceleration MEMS sensors, three-phase current detection is achieved when the overhead line is in a galloping state.

[0111] Example 2

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

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

[0114] The MEMS sensors in the B-phase line device and the C-phase line device send the acceleration data measured by each of them to the data processing module of the A-phase line device through 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 the received magnetic field data and acceleration data and the relative position relationship set between the phase lines when they are in a static state.

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

[0117] The above embodiments are preferred embodiments of the present application. Ordinary technicians in this field can also make various changes or improvements on this basis. Without departing from the overall concept of the present application, these changes or improvements should fall within the scope of protection required by the present application.

Claims

1. An overhead line current accurate measurement system based on MEMS sensor array, characterized in that: It includes three-phase line installations located on overhead lines; The A-phase line device includes three TMR current sensors, one MEMS sensor and one data processing module, and 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 the A phase line A Located at the center of phase B line O B With C phase line center O C Connect line segment O B O C The midpoint of 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 TMR a Located on the connecting line segment O B O C On the vertical line, the other two TMR current sensors TMR b 、TMR c Both are located on the connecting line segment O B O C and are located on the side close to the B-phase overhead line and the C-phase overhead line respectively; The B-phase line device and the C-phase line device send 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 position relationship set between each phase line when in a static state.

2. The overhead line current accurate measurement system based on MEMS sensor array according to claim 1 is characterized in that: Each phase line device also includes an energy storage management unit for providing working power to the respective line device.

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

4. The overhead line current accurate measurement system based on MEMS sensor array according to claim 1 is characterized in that: The expression used by the data processing module to calculate the three-phase current is: ； ； ； ； ； ； ； ； ； In the formula, The currents of phase A, phase B, and phase C are respectively, TMR a 、TMR b 、TMR c The measured magnetic field strength, All are intermediate variables; TMR a 、TMR b 、TMR c The radius of the concentric circle, It is the original set distance between the middle A-phase line and the B / C-phase lines on both sides of the overhead line in the static state; are the horizontal displacement distance and vertical displacement distance of phase A line respectively, are the horizontal displacement distance and vertical displacement distance of phase B line respectively, They are the horizontal displacement distance and vertical displacement distance of the C phase line respectively. The horizontal displacement distance and vertical displacement distance of each phase line are calculated by the acceleration in the horizontal direction and the vertical direction measured by the MEMS sensors on the respective line devices.

5. The overhead line current accurate measurement system based on MEMS sensor array according to claim 1 is characterized in that: The horizontal and vertical accelerations measured by the MEMS sensor are used to calculate the horizontal and vertical displacement distances of the line, specifically: ； ； In the formula, are the initial positions of the conductor in the horizontal and vertical directions, are the initial velocities of the conductor in the horizontal and vertical directions respectively, and the sensor is installed to ensure that the three-phase conductor is in a stable static state, that is, it satisfies: , , , ; Respectively represent the lines in The dividing moment Horizontal and vertical accelerations; For the A divided time interval.

6. A method for accurately measuring overhead line current based on a MEMS sensor array, characterized in that: The overhead line current accurate measurement system based on the MEMS sensor array as described in any one of claims 1 to 3, wherein the overhead line current accurate measurement method comprises: The three TMR current sensors and MEMS sensors in the A-phase line device transmit the magnetic field data and acceleration data measured by each to the data processing module; The MEMS sensors in the B-phase line device and the C-phase line device send the acceleration data measured by each of them to the data processing module of 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 all the received magnetic field data and acceleration data and the relative position relationship set between the phase lines when they are in a static state.

7. The method for accurately measuring overhead line current based on a MEMS sensor array according to claim 6, characterized in that: The expression used by the data processing module to calculate the three-phase current is: ； ； ； ； ； ； ； ； ； In the formula, The currents of phase A, phase B, and phase C are respectively, TMR a 、TMR b 、TMR c The measured magnetic field strength, All are intermediate variables; TMR a 、TMR b 、TMR c The radius of the concentric circle, It is the original set distance between the middle A-phase line and the B / C-phase lines on both sides of the overhead line in the static state; are the horizontal displacement distance and vertical displacement distance of phase A line respectively, are the horizontal displacement distance and vertical displacement distance of phase B line respectively, They are the horizontal displacement distance and vertical displacement distance of the C phase line respectively. The horizontal displacement distance and vertical displacement distance of each phase line are calculated by the acceleration in the horizontal direction and the vertical direction measured by the MEMS sensors on the respective line devices.

8. The overhead line current accurate measurement system based on MEMS sensor array according to claim 7, characterized in that: The horizontal and vertical accelerations measured by the MEMS sensor are used to calculate the horizontal and vertical displacement distances of the line, specifically: ； ； In the formula, are the initial positions of the conductor in the horizontal and vertical directions, are the initial velocities of the conductor in the horizontal and vertical directions respectively, and the sensor is installed to ensure that the three-phase conductor is in a stable static state, that is, it satisfies: , , , ; Respectively represent the lines in The dividing moment Horizontal and vertical accelerations; For the A divided time interval.

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