CN114487543A - Switch cabinet bus current monitoring method - Google Patents
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Abstract
The invention relates to a bus current monitoring method of a switch cabinet, which comprises a state diagnosis monitoring system, wherein the state diagnosis monitoring system comprises a temperature monitoring unit, a current monitoring unit, a calculating unit and a diagnosis unit, the temperature monitoring unit comprises actually-measured temperature sensors on the outer surfaces of sub-chambers and actually-measured temperature sensors of the environment of a cabinet body, the current monitoring unit is connected with a plurality of intelligent sensors, each intelligent sensor is connected with a plurality of magnetic sensors, each magnetic sensor comprises a TMR (triple reference magneto resistance) effect sensor and a magnetostatic shield, the TMR magneto resistance effect sensors are respectively arranged on a three-phase bus of the switch cabinet, and each intelligent sensor comprises a data sensing and acquisition module, a compensation and correction module, a data processing module, a data network communication module, a human-computer interface, a task management and scheduling module and a power supply module; the invention has the advantages of simple structure, no magnetic field interference, accurate measurement result, high precision and low cost.
Description
Technical Field
The invention belongs to the technical field of switch cabinet monitoring, and particularly relates to a switch cabinet bus current monitoring method.
Background
Along with the continuous propulsion of smart power grids construction, the electric wire netting has produced very big demand to various can realize detecting and control electrical equipment, and the prerequisite that realizes smart power grids real-time supervision and control is just to have advanced sensing and measurement technique as the support, among the prior art, the current measurement of conductors such as cubical switchboard or looped netowrk cabinet cable outgoing line all adopts two kinds of measuring methods of contact or non-contact, wherein, the contact exists and needs to carry out electrical connection with the conductor of being surveyed, the line structure of former conductor has not only been destroyed to this kind of mode, make cubical switchboard or looped netowrk cabinet cable outgoing line have uncertain operation safety risk, it is more important: great potential safety hazard is caused to the personnel of the working personnel in the contact type measurement process; in the existing non-contact measuring equipment, due to mutual influence of magnetic fields among the three currents, the defects of large magnetic field interference and inaccurate measuring result exist; therefore, it is very necessary to provide a method for monitoring the bus current of the switch cabinet, which has the advantages of simple structure, no magnetic field interference, accurate measurement result, high precision and low cost.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides the switch cabinet bus current monitoring method which is simple in structure, free from magnetic field interference, accurate in measurement result, high in precision and low in cost.
The purpose of the invention is realized as follows: a bus current monitoring method of a switch cabinet comprises a state diagnosis monitoring system, wherein the state diagnosis monitoring system comprises a temperature monitoring unit, a current monitoring unit, a calculating unit and a diagnosis unit, the temperature monitoring unit comprises a sub-chamber outer surface actual measurement temperature sensor and a cabinet body environment actual measurement temperature sensor, the current monitoring unit is connected with a plurality of intelligent sensors, each intelligent sensor is connected with a plurality of magnetic sensors, the magnetic sensors comprise TMR (triple magneto resistance) effect sensors and static magnetic shields, the TMR effect sensors are respectively arranged on a three-phase bus of the switch cabinet, each intelligent sensor comprises a data sensing and collecting module, a compensation and correction module, a data processing module, a data network communication module, a human-computer interface, a task management and scheduling module and a power supply module, the TMR effect sensors are used for detecting the current of each phase bus of the switch cabinet at the installation position of the TMR effect sensors, and the detected current data is transmitted to the corresponding intelligent sensor, the intelligent sensor transmits the collected detection data transmitted by each magnetic sensor to the current monitoring unit, and the current monitoring unit transmits the received detection data to the state diagnosis monitoring system.
The method comprises the following steps:
step 1): respectively installing magnetic sensors close to the phase A, the phase B and the phase C busbars;
step 2): establishing a current measurement magnetic sensor array topological model;
step 3): measuring the current based on the linearity and the superposition of the magnetic field;
step 4): calculating an inductance matrix of the corresponding magnetic sensor current measurement;
step 5): the actual current value on the bus is obtained by measuring the voltage output value of the magnetic sensor;
step 6): the magnetic sensor uploads the data to the intelligent sensor, and the data are summarized by the intelligent sensor and then uploaded to the current monitoring unit;
step 7): performing analog simulation on the distribution condition of the magnetic field in the switch cabinet by using ANSYS;
step 8): establishing a related AC/DC measurement mathematical model according to the magnetic field distribution;
step 9): the calculating unit analyzes and calculates a current value through the acquired current data;
step 10): the diagnosis unit verifies the magnetic sensor array topology model according to the current values calculated in the step 9), and diagnoses the current equipment state according to the summarized data information uploaded in the step 6).
The temperature monitoring unit collects temperature signals through actually measured temperature sensors on the outer surfaces of the sub-chambers and actually measured temperature sensors on the environment of the cabinet body, and transmits received signal data to the state diagnosis monitoring system to calculate the temperature change trend, namely temperature rise, of the processed temperature data.
The selectable power supply modes of the power supply module comprise a battery power supply mode, a laser energy supply mode, a solar power supply mode, an electromagnetic induction power taking mode and an energy collecting chip function mode.
The TMR magnetoresistive effect sensor is characterized in that the current is detected by using a magnetic field generated by the current in an electrically insulated state, and when the current I exists in a conductorpWhen the sensor is used, a magnetic field proportional to current is generated around the conductor, and the TMR magnetoresistive effect sensor detects the magnetic field intensity of the magnetic field to generate an electric signal output V in linear relation with the magnetic fieldoutThe conversion from the magnetic signal for measurement to the electric signal is completed, and the principle of the TMR magnetoresistive effect sensor for measuring the current specifically comprises the following steps: when the switch cabinet passes through power frequency current, a rotating magnetic field is usually generated in the cabinet, the bus bar in the cabinet is used as a center, the magnetic field intensity of a certain point close to the bus bar is approximately in direct proportion to the current flowing on the bus bar, and is approximately in inverse proportion to the vertical distance from the point to the bus bar, the magnetic field intensity is expressed as B ^ i/d, namely the magnetic field intensity of the point where the TMR magnetoresistance effect sensor is located is expressed as: k represents1I/d (1), wherein d is the vertical distance from the TMR magnetoresistive sensor to the bus bar, i is the current flowing on the bus bar, and k is1As a constant, in the linear measurement range, the output voltage value of the TMR magnetoresistive effect sensor and the input magnetic field strength satisfy a linear relationship, and therefore, the output voltage can be expressed as u ═ k2B (2) where u is the maximum value of the output voltage of the TMR magnetoresistive sensor, and k2In order to measure the constant, the combination of the formula (1) and the formula (2) shows that the actual current value and the output voltage value of the TMR magnetoresistive effect sensor necessarily satisfy a linear relation: where c is a measurable constant coefficient, which can be determined by current calibration, and the value of c in the input/output relation of the TMR magnetoresistive sensor is determinedAnd the output voltage is correspondingly processed to obtain the current magnitude, so that the current is measured.
The TMR magneto-resistive effect sensor adopts a push-pull Wheatstone full-bridge structure which comprises two groups of non-shielding high-sensitivity TMR elements with opposite magnetic sensitivity directions.
The electrostatic shield is made of permalloy high-permeability magnetic materials based on the Biao-Saval law and the ampere loop theorem, an interference magnetic field is separated from a protected area or element, and a static magnetic field or low frequency less than 100kHz is prevented from entering the area needing protection or influencing a protected magnetic sensitive element.
The establishing of the current measurement magnetic sensor array topology model in the step 2) is specifically as follows: three-phase busbars of a switch cabinet can be regarded as parallel copper bars, the position relation between the copper bars and magnetic sensors can be expressed by taking the end point of the left edge of the section of the A-phase busbar as the original point of a three-dimensional coordinate system (x, y and z), assuming that the width of each-phase busbar is c and the thickness of each-phase busbar is d, assuming that the distance between every two adjacent-phase busbars is L, installing the magnetic sensors close to each-phase busbar, assuming that the distance between every corresponding magnetic sensor and the corresponding-phase busbar is b and the distance to the left edge of the corresponding-phase busbar is a, therefore, the two parameters of a and b determine the topological structure of the magnetic sensor array, and the distance L between the busbars, the actual width d and the thickness of each-phase busbar can be measured according to the switch cabinet in practical application.
The step 3) of measuring the current based on the linearity and the superposition of the magnetic field specifically comprises the following steps: the basic premise of measuring the current by applying the magnetic sensor array is that the linearity and the superposition of a magnetic field comprise the linearity superposition on space and frequency, the linearity superposition on the space refers to the linear relation between the magnetic field intensity generated by a point appointed by the current in the space and the intensity of the current, and for multi-phase current, the magnetic field intensity of the point is the vector superposition of the magnetic field intensity generated by each phase current at the point; frequency linearity means that for a given point in space, the magnetic induction coefficient of a current with a specific frequency at the point is a certain value, and for a current with known frequency and phase, the induced magnetic field generated at the specific point is in the same frequency and phase with the induced magnetic field, that is, the magnetic field at the specific point is the superposition of the induced magnetic fields of the frequency components of a given current at the point.
The calculating of the inductance matrix corresponding to the current measurement of the magnetic sensor in step 4) and the measuring of the voltage output value of the magnetic sensor in step 5) are performed to obtain an actual current value on the bus, specifically: A. b, C magnetic field distribution is around the three-phase bus, the magnetic field intensity at any point in the bus indoor space is the result of the vector superposition of A, B, C three-phase magnetic fields, the magnetic field intensity measured by the magnetic sensor is the vector sum of the magnetic field generated by the three-phase bus at the point, when the perpendicular distance d from the magnetic sensor to the bus is fixed, the output value of the TMR magnetoresistive effect sensor is u-c.i, the three-phase current symmetry is assumed, therefore, the voltage output value measured by each magnetic sensor is:
in the formula, cijThe voltage value of the sensor I at the bus bar j is represented, and the above formula is written into a matrix form:
in the formula
The inductance matrix for measuring the current of the magnetic sensor can be obtained by collecting the output of the three-phase magnetic sensor by individually electrifying the magnetic sensor phase by phase, calculating the corresponding inductance, for example, firstly, individually electrifying the A-phase busbar, B, C disconnecting two phases, and calculating c according to the voltage output signal of the three-phase magnetic sensor11、c12、c13The values of the other two groups of vectors can be calculated in the same way, and finally the value of the coefficient matrix C is obtained; after obtaining the coefficient matrix C, the actual current value on the bus is obtained by measuring the voltage output value of the magnetic sensor,
since the coefficient matrix needs to ensure the reversibility, the reversibility is ensured by adopting a method of multiplying the coefficient matrix by a transposed matrix thereof:
i ═ CT·C]-1CT·u。
The invention has the beneficial effects that: the invention relates to a method for monitoring bus current of a switch cabinet, which comprises the steps of respectively installing magnetic sensors close to phase A, phase B and phase C busbars, establishing a current measurement magnetic sensor array topological model, measuring current based on the linearity and the superposition of a magnetic field, calculating an induction coefficient matrix of the corresponding magnetic sensor for current measurement, the actual current value on the bus is obtained by measuring the voltage output value of the magnetic sensor, the magnetic sensor uploads the data to the intelligent sensor, the collected signals are uploaded to a current monitoring unit through an intelligent sensor, ANSYS is utilized to simulate the magnetic field distribution condition in the switch cabinet, establishing a related AC/DC measurement mathematical model according to magnetic field distribution, analyzing and calculating a current value through acquired current data by a calculation unit, verifying a magnetic sensor array topological model according to the calculated current value by a diagnosis unit, and diagnosing the current equipment state according to uploaded summarized data information; the data sensing and collecting module in the intelligent sensor is responsible for data collection, the compensating and correcting module is responsible for analog-to-digital conversion of data, the data processing module is responsible for controlling the operation of the whole node, the data collected by the data processing module and the data sent by other nodes are stored and processed, the data network communication module is responsible for carrying out wireless communication with other sensor nodes, the control information and the sensing data are received and sent, a human-computer interface provides human-computer interaction, the task management and scheduling module is responsible for issuing and adjusting work tasks, and the whole node of the power supply module provides energy required by operation; the temperature monitoring unit is used for collecting temperature signals of the switch cabinet, and the actually measured temperature sensors on the outer surfaces of the sub-chambers and the cabinet body environment are used for calculating temperature rise, so that the state diagnosis system can analyze and diagnose the state of the equipment through temperature and monitored current data, the calculation unit calculates the current of a corresponding bus based on a sensor array topological model, and the diagnosis unit diagnoses and analyzes the current equipment state according to summarized data information; the TMR magnetoresistive effect sensor is adopted to realize non-contact measurement of the bus current of the switch cabinet based on a magnetic sensor array topological model, influence and potential safety hazard on a switch cabinet circuit are avoided, mutual interference of three-phase magnetic fields of the switch cabinet is effectively removed through magnetostatic shielding, and measurement precision is ensured; the invention has the advantages of simple structure, no magnetic field interference, accurate measurement result, high precision and low cost.
Drawings
FIG. 1 is a schematic diagram of a condition diagnosing and monitoring system according to the present invention.
FIG. 2 is a schematic diagram of a temperature monitoring unit according to the present invention.
Fig. 3 is a schematic diagram of the composition structure of the intelligent sensor of the present invention.
Fig. 4 is a schematic diagram of an alternative power supply mode of the power supply module of the present invention.
FIG. 5 is a schematic diagram of the TMP magnetoresistive effect (quad array) sensor structure of the present invention.
FIG. 6 is a schematic structural diagram of a topological model of a parallel magnetic sensor array according to the present invention.
FIG. 7 is a flow chart of the present invention.
In the figure: 1. the system comprises a state diagnosis monitoring system 2, a temperature monitoring unit 21, measured temperature sensors 22 on the outer surfaces of all the compartments, a measured temperature sensor 3 of the environment of the cabinet, a current monitoring unit 4, a calculating unit 5, a diagnosis unit 6, an intelligent sensor 61, a data sensing and collecting module 62, a compensation and correction module 63, a data processing module 64, a data network communication module 65, a human-computer interface 66, a task management and scheduling module 67, a power supply module 7, a magnetic sensor 71, a TMR (tunneling magneto resistance) effect sensor 72 and static magnetic shielding.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Example 1
As shown in fig. 1-7, the method for monitoring bus current of switch cabinet includes a state diagnosis monitoring system 1, the state diagnosis monitoring system 1 includes a temperature monitoring unit 2, a current monitoring unit 3, a calculating unit 4 and a diagnosing unit 5, the temperature monitoring unit 2 includes measured temperature sensors 21 on the outer surfaces of the sub-chambers and measured temperature sensors 22 on the environment of the cabinet, the current monitoring unit 3 is connected with a plurality of intelligent sensors 6, each intelligent sensor 6 is connected with a plurality of magnetic sensors 7, the magnetic sensors 7 include TMR magnetoresistive effect sensors 71 and static magnetic shields 72, the TMR magnetoresistive effect sensors 71 are respectively disposed on the three-phase bus of the switch cabinet, the intelligent sensors 6 include a data sensing and collecting module 61, a compensation and correction module 62, a data processing module 63, a data network communication module 64, a data network communication module, a data network module, and a data transmission module, The TMR magneto-resistive effect sensor 71 is used for detecting the current of each phase bus of the switch cabinet at the installation position of the TMR magneto-resistive effect sensor and transmitting the detected current data to the intelligent sensor 6 corresponding to the TMR magneto-resistive effect sensor, the intelligent sensor 6 transmits the collected detection data transmitted by each magnetic sensor 7 to the current monitoring unit 3, and the current monitoring unit 3 transmits the received detection data to the state diagnosis and monitoring system 1.
The invention is a method for monitoring the bus current of a switch cabinet, in use, respectively installing magnetic sensors 7 near the A-phase, B-phase and C-phase busbars, establishing a current measurement magnetic sensor array topological model, measuring the current based on the linearity and the superposition of the magnetic field, calculating the induction coefficient matrix of the corresponding magnetic sensor current measurement, obtaining the actual current value on the bus by measuring the voltage output value of the magnetic sensors 7, uploading the data to an intelligent sensor 6 by the magnetic sensors 7, uploading the data to a current monitoring unit 3 after being summarized by the intelligent sensor 6, performing analog simulation on the magnetic field distribution condition in the switch cabinet by using ANSYS, establishing a related mathematical model for measuring alternating current and direct current according to the magnetic field distribution, analyzing and calculating the current value by a calculating unit 4 through the acquired current data, verifying the topological model of the magnetic sensor array by a diagnosing unit 5 according to the calculated current value, diagnosing the current equipment state according to the uploaded summarized data information; a data sensing and collecting module 61 in the intelligent sensor 6 is responsible for data collection, a compensation and correction module 62 is responsible for analog-to-digital conversion of data, a data processing module 63 is responsible for controlling the operation of the whole node, the data collected by the data processing module and the data sent by other nodes are stored and processed, a data network communication module 64 is responsible for carrying out wireless communication with other sensor nodes, control information and sensing data are received and sent, a human-computer interface 65 provides human-computer interaction, a task management and scheduling module 66 is responsible for issuing and adjusting work tasks, and a power supply module 67 provides energy required by the operation of the whole node; the actually measured temperature sensors 21 on the outer surfaces of the sub-chambers of the temperature monitoring unit 2 and the actually measured temperature sensor 22 on the environment of the cabinet body are responsible for collecting temperature signals of the switch cabinet so as to calculate temperature rise, so that the state diagnosis system 1 can analyze and diagnose the state of the equipment through temperature and monitored current data, the calculation unit 4 calculates the current of a corresponding bus based on a sensor array topological model, and the diagnosis unit 5 diagnoses and analyzes the current equipment state according to summarized data information; the TMR magnetoresistance effect sensor 71 is adopted to realize non-contact measurement of the bus current of the switch cabinet based on a magnetic sensor array topological model, influence and potential safety hazards on the circuit of the switch cabinet are avoided, mutual interference of three-phase magnetic fields of the switch cabinet is effectively removed through the magnetostatic shielding 72, and the measurement precision is ensured; the invention has the advantages of simple structure, no magnetic field interference, accurate measurement result, high precision and low cost.
Example 2
As shown in fig. 1-7, the method for monitoring bus current of switch cabinet includes a state diagnosis monitoring system 1, the state diagnosis monitoring system 1 includes a temperature monitoring unit 2, a current monitoring unit 3, a calculating unit 4 and a diagnosing unit 5, the temperature monitoring unit 2 includes measured temperature sensors 21 on the outer surfaces of the sub-chambers and measured temperature sensors 22 on the environment of the cabinet, the current monitoring unit 3 is connected with a plurality of intelligent sensors 6, each intelligent sensor 6 is connected with a plurality of magnetic sensors 7, the magnetic sensors 7 include TMR magnetoresistive effect sensors 71 and static magnetic shields 72, the TMR magnetoresistive effect sensors 71 are respectively disposed on the three-phase bus of the switch cabinet, the intelligent sensors 6 include a data sensing and collecting module 61, a compensation and correction module 62, a data processing module 63, a data network communication module 64, a data network communication module, a data network module, and a data transmission module, The TMR magneto-resistive effect sensor 71 is used for detecting the current of each phase bus of the switch cabinet at the installation position of the TMR magneto-resistive effect sensor and transmitting the detected current data to the intelligent sensor 6 corresponding to the TMR magneto-resistive effect sensor, the intelligent sensor 6 transmits the collected detection data transmitted by each magnetic sensor 7 to the current monitoring unit 3, and the current monitoring unit 3 transmits the received detection data to the state diagnosis and monitoring system 1.
The method comprises the following steps:
step 1): magnetic sensors 7 are respectively arranged near the phase A, the phase B and the phase C busbars;
step 2): establishing a current measurement magnetic sensor array topological model;
step 3): measuring the current based on the linearity and the superposition of the magnetic field;
step 4): calculating an inductance matrix of the current measurement of the corresponding magnetic sensor 7;
step 5): the actual current value on the bus is obtained by measuring the voltage output value of the magnetic sensor 7;
step 6): the magnetic sensor 7 uploads the data to the intelligent sensor 6, and the data are gathered by the intelligent sensor 6 and then uploaded to the current monitoring unit 3;
step 7): performing analog simulation on the distribution condition of the magnetic field in the switch cabinet by using ANSYS;
step 8): establishing a related AC/DC measurement mathematical model according to the magnetic field distribution;
step 9): the calculating unit 4 analyzes and calculates a current value through the acquired current data;
step 10): the diagnosis unit 5 verifies the magnetic sensor array topology model according to the current values calculated in the step 9), and diagnoses the current equipment state according to the summarized data information uploaded in the step 6).
For better effect, the temperature monitoring unit 2 collects temperature signals through the actually measured temperature sensors 21 on the outer surfaces of the respective sub-chambers and the actually measured temperature sensor 22 on the environment of the cabinet, and transmits the received signal data to the state diagnosing and monitoring system 1 for calculating the temperature change trend, namely temperature rise, after the temperature data is processed.
For better effect, the selectable power supply modes of the power supply module 67 include a battery power supply mode, a laser power supply mode, a solar power supply mode, an electromagnetic induction power taking mode and an energy collection chip function mode.
For better effect, the TMR magneto-resistive effect sensor 71 is electrically insulated and detects current by using magnetic field generated by current when current I exists in conductorpWhen a magnetic field proportional to the current is generated around the conductor, the TMR magnetoresistive sensor 71 detects the magnetic field strength of the magnetic field to generate an electric signal output V in linear relation to the magnetic fieldoutThe conversion from the magnetic signal for measurement to the electric signal is completed, and the principle of the TMR magnetoresistive effect sensor 71 for measuring the current is specifically: when the switch cabinet passes through power frequency current, a rotating magnetic field is usually generated in the cabinet, the bus bar in the cabinet is used as a center, the magnetic field intensity of a certain point close to the bus bar is approximately in direct proportion to the current flowing on the bus bar, and is approximately in inverse proportion to the vertical distance from the point to the bus bar, the magnetic field intensity is expressed as B ^ i/d, namely the magnetic field intensity of the point where the TMR magnetoresistance effect sensor 71 is located is expressed as: k represents1I/d (1), wherein d is the vertical distance from the TMR magnetoresistive sensor to the bus bar, i is the current flowing on the bus bar, and k is1As a constant, in the linear measurement range, the output voltage value of the TMR magnetoresistive effect sensor 71 and the input magnetic field strength satisfy a linear relationship, and therefore, the output voltage can be expressed as u ═ k2B (2) where u is a TMR magnetoresistive sensor outputMaximum value of the output voltage, k2As a measurable constant, it can be seen from the combination of the equations (1) and (2) that the actual current value and the output voltage value of the TMR magnetoresistive effect sensor 71 satisfy a linear relationship: and u is c · i/d, wherein c is a measurable constant coefficient and can be determined by current calibration, and when the value of the coefficient c in the input-output relation of the TMR magnetoresistive sensor 71 is determined, the output voltage is correspondingly processed to obtain the current, so that the current is measured.
For better effect, the TMR magnetoresistive effect sensor 71 employs a push-pull wheatstone full bridge configuration comprising two sets of non-shielded high-sensitivity TMR elements with opposite magnetic sensitivity directions.
For better effect, the electrostatic shield 72 is made of permalloy high permeability magnetic material based on the biot-savart law and ampere loop theorem, and separates the interference magnetic field from the protected area or element, and prevents static magnetic field or low frequency less than 100kHz from entering the area needing protection or influencing the magnetic sensitive element to be protected.
For better effect, the establishing of the topological model of the current measurement magnetic sensor array in the step 2) is specifically as follows: three-phase busbars of a switch cabinet can be regarded as parallel copper bars, the position relation between the copper bars and a magnetic sensor 7 can be expressed by taking the end point of the left edge of the section of the A-phase busbar as the original point of a three-dimensional coordinate system (x, y and z), assuming that the width of each-phase busbar is c and the thickness of each-phase busbar is d, assuming that the distance between every two adjacent-phase busbars is L, installing the magnetic sensor 7 close to each-phase busbar, assuming that the distance between each corresponding magnetic sensor 7 and the corresponding-phase busbar is b and the distance to the left edge of the corresponding-phase busbar is a, therefore, the two parameters of a and b determine the topological structure of a sensor magnetic sensor 7 array, and the distance L between the busbars, the actual width d and the thickness of each-phase busbar can be measured according to the switch cabinet which is actually applied.
For better effect, the current is measured in step 3) based on linearity and superposition of the magnetic field, specifically: the basic premise of measuring the current by applying the magnetic sensor array is that the linearity and the superposition of a magnetic field comprise the linearity superposition on space and frequency, the linearity superposition on the space refers to the linear relation between the magnetic field intensity generated by a point appointed by the current in the space and the intensity of the current, and for multi-phase current, the magnetic field intensity of the point is the vector superposition of the magnetic field intensity generated by each phase current at the point; frequency linearity means that for a given point in space, the magnetic induction coefficient of a current with a specific frequency at the point is a certain value, and for a current with known frequency and phase, the induced magnetic field generated at the specific point is in the same frequency and phase with the induced magnetic field, that is, the magnetic field at the specific point is the superposition of the induced magnetic fields of the frequency components of a given current at the point.
For better effect, the calculating of the inductance matrix of the corresponding magnetic sensor current measurement in step 4) and the measuring of the voltage output value of the magnetic sensor in step 5) are performed to obtain the actual current value on the bus, specifically: A. b, C magnetic field distribution is around the three-phase bus, the magnetic field intensity at any point in the bus indoor space is the result of the vector superposition of A, B, C three-phase magnetic fields, the magnetic field intensity measured by the magnetic sensor 7 is the vector sum of the magnetic field generated by the three-phase bus at the point, when the vertical distance d between the magnetic sensor 7 and the bus is fixed, the output value of the TMR magnetoresistive effect sensor 71 is u-c · i, assuming that three-phase currents are symmetrical, therefore the voltage output value measured by each magnetic sensor 7 is:
in the formula, cijThe voltage value of the sensor I at the bus bar j is represented, and the above formula is written into a matrix form:
in the formula
The inductance matrix for measuring the current of the magnetic sensor 7 may be obtained by collecting the output of the three-phase magnetic sensor 7 by individually applying current to each phase, calculating the corresponding inductance, for example, individually applying current to the a-phase busbar, B, C disconnecting two phases, and calculating c according to the voltage output signal of the three-phase magnetic sensor 711、c12、c13The other two groups can be calculated by the same methodThe value of the vector finally obtains the value of the coefficient matrix C; after the coefficient matrix C is obtained, the actual current value on the bus is obtained by measuring the voltage output value of the magnetic sensor 7,
since the coefficient matrix needs to ensure the reversibility, the reversibility is ensured by adopting a method of multiplying the coefficient matrix by a transposed matrix thereof:
i ═ CT·C]-1CT·u。
The invention is a method for monitoring the bus current of a switch cabinet, in use, respectively installing magnetic sensors 7 near the A-phase, B-phase and C-phase busbars, establishing a current measurement magnetic sensor array topological model, measuring the current based on the linearity and the superposition of the magnetic field, calculating the induction coefficient matrix of the corresponding magnetic sensor current measurement, obtaining the actual current value on the bus by measuring the voltage output value of the magnetic sensors 7, uploading the data to an intelligent sensor 6 by the magnetic sensors 7, uploading the data to a current monitoring unit 3 after being summarized by the intelligent sensor 6, performing analog simulation on the magnetic field distribution condition in the switch cabinet by using ANSYS, establishing a related mathematical model for measuring alternating current and direct current according to the magnetic field distribution, analyzing and calculating the current value by a calculating unit 4 through the acquired current data, verifying the topological model of the magnetic sensor array by a diagnosing unit 5 according to the calculated current value, diagnosing the current equipment state according to the uploaded summarized data information; a data sensing and collecting module 61 in the intelligent sensor 6 is responsible for data collection, a compensation and correction module 62 is responsible for analog-to-digital conversion of data, a data processing module 63 is responsible for controlling the operation of the whole node, the data collected by the data processing module and the data sent by other nodes are stored and processed, a data network communication module 64 is responsible for carrying out wireless communication with other sensor nodes, control information and sensing data are received and sent, a human-computer interface 65 provides human-computer interaction, a task management and scheduling module 66 is responsible for issuing and adjusting work tasks, and a power supply module 67 provides energy required by the operation of the whole node; the actually measured temperature sensors 21 on the outer surfaces of the sub-chambers of the temperature monitoring unit 2 and the actually measured temperature sensor 22 on the environment of the cabinet body are responsible for collecting temperature signals of the switch cabinet so as to calculate temperature rise, so that the state diagnosis system 1 can analyze and diagnose the state of the equipment through temperature and monitored current data, the calculation unit 4 calculates the current of a corresponding bus based on a sensor array topological model, and the diagnosis unit 5 diagnoses and analyzes the current equipment state according to summarized data information; the TMR magnetoresistance effect sensor 71 is adopted to realize non-contact measurement of the bus current of the switch cabinet based on a magnetic sensor array topological model, influence and potential safety hazards on the circuit of the switch cabinet are avoided, mutual interference of three-phase magnetic fields of the switch cabinet is effectively removed through the magnetostatic shielding 72, and the measurement precision is ensured; the invention has the advantages of simple structure, no magnetic field interference, accurate measurement result, high precision and low cost.
Claims (10)
1. The monitoring method of the bus current of the switch cabinet comprises a state diagnosis monitoring system and is characterized in that: the state diagnosis monitoring system comprises a temperature monitoring unit, a current monitoring unit, a calculation unit and a diagnosis unit, wherein the temperature monitoring unit comprises a sub-chamber outer surface actual measurement temperature sensor and a cabinet body environment actual measurement temperature sensor, the current monitoring unit is connected with a plurality of intelligent sensors, each intelligent sensor is connected with a plurality of magnetic sensors, each magnetic sensor comprises a TMR (triple tunneling magneto resistance) effect sensor and a static magnetic shield, the TMR effect sensors are respectively arranged on a three-phase bus of the switch cabinet, each intelligent sensor comprises a data sensing and acquisition module, a compensation and correction module, a data processing module, a data network communication module, a human-computer interface, a task management and scheduling module and a power supply module, and the TMR effect sensor is used for detecting the current of each phase bus of the switch cabinet at the installation position and transmitting the detected current data to the intelligent sensor corresponding to the TMR effect sensor, the intelligent sensor transmits the collected detection data transmitted by each magnetic sensor to the current monitoring unit, and the current monitoring unit transmits the received detection data to the state diagnosis monitoring system.
2. The method for monitoring the bus current of the switch cabinet according to claim 1, wherein: the method comprises the following steps:
step 1): respectively installing magnetic sensors close to the phase A, the phase B and the phase C busbars;
step 2): establishing a current measurement magnetic sensor array topological model;
step 3): measuring the current based on the linearity and the superposition of the magnetic field;
step 4): calculating an inductance matrix of the corresponding magnetic sensor current measurement;
step 5): the actual current value on the bus is obtained by measuring the voltage output value of the magnetic sensor;
step 6): the magnetic sensor uploads the data to the intelligent sensor, and the data are summarized by the intelligent sensor and then uploaded to the current monitoring unit;
step 7): performing analog simulation on the distribution condition of the magnetic field in the switch cabinet by using ANSYS;
step 8): establishing a related AC/DC measurement mathematical model according to the magnetic field distribution;
step 9): the calculating unit analyzes and calculates a current value through the acquired current data;
step 10): the diagnosis unit verifies the magnetic sensor array topology model according to the current values calculated in the step 9), and diagnoses the current equipment state according to the summarized data information uploaded in the step 6).
3. The method for monitoring the bus current of the switch cabinet according to claim 1, wherein: the temperature monitoring unit collects temperature signals through actually measured temperature sensors on the outer surfaces of the sub-chambers and actually measured temperature sensors on the environment of the cabinet body, and transmits received signal data to the state diagnosis monitoring system to calculate the temperature change trend, namely temperature rise, of the processed temperature data.
4. The method for monitoring the bus current of the switch cabinet according to claim 1, wherein: the selectable power supply modes of the power supply module comprise a battery power supply mode, a laser energy supply mode, a solar power supply mode, an electromagnetic induction power taking mode and an energy collecting chip function mode.
5. The method for monitoring the bus current of the switch cabinet according to claim 1, wherein: the TMR magnetoresistive effect sensor is characterized in that the current is detected by using a magnetic field generated by the current in an electrically insulated state, and when the current I exists in a conductorpWhen the sensor is used, a magnetic field proportional to current is generated around the conductor, and the TMR magnetoresistive effect sensor detects the magnetic field intensity of the magnetic field to generate an electric signal output V in linear relation with the magnetic fieldoutThe conversion from the magnetic signal for measurement to the electric signal is completed, and the principle of the TMR magnetoresistive effect sensor for measuring the current specifically comprises the following steps: when the switch cabinet passes through power frequency current, a rotating magnetic field is usually generated in the cabinet, the bus bar in the cabinet is used as a center, the magnetic field intensity of a certain point close to the bus bar is approximately in direct proportion to the current flowing on the bus bar, and is approximately in inverse proportion to the vertical distance from the point to the bus bar, the magnetic field intensity is expressed as B ^ i/d, namely the magnetic field intensity of the point where the TMR magnetoresistance effect sensor is located is expressed as: k represents1I/d (1), wherein d is the vertical distance from the TMR magnetoresistive sensor to the bus bar, i is the current flowing on the bus bar, and k is1As a constant, in the linear measurement range, the output voltage value of the TMR magnetoresistive effect sensor and the input magnetic field strength satisfy a linear relationship, and therefore, the output voltage can be expressed as u ═ k2B (2) where u is the maximum value of the output voltage of the TMR magnetoresistive sensor, and k2For measurable constants, the combination of the formula (1) and the formula (2) shows that the actual current value and the output voltage value of the TMR magnetoresistive effect sensor necessarily satisfy a linear relation: u ═ c · i/d, where c is a measurable constant, which can be determined by current calibrationAnd finally, when the value of the coefficient c in the input and output relational expression of the TMR magnetoresistive effect sensor is determined, the output voltage is correspondingly processed to obtain the current, so that the current is measured.
6. The method for monitoring the bus current of the switch cabinet according to claim 4, wherein: the TMR magneto-resistive effect sensor adopts a push-pull Wheatstone full-bridge structure which comprises two groups of non-shielding high-sensitivity TMR elements with opposite magnetic sensitivity directions.
7. The method for monitoring the bus current of the switch cabinet according to claim 1, wherein: the electrostatic shield is made of permalloy high-permeability magnetic materials based on the Biao-Saval law and the ampere loop theorem, an interference magnetic field is separated from a protected area or element, and a static magnetic field or low frequency less than 100kHz is prevented from entering the area needing protection or influencing a protected magnetic sensitive element.
8. The method for monitoring the bus current of the switch cabinet according to claim 2, wherein: the establishing of the current measurement magnetic sensor array topology model in the step 2) is specifically as follows: three-phase busbars of a switch cabinet can be regarded as parallel copper bars, the position relation between the copper bars and magnetic sensors can be expressed by taking the end point of the left edge of the section of the A-phase busbar as the original point of a three-dimensional coordinate system (x, y and z), assuming that the width of each-phase busbar is c and the thickness of each-phase busbar is d, assuming that the distance between every two adjacent-phase busbars is L, installing the magnetic sensors close to each-phase busbar, assuming that the distance between every corresponding magnetic sensor and the corresponding-phase busbar is b and the distance to the left edge of the corresponding-phase busbar is a, therefore, the two parameters of a and b determine the topological structure of the magnetic sensor array, and the distance L between the busbars, the actual width d and the thickness of each-phase busbar can be measured according to the switch cabinet in practical application.
9. The method for monitoring the bus current of the switch cabinet according to claim 2, wherein: the step 3) of measuring the current based on the linearity and the superposition of the magnetic field specifically comprises the following steps: the basic premise of measuring the current by applying the magnetic sensor array is that the linearity and the superposition of a magnetic field comprise the linearity superposition on space and frequency, the linearity superposition on the space refers to the linear relation between the magnetic field intensity generated by a point appointed by the current in the space and the intensity of the current, and for multi-phase current, the magnetic field intensity of the point is the vector superposition of the magnetic field intensity generated by each phase current at the point; frequency linearity means that for a given point in space, the magnetic induction coefficient of a current with a specific frequency at the point is a certain value, and for a current with known frequency and phase, the induced magnetic field generated at the specific point is in the same frequency and phase with the induced magnetic field, that is, the magnetic field at the specific point is the superposition of the induced magnetic fields of the frequency components of a given current at the point.
10. The method for monitoring the bus current of the switch cabinet according to claim 2, wherein: the calculating of the inductance matrix corresponding to the current measurement of the magnetic sensor in step 4) and the measuring of the voltage output value of the magnetic sensor in step 5) are performed to obtain an actual current value on the bus, specifically: A. b, C magnetic field distribution is around the three-phase bus, the magnetic field intensity at any point in the bus indoor space is the result of the vector superposition of A, B, C three-phase magnetic fields, the magnetic field intensity measured by the magnetic sensor is the vector sum of the magnetic field generated by the three-phase bus at the point, when the perpendicular distance d from the magnetic sensor to the bus is fixed, the output value of the TMR magnetoresistive effect sensor is u-c.i, the three-phase current symmetry is assumed, therefore, the voltage output value measured by each magnetic sensor is:
in the formula, cijThe voltage value of the sensor I at the bus bar j is represented, and the above formula is written into a matrix form:
in the formula
An inductance matrix for magnetic sensor current measurement, whichThe value can be obtained by collecting the output of the three-phase magnetic sensor by independently electrifying the phase by phase, calculating the corresponding inductance, for example, firstly independently electrifying the A-phase busbar, B, C disconnecting the two phases, and calculating c according to the voltage output signal of the three-phase magnetic sensor11、c12、c13The values of the other two groups of vectors can be calculated in the same way, and finally the value of the coefficient matrix C is obtained; after obtaining the coefficient matrix C, the actual current value on the bus is obtained by measuring the voltage output value of the magnetic sensor,
since the coefficient matrix needs to ensure the reversibility, the reversibility is ensured by adopting a method of multiplying the coefficient matrix by a transposed matrix thereof:
i ═ CT·C]-1CT·u。
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114966160A (en) * | 2022-07-29 | 2022-08-30 | 浙江大学 | Laminated busbar and power device current detection device based on tunnel magnetoresistance |
| CN115238329A (en) * | 2022-09-23 | 2022-10-25 | 国网浙江省电力有限公司宁波供电公司 | Busbar connector design method based on busbar connection relation and busbar connector |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114966160A (en) * | 2022-07-29 | 2022-08-30 | 浙江大学 | Laminated busbar and power device current detection device based on tunnel magnetoresistance |
| CN114966160B (en) * | 2022-07-29 | 2022-10-25 | 浙江大学 | Laminated busbar and power device current detection device based on tunnel magnetoresistance |
| CN115238329A (en) * | 2022-09-23 | 2022-10-25 | 国网浙江省电力有限公司宁波供电公司 | Busbar connector design method based on busbar connection relation and busbar connector |
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