CN210982613U - Dielectric polarization capacitance type electrostatic field measuring system - Google Patents
Dielectric polarization capacitance type electrostatic field measuring system Download PDFInfo
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- CN210982613U CN210982613U CN201921652255.0U CN201921652255U CN210982613U CN 210982613 U CN210982613 U CN 210982613U CN 201921652255 U CN201921652255 U CN 201921652255U CN 210982613 U CN210982613 U CN 210982613U
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Abstract
The utility model relates to a dielectric polarization capacitance formula electrostatic field measurement system belongs to electromagnetic field measurement technique and measuring instrument and makes technical field. The utility model discloses a capacitanc sensor among the measurement system lets surveyed electrostatic field and voltage source electrostatic field constitute the dielectric in the interact of polarization in two directions for the dielectric constant changes, and the capacitance value changes, and then will be surveyed the field intensity and turn into the change of sensor port capacitance value. The capacitance value of the sensor port is measured by the capacitance measuring instrument, and the field intensity of the measured electrostatic field can be obtained. The voltage source can make the dielectric work at a proper working point, and the output-input proportionality coefficient of the sensor is improved. The utility model discloses an electrostatic field measurement method, measurable quantity weak electrostatic field, measuring range is big moreover, and measuring sensitivity, resolution ratio and degree of accuracy are all high. The utility model discloses a measurement system does not take moving part, and system architecture and measuring circuit are simple, have advantages such as sensitivity height, small, easy realization, stability are good.
Description
Technical Field
The utility model relates to a dielectric polarization capacitance formula electrostatic field measurement system belongs to electromagnetic field measurement technique and measuring instrument and makes technical field.
Background
In many scientific research and engineering fields, electrostatic field measurement is a task that must be completed. For example, in a high voltage direct current transmission system, electrostatic field measurements around lines and equipment and on the surface of the ground are important basic data for determining whether the system meets electromagnetic environment requirements and the operational reliability of the system.
For electrostatic field measurement, the conventional measurement systems are mainly classified into two types: an electrostatic field measuring system based on a charge induction principle and an electrostatic field measuring system based on a photoelectric principle. Both have significant disadvantages.
The structure of the first type of electrostatic field measurement system based on the charge induction principle is shown in FIG. 1 (references: Zhang Jian Gong, et al. DC electric field measurement device develops [ J ]. high voltage technology, 2009,35(12): 3027-. A typical configuration of a sensor based on the charge induction principle used in this system is a "field mill", as shown in fig. 2. The working principle is as follows: the motor 202 drives the grounded metal blade, i.e. the grounded shield 204, to rotate at a constant speed through the rotating shaft 203, and the lower electrode 205 is grounded through the resistor 206. When the blade rotates to coincide with the electrode, the detected electrostatic field 201 is shielded, the electrode cannot sense the electrostatic field, and no induced charge exists on the electrode or the existing charge is discharged to the ground; when the blade rotates to the state that the blade gap is opposite to the electrode or the electrode is exposed (the state in fig. 2), the electrode senses an electrostatic field 201, charges are induced on the electrode, and the accumulation and the dispersion of the charges are conducted through a resistor, so that the grounding wire of the electrode forms a current, a voltage is formed on the resistor, the voltage drives a subsequent circuit, and the corresponding field intensity can be obtained by measuring the current or the voltage.
It can be seen that a "field mill" is a sensor that converts the measured static field strength into current pulses. If there is no rotating shield blade, since the electrostatic field does not change with time, there will only be a change from no charge to induced charge on the electrodes, only one current pulse will be generated, and the field strength error calculated by current driving the following circuit with only one pulse will be large. The advantage of this "field mill" type is that the electrostatic field is converted into a continuous current pulse. The defects of the device are that the device is provided with moving parts, is easy to age and damage, and has poor stability, low resolution and large volume. It is obvious that a rotating or moving part in an electrical quantity measuring instrument is not the state that a general measuring instrument should have.
The second type of electrostatic field measurement system based on photoelectric principle is shown in FIG. 3 (refer to the issued patent of invention: a photoelectric integrated strong electric field measurement system, grant No. CN 1844941B, Zen , good and short). In fig. 3, a laser light source 301 outputs a linearly polarized light beam, which is coupled to a sensor 303 through a polarization maintaining fiber 302, the polarized light is modulated by an external measured electrostatic field 304, the output laser light is transmitted to a photoelectric converter 306 through a single mode fiber 305, and the conversion from the optical power to a voltage signal is completed, the voltage signal is input to an electrical signal detector 308 through a cable 307, and the measured field strength can be obtained through the detection of the voltage signal.
The electric field sensor based on photoelectric principle (refer to the patent of invention granted: an antenna-free photoelectric integrated sensor for measuring strong electric field, publication No. CN 1858602B, Zhang , He jin Liang) used in the system is made by utilizing the phenomenon that the electric field affects the polarization of light in transmission, the structure is very simple, and a common structure is as shown in FIG. 4, a wafer 401 with photoelectric effect is adopted, light waveguides 402 with two Y-shaped branches at two ends and mutually parallel middle are formed on the surface, and a metal shielding layer 403 is additionally arranged on one of two parallel light waveguides. When the electric field sensor is in the measured electrostatic field 404, the two optical waveguides form a differential sensor, one optical waveguide is used as the electric field sensor and is normally acted by the electric field, and the other optical waveguide is provided with a metal shielding layer and cannot sense the electric field, so that the light characteristics in the two optical paths are different, and the size of the measured electrostatic field can be reflected by measuring the difference of the light characteristics in the two optical fibers.
Although the photoelectric principle type sensor has a simple structure, the optical system is very complex, so that the measurement stability is poor, the cost is high, and the maintenance is complex. And the light is affected to a very low degree by the electric field, the sensitivity and accuracy of such a sensor or system is low and not suitable for measuring low electric fields.
Disclosure of Invention
The utility model discloses to above-mentioned shortcoming that current "field mill" formula electrostatic field measurement system has moving part and photoelectric type system implementation complicacy etc. are not enough, provide a dielectric polarization capacitanc electrostatic field measurement system. The measuring system adopts a capacitance type electrostatic field sensor as a measuring key component, converts the measured field intensity into the change of a sensor port capacitance value by utilizing dielectric polarization characteristics, and obtains the size of the measured electrostatic field by measuring the capacitance value.
The utility model provides a dielectric polarization capacitanc electrostatic field measurement system, include:
the sensor comprises a pair of electrodes and a capacitor core, wherein the pair of electrodes are two conductor plates which are bonded on the end surfaces of two sides of the capacitor core, and the two conductor plates are connected with two leads to form a port of the sensor so as to form the sensor for measuring the capacitive electrostatic field;
the voltage source is a direct-current power supply, one end of the voltage source is connected with one electrode on one side of the sensor, the other end of the voltage source is connected with the other electrode of the sensor through the capacitance measuring instrument, and the voltage source is used for applying bias voltage to the sensor to enable the dielectric medium forming the capacitor core to be polarized and enable the dielectric medium to work in an area with large capacitance value variation of the sensor;
the capacitance measuring instrument is connected to a port of the sensor after being connected with the voltage source in series and is used for measuring the capacitance value of the sensor port and uploading the measured capacitance value of the sensor port to the processor;
and the processor is connected with the output end of the capacitance measuring instrument and used for receiving the capacitance measuring data of the sensor port output by the capacitance measuring instrument, converting the measured capacitance into a field intensity value of the electrostatic field according to the relation between the capacitance value change of the sensor obtained by calibration and the measured electrostatic field, and outputting the measuring result of the measured electrostatic field.
The utility model provides a dielectric polarization capacitanc electrostatic field measurement system compares with prior art and has following advantage:
(1) the utility model provides a dielectric polarization capacitance formula electrostatic field measurement system wherein adopts capacitanc electrostatic field sensor, utilizes the influence of being surveyed the electrostatic field to the dielectric parameter, turns into the field intensity of being surveyed the electrostatic field capacitance value change of capacitanc sensor port, obtains being surveyed the electrostatic field through measuring the capacitance value change. The working principle of the magnetic field sensor is similar to that of an existing static magnetic field measuring system based on a Hall effect sensor and a fluxgate sensor, and the measurement is realized by using the principle that the material parameters change under the action of the material field.
(2) The utility model discloses a dielectric polarization capacitance formula electrostatic field measurement system lets in being surveyed the electrostatic field and gets into sensor capacitor core from the side that does not have the electrode, has effectively avoided the shielding influence of metal electrode pair by being surveyed the electrostatic field, and sensor structure is ingenious. The utility model discloses a capacitive sensor that measuring method adopted comprises cylindrical capacitor core and a pair of electrode of pasting at capacitor core terminal surface, and two terminal output capacitance values of sensor are constituteed to the electrode, and the terminal surface that does not have the electrode can let the electrostatic field of being surveyed get into the sensor capacitor in-core, acts on the dielectric material of capacitor core, has both avoided the shielding influence of metal electrode pair quilt survey electric field, has constituted the electric capacity of sensor by metal electrode again.
(3) The electric field measuring system effectively improves the sensitivity and the accuracy of the sensor by two measures. Firstly, the interaction of polarization of dielectric materials in two directions is utilized to form the relationship between a measured electrostatic field and the capacitance value variation of a sensor; secondly, applying bias voltage on the sensor to enable the dielectric to work at the nonlinear inflection point of the dielectric; these two measures can all increase the sensor capacitance value along with the variable quantity of being surveyed the field intensity to improve the utility model discloses a measurement system's sensitivity and the degree of accuracy.
(4) The utility model discloses a do not contain moving part among the measurement system, and the sensor size is little. The utility model discloses a measurement system adopts capacitanc electrostatic field sensor to replace traditional "field mill" formula sensor as measuring key component, does not contain moving part, and fundamentally has overcome "field mill" formula sensor and has moving part and make measurement system shortcoming such as easy aging damage and bulky. Additionally, the utility model discloses a sensor size is little, the electrostatic field in the measurable quantity narrow region.
(5) The utility model discloses a measurement system simple structure easily realizes, and is with low costs. The utility model discloses a measurement system adopts the capacitance value at capacitance measuring instrument direct measurement sensor both ends, through the change of capacitance value alright obtain the strong little of surveyed quiet field. For photoelectric circuit and processing among the existing photoelectric type measurement system, the utility model discloses a measurement system realizes that the complexity will be low a lot, and the cost is low a lot.
Drawings
Fig. 1 is a schematic structural diagram of a conventional electrostatic field measurement system based on a charge induction principle.
Fig. 2 is a schematic diagram of a specific structure of a sensor 101 in the measurement system shown in fig. 1, wherein the sensor 101 is colloquially called a "field mill".
Fig. 3 is a schematic structural diagram of an existing electrostatic field measurement system based on the photoelectric principle.
Fig. 4 is a schematic diagram showing a specific structure of the sensor 303 in the measurement system shown in fig. 3.
Fig. 5 is a schematic structural diagram of a dielectric polarization capacitance type electrostatic field measurement system according to the present invention. In fig. 5, 1 is an electrode, 2 is a condenser core, 3 is a voltage source, 4 is a capacitance measuring instrument, 5 is a processor, and 6 is a measured electrostatic field.
Fig. 6 is a schematic diagram of the voltage source 3 in the measurement system shown in fig. 5. In fig. 6, 601 is a dc power supply, 602 is a first switch, 603 is a second switch, and 604 is a commutation bypass line.
Detailed Description
The utility model provides a dielectric polarization capacitance formula electrostatic field measurement system, its structure is as shown in figure 5, include:
the sensor comprises a pair of electrodes 1 and a capacitor core 2, wherein the pair of electrodes 1 are two conductor plates which are bonded on the end surfaces of two sides of the capacitor core 2, and two conducting wires are connected with the two conductor plates to form a port of the sensor, so that the sensor for measuring the capacitive electrostatic field is formed;
the voltage source 3 is a direct-current power supply, one end of the voltage source 3 is connected with the electrode 1 on one side of the sensor, the other end of the voltage source 3 is connected with the other electrode 1 of the sensor through the capacitance measuring instrument 4, and the voltage source 3 is used for applying bias voltage to the sensor to enable the dielectric medium forming the capacitor core 2 to be polarized and enable the dielectric medium to work in an area with large capacitance value variation of the sensor;
the capacitance measuring instrument 4 is connected to a port of the sensor after being connected with the voltage source 3 in series, and is used for measuring the capacitance value of the sensor port and uploading the measured capacitance value of the sensor port to the processor 5;
and the processor 5 is connected with the output end of the capacitance measuring instrument 4 and used for receiving the capacitance measurement data of the sensor port output by the capacitance measuring instrument 4, converting the measured capacitance value into the field intensity value of the electrostatic field according to the relationship between the capacitance value change of the sensor obtained by calibration and the measured electrostatic field, and outputting the measurement result of the measured electrostatic field.
The following describes specific embodiments and steps of the dielectric polarization capacitance type electrostatic field measurement system according to the present invention with reference to fig. 5 and 6:
(1) sensor fabrication
As shown in fig. 5, the sensor is composed of a pair of electrodes 1 and a capacitor core 2, the pair of electrodes are two conductor plates which are respectively bonded on the two side end surfaces of the capacitor core, and two conducting wires are connected with the two conductor plates to form a port of the sensor; the sensor is used for sensing the measured electrostatic field, and the measured electrostatic field enters the sensor capacitor core from the side surface of the cylindrical capacitor core without the electrode.
The two electrodes 1 of the sensor can be a copper plate, an aluminum plate and a stainless steel plate; the thickness is about 1 mm; the shape of the capacitor core 2 is consistent with the end face shape of the capacitor core, and can be round or square; the size should be slightly smaller than the end face of the condenser core 2. The capacitor core 2 is made of a dielectric material, which can be a material with a large dielectric constant, such as deionized water, liquid ammonia, mica, barium titanate composite material, and the like, and the larger the dielectric constant is, the better the non-linearity degree is, and the larger the capacitance value and the capacitance variation are. For liquid dielectrics a plastic container is made which is filled with the dielectric and sealed. The shape of the condenser core 2 can be a cylinder, a drum (the shape that two round end surfaces are smaller and the middle is thicker) or a rectangular surface. The two electrodes 1 are firmly fixed to the end faces with an adhesive, respectively. The length of the condenser core 2 (the distance between the two electrodes 1) is typically more than 2 times the diameter (or width).
In order to measure the electrostatic field on the ground of the HVDC line, the value is generally in the order of 4kV/m, and the capacitance value in the order of pF is considered in the range of a common capacitor measuring instrument (like the TH2838 of the L CR digital bridge tester), so the capacitor core of the sensor can be made to be 100mm in area2The capacitor core is a sintered barium titanate sheet with the maximum relative dielectric constant of 160.
(2) Voltage source 3 and commutation and voltage value-taking strategies thereof
And (2) applying a voltage source 3 to the port of the sensor manufactured in the step (1), wherein the voltage source 3 is used for enabling the dielectric medium of the capacitor core 2 to work at a proper working point and generating transverse polarization, and the transverse polarization and the polarization of the dielectric medium by the electrostatic field to be measured form two-direction polarization, so that the coupling relation between the electrostatic field to be measured and the capacitance value of the sensor is formed. Therefore, the voltage of the voltage source is taken into consideration that the dielectric medium works at a reasonable working point, and the proportional relation of the sizes of the electrostatic fields in the two directions is also considered, so that the proportional coefficient of the sensor is made to be as large as possible.
The voltage source 3 can adopt a positive-negative reversing structure, as shown in fig. 6, a first switch 602 and a second switch 603 are connected in series with a direct current power supply 601, and a reversing bypass line 604 is arranged beside the first switch and the second switch; when the first switch 602 and the second switch 603 are closed downward, the voltage at the port of the voltage source 3 is positive left and negative right, and both are closed upward and connected to the commutation bypass line 604, the voltage at the port of the voltage source 3 is positive left and negative right, and the polarities of the voltages applied to the sensor before and after each commutation are opposite, so as to obtain two measured electrostatic field values in different voltage directions, which are used as the basis for judging whether the sensor is orthogonal to the measured electrostatic field direction or not, and when the two values are the same, the sensor is orthogonal to the measured electrostatic field direction, thereby realizing the direction measurement of the measured electrostatic field and the accurate measurement of the size of the electrostatic field. For measuring the ground electrostatic field of the hvdc transmission line the voltage value of the voltage source is taken to be 40V, which generates an electric field of about 2kV/m, around 1/2 measured. The performance requirement for the voltage source 3 is that the output voltage is stable and is affected as little as possible by temperature and external environmental changes. The switch in the voltage source can use a common relay or a semiconductor switch, and the closing frequency of the switch can be about 5 times per second.
(3) And determining the relation between the capacitance change of the sensor port and the measured electrostatic field.
Placing the sensor applied with the voltage source in the step (2) in a measured electrostatic field, enabling the measured electrostatic field to enter the capacitor core from the cylindrical surface of the capacitor core, polarizing the dielectric medium of the capacitor core in the vertical direction (namely, the transverse polarization direction of the voltage source 3 to the dielectric medium), forming the polarization of the dielectric medium in the vertical direction and the transverse direction, and forming a coupling relation between the polarization of the measured electrostatic field to the capacitor core and the polarization of the voltage source to the capacitor core in the two directions; through the coupling relation, the capacitance of the sensor port is changed by the measured electrostatic field;
the method comprises the steps of using the field intensity of a measured electrostatic field as the input quantity of a sensor, using the capacitance change of the sensor as the output quantity, determining the proportional coefficient of the output quantity and the input quantity, determining the proportional coefficient by adopting a calibration method, namely applying a known standard electrostatic field source to the sensor, obtaining the proportional coefficient by measuring the capacitance change of the sensor, and obtaining a plurality of proportional coefficients or a proportional coefficient table by adopting the standard electrostatic field sources with different intensities and repeating the process for a plurality of times.
The larger the proportionality coefficient of the output quantity, namely the capacitance variation, of the sensor to the input quantity, namely the measured electrostatic field value, the better, and the larger the proportionality coefficient, namely the capacitance variation, of the sensor to the input quantity, namely the measured electrostatic field value, the better, and the performance of the measuring system, such as accuracy. When the electrostatic field to be measured is absent, the transverse electrostatic field generated by the voltage source 3 causes the degree of polarization of the dielectric material of the condenser core 2 to be determined, the dielectric constant of which is also a fixed value, the sensor having a sensor geometry selected in relation to the dielectric materialFixed capacitance value C0. When the measured electrostatic field (denoted as E)t) When present, it will produce polarization in the vertical direction of the dielectric material, which will cause the direction and magnitude of the polarized dipole produced by the transverse polarization to change, thereby reducing the dielectric constant, E, of the dielectric materialtThe larger the value of (E), the larger the reduction degree of the pair, so that the relation between the reduction quantity of the capacitance and the measured electrostatic field is formed, namely, the Delta C is equal to K (E)t)EtCoefficient K (E)t) For sensor output input proportionality coefficient, EtIs related to sensor geometry, voltage value of bias voltage source, dielectric material characteristics, etc. This coefficient K needs to be obtained by calibration after the measurement system has been made using known standard electrostatic field sources.
(4) Type 4 selection of capacitance measuring instrument
The capacitance measuring instrument can be any one based on the inductance-capacitance resonance type, such as the digital bridge tester TH2838 with L CR, and the measuring instrument is connected to two ends of the capacitance sensor through the voltage source 3 to measure the capacitance value of the two ends of the sensor, and upload the measured capacitance value to the processor 5.
(5) The processor 5 effects a conversion from the measured capacitance value to an electrostatic field value
And (4) injecting the capacitance change of the sensor port obtained in the step (3) and the proportionality coefficient of the measured electrostatic field into the processor 5, fitting a proportionality coefficient curve based on the proportionality coefficients, and converting the measured capacitance change value of the sensor port into the size of the electrostatic field according to the curve to realize the measurement of the electrostatic field.
(6) Debugging and measurement implementation after manufacturing of measurement system
The output and input proportionality coefficients are obtained by calibration after the measuring system is manufactured. The calibration method can utilize two circular plate electrodes which are more than 10 times of the probe to form a parallel plate capacitor, the distance between the two plates is smaller than the diameter of a polar plate of 1/5, and the direct current voltage applied between the polar plates is controlled to obtain electrostatic fields with different values, so that the electrostatic fields are used as standard electrostatic fields for calibration. A plurality of proportionality coefficients can be obtained through calibration, and curve fitting is carried out on the proportionality coefficients so as to adapt to accurate measurement of the electrostatic field on the non-calibration point. During calibration, the sensor is placed in a direction which is vertical to the transverse direction of the sensor.
When implementing the measurement, if the direction of surveyed electrostatic field is known, when measuring the electrostatic field of high voltage direct current power transmission line below ground surface (this is the utility model discloses a measurement system's one of the main measuring object), known electric field direction must be perpendicular to earth surface, then as long as guarantee that the sensor level is placed (can install the spirit level additional on the sensor) this moment, alright obtain correct electric field measurement result. Because the utility model discloses a sensor is the folk prescription to the sensor, so if want the unknown electrostatic field of measuring direction, must correctly place the sensor, make to be surveyed electric field and sensor horizontal perpendicular, just so can guarantee that the state of measurement is unanimous with the demarcation state of sensor to obtain accurate measuring result. Because a reversing voltage source is adopted, the transverse polarization direction of the dielectric medium can be reversed, if the electric field values measured in the two directions are different, the transverse direction of the sensor is not perpendicular to the direction of the measured electrostatic field, the system can obtain the direction deviation of the sensor according to the measured values in the two directions, a prompt function is set to prompt a user to adjust the direction of the sensor, and the user adjusts the direction of the sensor according to the prompt until the system requirement is met, so that the accurate measurement of the size of the electrostatic field can be realized, the direction of the electric field is just above the probe, and the direction of the electric field is upward (corresponding to the right direction) or downward according to the positive and negative values given by the system.
Claims (1)
1. A dielectric polarization capacitance electrostatic field measurement system, the measurement system comprising:
the sensor comprises a pair of electrodes and a capacitor core, wherein the pair of electrodes are two conductor plates which are bonded on the end surfaces of two sides of the capacitor core, and the two conductor plates are connected with two leads to form a port of the sensor so as to form the sensor for measuring the capacitive electrostatic field;
the voltage source is a direct-current power supply, one end of the voltage source is connected with one electrode on one side of the sensor, the other end of the voltage source is connected with the other electrode of the sensor through the capacitance measuring instrument, and the voltage source is used for applying bias voltage to the sensor to enable the dielectric medium forming the capacitor core to be polarized and enable the dielectric medium to work in an area with large capacitance value variation of the sensor;
the capacitance measuring instrument is connected to a port of the sensor after being connected with the voltage source in series and is used for measuring the capacitance value of the sensor port and uploading the measured capacitance value of the sensor port to the processor;
and the processor is connected with the output end of the capacitance measuring instrument and used for receiving the capacitance measuring data of the sensor port output by the capacitance measuring instrument, converting the measured capacitance into a field intensity value of the electrostatic field according to the relation between the capacitance value change of the sensor obtained by calibration and the measured electrostatic field, and outputting the measuring result of the measured electrostatic field.
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| CN110596472A (en) * | 2019-09-29 | 2019-12-20 | 清华大学 | Dielectric polarization capacitance type electrostatic field measuring method and system |
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Inventor after: Yuan Jiansheng Inventor after: Gan Mengying Inventor before: Yuan Jiansheng Inventor before: Beautiful |