CN115629241A - Alternating current-direct current environment synthetic electric field measuring instrument and measuring method - Google Patents
Alternating current-direct current environment synthetic electric field measuring instrument and measuring method Download PDFInfo
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- CN115629241A CN115629241A CN202211293845.5A CN202211293845A CN115629241A CN 115629241 A CN115629241 A CN 115629241A CN 202211293845 A CN202211293845 A CN 202211293845A CN 115629241 A CN115629241 A CN 115629241A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/12—Measuring electrostatic fields or voltage-potential
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/08—Measuring electromagnetic field characteristics
- G01R29/0807—Measuring electromagnetic field characteristics characterised by the application
- G01R29/0814—Field measurements related to measuring influence on or from apparatus, components or humans, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning
- G01R29/0821—Field measurements related to measuring influence on or from apparatus, components or humans, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning rooms and test sites therefor, e.g. anechoic chambers, open field sites or TEM cells
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/08—Measuring electromagnetic field characteristics
- G01R29/0864—Measuring electromagnetic field characteristics characterised by constructional or functional features
- G01R29/0892—Details related to signal analysis or treatment; presenting results, e.g. displays; measuring specific signal features other than field strength, e.g. polarisation, field modes, phase, envelope, maximum value
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Abstract
An alternating current-direct current environment synthetic electric field measuring instrument and a measuring method thereof are disclosed, the synthetic electric field measuring instrument comprises: the device comprises a sensing electrode, a rotor, a motor, a rotating speed sensor, a monitoring and adjusting module, a sampling resistor, an operational amplifier, a phase inverter, a rectifying circuit, an analog-digital converter, a central controller, a wireless communication module, a low-pass filter and a band-pass filter; when the measured field intensity is less than or equal to the set field intensity threshold value, the alternating signal is amplified by the operational amplifier and then input into the band-pass filter, the alternating signal filtered by the band-pass filter is divided into two paths, the first path is input into the rectifying circuit after passing through the phase inverter, and the second path is directly input into the rectifying current; when the measured field intensity is larger than the set field intensity threshold value, the alternating signal passes through the band-pass filter and then is input into the operational amplifier, the alternating signal amplified by the operational amplifier is divided into two paths, the first path passes through the phase inverter and then is input into the rectifying circuit, and the second path directly inputs the rectifying current. The invention realizes the measurement of the synthesized electric field resisting the interference of the power frequency electric field in the alternating current environment.
Description
Technical Field
The invention belongs to the technical field of power measurement, and particularly relates to an alternating current and direct current environment synthetic electric field measuring instrument and a measuring method.
Background
With the development of the high-voltage direct-current transmission technology, an alternating-current and direct-current parallel electromagnetic environment appears, including an alternating-current and direct-current parallel transmission line and a converter station, wherein the converter station is a transformer substation for converting direct current into alternating current, and needs to monitor a synthetic electric field in an environment with an alternating-current electric field, and the synthetic electric field is a synthetic field formed by an electric field generated by a charged direct-current conductor and an electric field generated by ions in a direct-current transmission project and is a direct-current electric field. Therefore, a synthetic electric field measuring instrument resistant to the interference of the power frequency electric field is needed.
In the prior art, a synthesized electric field measuring instrument shown in fig. 1 monitors an alternating current-direct current synthesized electric field by using a field intensity probe of a field mill type. During measurement, the motor drives the rotor to rotate, so that the sensing electrode is periodically exposed to an external direct current electric field, the rotor rotates the fan blades, the area of the sensing electrode exposed to the direct current electric field is periodically changed, and an alternating signal is generated on the sensing resistor, wherein the amplitude of the alternating signal is in direct proportion to the amplitude of the direct current electric field. The frequency of the alternating signal is equal to the rotor speed multiplied by the number of sensing electrodes. The alternating signal is amplified by the gain of the operational amplifier, the output of the operational amplifier is divided into two paths, one path is inverted by the phase inverter, and the other path is the original signal. The monitoring and adjusting module monitors the rotating speed of the rotor through a rotating speed sensor, the rotating speed sensor outputs a square wave signal with the same frequency as the working frequency, the square wave signal controls the switching of a rectifier switch in the rectifier circuit, the first half period of an output signal of the operational amplifier and the second half period of an output signal of the inverter are taken, and the rectifier circuit obtains a half-wave rectifier signal. And then filtering is carried out through a low-pass filter to obtain a direct current signal, a digital signal is obtained through an analog-digital converter, and a synthetic electric field is obtained through processing and calibration. However, the problem of the synthesized electric field measuring instrument is that in an alternating electric field environment, the synthesized electric field can also inductively receive an alternating electric field signal, which is equivalent to modulating on the basis of the synthesized electric field operating frequency signal, so that the signal is a non-sine or cosine signal, and at the moment, a disordered signal can be obtained by a method of inverting through an inverter and rectifying through switching of a switch.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides an alternating current and direct current environment synthetic electric field measuring instrument and a measuring method, which are used for realizing synthetic electric field measurement resistant to power frequency electric field interference in an alternating current environment to obtain the field intensity and polarity of a synthetic electric field.
The invention adopts the following technical scheme.
The invention provides an alternating current-direct current environment synthetic electric field measuring instrument, which comprises: the device comprises a sensing electrode, a rotor, a motor, a rotating speed sensor, a monitoring and adjusting module, a sampling resistor, an operational amplifier, a phase inverter, a rectifying circuit, an analog-digital converter, a central controller, a wireless communication module and a low-pass filter; during measurement, the motor drives the rotor to rotate, so that the sensing electrode is periodically exposed to an external direct current electric field, an alternating signal is generated on the sampling resistor, the alternating signal is amplified by the operational amplifier and then divided into two paths, the first path is input into the rectifying circuit after passing through the phase inverter, and the second path is directly input into the rectifying current.
The synthetic electric field measuring instrument includes: a band-pass filter; when the measured field intensity is less than or equal to the set field intensity threshold value, the alternating signal is amplified by the operational amplifier and then input into the band-pass filter, the alternating signal filtered by the band-pass filter is divided into two paths, the first path is input into the rectifying circuit after passing through the phase inverter, and the second path is directly input into the rectifying current; when the measured field intensity is larger than the set field intensity threshold value, the alternating signal passes through the band-pass filter and then is input into the operational amplifier, the alternating signal amplified by the operational amplifier is divided into two paths, the first path passes through the phase inverter and then is input into the rectifying circuit, and the second path directly inputs the rectifying current.
The value range of the field intensity threshold is set to be more than or equal to 20kV/m.
The band-pass filter is used for filtering out 50Hz power frequency signals, 50Hz power frequency signals and interference signals generated by the intermodulation of the working frequency.
The center frequency of the band-pass filter is the working frequency of the synthetic electric field measuring instrument, and the working frequency is the product of the rotating speed of the rotor and the number of the sensing electrodes.
During measurement, the motor drives the rotor to rotate, so that the sensing electrode is periodically exposed to an external direct current electric field, the rotor rotates the fan blades, the area of the sensing electrode exposed to the direct current electric field is periodically changed, an alternating signal is generated on the sensing resistor, and the amplitude of the alternating signal is in direct proportion to the amplitude of the direct current electric field.
The monitoring and adjusting module monitors the rotating speed of the rotor through a rotating speed sensor, and the rotating speed sensor outputs square wave signals with the same frequency as the working frequency.
The square wave signal controls the switching of a rectifier switch in the rectifier circuit;
the rectifying circuit takes the first half cycle of the output signal of the operational amplifier and the second half cycle of the output signal of the inverter as input, and takes the half-wave rectified signal as output.
And filtering the half-wave rectification signal through a low-pass filter to obtain a direct current signal.
The direct current signal passes through an analog-digital converter to obtain a digital signal;
the central controller is used for processing and calibrating the acquired digital signals to obtain a synthesized electric field, receiving starting and stopping commands transmitted from the upper computer through the wireless communication module and controlling the starting and stopping of the motor; the central controller and the upper computer are communicated through the wireless communication module.
And a plurality of synthetic electric field measuring instruments and an upper computer are arranged on the synthetic electric field measuring site, and a wireless communication mode is adopted between the upper computer and the plurality of synthetic electric field measuring instruments.
The invention also provides a measuring method of the alternating current-direct current environment synthetic electric field measuring instrument, which comprises the following steps:
step 1, collecting working frequency f of synthetic electric field measuring instrument 0 ；
step 4, transforming the synthetic electric field measuring instrument, namely when the measured field intensity is less than or equal to a set field intensity threshold value, connecting a band-pass filter between the sampling resistor and the operational amplifier in series; when the measured field intensity is larger than the set field intensity threshold value, the band-pass filter is connected between the operational amplifier and the phase inverter in series;
and 5, applying a synthetic electric field to the synthetic electric field measuring instrument after the step 4 is implemented in an alternating-current electric field environment, monitoring the fluctuation rate of the measured value of the synthetic electric field, judging that the synthetic electric field measuring instrument meets the requirement of power frequency electric field interference resistance when the fluctuation rate is less than or equal to 5%, and measuring the synthetic electric field by using the synthetic electric field measuring instrument.
Preferably, in step 1, the operating frequency f 0 Is the product of the rotor speed and the number of sensing electrodes.
Preferably, in step 2, the power frequency and modulation interference rejection ratio is not less than 20dB.
Preferably, in step 5, the fluctuation ratio Δ of the synthesized electric field measurement value satisfies the following relation:
in the formula (I), the compound is shown in the specification,
E max for the maximum value of the resultant electric field measurement,
Compared with the prior art, the synthetic electric field measuring instrument for measuring the synthetic electric field has the beneficial effects that the synthetic electric field measuring instrument for measuring the synthetic electric field is designed, and the synthetic electric field measurement which is resistant to the interference of a power frequency electric field in an alternating current environment (the power frequency electric field) is realized. Analyzing the influence of the power frequency electric field on the measuring mechanism of the synthetic electric field measuring instrument, and providing a band-pass filter for filtering power frequency signals outside the working frequency of the synthetic electric field measuring instrument and interference signals generated by modulation of the power frequency signals; the design scheme of the synthetic electric field measuring instrument keeps the measurement of the polarity of the synthetic electric field.
The band-pass filter designed by the invention has the capability of inhibiting the power frequency 50Hz signal by more than 20dB.
Drawings
FIG. 1 is a schematic wiring diagram of a prior art composite electric field measuring instrument;
FIG. 2 is a waveform diagram of a signal before rectification of a synthetic electric field measuring instrument without interference of a power frequency electric field in the prior art;
FIG. 3 is a waveform diagram of rectified signals of the synthesized electric field measuring apparatus without interference of the power frequency electric field in the prior art;
FIG. 4 is a waveform diagram of a signal before rectification of a synthetic electric field measuring instrument interfered by a power frequency electric field in the prior art;
FIG. 5 is a waveform diagram of a signal rectified by the electric field measuring instrument after interference of the power frequency electric field in the prior art;
FIG. 6 is a schematic wiring diagram of a measuring apparatus for a combined AC/DC electric field;
FIG. 7 is a schematic wiring diagram of another AC/DC environment combined electric field measuring instrument according to the present invention;
FIG. 8 is a circuit diagram of a band pass filter in an embodiment of the invention;
fig. 9 is a graph of the filtering performance of the band-pass filter in the embodiment of the present invention.
The reference numerals in fig. 1, 6, 7 are illustrated as follows:
1-a sensing electrode; 2-a rotor; 3, a motor; 4-a rotation speed sensor; 5-a monitoring and adjusting module; 6-sampling resistance; 7-an operational amplifier; an 8-inverter; 9-a rectifying circuit; 10-analog-to-digital converter; 11-a central controller; 12-a wireless communication module; 13 a low-pass filter; 14-band pass filter.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The embodiments described herein are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art without inventive step, are within the scope of protection of the present invention.
The composite electric field is monitored in the environment with the alternating electric field, and the influence of the alternating electric field on the composite electric field measured by the composite electric field measuring instrument needs to be considered. The actual measurement shows that the alternating current electric field can obviously influence the measurement of the synthetic electric field, so that the measurement value of the synthetic electric field measuring instrument has obvious fluctuation and is seriously deviated from the normal measurement value. The measurement of the alternating current-direct current parallel line shows that the alternating current line has a large influence on the distribution of the direct current synthetic electric field, and the amplitude of the synthetic electric field on one side close to the alternating current line is much smaller than that of the synthetic electric field far away from the alternating current line by taking the midpoint of the direct current line as the center. Under the AC line, the measured value of the DC synthetic electric field at different point positions shows great fluctuation, even the polarity of the DC synthetic electric field is changed, the situation that the DC synthetic electric field is reduced along with the increase of the distance from the DC line under the conventional DC line is not presented any more, and the larger the fluctuation of the synthetic electric field at the place where the power frequency electric field is larger is, the influence of the power frequency electric field on the measured value of the synthetic electric field is displayed. In the synthetic electric field measuring instrument in the prior art, signal waveforms before and after rectification of the synthetic electric field measuring instrument before interference of the power frequency electric field and signal waveforms before and after rectification of the synthetic electric field measuring instrument after interference of the power frequency electric field are shown in fig. 2 to 5.
In addition, the synthetic electric field measuring instrument is placed in a power frequency electric field environment for testing, and the working frequency f of the rotor 0 The working frequency signal f generated by the rotation of the rotor is superimposed on the power frequency electric field signal 0 Many new frequency component intermodulation signals, e.g. 2f 0 -3×50Hz，f 0 -2×50Hz，f 0 -50Hz，f 0 +50Hz, etc., nor is the waveform a sine wave. After rectification, the switching frequency of the rectifier switch is according to f 0 Designed, signals are composed ofThe waveform after being modulated and rectified by the alternating signal is more disordered, and the corresponding frequency spectrum components are very rich. Resulting in large fluctuations and deviations in the resultant electric field measurements. Moreover, the spectrum analysis method cannot judge the polarity of the synthesized electric field after losing the phase information of the working frequency.
Therefore, the invention provides an alternating current and direct current environment synthetic electric field measuring instrument, which comprises: the device comprises a sensing electrode 1, a rotor 2, a motor 3, a rotating speed sensor 4, a monitoring and adjusting module 5, a sampling resistor 6, an operational amplifier 7, an inverter 8, a rectifying circuit 9, an analog-digital converter 10, a central controller 11, a wireless communication module 12 and a low-pass filter 13; during measurement, the motor drives the rotor to rotate, so that the sensing electrode is periodically exposed to an external direct current electric field, an alternating signal is generated on the sampling resistor, the alternating signal is amplified by the operational amplifier and then divided into two paths, the first path is input into the rectifying circuit after passing through the phase inverter, and the second path is directly input into the rectifying current.
The synthetic electric field measuring instrument includes: a band-pass filter 14.
When the measured field intensity is less than or equal to the set field intensity threshold value, the alternating signal is amplified by the operational amplifier and then input into the band-pass filter, the alternating signal filtered by the band-pass filter is divided into two paths, the first path is input into the rectifying circuit after passing through the phase inverter, and the second path is directly input into the rectifying current; that is, as shown in fig. 6, the input terminal of the band-pass filter 14 is connected to the output terminal of the operational amplifier 7, the output terminal of the band-pass filter 14 is connected to the input terminal of the inverter 8 and the input terminal of the rectifier circuit 9, and the center frequency of the band-pass filter 14 is the operating frequency f of the composite electric field measuring instrument 0 。
When the measured field intensity is greater than the set field intensity threshold value, the alternating signal passes through the band-pass filter and then is input into the operational amplifier, the alternating signal amplified by the operational amplifier is divided into two paths, the first path passes through the phase inverter and then is input into the rectifying circuit, and the second path directly inputs the rectifying current; as shown in fig. 7, the input terminal of the band-pass filter 14 is connected to the output terminal of the rotation speed sensor 4, the output terminal of the band-pass filter 14 is connected to the input terminal of the inverter 7, and the center frequency of the band-pass filter 14 is the operating frequency of the synthetic electric field measuring instrumentf 0 。
It should be noted that the range of the set field strength threshold in the embodiment of the present invention is greater than or equal to 20kV/m, which is a non-limiting preferred choice, and those skilled in the art can select different set field strength thresholds according to the measurement requirement.
When the signal of the measured field strength is small, a band-pass filter is preferably connected after the operational amplifier, so that the signal-to-noise ratio of the operating frequency is not reduced by the front-end filtering. For the time when the signal of the measured field intensity is large, a band-pass filter is preferably connected in front of the operational amplifier to prevent the signal from being too large to generate nonlinear amplification in the operational amplifier.
In this embodiment, a band-pass filter is connected in series to a suitable position in the synthesized electric field measuring instrument, and other circuits maintain the structure of the synthesized electric field measuring instrument in the prior art, and the center frequency of the band-pass filter is the working frequency f of the synthesized electric field measuring instrument 0 The interference signal generated by the intermodulation of 50Hz power frequency signal, 50Hz power frequency signal and working frequency can be filtered.
The center frequency of the band-pass filter is the working frequency of the synthetic electric field measuring instrument, and the working frequency is the product of the rotating speed of the rotor and the number of the sensing electrodes. The synthesized electric field measuring apparatus shown in fig. 1 is a field mill type synthesized electric field measuring apparatus, during measurement, the motor 3 drives the rotor 2 to rotate, so that the sensing electrode 1 is periodically exposed to an external direct current electric field, the rotor 2 rotates the fan blades, so that the area of the sensing electrode 1 exposed to the direct current electric field is periodically changed, and an alternating signal is generated on the sampling resistor 6, wherein the amplitude of the alternating signal is proportional to the amplitude of the direct current electric field. The frequency of the alternating signal is equal to the rotor speed multiplied by the number of sensing electrodes.
The alternating signal is gain amplified by the operational amplifier 7, the output of the operational amplifier 7 is divided into two paths, one path is inverted by the inverter 8, and the other path is the original signal. The monitoring and adjusting module 5 monitors the rotating speed of the rotor 2 through the rotating speed sensor 4, the rotating speed sensor 4 outputs a square wave signal with the same frequency as the working frequency, the square wave signal controls the switching of a rectifying switch in the rectifying circuit 9, the first half period of an output signal of the operational amplifier 7 and the second half period of an output signal of the inverter 8 are taken, and the rectifying circuit 9 obtains a half-wave rectifying signal. Then, the low-pass filter 13 filters the signal to obtain a dc signal, and the analog-to-digital converter 10 processes and calibrates the digital signal to obtain a synthesized electric field.
During measurement, the motor drives the rotor to rotate, so that the sensing electrode is periodically exposed to an external direct current electric field, the rotor rotates the fan blades, the area of the sensing electrode exposed to the direct current electric field is periodically changed, an alternating signal is generated on the sensing resistor, and the amplitude of the alternating signal is in direct proportion to the amplitude of the direct current electric field.
The monitoring and adjusting module monitors the rotating speed of the rotor through a rotating speed sensor, and the rotating speed sensor outputs square wave signals with the same frequency as the working frequency.
The square wave signal controls the switching of a rectifier switch in the rectifier circuit;
the rectifying circuit takes the first half cycle of the output signal of the operational amplifier and the second half cycle of the output signal of the inverter as input, and takes the half-wave rectified signal as output.
And filtering the half-wave rectification signal through a low-pass filter to obtain a direct current signal.
The direct current signal passes through an analog-digital converter to obtain a digital signal;
the central controller is used for processing and calibrating the acquired digital signals to obtain a synthesized electric field, receiving starting and stopping commands transmitted from the upper computer through the wireless communication module and controlling the starting and stopping of the motor; the central controller is communicated with the upper computer through the wireless communication module.
And a plurality of synthetic electric field measuring instruments and an upper computer are arranged on the synthetic electric field measuring site, and a wireless communication mode is adopted between the upper computer and the plurality of synthetic electric field measuring instruments.
The invention also provides a measuring method of the alternating current-direct current environment synthetic electric field measuring instrument, which comprises the following steps:
step 1, collecting working frequency f of synthetic electric field measuring instrument 0 ；
Preferably, in step 1, the operating frequency f 0 Is a rotorThe product of the rotational speed and the number of sensing electrodes.
preferably, in step 2, the power frequency and modulation interference rejection ratio is not less than 20dB.
preferably, in step 5, the fluctuation ratio Δ of the synthesized electric field measurement value satisfies the following relation:
in the formula (I), the compound is shown in the specification,
E max for the maximum value of the resultant electric field measurement,
Step 4, the synthetic electric field measuring instrument is reformed, namely when the measured field intensity is less than or equal to the set field intensity threshold value, the band-pass filter is connected in series between the sampling resistor and the operational amplifier; when the measured field intensity is larger than the set field intensity threshold value, the band-pass filter is connected between the operational amplifier and the phase inverter in series;
and 5, applying a synthetic electric field to the synthetic electric field measuring instrument after the step 4 is implemented in an alternating-current electric field environment, monitoring the fluctuation rate of the measured value of the synthetic electric field, judging that the synthetic electric field measuring instrument meets the requirement of power frequency electric field interference resistance when the fluctuation rate is less than or equal to 5%, and measuring the synthetic electric field by using the synthetic electric field measuring instrument.
In this embodiment, a band-pass filter is designed, the center frequency is 66Hz, the attenuation to 50Hz power frequency signals is about 20dB, and the circuit diagram of the band-pass filter is shown in fig. 8.
The design of a second-order band-pass active filter is adopted, and in the optimized design, the resistance R3=1.33M omega, the resistance R4=10.2k omega, the resistance R5=1M omega, the resistance R6=383k omega, and the resistance R7=4.75k omega; capacitance C1=24nf, C2=24nf; the operational amplifier U1 employs LT6023. The filtering performance of the band-pass filter is shown in fig. 9, and it can be seen from fig. 9 that the center frequency of the band-pass filter is 66Hz, and the rejection of 50Hz signals is greater than 20dB.
The introduction of the band-pass filter also causes certain insertion loss to the working frequency signal of the synthetic electric field instrument, and the synthetic electric field instrument needs to be calibrated again before being used for synthesizing an electric field. The improved design scheme has the advantages that the polarity and the field intensity amplitude of the synthetic electric field can be measured, and the power frequency electric field signal and the modulation signal can be well inhibited.
The measurement specification of the synthetic electric field requires the measurement of the field intensity and polarity of the synthetic electric field, the method provided by the invention can better meet the requirement of the measurement specification, and finally, the filter method is adopted to carry out improved design on the synthetic electric field instrument.
In the embodiment of the invention, when the alternating current-direct current environment synthetic electric field measuring instrument measures the synthetic electric field, whether power frequency electric field interference exists in the environment is firstly identified, and the method comprises the following steps:
1) Monitoring whether an AC power transmission and transformation project exists within a certain range (typically 50 m) on site. If present, a synthetic electric field meter is considered.
2) The point position to be monitored by the direct current synthetic electric field is monitored on site by a power frequency electric field probe, the power frequency electric field intensity is smaller, and the typical value is less than or equal to 100V/m, and the direct current synthetic electric field can be measured by a conventional synthetic electric field measuring instrument or a synthetic electric field measuring instrument resisting the interference of the power frequency electric field. If the power frequency electric field measurement value is larger, the typical value is more than or equal to 500V/m, a synthetic electric field measuring instrument capable of resisting the interference of the power frequency electric field is adopted for measurement.
3) If the condition for measuring the power frequency electric field is not available, a proper instrument is not available. The existing resultant electric field measurements should be observed. Observing the monitoring value of the composite electric field measuring instrument in the inner part, if the following characteristics occur: the amplitude of the combined electric field on the side close to the ac line is much smaller than the amplitude of the combined electric field far from the ac line, with the midpoint of the dc line as the center. Under the alternating current circuit, the measured value of the direct current synthetic electric field at different point positions shows great fluctuation, even the polarity of the direct current synthetic electric field is changed, the direct current synthetic electric field is not reduced along with the increase of the distance from the direct current circuit under the conventional direct current circuit, and the larger the fluctuation of the synthetic electric field at the position where the power frequency electric field is larger is, the influence of the power frequency electric field on the measured value of the synthetic electric field is displayed. A synthetic electric field measuring instrument resistant to interference of a power frequency electric field should be used.
4) And for the used synthetic electric field measuring instrument, whether the synthetic electric field measuring instrument has the power frequency electric field interference resistance or not is not clear, in the power frequency electric field environment, an oscilloscope is adopted to check the rectified waveform of the synthetic electric field measuring instrument, and if the waveform is the following standard half-wave shaped waveform, the waveform is not interfered by the power frequency electric field.
Secondly, if the synthetic electric field measuring instrument which is resistant to the interference of the power frequency electric field does not exist, and only a conventional synthetic electric field measuring instrument exists, the following improvement scheme is adopted for the conventional synthetic electric field measuring instrument:
1) Identifying the operating frequency f of a synthetic electric field measuring instrument 0 The number is the number of the sensing electrodes multiplied by the rotor speed.
2) Comparing the operating frequencies f 0 With power frequency electric field signal, and power frequency signal and operating frequency signal f 0 Many new frequency component intermodulation signals, e.g., 2f 0 -3×50Hz，f 0 -2×50Hz，f 0 -50Hz，f 0 +50Hz, etc., the design requirements for anti-interference of the confirmed operating frequency and the design requirements for the band-pass filter should reach 20dB for power frequency and modulation interference rejection ratio.
3) In the environment of an alternating current electric field, an oscilloscope is adopted to monitor the signal waveform before rectification and the signal waveform after rectification, and if the rectified waveform is as follows and is not a standard half-wave rectification signal, the interference of a power frequency electric field is determined.
4) The designed band pass filter is inserted before the rectifier circuit.
5) The insertion of the band pass filter causes insertion loss, i.e. the signal amplitude is reduced compared to before the insertion, and the calibrated synthetic electric field measuring instrument should be retested.
6) The designed synthetic electric field measuring instrument capable of resisting the interference of the power frequency electric field is tested in an alternating current electric field environment (such as the power frequency electric field intensity of 1 kV/m), a stable synthetic electric field (such as the synthetic electric field intensity of 1 kV/m) is applied, the fluctuation of the measured value of the synthetic electric field is observed, and if the fluctuation is very small, such as the (maximum value-average value)/average value in the measured value is less than or equal to 5%, the synthetic electric field measuring instrument is considered to meet the requirement of resisting the interference of the power frequency electric field.
The invention overcomes the technical difficulty, and filters the power frequency signal and the signal generated by modulating the power frequency and the working frequency, so that the measurement of the synthesized electric field is accurate in the alternating current and direct current environment.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (14)
1. An alternating current-direct current environment resultant electric field measuring instrument comprises: the device comprises a sensing electrode, a rotor, a motor, a rotating speed sensor, a monitoring and adjusting module, a sampling resistor, an operational amplifier, a phase inverter, a rectifying circuit, an analog-digital converter, a central controller, a wireless communication module and a low-pass filter; during measurement, the motor drives the rotor to rotate, so that the sensing electrode is periodically exposed to an external direct current electric field, an alternating signal is generated on the sampling resistor, the alternating signal is amplified by the operational amplifier and then divided into two paths, the first path is input into the rectifying circuit after passing through the phase inverter, and the second path is directly input into the rectifying current; it is characterized in that the preparation method is characterized in that,
the synthetic electric field measuring instrument includes: a band-pass filter;
when the measured field intensity is less than or equal to the set field intensity threshold value, the alternating signal is amplified by the operational amplifier and then input into the band-pass filter, the alternating signal filtered by the band-pass filter is divided into two paths, the first path is input into the rectifying circuit after passing through the phase inverter, and the second path is directly input into the rectifying current;
when the measured field intensity is larger than the set field intensity threshold value, the alternating signal is input into the operational amplifier after passing through the band-pass filter, the alternating signal amplified by the operational amplifier is divided into two paths, the first path is input into the rectifying circuit after passing through the phase inverter, and the second path is directly input into the rectifying current.
2. The AC/DC environment resultant electric field measuring instrument according to claim 1,
the value range of the field intensity threshold is set to be more than or equal to 20kV/m.
3. The AC/DC environment resultant electric field measuring instrument according to claim 1,
the band-pass filter is used for filtering out 50Hz power frequency signals, and interference signals generated by the intermodulation of the 50Hz power frequency signals and the working frequency.
4. The AC/DC environment resultant electric field measuring instrument according to claim 1,
the center frequency of the band-pass filter is the working frequency of the synthetic electric field measuring instrument, and the working frequency is the product of the rotating speed of the rotor and the number of the sensing electrodes.
5. The AC/DC environment resultant electric field measuring instrument according to claim 1,
during measurement, the motor drives the rotor to rotate, so that the sensing electrode is periodically exposed to an external direct current electric field, the rotor rotates the fan blades, the area of the sensing electrode exposed to the direct current electric field is periodically changed, an alternating signal is generated on the sensing resistor, and the amplitude of the alternating signal is in direct proportion to the amplitude of the direct current electric field.
6. The AC/DC environmental synthetic electric field measuring instrument according to claim 5,
the monitoring and adjusting module monitors the rotating speed of the rotor through a rotating speed sensor, and the rotating speed sensor outputs square wave signals with the same frequency as the working frequency.
7. The AC/DC environmental synthetic electric field measuring instrument according to claim 6,
the square wave signal controls the switching of a rectifier switch in the rectifier circuit;
the rectifying circuit takes the first half cycle of the output signal of the operational amplifier and the second half cycle of the output signal of the inverter as input, and takes the half-wave rectified signal as output.
8. The alternating current and direct current environment resultant electric field measuring instrument according to claim 7,
and filtering the half-wave rectification signal through a low-pass filter to obtain a direct current signal.
9. The AC/DC environmental synthetic electric field measuring instrument according to claim 8,
the direct current signal passes through an analog-digital converter to obtain a digital signal;
the central controller is used for processing and calibrating the acquired digital signals to obtain a synthesized electric field, receiving starting and stopping commands transmitted from the upper computer through the wireless communication module and controlling the starting and stopping of the motor; the central controller and the upper computer are communicated through the wireless communication module.
10. The AC/DC environmental synthetic electric field measuring instrument according to claim 9,
and a plurality of synthetic electric field measuring instruments and an upper computer are arranged on the synthetic electric field measuring site, and a wireless communication mode is adopted between the upper computer and the plurality of synthetic electric field measuring instruments.
11. A measuring method suitable for the alternating current and direct current environment resultant electric field measuring instrument according to any one of claims 1 to 10,
the method comprises the following steps:
step 1, collecting the working frequency f of the synthetic electric field measuring instrument 0 ；
Step 2, determining a power frequency and modulation interference suppression ratio based on the level of the power frequency electric field intensity in the AC/DC environment and the suppression requirements on the power frequency and modulation interference;
step 3, designing a band-pass filter to work at a frequency f 0 The central frequency of the band-pass filter is used, and the power frequency and the modulation interference rejection ratio are used as the attenuation ratio of the band-pass filter to a 50Hz power frequency signal;
step 4, the synthetic electric field measuring instrument is reformed, namely when the measured field intensity is less than or equal to the set field intensity threshold value, the band-pass filter is connected in series between the sampling resistor and the operational amplifier; when the measured field intensity is larger than the set field intensity threshold value, the band-pass filter is connected between the operational amplifier and the phase inverter in series;
and 5, applying a synthetic electric field to the synthetic electric field measuring instrument after the step 4 is implemented in an alternating-current electric field environment, monitoring the fluctuation rate of the measured value of the synthetic electric field, judging that the synthetic electric field measuring instrument meets the requirement of power frequency electric field interference resistance when the fluctuation rate is less than or equal to 5%, and measuring the synthetic electric field by using the synthetic electric field measuring instrument.
12. The AC/DC environment resultant electric field measuring method according to claim 11,
in step 1, the operating frequency f 0 Is the product of the rotor speed and the number of sensing electrodes.
13. The method according to claim 11, wherein in step 2, the power frequency and modulation interference rejection ratio is not less than 20dB.
14. The method according to claim 11, wherein in step 5, the fluctuation ratio Δ of the synthesized electric field measurement value satisfies the following relation:
in the formula (I), the compound is shown in the specification,
E max for the maximum value of the resultant electric field measurement,
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