CN106771510A - A kind of method for improving residual current lower range certainty of measurement - Google Patents
A kind of method for improving residual current lower range certainty of measurement Download PDFInfo
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- CN106771510A CN106771510A CN201510813435.2A CN201510813435A CN106771510A CN 106771510 A CN106771510 A CN 106771510A CN 201510813435 A CN201510813435 A CN 201510813435A CN 106771510 A CN106771510 A CN 106771510A
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- residual current
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- lower range
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/145—Indicating the presence of current or voltage
- G01R19/15—Indicating the presence of current
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- General Physics & Mathematics (AREA)
- Measurement Of Current Or Voltage (AREA)
Abstract
The present invention relates to a kind of method for improving residual current lower range certainty of measurement, including distribution line residual current is sampled by residual current transformer；The residual current to being sampled to carry out data processing obtain with its with frequency with phase 50mA current signal；The current signal of the 50mA is fed back to the input of residual current transformer；The residual current is measured in the output linearity area of the residual current transformer；The numerical value that the residual current will be measured subtracts the residual current measurement result that 50mA is met high-precision requirement.Technical solution of the present invention reduces residual current measurement error so that low-voltage network residual current monitoring data accurate and effective, the accurate measurement of residual current, can enable three-level protective system effectively interoperation, the reliability service of power distribution network residual current.
Description
Technical field：
The present invention relates to the field of high-precision measurement of power distribution network residual current, it is more particularly to a kind of raising and remains
The method of aftercurrent lower range certainty of measurement.
Background technology：
Universal (the measurement more than ± 10% of the residual current measurement error of country's residual current operated protective device at present
Scope 30-1000mA), residual current measurement error is bigger than normal so that residual current monitoring system data distortion,
Prevent the three-level protective system of Rural Power Distribution Network residual current from effective interoperation, operational reliability drop
It is low.
Improve residual current operated protective device residual current certainty of measurement, it is important to improve the measurement essence of lower range
Degree.
The content of the invention：
It is an object of the invention to provide a kind of method for improving residual current lower range certainty of measurement, reduce surplus
Aftercurrent measurement error so that low-voltage network residual current monitoring data accurate and effective.
To achieve the above object, the present invention uses following technical scheme：One kind improves residual current lower range
The method of certainty of measurement, including：
Distribution line residual current is sampled by residual current transformer；
The residual current to being sampled to carry out data processing obtain with its with frequency with phase 50mA electricity
Stream signal；
The current signal of the 50mA is fed back to the input of residual current transformer；
The residual current is measured in the output linearity area of the residual current transformer；
The numerical value that the residual current will be measured subtracts the residue electricity that 50mA is met high-precision requirement
Flow measurement result.
Under load resistance, the change curve of the residual current transformer output characteristics includes three sections：Rise
The saturation region of the inelastic region of beginning section, the linear zone in stage casing and latter end；The linear zone is with residual current
Increase, the output voltage of residual current transformer is consequently increased.
Data processing is carried out to the residual current by data processing circuit；The data processing circuit bag
Include amplifier circuit, sine wave square wave conversion circuit, phase demodulation low-pass filter circuit, level shifting circuit,
Function generator and current amplification circuit；The phase demodulation low-pass filter circuit, level shifting circuit and function
Generator constitutes a phaselocked loop PLC circuit；The residual current being sampled to sequentially passes through amplifier
Circuit and sine wave square wave conversion circuit obtain a square-wave signal synchronous with distribution line residual current,
And as an input of the phaselocked loop PLC circuit.
The phase demodulation low-pass filter circuit includes the RC low pass filters that phase discriminator and its output end are provided with；
The phase discriminator includes PDL；The PDL is made up of XOR gate, it is desirable to which the dutycycle of input waveform is
50%.
The square wave output pin of the function generator connects a pull-up resistor to voltage V+ so that its output
Square wave level between ± 12V；The square wave of the output is through level shifting circuit as phaselocked loop PDL
Another input of circuit；The sine wave pin output sine wave signal of the function generator, by institute
Current amplification circuit is stated, 50mA same-phase alternating currents are exported.
The function generator is ICL8038 function generators；Its pin 4,5 and 16 connects electricity respectively
Resistance R13, R14 and electric capacity C2；To make the sine wave and square wave of the ICL8038 function generators output
Dutycycle is 50%, takes R13=R14；The sine wave signal frequency of its output in 50Hz, when loop lock
It is 9V at timing pin 8, therefore takes R13=R14=20K, C2=0.2 μ F.
Resistance in the RC low pass filters is 100 kilohms, and electric capacity is 2.2 microfarads.
The PDL is CD4046PDL.
The sine wave distortion factor of the ICL8038 function generators is by adjusting its pin 1 and pin 12
Composition bridge circuit, makes the distortion factor be reduced to 0.1%.
With immediate prior art ratio, the present invention provides technical scheme has following excellent effect
1st, the accurate measurement of technical solution of the present invention residual current, can make the three-level of power distribution network residual current
Protection system can effectively interoperation, reliability service；
2nd, the frequency and phase of technical solution of the present invention automatic real-time track line voltage, is not take up doing and locates
The soft and hardware resource of device is managed, the complexity of programming is greatly reduced；
3rd, technical solution of the present invention disclosure satisfy that the high-acruracy survey result of requirement；
4th, technical solution of the present invention is met in 20mA to 600mA residual current measurement ranges, error
Control is within 3%.
Brief description of the drawings
Fig. 1 is the measurement circuitry connection diagram of the embodiment of the present invention；
Fig. 2 is the transformer output characteristic curve figure of the embodiment of the present invention；
Fig. 3 is the measuring circuit theory diagram of the embodiment of the present invention；
Fig. 4 is the amplifier circuit diagram of the embodiment of the present invention；
Fig. 5 is the sine wave/square wave conversion circuit schematic diagram of the embodiment of the present invention；
Fig. 6 is the phase demodulation low-pass filter circuit schematic diagram of the embodiment of the present invention；
Fig. 7 is the level shifting circuit schematic diagram of the embodiment of the present invention；
Fig. 8 is the sine wave generation circuit schematic diagram of the embodiment of the present invention；
Fig. 9 is the current amplification circuit schematic diagram of the embodiment of the present invention.
Specific embodiment
With reference to embodiment, the invention will be described in further detail.
Embodiment 1：
The invention of this example provides a kind of method for improving residual current lower range certainty of measurement, as shown in figure 1,
Distribution line residual current is sampled using residual current transformer, then by a series of circuits at
Reason obtains the 50mA current signals of and distribution line residual current in-phase synchronization.The electric current is applied
To residual current transformer, the measurement starting point of residual current is improved, avoid the output of residual current transformer
Characteristic nonlinearity area, 50mA is subtracted in the numerical value of protector CPU sampled measurements, you can obtain high-precision
The measurement result of degree.Methods described needs to use the AC signal synchronous with distribution line residual current, i.e.,
With distribution line residual current with frequently with the standard sine signal of phase.The present invention is completed using devices at full hardware circuit
The function, i.e., using phaselocked loop and Sine Function Generator integrated circuit, automatic real-time track line voltage
Frequency and phase, be not take up processing the soft and hardware resource of device, greatly reduce the complexity of programming.
This hardware circuit is divided into distribution line residual current amplifier, sine wave/square wave from principle and turns
Change, phase demodulation LPF, level conversion, sine wave are produced and the several parts of Current amplifier.Methods described
It is distribution line residual current to be sampled using residual current transformer, is amplified, then by zero passage
Comparator, obtains a square-wave signal synchronous with distribution line residual current, used as phase discriminator (PD)
One input.Phase discriminator, LPF and function generator ICL8038 constitute a phaselocked loop (PLC)
Circuit.When loop-locking, output sine wave is synchronous with line voltage, i.e., with the same phase of frequency, in time
Almost should not postpone.Principle assumption diagram is as shown in Figure 3.
(1) amplifier circuit
Millivolt magnitude voltage signals to residual current transformer are amplified, and allow the signal of amplification by mistake
Zero comparator recognizes that circuit is as shown in Figure 4.
(2) sine wave/square wave conversion circuit
Distribution line residual current is sampled using residual current transformer, then by Zero-cross comparator
Device, obtains a square-wave signal synchronous with distribution line residual current, and circuit is as shown in Figure 5.
(3) phase demodulation low-pass filter circuit
Phase discriminator in the present embodiment uses the PDl of CD4046.PDl is made up of XOR gate, it is desirable to defeated
The dutycycle for entering waveform is substantially 50%.Resistance R8 and electric capacity C1 constitutes low pass filter, circuit
As shown in Figure 6.
(4) level shifting circuit
Due to the output of the PDl of phase discriminator CD4046 be between -12V~+12V, and function occur
The control voltage signal of device ICL8038 requirement inputs must be between 1/3V+~V+, i.e. 4V~12V
Between.So level conversion must be done, ICL8038 circuits are enable to capture input control signal well.
Circuit is as shown in Figure 7.
(5) sine wave generation circuit
Function generator ICL8038 can just produce high-precision side by connecting a small amount of outer member
The waveforms such as ripple, sine wave, sawtooth waveforms.To reduce the sine wave distortion factor, by the sine wave of ICL8038
The distortion factor adjusts pin 1 and the composition bridge circuit of pin 12, the distortion factor is reduced to 0.1% or so.Pin 2
Export sine wave.Square wave output pin 9 connects a pull-up resistor to V+ so that the square wave level of output
Between ± 12V.The square wave of output through level conversion as PDl another input.Due to ICL8038
There is 90 ° of difference between the square wave and sine wave of output, when loop-locking, just meet PDl inputs
Output waveform dutycycle is 50% requirement, and circuit is as shown in Figure 8.
(6) current amplification circuit
Function generator ICL8038 pins 2 export sine wave and amplify output, can export 50mA same
Multi-phase alternating current electric current, circuit is as shown in Figure 9.
(7) circuit key parameter design
Low pass filter, in Fig. 6, the parameter designing of R8 and Cl：R8 and Cl catches performance to loop
And job stability has a great impact.If taking larger time constant R8 × C1, can make loop with
Track produces excessive delay when changing incoming frequency faster；If taking less time constant R8 × C1,
When can then make the fast-changing input signal of loop tracks.Cause the unusual change of phase-lock-ring output frequency.
Consider loop and catch performance and job stability.Selection R8=100K Ω, C1=2.2 μ F.
The parameter selection of ICL8038 outward elements R13, R14 and C2：To make what ICL8038 was exported
Sine wave and duty cycle square wave are 50%, take R13=R14.The sine wave signal frequency of output should be
50Hz or so, should be in 9V or so, so the C2 in allowed band at pin 8 when loop-locking
Should try one's best take it is bigger, finally take R13=R14=20K, C2=0.2 μ F.
Under certain load resistance, the change curve of residual current transformer error characteristics is shown in Fig. 2.Will
Fig. 2 curves are divided into three sections.It can be seen that the output valve of the bright transformer starting of a segment tables is very low, residual current
Be continuously increased and output voltage change it is disproportionate, only after residual current increases to certain numerical value, mutually
Sensor just has proportional output voltage values.B sections shows with the increase of residual current, transformer output
Voltage is consequently increased, and this section is it is considered that its output is linear change.C segment tables are bright, work as mutual inductance
After device output voltage reaches certain value, with the increase of input current the output voltage of transformer not followed by
It is continuous to increase, tend to be steady on the contrary, in addition it is on a declining curve, illustrate that transformer iron core has reached saturation state.
It can be seen that b sections can be accurate measurement use one section of region.
Understand that residual current transformer sampling error is controllable in 70mA to 700mA through experimental study
System is within 3%.To meet high accuracy (in 20mA to 600mA residual current measurement ranges, by mistake
Difference control is within 3%) measurement request, therefore to the additional 50mA of residual current transformer with frequency
In-phase current, surveys residual current transformer sampling scope and 70mA is moved to from 20mA to 600mA
To the range of linearity of 650mA, subtracted in the numerical value of residual current operated protective device CPU sampled measurements
50mA, you can be met the high-acruracy survey result of requirement.
Finally it should be noted that：The above embodiments are merely illustrative of the technical solutions of the present invention rather than to it
Limitation, those of ordinary skill in the art with reference to above-described embodiment although should be understood：Still can be right
Specific embodiment of the invention is modified or equivalent, and these are without departing from spirit of the invention and model
Any modification enclosed or equivalent, apply pending claims of the invention it
It is interior.
Claims (9)
1. it is a kind of improve residual current lower range certainty of measurement method, it is characterised in that：Including：
Distribution line residual current is sampled by residual current transformer；
The residual current to being sampled to carries out data processing and obtains believing with the electric current of the 50mA of phase with frequency with it
Number；
The current signal of the 50mA is fed back to the input of residual current transformer；
The residual current is measured in the output linearity area of the residual current transformer；
The numerical value that the residual current will be measured subtracts the residual current survey that 50mA is met high-precision requirement
Amount result.
2. a kind of method for improving residual current lower range certainty of measurement as claimed in claim 1, its feature
It is：Under load resistance, the change curve of the residual current transformer output characteristics includes three sections：Rise
The inelastic region of beginning section, the linear zone in stage casing and the saturation region of latter end；The linear zone is with remaining electricity
The increase of stream, the output voltage of residual current transformer is consequently increased.
3. a kind of method for improving residual current lower range certainty of measurement as claimed in claim 1, its feature
It is：Data processing is carried out to the residual current by data processing circuit；The data processing circuit bag
Include amplifier circuit, sine wave square wave conversion circuit, phase demodulation low-pass filter circuit, level shifting circuit,
Function generator and current amplification circuit；The phase demodulation low-pass filter circuit, level shifting circuit and function hair
Raw device constitutes a phaselocked loop PLC circuit；The residual current being sampled to sequentially passes through amplifier circuit
A square-wave signal synchronous with distribution line residual current, and conduct are obtained with sine wave square wave conversion circuit
One input of the phaselocked loop PLC circuit.
4. a kind of method for improving residual current lower range certainty of measurement as claimed in claim 3, its feature
It is：The phase demodulation low-pass filter circuit includes the RC low pass filters that phase discriminator and its output end are provided with；Institute
Stating phase discriminator includes PDL；The PDL is made up of XOR gate, it is desirable to which the dutycycle of input waveform is 50%.
5. a kind of method for improving residual current lower range certainty of measurement as claimed in claim 4, its feature
It is：The square wave output pin of the function generator connects a pull-up resistor to voltage V+ so that its output
Square wave level is between ± 12V；The square wave of the output is through level shifting circuit as phaselocked loop PDL circuits
Another input；The sine wave pin output sine wave signal of the function generator, by the electric current
Amplifying circuit, exports 50mA same-phase alternating currents.
6. a kind of method for improving residual current lower range certainty of measurement as claimed in claim 5, its feature
It is：The function generator is ICL8038 function generators；Its pin 4,5 and 16 connects electricity respectively
Resistance R13, R14 and electric capacity C2；To make the sine wave and square wave duty of the ICL8038 function generators output
Than being 50%, R13=R14 is taken；The sine wave signal frequency of its output is in 50Hz, the pin when loop-locking
It is 9V at 8, therefore takes R13=R14=20K, C2=0.2 μ F.
7. a kind of method for improving residual current lower range certainty of measurement as claimed in claim 6, its feature
It is：Resistance in the RC low pass filters is 100 kilohms, and electric capacity is 2.2 microfarads.
8. a kind of method for improving residual current lower range certainty of measurement as claimed in claim 4, its feature
It is：The PDL is CD4046PDL.
9. a kind of method for improving residual current lower range certainty of measurement as claimed in claim 6, its feature
It is：The sine wave distortion factor of the ICL8038 function generators is by adjusting 12 groups of its pin 1 and pin
Into bridge circuit, the distortion factor is set to be reduced to 0.1%.
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| CN201510813435.2A CN106771510B (en) | 2015-11-23 | 2015-11-23 | Method for improving low-range measurement precision of residual current |
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| CN201510813435.2A CN106771510B (en) | 2015-11-23 | 2015-11-23 | Method for improving low-range measurement precision of residual current |
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| CN106771510B CN106771510B (en) | 2020-01-24 |
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| CN203933437U (en) * | 2014-07-15 | 2014-11-05 | 湖南大学 | A kind of universal bridge-type inverter control circuit board based on two DSP |
| CN204177739U (en) * | 2014-10-09 | 2015-02-25 | 河北钢铁股份有限公司 | Two-phase lock-in amplifier |
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2015
- 2015-11-23 CN CN201510813435.2A patent/CN106771510B/en active Active
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|---|---|---|---|---|
| CN1145117A (en) * | 1994-12-28 | 1997-03-12 | 菲利浦电子有限公司 | DC and AC current sensor having a minor-loop orperated current transformer |
| CN1847865A (en) * | 2006-03-16 | 2006-10-18 | 西安爱科电子有限责任公司 | Energy feedback type AC/DC electronic load simulator |
| CN101285692A (en) * | 2008-06-04 | 2008-10-15 | 中国科学院长春光学精密机械与物理研究所 | Delicate signal detection device |
| CN102045062A (en) * | 2011-01-27 | 2011-05-04 | 中山大学 | Digital phase-locked loop based on Cordic algorithm |
| CN102684744A (en) * | 2012-05-18 | 2012-09-19 | 苏州东奇信息科技有限公司 | Power supply self-synchronizing phase inversion modulator-demodulator for power line communication |
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| CN103957007A (en) * | 2014-05-09 | 2014-07-30 | 武汉工程大学 | Random waveform weak signal detection method and system under low signal to noise ratio |
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