CN203965509U - Alien frequencies weak current Luo-coil measurement mechanism under thousand times of interference - Google Patents
Alien frequencies weak current Luo-coil measurement mechanism under thousand times of interference Download PDFInfo
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Abstract
Alien frequencies weak current Luo-coil measurement mechanism under thousand times of interference, by Luo-coil, input terminal, filtering circuit unit, automatic range switching unit, amplifying unit, level biasing circuit, 50Hz trap circuit, AD sampling unit, CPU, display screen, storage unit, operation knob, printer forms.The utility model can be realized the measurement of measuring alien frequencies (as 47Hz, 53Hz) weak current under thousands of times of power frequency interference currents, and in electric measurement field, particularly the electric system field tests under strong jamming background has important purposes.
Description
Technical field
The utility model relates to field of measuring technique.
Background technology
Most electric equipment operations are depressed in 50Hz industrial-frequency alternating current, in a lot of situations, need to measure the state parameter under power frequency 50Hz, be wherein direct measuring voltage current signal mostly, or by sensor, various physical quantitys be converted to voltage and current signal and then measure.Owing to existing very strong 50Hz to disturb in electrical network, so be difficult to measure because of 50Hz strong jamming in the more on-the-spot faint test signals of high voltage substation, often bring very large error even cannot measure.So, in a lot of electrical parameters measure projects, can adopt alien frequencies method to measure, on equipment, add the sine wave source (as 53Hz) that differs from power frequency, then utilize frequency-selective filtering technology to suppress 50Hz and disturb, only measure the corresponding parameter of this 53Hz signal, can try to achieve result A.Then by same method, in the symmetrical offset frequency of power frequency, measure 47Hz and try to achieve result B, get the average of A+B and can think the result C under 50Hz.The method both can two point symmetry frequency conversions be measured (as 47Hz, 53Hz), also can the symmetrical frequency conversion of multiple spot measure (as 45,47,53,55Hz) to improve accuracy and the confidence level of result.This frequency conversion (or claiming alien frequencies) error that mensuration can effectively avoid the strong jamming of 50Hz power frequency to bring, can have the environment of disturbance of industry frequency as high voltage substation, power plant's Measurement accuracy electrical equipment parameter.Frequency conversion method of testing is applied on multiple testing tool, as frequency-conversion anti-jamming dielectric loss tester, and parameter tester for pilot frequency line, frequency conversion ground connection parameter test system etc.
Frequency conversion method of testing will reach this final purpose of interference-free Measurement accuracy, relates generally to the technology of two aspects: frequency conversion and frequency-selecting.Frequency conversion is the mains supply of 50Hz to be transformed into all adjustable sinusoidal wave variable-frequency power sourcess of voltage and frequency, frequency-selecting be in the interference of various complexity at the scene by the weak signal extraction after frequency conversion out, and carry out Measurement accuracy.Converter technique development time early, comparative maturity comparatively speaking, the source as in " source-table " measuring system, does not relate to the output of measurements and calculations result.It is generally all isolated by isolating transformer and external interference simultaneously, and impact without interruption, only need to be by himself internal circuit program frequency conversion.So this part major technique difference of variable-frequency power sources is watt level, other technical indicator aspect there generally is not difference.
It is complicated a lot of that frequency-selecting technology is wanted comparatively speaking, and as the table in " source-table " measuring system, it will, under the disturbed condition of various complexity, be isolated faint frequency variation signal and measure Output rusults.Often the useful frequency variation signal amplitude of jam-to-signal strong several times to tens times, useful frequency variation signal " is flooded " in various undesired signals.And power frequency interference, high frequency interference, humorous wave interference in the signal of surveying, have been comprised, be superimposed with again frequency variation signal, it is disorderly and unsystematic complicated and changeable without clear and definite rule that waveform has become, will in the waveform of so mixed and disorderly complexity, reduce and extract useful feeble signal and also want Measurement accuracy, difficulty is well imagined.And test frequency and interfering frequency nearer, the difficulty of frequency-selecting is just larger.Obviously, frequency-selecting technology direct relation the accuracy of complete frequency conversion measuring system result, is that can integrated system reach the gordian technique of getting rid of this final purpose of interference Measurement accuracy, is the technical bottleneck of integrated system.
Existing frequency-selecting measuring technique is mainly based on analog filtering circuit or title hardware filtering circuit, as LC inductance capacitance device etc.But analog filtering circuit exists following shortcoming, 1, the interference that can only suppress and decay, can not completely real filtering interfering.2, analogue filter circuit is suitable for test signal and the very large situation (as 200Hz and 50Hz) of interfering frequency difference, for two very approaching frequencies (as 53Hz and 50Hz), is difficult to reach ideal effect; 3, limited by hardware circuit self-characteristic, its antijamming capability can only reach 1/10th; 4, inconsistent to different frequencies and amplitude response characteristic because of hardware circuit, be difficult to guarantee all measure accurately under each range of each frequency; 5, mimic channel is unfavorable for intellectuality, and robotization is integrated.
In transformer station, some measure the items often need to be measured size of current, generally also adopt and add alien frequencies signal source, then measure this non-power-frequency current size flowing through in metal frame or cable.But another difficult point is, the large and out-of-shape of transformer station's metal frame stock size, conductor diameter can reach 1 meter of left and right, and conventional clamp on amperemeter cannot vise so large conductor.Some local wiring is intensive and quantity is a lot, and clamp on amperemeter cannot play a role equally.So adopt flexible Luo-coil sample rate current, become a desirable selection scheme.
Luo-coil (Rogowski coil, Rockwell coil, Rogowski coil) is again current measurement coil, differential current sensor, is the toroid winding of a uniform winding on nonferromugnetic material.Output signal is electric current time differential.By a voltage signal to output, carry out the circuit of integration, just can truly reduce input current.This coil has electric current measurement in real time, fast response time, can saturated, almost there is no the feature of phase error; therefore it can be applicable to relay protection; silicon controlled rectifier; frequency control, the occasion of the large electric current such as the serious distortion of the signals such as electric resistance welding and electric furnace, short-circuit test, thunder and lightning signals collecting.
Because Luo-coil has a hollow, rather than an iron core, it has low inductance, and can comply with fast changing electric current.Dangerous without second open circuit; Can measure fortuitous conductor; Easy for installation, need not destroy conductor; In addition, because it does not have core sataration, it is high linearity, can bear larger electric current.This coil has electric current measurement in real time, fast response time, can saturated, almost there is no the feature of phase error; can be applicable to relay protection; silicon controlled rectifier, frequency control, the occasion of the large electric current such as the serious distortion of the signals such as electric resistance welding and electric furnace, short-circuit test, thunder and lightning signals collecting.A correct shaping Rogowski coil, and the winding of same distance are immune electromagnetic interference (EMI) to a great extent.
The utility model adopts flexible Luo-coil as gathering current sensor, can survey frequency several hertz to 1M, from several peaces to hundreds of kilo-ampere.It has splendid transient tracking ability, can be for measurement size very large or conductor current in irregular shape, can be applicable to the measurement of the electric current that the TA of traditional measurement electric current cannot normally use.
But Luo-coil is because its original induced signal is very faint, if common Luo-coil no-load voltage ratio is 1000A/50mV, so generally can only be used for measuring large electric currents more than hundreds of peaces.When tested alien frequencies signal is 10mA, the original induced signal of Luo-coil is only 0.5 μ V, need to have very high measuring accuracy and resolution, and under the noiseless environment in laboratory, Measurement accuracy is all very difficult.
The very hang-up of another existence is: alien frequencies (as 48 Hz or the 52Hz) electric current that needs the 10mA level of measurement, to mix with the 50Hz interference current of 10A level (or larger), also be strong thousands of times of interference ratio measured signal amplitude, and both frequencies are very approaching; Extraneous space also exists very strong electromagnetic interference (EMI) simultaneously.This measuring accuracy to instrument, resolution, antijamming capability has proposed very large challenge.Under this environment, to accurately propose and restore size and the waveform of the 0.5 μ V signal inducing of 10mA electric current, and this signal is submerged under the interference of thousands of times, the technical difficulty that need to overcome is very large, almost become " impossible mission ", can liken to visually and on an earsplitting building site, will accurately measure the sound size that a pin lands.
Summary of the invention
The utility model provides alien frequencies weak current Luo-coil measurement mechanism under a kind of thousand times of interference, object is to overcome the deficiency in currently available technology, design a kind of digitizing frequency-selective filtering measuring system that adopts Luo-coil sampling, can be under the 50Hz interference current of 1000 times the faint non-power-frequency current of Measurement accuracy 40-70Hz.Device core is based on high-performance CPU and wavelet transformation software algorithm and hardware filtering circuit.Measurement mechanism can resist thousand times to disturb and data accurate stable, and as at 10A, 50Hz disturbs lower accurate frequency-selecting to measure 10mA, the size of current of 53Hz and phase place.
The realization of the utility model core capabilities is mainly based on hardware filtering circuit and wavelet transformation operational analysis, can realize thousand times of frequency-selecting current measurements under interference, in electric measurement field, particularly the electric system field tests under strong jamming background has important purposes.
For addressing the above problem, the utility model adopts following technical scheme:
Alien frequencies weak current Luo-coil measurement mechanism under thousand times of interference, the utility model feature is that this installs by Luo-coil, input terminal, filtering circuit unit, automatic range switching unit, amplifying unit, level biasing circuit, 50Hz trap circuit, AD sampling unit, CPU, display screen, storage unit, operation knob, printer forms; Its syndeton is: the output line of Luo-coil is received input terminal, input terminal is connected to filtering circuit unit, filtering circuit unit is connected to automatic range switching unit, the output of automatic range switching unit is connected to amplifying unit, amplifying unit output is connected to level biasing circuit, the output of level biasing circuit is connected to 50Hz trap circuit, the output of 50Hz trap circuit is connected to AD sampling unit, AD sampling unit output digit signals is to CPU, and CPU is sent to result display screen and shows result after calculation process; CPU also connects storage unit, stores relevant parameters; CPU also attended operation knob, for man-machine interaction, connects printer and is used for printing measurement result; Wherein automatic range switching unit is controlled automatic conversioning broad by CPU according to correlation parameter.
The utility model device adopts flexible Luo-coil as sampling unit, and the length of Luo-coil is not less than 1 meter.
The utility model measurement device scope is 40-70Hz, and survey frequency stepping 0.1Hz is optional arbitrarily.
The utility model device adopts automatic range switching in order to measure electric current on a large scale.
The antijamming capability of the utility model device is mainly realized jointly by hardware filtering circuit and software filtering algorithm two parts.
The utility model device can in the situation that 50Hz noise amplitudes than large 1,000 times of tested 40-70Hz alien frequencies signal amplitude, still can Measurement accuracy alien frequencies signal.
Luo-coil is a kind of coil of hollow annular, has flexiblely and rigid two kinds, can directly be enclosed within on measured conductor and measure alternating current.The theoretical foundation that Luo-coil is measured electric current is Faraday's electromagnetic induction law and Ampere circuit law, when tested electric current passes through Luo-coil center along axis, the magnetic field of the volume generation respective change of surrounding in Circular Winding, the output voltage of coil is directly proportional to di/dt.That is to say, the output voltage of Luo-coil is directly proportional to the differential of tested electric current, as long as exported through integrator, can obtain the output voltage being directly proportional to primary current.The output signal line of Luo-coil is received filter unit by input terminal, and the PI filtering circuit that filter unit is comprised of inductance capacitance can be by the filtering of part high-frequency signal.Termination automatic range switching unit after filter unit, automatic range switching unit is in series by the resistance of a plurality of different resistances, in different positions, separates a plurality of ranges, the corresponding 20mA of difference, 200mA, 2A, 20A, the ranges such as 200A.CPU procedure identification is also automatically controlled and is switched corresponding relay, makes signal amplitude size in best measurement range.After range switches, voltage signal is sent into amplifying unit, and signal is amplified, and the AC signal access level biasing circuit after amplification carries out level shift, becomes the waveform direct current signal consistent with tested electric current.This signal is sent into 50Hz trap circuit again, and 50Hz composition is carried out to trap filtering.Then remaining waveform is sent into AD sampling unit, waveform is carried out to AD sampling, become digital signal, send into CPU and carry out software computing.
Signal carries out high-speed sampling analog to digital conversion through AD sample circuit, and the discernible digital signal of the program that converts to is sent into CPU.Then CPU carries out wavelet transformation analysis to digital signal, isolates the faint alien frequencies sine wave signal of required measurement from complicated waveform.CPU, by the separable voltage going out under assigned frequency of software, is converted into electric current according to certain no-load voltage ratio, and result is presented on display screen.CPU control store simultaneously, prints the functions such as menu operation.
The optional conventional DSP of the TI company model of CPU, as TMS320F2812, can be also other general processor, as ARM architecture processor.DSP also claims digital signal processor, is a kind of microprocessor with special construction.The Harvard structure that the inside of dsp chip adopts program and data to separate, has special hardware multiplier, extensively adopts stream line operation, and special DSP instruction is provided, and can be used for realizing rapidly various digital signal processing algorithms.According to the requirement of digital signal processing, dsp chip generally has some following principal features: (1) can complete multiplication and a sub-addition within an instruction cycle.(2) program and data space separately, can while access instruction and data.(3) in sheet, there is quick RAM, conventionally can be by independently data bus access simultaneously in two.(4) there is low expense or without the hardware supported of expense circulation and redirect.(5) interrupting fast processing and Hardware I/O supports.(6) there are a plurality of hardware address generators that operate within the monocycle.(7) can a plurality of operations of executed in parallel.(8) support stream line operation, the operations such as fetching, decoding and execution can overlappingly be carried out.
A frontier developing rapidly in wavelet transformation current application mathematics and engineering discipline, through the exploratory development of nearly 10 years, important mathematical form system was set up, and theoretical foundation is more sturdy.Traditional signal theory, is based upon on Fourier analysis basis, and Fourier transform is as a kind of variation of overall importance, and it has certain limitation.People start Fourier transform to carry out various improvement in actual applications, and wavelet analysis has produced thus.Wavelet analysis is a kind of emerging branch of mathematics, and it is the most perfect crystallization of functional, Fourier analysis, harmonic analysis, numerical analysis; In application, particularly, in signal processing, image processing, speech processes and numerous nonlinear science field, it is considered to the another effective Time-Frequency Analysis Method after Fourier analysis.Wavelet transformation is compared with Fourier transform, be a time and frequency domain local conversion thereby can information extraction from signal effectively, by calculation functions such as flexible and translations, function or signal are carried out to multiscale analysis, solved the indeterminable many difficult problems of Fourier transform.
Compared with prior art, alien frequencies weak current Luo-coil measurement mechanism tool of the present utility model has the following advantages: (1) frequency-selecting antijamming capability is strong, than in the past, simulate frequency selection circuit antijamming capability and improve more than hundreds of times, can be under the interference of thousands of times the faint non-power-frequency current signal of Measurement accuracy.(2) adopt Roche to sample, applicable to major diameter and irregular conductor.(3) can any 0.1Hz frequency conversion of digitizing frequency-selecting, under 50Hz strong jamming, also can select to approach very much 49Hz, 51Hz equifrequent is measured, and this has just guaranteed the equivalence of measurement result and power frequency.(4) can digitizedly carry out software calibration, guarantee the accuracy of measuring under each frequency and each range.(5) intelligent degree is high.Can automatic switching range, can preserve print result, can preserve and derive test waveform, be very beneficial for further technical Analysis.(6) circuit framework is clear, and analog front end circuit is simpler.(7) system core is partly CPU and software algorithm, is conducive to protect the intellectual property.
This measurement mechanism is in electric measurement field, and particularly in power plant, the electrical equipment parameter measurement field under the strong interference environments such as transformer station has a wide range of applications and economic worth.
Accompanying drawing explanation
Fig. 1 is structural representation of the present utility model.
Embodiment
With best embodiment, the utility model is described in detail below
.
As shown in Figure 1, alien frequencies weak current Luo-coil measurement mechanism under thousand times of interference, the utility model feature is, this installs by Luo-coil, input terminal, filtering circuit unit, automatic range switching unit, amplifying unit, level biasing circuit, 50Hz trap circuit, AD sampling unit, CPU, display screen, storage unit, operation knob, printer forms; Its syndeton is: the output line of Luo-coil is received input terminal, input terminal is connected to filtering circuit unit, filtering circuit unit is connected to automatic range switching unit, the output of automatic range switching unit is connected to amplifying unit, amplifying unit output is connected to level biasing circuit, the output of level biasing circuit is connected to 50Hz trap circuit, the output of 50Hz trap circuit is connected to AD sampling unit, AD sampling unit output digit signals is to CPU, and CPU is sent to result display screen and shows result after calculation process; CPU also connects storage unit, stores relevant parameters; CPU also attended operation knob, for man-machine interaction, connects printer and is used for printing measurement result; Wherein automatic range switching unit is controlled automatic conversioning broad by CPU according to correlation parameter.
The utility model device adopts flexible Luo-coil as sampling unit, and the length of Luo-coil is not less than 1 meter.
The utility model measurement device scope is 40-70Hz, and survey frequency stepping 0.1Hz is optional arbitrarily.
The utility model device adopts automatic range switching in order to measure electric current on a large scale.
The antijamming capability of the utility model device is mainly realized jointly by hardware filtering circuit and software filtering algorithm two parts.
The utility model device can in the situation that 50Hz noise amplitudes than large 1,000 times of tested 40-70Hz alien frequencies signal amplitude, still can Measurement accuracy alien frequencies signal.
The frequency-selective filtering function of the utility model device is mainly carried out high speed analysis computing based on Wavelet Transformation Algorithm and is realized by hardware filtering circuit and CPU.
The utility model device adopts flexible Luo-coil as sampling unit, and the length of Luo-coil is not less than 1 meter.
This system has been used SD card as data storage medium, and test data can be stored, and can derive, printable.
Claims (3)
1. alien frequencies weak current Luo-coil measurement mechanism under thousand times of interference, is characterized in that, this installs by Luo-coil, input terminal, filtering circuit unit, automatic range switching unit, amplifying unit, level biasing circuit, 50Hz trap circuit, AD sampling unit, CPU, display screen, storage unit, operation knob, printer forms; Its syndeton is: the output line of Luo-coil is received input terminal, input terminal is connected to filtering circuit unit, filtering circuit unit is connected to automatic range switching unit, the output of automatic range switching unit is connected to amplifying unit, amplifying unit output is connected to level biasing circuit, the output of level biasing circuit is connected to 50Hz trap circuit, the output of 50Hz trap circuit is connected to AD sampling unit, AD sampling unit output digit signals is to CPU, and CPU is sent to result display screen and shows result after calculation process; CPU also connects storage unit, stores relevant parameters; CPU is attended operation knob and printer also; Wherein automatic range switching unit is controlled automatic conversioning broad by CPU according to correlation parameter.
2. alien frequencies weak current Luo-coil measurement mechanism under thousand times of interference as claimed in claim 1, is characterized in that, this device adopts flexible Luo-coil as sampling unit, and the length of Luo-coil is not less than 1 meter.
3. alien frequencies weak current Luo-coil measurement mechanism under thousand times of interference as claimed in claim 1, is characterized in that: this measurement device scope is 40-70Hz survey frequency stepping 0.1Hz.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104459291A (en) * | 2014-12-15 | 2015-03-25 | 南车株洲电力机车有限公司 | Method and system for detecting AC signals of specific frequency |
| CN106707008A (en) * | 2016-12-27 | 2017-05-24 | 成都信息工程大学 | Electronic current transformer and working method thereof |
| CN111025218A (en) * | 2019-12-30 | 2020-04-17 | 珠海市科荟电器有限公司 | System and method for on-line real-time self-calibration of clamp-on ammeter |
| CN112611945A (en) * | 2020-11-30 | 2021-04-06 | 贵州电网有限责任公司 | Distribution network pin insulator detection device and detection method |
| CN113093084A (en) * | 2021-03-26 | 2021-07-09 | 天津市职业大学 | Online detection system and detection method for internal resistance and on-off performance of Rogowski coil |
| CN116298492A (en) * | 2023-05-23 | 2023-06-23 | 山东棋盘信息科技有限公司 | Alternating current mixed signal detection system and method |
-
2014
- 2014-06-13 CN CN201420315938.8U patent/CN203965509U/en not_active Expired - Lifetime
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104459291A (en) * | 2014-12-15 | 2015-03-25 | 南车株洲电力机车有限公司 | Method and system for detecting AC signals of specific frequency |
| CN106707008A (en) * | 2016-12-27 | 2017-05-24 | 成都信息工程大学 | Electronic current transformer and working method thereof |
| CN111025218A (en) * | 2019-12-30 | 2020-04-17 | 珠海市科荟电器有限公司 | System and method for on-line real-time self-calibration of clamp-on ammeter |
| CN111025218B (en) * | 2019-12-30 | 2022-07-08 | 珠海市科荟电器有限公司 | System and method for online real-time self-calibration of clamp-on ammeter |
| CN112611945A (en) * | 2020-11-30 | 2021-04-06 | 贵州电网有限责任公司 | Distribution network pin insulator detection device and detection method |
| CN113093084A (en) * | 2021-03-26 | 2021-07-09 | 天津市职业大学 | Online detection system and detection method for internal resistance and on-off performance of Rogowski coil |
| CN113093084B (en) * | 2021-03-26 | 2022-11-15 | 天津市职业大学 | Online detection system and detection method for internal resistance and on-off performance of Rogowski coil |
| CN116298492A (en) * | 2023-05-23 | 2023-06-23 | 山东棋盘信息科技有限公司 | Alternating current mixed signal detection system and method |
| CN116298492B (en) * | 2023-05-23 | 2023-08-22 | 山东棋盘信息科技有限公司 | Alternating current mixed signal detection system and method |
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Granted publication date: 20141126 |