CN102156214B - Double-light-path leakage current optical fiber sensor device - Google Patents

Abstract

The invention discloses a double-light-path leakage current optical fiber sensor device and belongs to the technical field of monitoring pollution flashover of electric equipment on line. The device comprises a fixed bracket, a sensor head, an optical fiber, a converter, a modulator, an acquisition card and a computer, and is mainly characterized in that: the sensor head consists of two light emitting diodes (LEDs) and two protective circuits, is coupled to silicon photoelectric diodes of two photoelectric detectors of the converter through two optical fibers respectively, and is used for measuring positive and negative half cyclic waves of the leakage current respectively and the positive and negative half cyclic waves of the leakage current are synthesized into a complete full-wave signal by a differential comparison circuit of the converter. The invention has the characteristics that: the device monitors the full wave of an insulator string on line in real time, and has high anti-jamming capability, high safety, and high sensitivity and monitoring accuracy, and is convenient to install, easy and convenient to operate and the like. The device can be widely used for monitoring the full-wave leakage current of the insulator string on line in an alternating current (AC) transmission line for a transformer substation and an overhead transmission line, and particularly applicable to on-line monitoring of the full-wave leakage current of the insulator string in a high-voltage AC line.

Description

A kind of Double-light-path leakage current optical fiber sensor device

Technical field

The invention belongs to electrical equipment pollution flashover on-line monitoring technique field, be specifically related to the leakage current sensor device of the insulator chain of on-line monitoring in transformer station and the overhead transmission line.

Background technology

In recent years, because the developing rapidly of the electrical equipment state inspection of electric system, high precision, high accuracy, high efficiency sensor constantly come out and are applied to gradually in the on-line monitoring of power equipment.For transmission line of electricity, the pollution flashover of insulator chain is all serious safe operations that is threatening power system transmission line all the time, and the pollution flashover that therefore prevents insulator chain is the focus that power department guarantees the transmission line of electricity safe operation.Because the development of pollution flashover discharge and the leakage current of insulator chain are closely related, the leakage current of determination and analysis insulator chain is a kind of effective means of Criterion of Polluted Insulator on-line monitoring, so the leakage current sensor device of the insulator chain of development high precision, high accuracy is very important problem.

Along with the development of modern power electronic, optical-fibre communications and Digital Signal Processing, be faced with huge challenge based on the traditional sensors of electromagnetic induction principle, launched novel based on the electric current of photoelectric technology, the development of voltage sensor both at home and abroad.Higher to the manufacturing of the fiber grating sensors technological requirement in the practical application, stability problem is not fine solution also, so brought great difficulty for the practical application of photo-electric electric current, voltage sensor.After Corning Incorporated in 1970 succeeded in developing the optical fiber that coefficient of losses is 0.2dB/km first with high purity quartz, optical fiber communication technology obtained very fast development.Meanwhile under the requirement of accurate measuring fiber signal transmission and improvement optical device performance, optical fiber sensing technology correspondingly obtains develop rapidly.In view of optical fiber sensing technology has highly sensitive, bandwidth, dynamic range is large, reliability is strong, anti-electromagnetic interference (EMI) and unique advantage such as can work under rugged surroundings, Fibre Optical Sensor just little by little is introduced in the electric system.

Existing insulator chain fibre optic current sensor device, it is " based on the insulator leakage current fiber optic sensor system of light emitting diode " patent of 201010538230.5 such as application number, comprise fixed support, sensor probe, optical fiber, photoelectric commutator, signal modulator, data collecting card and computing machine etc., its sensor probe is fixed on the two ends of certain a slice insulator in the monitored insulator chain by state's fixed rack, light signal is monitored out and be converted to LED in the sensor probe with the leakage current of detected insulator chain, is transmitted through the fiber to signal modulator again, process and analyze in data collecting card and the computing machine.The shortcoming of this current sensor system is: sensing system adopts a leakage current that gathers insulator chain based on the sensor probe of light emitting diode, because light emitting diode has the unidirectional general character, therefore cause this sensor only can extract the signal of half cycle of insulator chain leakage current, thereby so that system has lost the other half cycles signal of tested insulator chain leakage current waveform when detecting, finally cause the signal message that detects leakage current sufficiently complete, can not carry out complete portrayal for the leakage current all-wave, affect the accuracy of on-line monitoring, can not satisfy the high accuracy of the electrical equipment of modern power systems, high efficiency requirement.

Summary of the invention

Purpose of the present invention is for the deficiency of the optical fibre current sensor system of existing insulator chain, a kind of Double-light-path leakage current optical fiber sensor device is provided, it is strong that this device has an anti-electromagnetic interference capability, sensing sensitivity is high, the linearity is good, can detect in real time the leakage current all-wave, and detect the precision height of leakage current, the characteristics such as the real time execution reliability is high, and is practical.

The technical scheme that realizes the object of the invention is: a kind of Double-light-path leakage current optical fiber sensor device mainly comprises fixed support, sensor head, optical fiber, converter, modulator, capture card and computing machine etc.Be that " based on the insulator leakage current fiber optic sensor system of light emitting diode " patent of 20101053823.5 is identical with application number, described sensor head is fixed in the two ends of arbitrary insulator in the tested insulator chain by fixed support, the LED that is fixed in the sensor head at fixed support trailing arm middle part detects and is converted into light signal with the leakage current of tested insulator chain, process optical fiber is further being processed and is being analyzed by cable transmission to computing machine or the portable computer in control room after being sent to converter and modulator processing.It is characterized in that:

Described sensor head is made of two LEDs 1 and LED2 and two holding circuits.The series connection of the same polarity port of described two LEDs 1 and LED2 is in order to the leakage current of the positive and negative half cycles that detects respectively tested insulator chain.Described each holding circuit is made of a conducting diode D, a voltage stabilizing diode VSD and discharge tube GDT parallel connection.Each conducting diode D is in parallel with LED 1 or LED2 reversed polarity, being used for dredging can not be by the half cycles leakage current of light emitting diode, each voltage stabilizing diode VSD is in parallel with LED 1 or LED2 same polarity, and in parallel with discharge tube GDT, be used for preventing that the port of light emitting diode from bearing superpotential and flowing through large electric current, thereby guarantee its safety and stability.Described two LEDs 1 and LED2 and holding circuit are encapsulated in the sensor head shell; be connected with the coupling mechanism joint of two optical fiber one ends by two coupling mechanism interfaces that are fixed on the sensor head shell respectively, derive from sensor head in order to the light signal that two light emitting diodes are sent and enter optical fiber.The coupling mechanism joint of described two optical fiber other ends links to each other with two coupling mechanism interfaces on the converter respectively, processes in order to optical signal transmission to the photodetector in the converter that the insulator chain leakage current that light emitting diode is detected is changed out.

The IC printed board that described converter consists of for the differential comparison circuit DA by two photodetector CA1 and CA2 and a routine, thereby conveniently install, dismantle and carry.Described each photodetector CA1 or CA2 are by a silicon photoelectric diode SPD1 or SPD2 and a conventional operational amplifier A ₁Or A ₂Form the negative feedback operational amplification circuit.That is: the negative pole of each silicon photoelectric diode SPD1 or SPD2 elder generation series capacitance C ₁Or C ₂After, again with operational amplifier A ₁Or A ₂Negative input link to each other positive pole and the operational amplifier A of two silicon photoelectric diode SPD1 and SPD2 ₁And A ₂Electrode input end ground connection respectively, operational amplifier A ₁Or A ₂Negative input elder generation serial Feedback resistance R _F1Or R _F2After be connected with its output terminal again and be combined into a degenerative operational amplification circuit.Described two silicon photoelectric diode SPD1 and SPD2 are installed in respectively two coupling mechanism interfaces of aforesaid two optical fiber other ends, process in order to the positive and negative half cycles that receives respectively the insulator chain leakage current that described sensor head detects.The output terminal of described two negative feedback operational amplification circuits, respectively resistance in series R ₁, R ₂After more respectively with the first order operational amplifier A of differential comparison circuit DA ₃With second level operational amplifier A ₄Electrode input end connect, in order to the positive and negative half cycles electric current of the reflection insulator chain leakage current after two photodetector CA1 and CA2 are processed, be transferred to respectively the first order operational amplifier A of differential comparison circuit DA ₃With second level operational amplifier A ₄Process.The output characteristics of two silicon photoelectric diode SPD1 and SPD2 directly affects the Output rusults of sensor device of the present invention.Silicon photoelectric diode is done the time spent to load, the electric current I in the load _L0For:

$I_{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">L</figure-callout>}0}=I_p-I_0(e^{I_{L0}(R_s+R_L)/{\mathrm{AV}}_T}-1)-\frac{I_{L0}(R_S+R_L)}{R_d}---\left(1\right)$

I wherein _pFor silicon photoelectric diode is subjected to the photocurrent that produces after the optical radiation, I ₀Be the reverse saturation current of silicon photoelectric diode, R _sBe the resistance in series of silicon photoelectric diode, R _LPull-up resistor, R _dBe its parallel resistance, q is electron charge, and k is Boltzmann constant, and Δ f is bandwidth of operation, and T is absolute temperature.For silicon materials, constant A ≈ 2, V _T=kT/q.By following formula as can be known, the load current of its output and photocurrent and nonlinear relationship, load current is under short-circuit conditions, because R _s＜＜R _d, then:

$I_{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">L</figure-callout>}0}=I_P-I_0(e^{I_{L0}{R}_S/{\mathrm{AV}}_T}-1)---\left(2\right)$

When the very little and output current of the reverse saturation current of diode is little, i.e. I _L0R _s＜＜AV _T, can obtain I _S≈ I _P, i.e. output current I _SPhotocurrent I with diode _PSubstantially linear, hence one can see that should choose R _dGreatly, R _sLittle, I ₀Little diode, and to keep load to be output as the short circuit duty, we are used in combination silicon photoelectric diode and negative feedback operational amplifier for this reason, because the equivalent input impedance of negative feedback operational amplifier is:

$R_{\mathrm{in}}=\left[\frac{{\mathrm{<figure-callout\; id="1"\; label="R\; f"\; filenames="HSA00000485826900011.png,HSA00000485826900052.png"\; state="\{\{state\}\}">R</figure-callout>}}_f}{1+A_0}\right]//R_{\mathrm{id}}\&ap;\frac{{\mathrm{<figure-callout\; id="1"\; label="R\; f"\; filenames="HSA00000485826900011.png,HSA00000485826900052.png"\; state="\{\{state\}\}">R</figure-callout>}}_f}{1+A_0}---\left(3\right)$

A wherein ₁=A ₂=A ₀Be the open-loop gain of negative feedback operational amplifier, R _F1=R _F2=R _fBe feedback resistance, R _IdBe the internal resistance of silicon photoelectric diode, general R _IdThe order of magnitude more than megaohm, A ₀＞10 ⁶, so R _InVery little, the input impedance of operational amplifier is close to zero, thereby the pull-up resistor that can guarantee silicon photoelectric diode is zero.

The linearity owing to silicon photoelectric diode measurement electric current is again:

$P=\frac{I_p-I_{L0}}{I_{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">L</figure-callout>}0}}$

$=\frac{I_0(e^{I_{L0}(R_S+R_L)/{\mathrm{AV}}_T}-1)+(R_S+R_L)I_{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">L</figure-callout>}0}/R_d}{I_{L0}}$ (4)

R when silicon photoelectric diode _sLess R _dLarger, I ₀Less, linear P value is less, and namely linearity is better.R when the silicon photoelectric diode load short circuits _L=0, and R _s＜＜R _d, then abbreviation (4) formula is:

$P=\frac{I_0}{I_{L0}}(e^{I_{L0}{R}_S/{\mathrm{AV}}_T}-1)---\left(5\right)$

Hence one can see that, and the combinational circuit of silicon photoelectric diode and amplifier can guarantee that silicon photoelectric diode works near under the short-circuit condition in load, and I _L0And R _sVery I is to improve the linearity P that measures electric current.And its output signal-to-noise ratio R _{S, N}When the short circuit of silicon photoelectric diode load circuit be:

$R_{S,N}=I_S/I_{\mathrm{ni}}=I_S/{[2q{I}_S\mathrm{\&Delta;f}+4\mathrm{kT}(\frac{1}{R_d}+\frac{1}{R_f})+I_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HSA00000485826900032.png"\; state="\{\{state\}\}">n</figure-callout>}}^2+E_n^2(\frac{1}{R_d}+\frac{1}{R_f}{)}^2]}^{1/2}\mathrm{\&Delta;f}---\left(6\right)$

The signal to noise ratio (S/N ratio) R of this photoelectric detective circuit _{S, N}At feedback resistance R _F1＜＜10 ⁶The time with R _fIncrease and obviously increase, at feedback resistance R _f＞10 ⁶The time R _{S, N}With R _fIncrease and rise.Silicon photoelectric diode is to work under zero the short-circuit condition also greatly to have improved the output signal-to-noise ratio of silicon photoelectric diode simultaneously at pull-up resistor, thereby has guaranteed that sensor device detects the accuracy of small leakage current.

The differential comparison circuit DA of described converter is by the operational amplifier A of two-stage routine ₃And A ₄Consist of two-stage calculation amplifier A ₃And A ₄Electrode input end receive respectively the electric signal V of two aforementioned photodetector CA1 and CA2 output _1outAnd V _2out, first order operational amplifier A ₃Negative input pass through resistance R ₃Ground connection, first order operational amplifier A ₃Output end signal

Pass through resistance R ₄Be connected to second level operational amplifier A ₄Input end, the output terminal of first and second grade operational amplifier is respectively by feedback resistance R _F3And R _F4After be connected with its negative input respectively again, form the negative feedback computing circuit.The output terminal of second level operational amplifier is connected by the input end of cable with the post amplifier of modulator, in order to the output signal V with converter _{o Out}Being transferred to modulator modulates.Described differential comparison circuit DA can realize that not only the difference of signal is synthetic, and signal can be amplified again through scale operation and the superposition of two-stage, be convenient to observation.The two path signal that photodetector CA1 and CA2 convert in the converter in the reality is all positive ripple signal, both differ the phase place of 180 degree, through synthesizing the all-wave signal that can reflect leakage current, the output signal V of two photodetectors behind the differential comparison circuit DA _1outAnd V _2outInput signal as the differential comparison circuit.The first order of differential comparison circuit is output as:

${\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_{0^1\mathrm{out}}=(1+\frac{R_{f3}}{R_3}){\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000485826900011.png,HSA00000485826900052.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1\mathrm{out}}---\left(7\right)$

Utilize superposition principle to get, second level circuit is output as:

${\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_{0\mathrm{out}}=-\frac{R_{f4}}{R_4}{\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_{0^1\mathrm{out}}+(1+\frac{R_{f4}}{R_4}){\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000485826900032.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2\mathrm{out}}---\left(8\right)$

Get R ₃=R _F4, R ₄=R _F3, then:

$U_{\mathrm{oout}}=(1+\frac{R_{f4}}{R_4})({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000485826900032.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2\mathrm{out}}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000485826900011.png,HSA00000485826900052.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1\mathrm{out}})---\left(9\right)$

Can be drawn the differential amplification signal of two paths of signals by (9) formula.The output terminal of described converter is cable interface, draws through signal to the modulator of opto-electronic conversion and differential amplification for stube cable and processes.

Described modulator is composed in series for conventional post amplifier A and second order filter F.The output terminal of modulator is connected with capture card by cable, and capture card is connected with computing machine by signal wire.Modulator receives the signal V of the reflection insulator chain leakage current all-wave of aforementioned converter output _{o Out}, through further amplifying and after filtering processes, by cable transmission to the capture card image data, finally by by the signal wire of the output terminal of capture card the data transmission that collects being observed, recorded and process to computing machine.

Using method of the present invention is: use fixed support sensor head to be fixed on the two ends of certain a slice insulator in the insulator chain, then the end coupling mechanism joint with optical fiber links to each other with the output terminal coupling mechanism interface of sensor head, with the optical fiber reasonable Arrangement, avoid significant bending, and making it along the shaft tower fixing-stable, the other end coupling mechanism joint of optical fiber is connected on the coupling mechanism interface of converter input end.Converter and modulator are fixed on the easy-to-install position, middle and lower part of transmission tower, use signal cable with converter and modulator connected device.Use at last signal cable to connect modulator, signal guidance to capture card is gathered, by signal wire signal guidance is observed to the computing machine away from the shaft tower position again.

The present invention adopts mainly has following effect after the above-mentioned technical scheme:

1 sensor head of the present invention adopts two cheap LEDs, the positive and negative half cycles signal that flows through respectively the insulator chain leakage current of LED is converted into light signal detects.Therefore can carry out real time on-line monitoring to the all-wave leakage current of insulator chain, easy to use, safety, easy to operate.

2 the present invention adopt double light path optical fiber, the light signal that respectively positive half cycles and the negative half period ripple signal of leakage current is transformed conducts to respectively converter and processes, the high anti-jamming capacity of optical fiber is strong, can avoid signal in collection and transmission, to be subject to strong electromagnetic changeable in the high-tension circuit, high-pressure side signal with the measuring object place is sent to the signal processing circuit that is positioned at low pressure end simultaneously, play the voltage isolation, guarantee staff's job safety, thereby antijamming capability of the present invention is strong, and is safe.

3 converters of the present invention adopt two silicon photoelectric diode unit amplifiers as optical detector, the light signal that comes the detection fiber conduction.It is zero that silicon photoelectric diode and amplifier are used in combination the pull-up resistor that can guarantee silicon photoelectric diode, thereby greatly reduce the noise that silicon photoelectric diode self brings, reduce the linear response deviation of silicon photoelectric diode, improve the signal to noise ratio (S/N ratio) that this sensor device is measured.

The differential comparison circuit of 4 converters of the present invention has adopted the difference ratio computing circuit of high input resistance.Two ways of optical signals that sensor head is sent here is converted to input difference comparator circuit behind the electric signal through silicon photoelectric diode, after the amplification of process two-stage scale operation circuit and difference were done to subtract, signal was synthesized one road complete all-wave signal and processes via cable transmission to modulator.

5 modulator volumes of the present invention are little, are connected with converter by cable.Modulator can together be installed on the shaft tower of transmission line of electricity with converter, also can be used as portable equipment and carries application.The signal of modulator output can directly be sent to computing machine or oscillograph records and processes, thereby the convenient installation of this sensor device, and easy to carry, the precision of real time on-line monitoring is high, and is easy and simple to handle.

6 the present invention are highly sensitive to the collection of leakage current, can Measurement accuracy to the leakage current all-wave signal that is superimposed with the amplitude pulse, the sensing range of sensor is 0.2mA～80mA, frequency range is 5Hz～10kHz, sensitivity is about 40mV/mA.

The present invention can be widely used in the all-wave on-line monitoring of the leakage current of insulator chain in the alternating current circuit of transformer station and overhead transmission line, is specially adapted to the all-wave on-line monitoring of the leakage current of the insulator chain of alternating current circuit in the transformer station of voltage levels and the overhead transmission line.

Description of drawings

Fig. 1 is structure principle chart of the present invention;

Fig. 2 is the basic circuit diagram of the sensor head of Fig. 1;

Fig. 3 is the circuit theory diagrams of the converter of Fig. 1;

Fig. 4 is the sinusoidal current test response oscillogram of present embodiment;

Among the figure: curve a is the sinusoidal current signal that function generator produces, and in contrast, frequency 50HZ, curve b are the voltage waveform that the present invention records.

Fig. 5 is the square wave current test response oscillogram of present embodiment;

Among the figure: curve a is the square wave current signal that function generator produces, and in contrast, frequency 50HZ, curve b are the voltage waveform that the present invention records.

Fig. 6 is the triangular current test response oscillogram of present embodiment;

Among the figure: curve a is the triangular current signal that function generator produces, and in contrast, frequency 50HZ, curve b are the voltage waveform that the present invention records.

Fig. 7 is the pulse current test response oscillogram of present embodiment;

Among the figure: curve a is the pulse current waveform through sampling resistor, and curve b is the waveform voltage signal that the present invention records.

Fig. 8 is the gamut linearity curve map of the measurement of present embodiment;

Fig. 9 is the linearity curve map that present embodiment is measured the faint leakage current of 0.2mA～0.8mA;

Figure 10 is the amplitude-frequency response characteristic curve of leakage current optical fiber sensor device in the present embodiment.

Among the figure: 1 sensor head, 2 optical fiber, 3 converters, 4 modulators, 5 cables.LED1, LED2 light emitting diode, D conducting diode, VSD voltage stabilizing diode, GDT discharge tube, SPD1, SPD2 silicon photoelectric diode, R ₁, R ₂, R ₃, R ₄, R _F1, R _F2, R _F3, R _F4Resistance, C ₁, C ₂Electric capacity, A ₁, A ₂, A ₃, A ₄, the A amplifier, CA1, CA2 photodetection, F wave filter, I _L01, I _L02The silicon photoelectric diode output current.

Embodiment

Further specify the present invention below in conjunction with embodiment.

Embodiment

Shown in Fig. 1～3, a kind of Double-light-path leakage current optical fiber sensor device mainly comprises fixed support, sensor head 1, optical fiber 2, converter 3, modulator 4, capture card and computing machine etc.It is characterized in that:

Described sensor head 1 is made of two LEDs 1 and LED2 and two holding circuits.The series connection of the same polarity port of described two LEDs 1 and LED2 is in order to the leakage current of the positive and negative half cycles that detects respectively tested insulator chain.Described each holding circuit is made of a conducting diode D, a voltage stabilizing diode VSD and discharge tube GDT parallel connection.Each conducting diode D is in parallel with LED 1 or LED2 reversed polarity, being used for dredging can not be by the half cycles leakage current of light emitting diode, each voltage stabilizing diode VSD is in parallel with LED 1 or LED2 same polarity, and in parallel with discharge tube GDT, be used for preventing that the port of light emitting diode from bearing superpotential and flowing through large electric current, thereby guarantee its safety and stability.Described two LEDs 1 and LED2 and holding circuit are encapsulated in the shell of sensor head 1; be connected with the coupling mechanism joint of two optical fiber 2 one ends by two coupling mechanism interfaces that are fixed on the sensor head shell respectively, derive from sensor head in order to the light signal that two light emitting diodes are sent and enter optical fiber 2.The coupling mechanism joint of described two optical fiber 2 other ends links to each other with two coupling mechanism interfaces on the converter 3 respectively, processes in order to optical signal transmission to the photodetector in the converter 3 that the insulator chain leakage current that LED is detected is changed out.

The IC printed board that described converter 3 consists of for the differential comparison circuit DA by two photodetector CA1 and CA2 and a routine, thereby conveniently install, dismantle and carry.Described each photodetector CA1 or CA2 are by a silicon photoelectric diode SPD1 or SPD2 and a conventional operational amplifier A ₁Or A ₂Form the negative feedback operational amplification circuit.That is: the negative pole of each silicon photoelectric diode SPD1 or SPD2 elder generation series capacitance C ₁Or C ₂After, again with operational amplifier A ₁Or A ₂Negative input link to each other positive pole and the operational amplifier A of two silicon photoelectric diode SPD1 and SPD2 ₁And A ₂Electrode input end ground connection respectively, operational amplifier A ₁Or A ₂Negative input elder generation serial Feedback resistance R _F1Or R _F2After be connected with its output terminal again and be combined into a degenerative operational amplification circuit.Described two silicon photoelectric diode SPD1 and SPD2 are installed in respectively two coupling mechanism interfaces of aforesaid two optical fiber 2 other ends, process in order to the positive and negative half cycles that receives respectively the insulator chain leakage current that described sensor head 1 detects.The output terminal of described two negative feedback operational amplification circuits is resistance in series R respectively ₁, R ₂After more respectively with the first order operational amplifier A of differential comparison circuit DA ₃With second level operational amplifier A ₄Electrode input end connect, in order to the positive and negative half cycles electric current of the reflection insulator chain leakage current after two photodetector CA1 and CA2 are processed, be transferred to respectively the first order operational amplifier A of differential comparison circuit DA ₃With second level operational amplifier A ₄Process.The output characteristics of two silicon photoelectric diode SPD1 and SPD2 directly affects the Output rusults of sensor device of the present invention.Described two silicon photoelectric diode SPD1 and SPD2 measurement lower limit all can reach 1 * 10 ^-8W, resolution 1 * 10 ^-12W.Described two conventional operational amplifier A ₁And A ₂, its open-loop gain is all much larger than 10 ⁶Silicon photoelectric diode is done the time spent to load, the electric current I in the load _L0For:

${\mathrm{<figure-callout\; id="0"\; label="I\; L"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">I</figure-callout>}}_L=I_P-I_0(e^{I_{L0}(R_S+R_L)/{\mathrm{AV}}_T}-1)-\frac{I_{L0}(R_S+R_L)}{R_d}---\left(1\right)$

Wherein I is that silicon photoelectric diode is subjected to the photocurrent that produces after the optical radiation, I ₀Be the reverse saturation current of silicon photoelectric diode, R _sBe the resistance in series of silicon photoelectric diode, R _LPull-up resistor, R _dBe its parallel resistance, q is electron charge, and k is Boltzmann constant, and Δ f is bandwidth of operation, and T is absolute temperature.For silicon materials, constant A ≈ 2, V _T=kT/q.By following formula as can be known, the load current of its output and photocurrent and nonlinear relationship, load current is under short-circuit conditions, because R _s＜＜R _d, then:

${\mathrm{<figure-callout\; id="0"\; label="I\; L"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">I</figure-callout>}}_L=I_P-I_0(e^{I_{L0}{R}_S/{\mathrm{AV}}_T}-1)---\left(2\right)$

When the very little and output current of the reverse saturation current of diode is little, i.e. I _L0R _s＜＜AV _T, can obtain I _S≈ I _P, i.e. output current I _SPhotocurrent I with diode _PSubstantially linear, hence one can see that should choose R _dGreatly, R _sLittle, I ₀Little diode, and to keep load to be output as the short circuit duty, we are used in combination silicon photoelectric diode and negative feedback operational amplifier for this reason, because the equivalent input impedance of negative feedback operational amplifier is:

$R_{\mathrm{in}}=\left[\frac{{\mathrm{<figure-callout\; id="1"\; label="R\; f"\; filenames="HSA00000485826900011.png,HSA00000485826900052.png"\; state="\{\{state\}\}">R</figure-callout>}}_f}{1+A_0}\right]//R_{\mathrm{id}}\&ap;\frac{{\mathrm{<figure-callout\; id="1"\; label="R\; f"\; filenames="HSA00000485826900011.png,HSA00000485826900052.png"\; state="\{\{state\}\}">R</figure-callout>}}_f}{1+A_0}---\left(3\right)$

A wherein ₁=A ₂=A ₀Be the open-loop gain of negative feedback operational amplifier, R _F1=R _F2=R _fBe feedback resistance, R _IdBe the internal resistance of silicon photoelectric diode, general R _IdThe order of magnitude more than megaohm, A ₀＞10 ⁶, so R _InVery little, the input impedance of operational amplifier is close to zero, thereby the pull-up resistor that can guarantee silicon photoelectric diode is zero.

The linearity owing to silicon photoelectric diode measurement electric current is again:

$P=\frac{I_p-I_{L0}}{{\mathrm{<figure-callout\; id="0"\; label="I\; L"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">I</figure-callout>}}_L}$

$=\frac{I_0(e^{I_{L0}(R_S+R_L)/{\mathrm{AV}}_T}-1)+(R_S+R_L){\mathrm{<figure-callout\; id="0"\; label="I\; L"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">I</figure-callout>}}_L/R_d}{I_{L0}}$ (4)

R when silicon photoelectric diode _sLess R _dLarger, I ₀Less, linear P value is less, and namely linearity is better.R when the silicon photoelectric diode load short circuits _L=0, and R _s＜＜R _d, then abbreviation (4) formula is:

$P=\frac{I_0}{I_{L0}}(e^{I_{L0}{R}_S/{\mathrm{AV}}_T}-1)---\left(5\right)$

Hence one can see that, and the combinational circuit of silicon photoelectric diode and amplifier can guarantee that silicon photoelectric diode works near under the short-circuit condition in load, and I _L0And R _sVery I is to improve the linearity P that measures electric current.And its output signal-to-noise ratio R _{S, N}When the short circuit of silicon photoelectric diode load circuit be:

$R_{S,N}=I_S/I_{\mathrm{ni}}=I_S/{[2q{I}_S\mathrm{\&Delta;f}+4\mathrm{kT}(\frac{1}{R_d}+\frac{1}{R_f})+I_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HSA00000485826900032.png"\; state="\{\{state\}\}">n</figure-callout>}}^2+E_n^2{(\frac{1}{R_d}+\frac{1}{R_f})}^2]}^{1/2}\mathrm{\&Delta;f}---\left(6\right)$

The signal to noise ratio (S/N ratio) R of this photoelectric detective circuit _{S, N}At feedback resistance R _F1＜＜10 ⁶The time with R _fIncrease and obviously increase, at feedback resistance R _f＞10 ⁶The time R _{S, N}With R _fIncrease and rise.Silicon photoelectric diode is to work under zero the short-circuit condition also greatly to have improved the output signal-to-noise ratio of silicon photoelectric diode simultaneously at pull-up resistor, thereby has guaranteed that sensor device detects the accuracy of small leakage current.

The differential comparison circuit DA of described converter 3 is by the operational amplifier A of two-stage routine ₃And A ₄Consist of two-stage calculation amplifier A ₃And A ₄Electrode input end receive respectively the electric signal V of two aforementioned photodetector CA1 and CA2 output _IoutAnd V _2out, first order operational amplifier A ₃Negative input pass through resistance R ₃Ground connection, first order operational amplifier A ₃Output end signal

Pass through resistance R ₄Be connected to second level operational amplifier A ₄Input end, the output terminal of first and second grade operational amplifier is respectively by feedback resistance R _F3And R _F4After be connected with its negative input respectively again, form the negative feedback computing circuit.The output terminal of second level operational amplifier is connected with the input end of the post amplifier of modulator 4 by cable 5, in order to the output signal V with converter 3 _{o Out}Being transferred to modulator 4 modulates.Described differential comparison circuit DA can realize that not only the difference of signal is synthetic, and signal can be amplified again through scale operation and the superposition of two-stage, be convenient to observation.The two path signal that photodetector CA1 and CA2 convert in the converter 3 in the reality is all positive ripple signal, both differ the phase place of 180 degree, through synthesizing the all-wave signal that can reflect leakage current, the output signal V of two photodetectors behind the differential comparison circuit DA _{1 out}And V _2outInput signal as the differential comparison circuit.The first order of differential comparison circuit is output as:

${\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_{0^1\mathrm{out}}=(1+\frac{R_{f3}}{R_3}){\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000485826900011.png,HSA00000485826900052.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1\mathrm{out}}---\left(7\right)$

Utilize superposition principle to get, second level circuit is output as:

${\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_{0\mathrm{out}}=-\frac{R_{f4}}{R_4}{\mathrm{<figure-callout\; id="0"\; label="U"\; filenames="HSA00000485826900022.png,HSA00000485826900031.png"\; state="\{\{state\}\}">U</figure-callout>}}_{0^1\mathrm{out}}+(1+\frac{R_{f4}}{R_4}){\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000485826900032.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2\mathrm{out}}---\left(8\right)$

Get R ₃=R _F4, R ₄=R _F3, then:

$U_{\mathrm{oout}}=(1+\frac{R_{f4}}{R_4})({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HSA00000485826900032.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2\mathrm{out}}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HSA00000485826900011.png,HSA00000485826900052.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1\mathrm{out}})---\left(9\right)$

Can be drawn the differential amplification signal of two paths of signals by (9) formula.The output terminal of described converter 3 is cable interface, draws through signal to the modulator 4 of opto-electronic conversion and differential amplification for stube cable 5 and processes.

Described modulator 4 is composed in series for conventional post amplifier A and second order filter F.The output terminal of modulator 4 is connected with capture card by cable 5, and capture card is connected with computing machine by signal wire.Modulator 4 receives the signal V of the reflection insulator chain leakage current all-wave of aforementioned converter 3 outputs _{o Out}, through further amplifying and after filtering processes, transfer to the capture card image data by cable 5, finally by by the usb signal line of the output terminal of capture card the data transmission that collects being observed, recorded and process to computing machine.

The amplitude of the detection leakage current of a kind of Double-light-path leakage current optical fiber sensor device of the present invention is that 0.2mA～80mA, detection frequency are that 5Hz～10kHz, sensitivity are about 40mV/mA.

Test findings

A kind of Double-light-path leakage current optical fiber sensor device to present embodiment carries out following test:

The test of responsiveness and the linearity.Method of testing is: use function generator to produce sine, square wave, triangular wave and the monopulse voltage signal of different voltage magnitudes, the noninductive resistance of known resistance is as load, sensor head is connected into circuit, the electric current of circuit is test signal, then converter is connected with sensor head through optical fiber, follow-uply connect converter and modulator with cable, and signal that will be last inputs oscillograph, read magnitude of voltage on the sample resistance by oscillograph.Change output voltage amplitude and signal type, record current voltage data and waveform adopt trace-point method to draw out response curve and the linearity curve of current sensor apparatus of the present invention.Such as Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 and shown in Figure 9.

Know from above-mentioned test findings: such as Fig. 4, Fig. 5, Fig. 6 and shown in Figure 7, the measurement of sensor device offset of sinusoidal, square wave, triangular wave and pulse current among the present invention all relatively reflects the basic condition of source signal, from Fig. 8, Fig. 9 and Figure 10, the linear response deviation of waveform is less in 0.1mA～80mA scope, the linearity is stable, sensitivity is stabilized in 40mV/mA, and degree of fitting all reaches more than 99%, and to 5Hz low frequency signal and 5kHz high-frequency signal all can be stable Measurement accuracy to current amplitude.The present invention can satisfy engineering reality to the requirement of overhead transmission line insulator chain On-line Monitoring of Leakage Current in sum, and has a precision height, the linearity is good, highly sensitive, the characteristics such as antijamming capability is strong, and load and unload very conveniently, can be widely used in the HVAC power transmission line of newly-built and transformer station that put into operation and overhead transmission line.

Claims (1)

1. a Double-light-path leakage current optical fiber sensor device mainly comprises fixed support, sensor head (1), optical fiber (2), converter (3), modulator (4), capture card and computing machine, it is characterized in that:

Described sensor head (1) is made of two LEDs 1 and LED2 and two holding circuits, the same polarity port series connection of described two LEDs 1 and LED2, described each holding circuit is by a conducting diode D, a voltage stabilizing diode VSD and a discharge tube GDT formation in parallel, each conducting diode D is in parallel with LED 1 or LED2 reversed polarity, each voltage stabilizing diode VSD is in parallel with LED 1 or LED2 same polarity, and in parallel with discharge tube GDT, described two LEDs 1 and LED2 and holding circuit are encapsulated in the shell of sensor head (1), two LEDs 1 are connected with LED2 by two coupling interfaces that are fixed on the shell of sensor head (1) and are connected with the coupling mechanism joint of two optical fiber (2) one ends, and the coupling mechanism joint of described two optical fiber (2) other end links to each other with two coupling mechanism interfaces on the converter (3) respectively;

The IC printed board that described converter (3) consists of for the differential comparison circuit DA by two photodetector CA1 and CA2 and a routine, described each photodetector CA1 or CA2 are by a silicon photoelectric diode SPD1 or SPD2 and a conventional operational amplifier A ₁Or A ₂Form the negative feedback operational amplification circuit, that is: the series capacitance C of the negative pole of each silicon photoelectric diode SPD1 or SPD2 elder generation ₁Or C ₂After, again with operational amplifier A ₁Or A ₂Negative input link to each other positive pole and the operational amplifier A of two silicon photoelectric diode SPD1 and SPD2 ₁And A ₂Electrode input end ground connection respectively, operational amplifier A ₁Or A ₂Negative input elder generation serial Feedback resistance R _F1Or R _F2After be connected with its output terminal again and be combined into a degenerative operational amplification circuit, described two silicon photoelectric diode SPD1 and SPD2 are installed in respectively two coupling mechanism interfaces of aforesaid two optical fiber (2) other end, the output terminal of described two negative feedback operational amplification circuits, respectively resistance in series R ₁, R ₂After more respectively with the first order operational amplifier A of differential comparison circuit DA ₃With second level operational amplifier A ₄Electrode input end connect;

The differential comparison circuit DA of described converter (3) is by the operational amplifier A of two-stage routine ₃And A ₄Consist of first order operational amplifier A ₃Negative input pass through resistance R ₃Ground connection, first order operational amplifier A ₃Output end signal pass through resistance R ₄Be connected to second level operational amplifier A ₄Input end, the output terminal of first and second grade operational amplifier is respectively by feedback resistance R _F3And R _F4After be connected with its negative input respectively again, form the negative feedback computing circuit, the output terminal of second level operational amplifier is connected with the input end of the post amplifier of modulator (4) by cable (5);

Described modulator (4) is composed in series for conventional post amplifier A and second order filter F, and the output terminal of modulator (4) is connected with capture card by cable (5), and capture card is connected with computing machine by signal wire again.

Images