CN1687795A - Optical fibre current transformer and its loop detector of transformer - Google Patents
Optical fibre current transformer and its loop detector of transformer Download PDFInfo
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- CN1687795A CN1687795A CN 200510076618 CN200510076618A CN1687795A CN 1687795 A CN1687795 A CN 1687795A CN 200510076618 CN200510076618 CN 200510076618 CN 200510076618 A CN200510076618 A CN 200510076618A CN 1687795 A CN1687795 A CN 1687795A
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Abstract
本发明公开了一种光纤电流互感器及其互感器的闭环检测装置，该光纤电流互感器中光路采用全光纤连接，光纤电流互感器中的电路采用闭环检测模式。所述的闭环检测装置中前放单元接收光电探测器输出的光强电压信号，经A/D转换后输出给FPGA，FPGA将采集的电压信号输出给DSP，经DSP进行数字解调、数值滤波、积分处理后输出控制信号给FPGA；FPGA对接收DSP的控制信号输出给模拟输出电路；方波调制电路和数字阶梯波发生电路接收FPGA输出的控制信号，方波调制电路输出的方波信号与数字阶梯波发生电路输出的数字阶梯波高度信号经叠加后驱动相位调制器。本发明采用全光纤传输，其绝缘性能好，受电磁干扰影响小，测量频带宽，动态范围大，采用闭环控制无开路导致高压的危险。
The invention discloses a fiber optic current transformer and a closed-loop detection device for the transformer. The optical path of the fiber optic current transformer is connected by all optical fibers, and the circuit in the fiber optic current transformer adopts a closed-loop detection mode. In the closed-loop detection device, the pre-amplifier unit receives the light intensity voltage signal output by the photodetector, and outputs it to the FPGA after A/D conversion, and the FPGA outputs the collected voltage signal to the DSP, and performs digital demodulation and numerical filtering through the DSP , output control signal to FPGA after integral processing; FPGA outputs control signal to receive DSP to analog output circuit; The digital staircase wave height signal output by the digital staircase wave generating circuit drives the phase modulator after being superimposed. The invention adopts all-optical fiber transmission, has good insulation performance, is less affected by electromagnetic interference, has a wide measurement frequency range and a large dynamic range, and adopts closed-loop control without the risk of high voltage caused by an open circuit.
Description
Technical field
The present invention relates to a kind of sensor device, specifically, be meant a kind of optical fiber current mutual inductor of all optical fibre structure.This optical fiber current mutual inductor utilizes the Faraday effect in the magnetic field of transmission current generation, and the phase place of transmission light is changed, and the signal amplitude after interfering by measurement can be measured the current value in the lead indirectly.
Background technology
Current transformer (Current tranducer is called for short CT) is the visual plant that carries out electric energy metrical and relay protection in the electric system, and safe, the reliable and economical operation of its precision and reliability and electric system is closely related.Yet along with development of electric power industry, the electrical power transmission system capacity constantly increases, and the working voltage grade is more and more higher, and the highest voltage level of China's electrical network has reached 500KV at present, and to higher electric pressure development.And traditional electromagnetic current transducer principle is based on the electromagnetic induction of similar transformer principle, because its principle of work has determined technical some insoluble difficulties that have.As:
(1) electric pressure improves, and has increased the difficulty that insulate, and causes the insulation system complexity, and volume weight is bigger, install, transport inconvenience, and cost is the index rising.
(2) because the iron core magnetic characteristic is limited, it is seriously saturated under some bigger working current or fault current effect iron core may to take place, and makes measurement result the deviation that is difficult to allow occur, provides error message to electric system.
(3) if mutual inductor output is in open-circuit condition, output terminal can be responded to high pressure, might cause insulation fault or jeopardize miscellaneous equipment and staff's safety.
(4) at present fill with mineral oil as insulation and heat eliminating medium more conventional current mutual inductor inside, has catastrophic failure and may cause the danger of burning, exploding.
Present most of current transformer is a Faraday effect of utilizing crystal.The defective of the optical fiber current mutual inductor that crystal makes up is: dynamic range is little, sensitivity is low, the insertion loss is big.
Summary of the invention
The loop detector that the purpose of this invention is to provide a kind of optical fiber current mutual inductor and mutual inductor thereof, light path adopts full optical fiber to connect in this optical fiber current mutual inductor.Loop detector always works on the sensitivity peak optical fiber current mutual inductor, adopts closed loop detecting pattern of the present invention to improve the sensitivity that detects, and has enlarged the dynamic range of measuring.
A kind of optical fiber current mutual inductor of the present invention, by light source, photodetector, beam splitter, polarizer, phase-modulator, protect the off-delay optical cable, λ/4 wave plates, sensing head and signal processing unit constitute, described sensing head is formed through end face coating by sensor fibre, the tail optical fiber of light source and photodetector is gone into fine welding with two of beam splitter respectively, the tail optical fiber of beam splitter and polarizer go into fine welding, the tail optical fiber of polarizer and phase-modulator go into fine 45 ° of weldings, the tail optical fiber of phase-modulator is connected with an end of protecting the polarisation cable, the other end of protecting the polarisation cable is connected the λ/4 wave plate other ends and sensor fibre welding with λ/4 wave plates; Photodetector output intensity voltage signal is given signal processing unit, and the superposed signal of signal processing unit output square wave and staircase waveform is given phase-modulator; The light that phase-modulator place light source produces in the described optical fiber current mutual inductor should satisfy sin 4VNI ≈ 4VNI with the phase differential of the light that returns through mirror reflects, (V represents the Verdet constant, N represents to twine the optical fiber number of turns of lead, and I represents the current value in the lead), and 4VNI≤0.5 °～1 °.
The closed loop of optical fiber current mutual inductor of the present invention detects, its signal processing unit is formed by preceding putting unit, FPGA, DSP, square wave modulation circuit, digital ladder wave generation circuit, analog output circuit, light source driving circuit and power circuit, before put the unit and receive optical intensity voltage signal by described photodetector output, and it is carried out every straight, filtering, amplification, after the A/D conversion, export to FPGA, FPGA exports to DSP with the voltage signal of gathering, and the output control signal is given FPGA after DSP carries out digital demodulation, numerical filter, Integral Processing; FPGA exports to analog output circuit to the control signal that receives DSP, and analog output circuit amplifies output to the digital voltage signal that receives after the D/A conversion; Square wave modulation circuit receives the control signal of FPGA output and produces square-wave signal, numeral ladder wave generation circuit receives the control signal of FPGA output and produces digital staircase waveform altitude signal, and the digital staircase waveform altitude signal of the square-wave signal of square wave modulation circuit output and the output of digital ladder wave generation circuit is through stack rear drive phase-modulator; Phase-modulator is modulated the voltage signal that receives and is kept interference light intensity constant; Light source driving circuit output pulse signal driving light source.
The light that is sent by light source in the light path of optical fiber current mutual inductor of the present invention plays the inclined to one side linearly polarized light that forms through behind the beam splitter by polarizer, linearly polarized light injects phase-modulator after X-axis linearly polarized light and Y-axis linearly polarized light are resolved in 45 ° of deflections, enter λ/4 wave plates through X-axis linearly polarized light behind the phase-modulator and Y-axis linearly polarized light with orthogonal modes transmission in guarantor's polarisation cable, X-axis linearly polarized light and the Y-axis linearly polarized light changes right-circularly polarized light into respectively and left circularly polarized light enters sensor fibre behind λ/4 wave plates, in sensor fibre, be subjected to the effect of Faraday magneto-optic effect to produce phase difference θ=2VNI, right-circularly polarized light changes left circularly polarized light into after the reflectance coating reflection, left circularly polarized light changes right-circularly polarized light into, two-beam after the transformation is subjected to the effect of Faraday magneto-optic effect to make the phase differential of two-beam double Δ φ=2 Δ θ=4VNI through sensor fibre once more, after right-circularly polarized light after the transformation and left circularly polarized light pass through λ/4 wave plates once more, revert to X-axis linearly polarized light and Y-axis linearly polarized light, the place interferes at beam splitter, at last, the light that carries phase information is coupled into photodetector by beam splitter.
Optical fiber current mutual inductor of the present invention is compared with traditional electromagnetic current transducer, its advantage: (1) adopts full Optical Fiber Transmission, its good insulation preformance; Do not contain iron core, be subjected to electromagnetic interference effect little, the hysteresis phenomenon that does not have ferromagnetic resonance, magnetic saturation and big inductance to cause; (2) measure bandwidth, dynamic range is big, adopts closed-loop control not have the danger that open circuit causes high pressure; (3) little, the light weight, simple in structure of volume is easy to install.
Description of drawings
Fig. 1 is the structural representation of optical fiber current mutual inductor of the present invention.
Fig. 2 is that optical fiber current mutual inductor light path of the present invention is moved towards synoptic diagram.
Fig. 3 is the structured flowchart of optical fiber current mutual inductor signal processing unit of the present invention.
Fig. 4 is an optical fiber current mutual inductor closed loop testing process block diagram of the present invention.
Fig. 5 A is a preceding discharge road schematic diagram.
Fig. 5 B is fpga chip figure.
Fig. 5 C is dsp chip figure.
Fig. 5 D is staircase waveform, circuit and square-wave schematic diagram.
Fig. 5 E is the analog output circuit schematic diagram.
Fig. 5 F is the light source driving circuit schematic diagram.
Fig. 6 is the square wave modulation circuit output waveform figure.
Fig. 7 is a ladder wave generation circuit output waveform figure.
Among the figure: 1. put unit 94. square wave circuit for generatings, 95. staircase waveform circuit for generatings, 96. analog output circuits, 97. light source driving circuits, 98. power circuits before light source 2. circulators 3. polarizers 4. phase-modulators 5. are protected off-delay optical cable 6. λ/4 wave plates, 7. sensing heads, 71. sensor fibres, 72. reflectance coatings, 8. photodetectors, 9. signal processing unit 91.FPGA processor 92.DSP processors 93.
Embodiment
The essence of the optical fiber current mutual inductor of all optical fibre structure is that the principle of utilizing two-beam to interfere records.Because transmission current produces magnetic field, when a branch of circularly polarized light passed through sensor fibre, because the Faraday effect, the phase place of circularly polarized light changed in the sensor fibre, and phase change is θ
FBy measuring relevant two-beam, just can measure the current value in the lead indirectly.
(1) hardware configuration of all-fiber current transformator
See also shown in Figure 1, the present invention is a kind of optical fiber current mutual inductor, by light source 1, photodetector 8, sensing head 7, it is characterized in that: also comprise beam splitter 2, polarizer 3, phase-modulator 4, protect off-delay optical cable 5, λ/4 wave plates 6 and signal processing unit 7 constitute, described sensing head 7 is formed through end face plating reflectance coating 72 by sensor fibre 71, the tail optical fiber of light source 1 and photodetector 8 is gone into fine welding with two of beam splitter 2 respectively, the tail optical fiber of beam splitter 2 and polarizer 3 go into fine welding, the tail optical fiber of polarizer 3 and phase-modulator 4 go into fine 45 ° of weldings, the tail optical fiber of phase-modulator 4 is connected with an end of protecting off-delay optical cable 5, and the other end of protecting off-delay optical cable 5 is connected with λ/4 wave plates 6 that (two ends of guarantor's off-delay optical cable 5 can be wire jumper connection or welding with phase-modulator 4 and being connected of λ/4 wave plates 6.), sensor fibre 71 weldings of λ/4 wave plates, 6 other ends and sensing head 7; The optical intensity voltage signal output terminal of described photodetector 8 is connected with signal processing unit 9, and the superposed signal of signal processing unit 9 output square waves and staircase waveform is given phase-modulator 4; Described optical fiber current mutual inductor carries out the closed loop detection to reception and/or output signal.The phase differential of light satisfies sin 4VNI ≈ 4VNI in the described phase-modulator 4, and 4VNI≤0.5 °～1 °, V represents the Verdet constant, and N represents to twine the optical fiber number of turns of lead, and I represents the current value in the lead.In the phase-modulator 4 phase differential of light be meant light that the light that produces from light source 1 enters into phase-modulator 4 through beam splitter 2, polarizer 3 light and light produces from light source 1 through beam splitter 2, polarizer 3, phase-modulator 4, guarantor's off-delay optical cable 5, λ/4 wave plates 6 and sensing head 7 after the phase differential between the light of catoptron 72 reflected backs (seeing also shown in Figure 2), the i.e. left circularly polarized light in the phase-modulator 4 and the phase differential of right-circularly polarized light.Each optical device in the present invention adopts full optical fiber to connect.
In the present invention, described light source 1 is SLD light source or led light source, described beam splitter 2 is circulator or coupling mechanism, described phase-modulator 4 is PZT modulator or electrooptic modulator or integrated optical modulator, described λ/4 wave plates 6 are full optical-fibre wave plates, and the sensor fibre 71 of described sensing head 7 is single-mode fiber or circular birefringent fiber or low birefringent fiber or annealing optical fiber.
(2) light channel structure of all-fiber current transformator
See also shown in Figure 2, the light that is sent by light source 1 in the light path of optical fiber current mutual inductor forms linearly polarized light through beam splitter 2 backs partially by 3 of polarizers, going into of the tail optical fiber of polarizer 3 and phase-modulator 4 is fine with 45 ° of weldings, just being divided equally with the linearly polarized light of 45 ° of polarizations is two parts, transmit along the X-axis and the Y-axis of polarization maintaining optical fibre respectively, the linearly polarized light of these two orthogonal modess is subjected to phase modulation (PM) at phase-modulator 4 places, then this two-beam is through λ/4 wave plates 6, become left-handed respectively and circularly polarized light dextrorotation, and enter sensor fibre 71.Because transmission current produces magnetic field, in sensor fibre 71 because the Faraday magneto-optic effect, phase place of this two bundles circularly polarized light (Δ θ=2VNI) and that changes with different speed transmission, after the reflection of reflectance coating 72 places, it (is that left-handed rotation becomes right-handed rotation that the polarization mode of two bundle circularly polarized lights exchanges, right-handed rotation becomes left-handed rotation) pass sensor fibre 71 once more, the phase place of Faraday effect generation is doubled (Δ φ=2 Δ θ=4VNI).This two-beam by behind λ/4 wave plates 6, reverts to linearly polarized light once more, and the light of propagating along the polarization maintaining optical fibre X-axis originally becomes along the polarization maintaining optical fibre Y-axis and propagate, and originally becomes along the polarization maintaining optical fibre X-axis along the light of polarization maintaining optical fibre Y-axis propagation and propagates.The light of propagating along polarization maintaining optical fibre X-axis, Y-axis interferes at beam splitter 2 places respectively.At last, carry the light of phase information by the laggard photodetector 8 of beam splitter 2 couplings.Because the two-beam that interferes, in the optic path process, the X-axis of polarization maintaining optical fibre and the left-handed and dextrorotation pattern of Y-axis and sensor fibre have all been passed through respectively, difference slightly in time only, so the light of back light electric explorer 8 has only carried because the non-reciprocal phase that the Faraday effect produces is poor.
(3) circuit structure of all-fiber current transformator
Before put unit 93
Before put unit 93 and comprise every straight filtering, two-stage amplifying circuit and A/D change-over circuit.Because the output signal of optical fiber current mutual inductor is extremely faint, and there is a direct current biasing amount about the hundreds of millivolt in photodetector 8 output signals, therefore adopt the method for R-C coupling in the present invention, make the DC component in the prime output signal be unlikely to be coupled to next stage.The connection of each terminal is shown in Fig. 5 A, the optical intensity voltage signal end of fiber-optical probe 8 outputs is connected with 2 ends of the operational amplifier NO1 on preceding discharge road, the output terminal of operational amplifier NO1 is connected with the input end of operational amplifier NO2,6 ends of operational amplifier NO2 are connected with bleeder circuit, the output terminal of bleeder circuit is connected with 23 ends of A/D change-over circuit D0, A/D change-over circuit D0 read the end, write end, clock end, the carry end respectively with FPGA read the end, write end, clock end, the carry end connects, and the 10 bit address output terminals of A/D change-over circuit D0 are connected with the 10 bit address input ends of FPGA treatment circuit D2.
Optical fiber current mutual inductor of the present invention adopts closed loop to detect control, its sequential control that requires square-wave frequency modulation, A/D to gather demodulation numeral staircase waveform feedback has strict synchronized relation, takes all factors into consideration the time delay of the passage of each control signal experience when the design sequential control circuit.With the A/D trigger pulse is benchmark, and frequency division produces the trigger pip of modulated square wave signal and the generation of digit phase staircase waveform step, controls the carrying out of demodulating process simultaneously.Sequential adopts the phaselocked loop of crystal oscillator control to produce the AD sample frequency, produce timing control signal by frequency division and give the FPGA processor the AD sample frequency, FPGA produces modulated square wave sequential reconciliation timing preface respectively for simultaneously modulated square wave reconciliation circuit demodulation circuit timing control signal, makes square wave and staircase waveform strict synchronism by modulated square wave sequential control feedback staircase waveform sequential.
Because trigger pulse and modulated square wave that A/D trigger pulse, phase place step produce are to realize by the frequency division of strictness, so in case its sequential of first has accomplished that synchronously then other point also is a strict synchronism.
The connection of each terminal is shown in Fig. 5 B, 16 bi-directional data ends of FPGA treatment circuit D2 are connected with 16 bi-directional data ends of DSP treatment circuit D1, the 16 bit address input ends of FPGA treatment circuit D2 are connected with the 16 bit address output terminals of DSP treatment circuit D1, the control input end of FPGA treatment circuit D2 is connected with the control output end of DSP treatment circuit D1, the 12 bit data output terminals of FPGA treatment circuit D2 are connected with the 12 bit data input ends of digital ladder wave generation circuit D7, the sheet choosing end of FPGA treatment circuit D2, write the sheet choosing end of input end and digital ladder wave generation circuit D7, write input end and connect, the digital signal output end of FPGA treatment circuit D2 is connected with the digital input end of the D/A change-over circuit D6 of analog output circuit.
Because input of the present invention belongs to the category of Detection of Weak Signals, according to the Detection of Weak Signals theory, the present invention adopts the sync correlation detection technique, the signal of optical fiber current mutual inductor output can be extracted from very noisy.Basic implementation method is: 1, at first make the main circuit of detection system signal avoid the big place of Carrier To Noise Power Density by modulation, thereby make output noise less.At low frequency range, flicker noise can exceed several times, tens of times even hundreds of times than white noise.The present invention can make that signal is distortionless to be shifted out from low frequency range; 2, contrast as can be seen from signal and characteristics of noise, signal has frequency different with phase place two aspects with most noises.Filtering has utilized the identification of frequecy characteristic among the present invention, utilizes the identification of phase characteristic just can get rid of the noise of same frequency out of phase in a large number again.After demodulation module is finished demodulation, the data that demodulate are kept in the register, and send out interrupt request singal to DSP simultaneously, DSP enters the value that interrupt service routine reads register after receiving interrupt request singal.The connection of each terminal is shown in Fig. 5 C, 16 bi-directional data ends of DSP treatment circuit D1 are connected with 16 bi-directional data ends of FPGA treatment circuit D2, the 16 bit address input ends of FPGA treatment circuit D2 are connected with the 16 bit address output terminals of DSP treatment circuit D1, and the control input end of FPGA treatment circuit D2 is connected with the control output end of DSP treatment circuit D1.DSP treatment circuit and FPGA treatment circuit and the transmission that is connected realization data, address.
Square wave modulation circuit 94
Constant voltage circuit in the square wave modulation circuit 94 produces a constant voltage signal, and described constant voltage signal distributed the two-way voltage division signal, wherein reference voltage signal of voltage division signal output is given digital ladder wave generation circuit, another voltage division signal is exported to frequency dividing circuit, and frequency dividing circuit receives the pulse signal of FPGA treatment circuit and produces output one square-wave signal.In complete-digital closed-loop scheme of the present invention, realize phase modulation (PM) with square wave.The waveform of square wave output as shown in Figure 6.The cycle of square wave is 2 τ, highly is
The connection of each terminal is shown in Fig. 5 D, the reference voltage signal output terminal of square wave modulation circuit D3 after dividing potential drop is connected with the reference voltage signal input end of digital ladder wave generation circuit D7,6 ends of constant voltage circuit D3 are connected with 4 ends of frequency dividing circuit D4, the pulse input end of frequency dividing circuit D4 is connected with the pulse output end of FPGA treatment circuit D2, and the square-wave signal output terminal that frequency dividing circuit D4 produces is connected with the square wave input end of digital ladder wave generation circuit.
Numeral ladder wave generation circuit 95:
Numeral ladder wave generation circuit controlling and driving phase-modulator.The input signal of numeral ladder wave generation circuit is a digital signal D
m, output signal is voltage signal V
Out, this input/output relation becomes integral relation, V
Out=K
R∫ D
mDt, K
RBe the integration scale factor, the light wave that the effect of phase-modulator interferes two bundles produces an additional feedback phase φ
F, as Δ φ-φ
F=0, then realized the closed loop detection.Feedback phase shift φ
FTherefore equal the responsive phase place of optical fiber current mutual inductor, can only detect, thereby removed the influence of the luminous power fluctuation that optical device causes phase place.
In complete-digital closed-loop scheme of the present invention, realize phase compensation with digital staircase waveform.The phase relation of digital closed loop as shown in Figure 7.Wherein FW is the light of propagated forward, and BW is the light of back-propagating, and the bench height of staircase waveform is feedback phase.The transit time τ strict synchronism of each step width of staircase waveform and optical fiber sensor coil.In addition, when detecting owing to closed loop, the working point of system is best in linearity all the time
On the point, therefore have the extraordinary linearity and wide dynamic range.Square wave is produced by the reference signal control analog switch that logic produces, and staircase waveform is produced by analog to digital conversion by the digital feedback amount, and altitude signal is produced by analog to digital conversion by totalizer; The simulation overlaying scheme is adopted in the stack of square wave and staircase waveform.The connection of each terminal is shown in Fig. 5 D, the 12 bit data output terminals of FPGA treatment circuit D2 are connected with the 12 bit data input ends of digital ladder wave generation circuit D7, the sheet choosing end of FPGA treatment circuit D2, write the sheet choosing end of input end and digital ladder wave generation circuit D7, writing input end connects, the reference voltage signal output terminal of square wave modulation circuit D3 after dividing potential drop is connected with the reference voltage signal input end of digital ladder wave generation circuit D7, the digital staircase waveform altitude signal output terminal of the discharge circuit NO3 of numeral ladder wave generation circuit and the square-wave signal that square wave modulation circuit produces superpose, and the signal after the described stack is exported to phase-modulator.
Analog electrical output route D/A change-over circuit, two-stage amplifying circuit are formed, the D/A change-over circuit converts the digital signal of FPGA treatment circuit output to simulating signal, and described simulating signal is exported to the circuit of next stage (can be slave computer or checkout equipment) through the two-stage amplifying circuit.The connection of each terminal is shown in Fig. 5 E, the digital signal output end of FPGA treatment circuit D2 is connected with the digital input end of the D/A change-over circuit D6 of analog output circuit, and the input end of analog signal 3 of the amplifying circuit NO6 in the analog signal output 1 of D/A change-over circuit D6 and the two-stage amplifying circuit is connected.
Light source driving circuit 97
Light source driving circuit comprises high-precision constant flow source circuit, and light source tube core temperature-control circuit is formed.High-precision constant flow source circuit provides stable electric current output, makes light source output power stable; The thermo-sensitive resistor of light source tube core temperature-control circuit utilization stablizing tube core is operated in tube core under the stable temperature environment, makes light source works not be subjected to extraneous thermal effect, and output power is more stable.The connection of each terminal is shown in Fig. 5 F, constant-current source circuit adopts the Max873 chip, thereby the Max873 chip produces a constant voltage signal and obtains a steady current and come driving light source, and light source tube core temperature-control circuit adopts the electric bridge that is made of thermistor to control the light source die temperature.
Each module is chosen chip and is in the signal processing unit of the present invention: FPGA chooses the TMS320F206 chip, DSP chooses the EPF10K10TC144 chip, two amplifier OPA627U of preceding discharge route chip adds a bleeder circuit and adds A/D conversion TLV1571 chip composition again, square wave modulation circuit is made up of constant voltage circuit and 4/8 simulation multiplexer ADG509FBRN chip, and the ladder wave generation circuit is made up of D/A conversion DAC7545 chip and amplifier OPA627U chip.
Optical fiber current mutual inductor of the present invention adopts the closed loop detection scheme in control and in handling, enlarged the measurement range 0～3600A of electric current effectively, improve the system sensitivity of signal processing unit 9 integral body, and can eliminate the intensity noise that the variation of part light intensity causes.
Claims (9)
1, a kind of optical fiber current mutual inductor, comprise light source (1), photodetector (8), sensing head (7), it is characterized in that: also comprise beam splitter (2), polarizer (3), phase-modulator (4), protect off-delay optical cable (5), λ/4 wave plates (6) and signal processing unit (7) constitute, described sensing head (7) is formed through end face plating reflectance coating (72) by sensor fibre (71), the tail optical fiber of light source (1) and photodetector (8) is gone into fine welding with two of beam splitter (2) respectively, the tail optical fiber of beam splitter (2) and polarizer (3) go into fine welding, the tail optical fiber of polarizer (3) and phase-modulator (4) go into fine 45 ° of weldings, the tail optical fiber of phase-modulator (4) is connected with an end of protecting off-delay optical cable (5), the other end of protecting off-delay optical cable (5) is connected sensor fibre (71) welding of λ/4 wave plates (6) other end and sensing head (7) with λ/4 wave plates (6); The optical intensity voltage signal output terminal of described photodetector (8) is connected with signal processing unit (9), and the superposed signal of signal processing unit (9) output square wave and staircase waveform is given phase-modulator (4);
The phase differential of light satisfies sin4VNI ≈ 4VNI in the described phase-modulator (4), and 4VNI≤0.5 °～1 °, V represents the Verdet constant, and N represents to twine the optical fiber number of turns of lead, and I represents the current value in the lead;
Described optical fiber current mutual inductor carries out the closed loop detection to reception and/or output signal.
2, optical fiber current mutual inductor according to claim 1, it is characterized in that: described light source (1) is SLD light source or led light source, described beam splitter (2) is circulator or coupling mechanism, described phase-modulator (4) is PZT modulator or electrooptic modulator or integrated optical modulator, described λ/4 wave plates (6) are full optical-fibre wave plates, and the sensor fibre (71) of described sensing head (7) is single-mode fiber or circular birefringent fiber or low birefringent fiber or annealing optical fiber.
3, optical fiber current mutual inductor according to claim 1 is characterized in that: described guarantor's off-delay optical cable (5) two ends can be that wire jumper connects or welding with phase-modulator (4) and being connected of λ/4 wave plates (6).
4, optical fiber current mutual inductor according to claim 1, it is characterized in that: the light that is sent by light source (1) plays the inclined to one side linearly polarized light that forms through beam splitter (2) back by polarizer (3), described linearly polarized light injects phase-modulator (4) after X-axis linearly polarized light and Y-axis linearly polarized light are resolved in 45 ° of deflections, enter λ/4 wave plates (6) through described X-axis linearly polarized light behind the phase-modulator (4) and described Y-axis linearly polarized light with orthogonal modes transmission in guarantor's off-delay optical cable (5), described X-axis linearly polarized light and described Y-axis linearly polarized light change right-circularly polarized light respectively into and left circularly polarized light enters sensor fibre (71) behind λ/4 wave plates (6), in sensor fibre (71), be subjected to the effect of Faraday magneto-optic effect to produce phase difference θ=2VNI, described right-circularly polarized light changes left circularly polarized light into after reflectance coating (72) reflection, described left circularly polarized light changes right-circularly polarized light into, two-beam after the transformation is subjected to the effect of Faraday magneto-optic effect to make the phase differential of two-beam double Δ φ=2 Δ θ=4VNI through sensor fibre (71) once more, after right-circularly polarized light after the transformation and left circularly polarized light pass through λ/4 wave plates (6) once more, revert to X-axis linearly polarized light and Y-axis linearly polarized light, locate to interfere at beam splitter (2), at last, the light that carries phase information is coupled in the photodetector (8) by beam splitter (2).
5, optical fiber current mutual inductor according to claim 4, it is characterized in that: protecting to transmit in the off-delay optical cable (5) entering λ/4 wave plates (6) with orthogonal modes through the described X-axis linearly polarized light behind the phase-modulator (4), the X-axis linearly polarized light is transformed into left circularly polarized light and enters sensor fibre (71) behind λ/4 wave plates (6); Protecting to transmit in the off-delay optical cable (5) entering λ/4 wave plates (6) with orthogonal modes through the described Y-axis linearly polarized light behind the phase-modulator (4), the Y-axis linearly polarized light is transformed into right-circularly polarized light and enters sensor fibre (71) behind λ/4 wave plates (6).
6, the closed loop of optical fiber current mutual inductor according to claim 1 detects, it is characterized in that: described signal processing unit (9) is by preceding putting unit (93), FPGA processor (91), dsp processor (92), square wave modulation circuit (94), ladder wave generation circuit (95), analog output circuit (96), light source driving circuit (97) and power circuit (98) are formed, before put unit (93) and receive optical intensity voltage signal by described photodetector (8) output, and it is carried out every directly, filtering, amplify, after the A/D conversion, export to FPGA processor (91), FPGA processor (91) is exported to dsp processor (92) with the voltage signal of gathering, and carries out digital demodulation through dsp processor (92), numerical filter, the output control signal is given FPGA processor (91) after the Integral Processing; FPGA processor (91) is exported to analog output circuit (96) to the control signal that receives dsp processor (92), and analog output circuit (96) amplifies output to the digital voltage signal that receives after the D/A conversion; Square wave modulation circuit (94) receives the control signal of FPGA processor (91) output and produces square-wave signal, ladder wave generation circuit (95) receives the control signal of FPGA processor (91) output and produces digital staircase waveform altitude signal, and the digital staircase waveform altitude signal of the square-wave signal of square wave modulation circuit (94) output and ladder wave generation circuit (95) output is through stack rear drive phase-modulator (4); Phase-modulator (4) is modulated the voltage signal that receives and is kept interference light intensity constant; Light source driving circuit (97) output pulse signal driving light source (1).
7, the closed loop of optical fiber current mutual inductor according to claim 6 detects, it is characterized in that: FPGA chooses the TMS320F206 chip, DSP chooses the EPF10K10TC144 chip, two amplifier OPA627U of preceding discharge route chip adds a bleeder circuit and adds A/D conversion TLV1571 chip composition again, square wave modulation circuit is made up of constant voltage circuit and 4/8 simulation multiplexer ADG509FBRN chip, and the ladder wave generation circuit is made up of D/A conversion DAC7545 chip and amplifier OPA627U chip.
8, the closed loop of optical fiber current mutual inductor according to claim 6 detects, it is characterized in that: the optical intensity voltage signal end of fiber-optical probe (4) output is connected with 2 ends of the operational amplifier NO1 on preceding discharge road (93), the output terminal of operational amplifier NO1 is connected with the input end of operational amplifier NO2,6 ends of operational amplifier NO2 are connected with bleeder circuit, the output terminal of bleeder circuit is connected with 23 ends of A/D change-over circuit D0, A/D change-over circuit D0 read the end, write end, clock end, the carry end respectively with FPGA processor (91) read the end, write end, clock end, the carry end connects, and the 10 bit address output terminals of A/D change-over circuit D0 are connected with the 10 bit address input ends of FPGA treatment circuit D2; 16 bi-directional data ends of FPGA treatment circuit D2 are connected with 16 bi-directional data ends of DSP treatment circuit D1, the 16 bit address input ends of FPGA treatment circuit D2 are connected with the 16 bit address output terminals of DSP treatment circuit D1, the control input end of FPGA treatment circuit D2 is connected with the control output end of DSP treatment circuit D1, the 12 bit data output terminals of FPGA treatment circuit D2 are connected with 12 bit data input ends of digital ladder wave generation circuit 7, the sheet choosing end of FPGA treatment circuit D2, write the sheet choosing end of input end and digital ladder wave generation circuit D7, write input end and connect, the digital signal output end of FPGA treatment circuit D2 is connected with the digital input end of the D/A change-over circuit D6 of analog output circuit; 16 bi-directional data ends of DSP treatment circuit D1 are connected with 16 bi-directional data ends of FPGA treatment circuit D2, the 16 bit address input ends of FPGA treatment circuit D2 are connected with the 16 bit address output terminals of DSP treatment circuit D1, and the control input end of FPGA treatment circuit D2 is connected with the control output end of DSP treatment circuit D1.DSP treatment circuit and FPGA treatment circuit be connected the transmission that realizes data, address; The reference voltage signal output terminal of square wave modulation circuit D3 after dividing potential drop is connected with the reference voltage signal input end of digital ladder wave generation circuit D7,6 ends of constant voltage circuit D3 are connected with 4 ends of frequency dividing circuit D4, the pulse input end of frequency dividing circuit D4 is connected with the pulse output end of FPGA treatment circuit D2, and the square-wave signal output terminal that frequency dividing circuit D4 produces is connected with the square wave input end of digital ladder wave generation circuit; The 12 bit data output terminals of FPGA treatment circuit D2 are connected with the 12 bit data input ends of digital ladder wave generation circuit D7, the sheet choosing end of FPGA treatment circuit D2, write the sheet choosing end of input end and digital ladder wave generation circuit D7, writing input end connects, the reference voltage signal output terminal of square wave modulation circuit D3 after dividing potential drop is connected with the reference voltage signal input end of digital ladder wave generation circuit D7, the digital staircase waveform altitude signal output terminal of the discharge circuit NO3 of numeral ladder wave generation circuit and the square-wave signal that square wave modulation circuit produces superpose, and the signal after the described stack is exported to phase-modulator; The digital signal output end of FPGA treatment circuit D2 is connected with the digital input end of the D/A change-over circuit D6 of analog output circuit, and the input end of analog signal 3 of the amplifying circuit NO6 in the analog signal output 1 of D/A change-over circuit D6 and the two-stage amplifying circuit is connected.
9, optical fiber current mutual inductor according to claim 1 is characterized in that: described optical fiber current mutual inductor working temperature-40 ℃～+ 50 ℃, can survey magnitude of current scope 0～3600A.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2005100766187A CN100340860C (en) | 2005-06-13 | 2005-06-13 | Optical fibre current transformer and its loop detector of transformer |
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|---|---|---|---|
| CNB2005100766187A CN100340860C (en) | 2005-06-13 | 2005-06-13 | Optical fibre current transformer and its loop detector of transformer |
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| CN100340860C CN100340860C (en) | 2007-10-03 |
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