CN1540355A - Reflection type 'Sage-qinke' interferometer type current transformer prepared from full optical fiber - Google Patents
Reflection type 'Sage-qinke' interferometer type current transformer prepared from full optical fiber Download PDFInfo
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Abstract
The current transformer is composed of at least connected opto-electronic unit and optical fiber current induction unit. The opto-electronic unit generates optical signal in use for detection, and optical fiber current induction unit detects current passing through bus enwound by fiber winding. Reflection type 'Sage-naike' interference treating technique is adopted in the invention to overcome interference of diversified environmental factors such as temperature, vibration and electromagnetic interference with out need of introducing power source in high voltage area. Induction optical fiber winding can be prepared from ultra-low birefringence fiber or general low birefringence fiber or circular polarization holding fiber, which overcomes limitation of traditional fiber: large influence from environmental factors and large fluctuation of linear birefringence. In the invention, reflective coating at end face of fiber features of heat and cold proof, shock-resistant etc.
Description
Technical field
The present invention relates to a kind of optical fiber type current mutual inductor, be meant the reflective Sagnac interference treatment technology of a kind of employing especially, have high measurement accuracy, and can overcome the full fiber type current transformer that various environmental factors are disturbed; Belong to field of photoelectric technology.
Background technology
Mutual inductor is an indispensable visual plant in the transmission line of electricity, and its effect is exactly to concern according to a certain percentage the high voltage on the transmission line of electricity and big current values are dropped to the standard figures that can directly measure with instrument, so that directly measure with instrument.Mutual inductor also can be used as relay protection except that as measuring.The quantity of the mutual inductor that annual China produces is very huge.For example,, produce 760,474 of mutual inductors, realize 14.90 hundred million yuan of gross industrial output value according to 33 the emphasis mutual inductor enterprise statisticses in the whole nation in 1999.Wherein the mutual inductor of 110kV and above electric pressure is about 17,800.According to one's analysis, reach 100kV and when above, use the photo-electric mutual inductor, economically valuable in electric pressure.
A windings in series of traditional current transformer is in power circuit, and the Secondary Winding external circuit is connected to surveying instrument or relay protection and automaton.Its structure is similar with transformer, is wound with first and second winding on its iron core, by the electromagnetic coupled between first and second winding, will measure transducing signal and pass to secondary side from primary side.Between iron core and winding, and the insulation system that enough electric strengths are arranged between first and second winding, be used to guarantee all low-voltage equipments and high-tension isolation.Along with the increase of the power capacity of electric system transmission, electric pressure is more and more higher, and the insulation system of traditional current transformer also becomes increasingly complex, and volume and weight is increasing, and the cost of product is also more and more higher.For example, conventional oil-immersed current transformer, the price of 500kV product doubles than the price of 300kV.
The iron core of electromagnetic type current transformer has non-linear, and when electric system was short-circuited, the short-circuit current of high amplitude made this mutual inductor moment saturated, and the secondary current of its output seriously distorts, and causes the protection tripping, makes electric system generation major accident.The saturated of mutual inductor causes wave form distortion, and its frequency response characteristic is relatively poor, and frequency band is narrow, the system high-frequency difference in response, and make novel quick protection realize having difficulties based on the high frequency transient component.
Though electromagnetic transformer has obtained development more fully, wherein iron core formula current transformer has adapted to the growth requirement of power construction with the multiple structure of dry type, oil immersed type and gas-insulating type.Yet continuous growth along with the electric power transfer capacity; the line voltage grade improve constantly and protect the constantly perfect of requirement; general iron core formula current transformer structure exposes incompatible with it weakness gradually; its intrinsic volume is big, magnetic saturation, ferroresonance, dynamic range are little; weakness such as service band is narrow are difficult to satisfy the development need of Automation of Electric Systems of new generation, electric power digital network etc.
Along with developing rapidly of photoelectron technology, many scientific and technological developed countries have turned to sight and have utilized optical sensing technology and electronics method to develop novel electronic formula current transformer, are called for short photoelectric current inductor.International Power association is the standard of distributing electronic formula current transformer.The implication of electronic mutual inductor except comprising the mutual inductor of photo-electric, also comprises other various voltage, current transformers that utilize the Electronic Testing principle.
Photo-electricity mutual-inductor is to utilize photoelectron technology and optical fiber sensing technology to realize the new transformer of power system voltage, current measurement.It is the common name of various optics mutual inductors such as optical voltage transformer (OVT), optical current mutual inductor (OCT), combined type optics mutual inductor.The kind of photo-electric current transformer is a lot, but can roughly be divided into two kinds of active type and passives.Active type means at sensing head partly have the electronic circuit that needs with power supply; Passive does not then need power supply in the sensing head part.Both structures are different, but the conventional current mutual inductor of they and electromagnetic type by comparison, all has similar various advantages.
In the sensing head of the hot side of the photo-electric current transformer of the active formula of employing laser energy supply, what all adopt is electron device.With air core coil (Rogowski coil) bus current is become voltage signal at hot side, this voltage signal is an analog quantity, convert digital signal to through A/D, with electric light conversion (LED) circuit this digital signal is become light signal, by the optical fiber of insulation light signal is delivered to low potential side then.At low potential side, (PIN) is converted to digital electric signal with light signal by electrooptical device, for the usefulness of relay protection and electric energy metrical.Needing the occasion of analog quantity, available digital-to-analog conversion (D/A) circuit is converted to analog quantity with digital quantity.This photo-electric current transformer adopts LASER Light Source that luminous energy is delivered to hot side from low potential side by optical fiber, by electrooptical device transform light energy is become electric energy again, behind the power supply stabilizing circuit, gives each power electronics.The advantage of this mode is that out-put supply is more stable, nor is vulnerable to the influence of extraneous source of stray light, is a kind of high-tech technology.Electronics, optical communication, laser and computer technology that this photo-electric current transformer has adopted developed recently to get up have stronger vitality and higher technology content.
Compare with traditional electrical magnetic inductive current transformer, the photo-electric current transformer has following series of advantages:
1, photoelectric current inductor (OCT) material therefor is that insulating material such as glass, optical fiber come transmission information, so insulation system is simple, its cost generally raises with electric pressure and is linear increase;
2, photoelectric current inductor does not contain iron core, has eliminated problems such as magnetic saturation and ferroresonance;
3, induction secondary loop of mutual inductor can not be opened a way, and step-down side exists open circuit dangerous.Owing to only exist optical fiber to get in touch between the hot side of photoelectric current inductor and the step-down side, and optical fiber has the good insulation performance performance, can guarantee that high tension loop and secondary circuit isolate fully on electric, step-down side does not have opens a way that Keep Clear-High Voltage, can exempt electromagnetic interference (EMI);
4, dynamic range is big, the measuring accuracy height; When electrical network normally moved, the electric current that current transformer flows through was also little, but short-circuit current is generally very big, and along with the increase of net capacity, short-circuit current is increasing.Induction current transformer is difficult to realize large-range measuring because of there being the magnetic saturation problem, satisfies the needs of high-precision measuring and relay protection simultaneously.OCT has very wide dynamic range, and rated current can measure tens amperes of several kiloamperes, and the excess current scope can reach the training of several Wan An; An OCT can satisfy the needs of metering and relay protection, the redundant demand that can exempt a plurality of CT simultaneously;
5, frequency response range is wide, and the transit time of optical fiber on sensing head depended in the frequency response of sensing head part, and the frequency range of actual energy measurement depends mainly on the electronic circuit part.The photo-electric current transformer has been proved to be the harmonic wave that can measure on the high-voltage power line, also can carry out the measurement of power network current transient state, the big electric current of high frequency and direct current.And induction current transformer is the work that is difficult to carry out this respect;
6, danger such as inflammable, the explosive that does not produce because of trapped fuel; Induction current transformer generally adopts the way of trapped fuel to solve Insulation Problems, has danger such as inflammable, explosive so inevitably; And photo-electric current transformer insulation system is simple, can not adopt oil-insulation, structurally can avoid the danger of this respect.
7, little, in light weight, the conserve space of volume; The weight of photo-electric current transformer sensing head itself is generally less than 1 kilogram.The MOCT of the 345kV that announces according to US Westinghouse company, it highly is 2.7 meters, weight is 109 kilograms.And be 5.3m with the oil-immersed current transformer height of electric pressure, 2300 kilograms of weight, this gives transportation and installs and brought very big convenience.
8, the trend that has adapted to electric-power metering and protection digitizing, intellectuality and automation development; Along with the development of computing machine and digital technology, electric-power metering and relay protection realize robotization, intellectuality day by day.The 5A of induction current transformer or 1A output standard must adopt light switch technology ability and computer interface, and the photo-electric current transformer itself is exactly the digitizer that utilizes photoelectric technology, can directly export to computing machine, has avoided intermediate link.
In sum, though the photo-electric current transformer also exists processing request height, the bad solution of power issue at present, sensing head is to temperature and vibrate relatively problem such as sensitivity and need overcome, but the photo-electric current transformer has the incomparable advantage of traditional electromagnetic current transducer, it is simple in structure, highly sensitive, be a kind of desirable substitute products of traditional electromagnetic current transducer, will in the power industry in future, be widely used.Therefore, main developed country competitively invests development, and photoelectric current inductor has become the research focus of current transformer.
The signal of photo-electricity mutual-inductor and transmission form can adopt optical cable (optical fiber) to realize, and the extensive employing of the outstanding advantage of light signal and Fibre Optical Communication Technology make transformer station inner and and the higher level station between data transmission reliable more and rapidly.Photo-electricity mutual-inductor combines with optical fiber communication technology and microcomputer and forms fiber optic local area network and be applied to the important developing direction that electric system is the automation of transformation substations.Started the rosy prospect of following fiberize transformer station.
Worldwide to the applied research of photo-electric current transformer, rise from the sixties, form climax the seventies, precision was low, temperature effect does not have the better stage of solution but still be at that time.Entered since the eighties, the rise of photoelectron technology, PC microcomputer, single-chip microcomputer and digital processing unit technology is laid a good foundation for developing high performance photo-electric current transformer with ripe.
Till 2000, ABB AB has developed and can be used for the photoelectric current inductor of 69kV to the 765kV electric pressure, and measuring range of current is 5～2000A, and accuracy reaches ± and 0.2%.Simultaneously, they have developed composite electron formula voltage, the current transformer that is used for GIS, and current measuring range is 5A～2000A, the voltage measurement scope is 69～500kV, accuracy all reaches ± and 0.2%, voltage measurement is directly to use the electric capacity ring to measure, without voltage divider.
France Alstom company utilize the Faraday effect developed one the cover electronic current mutual inductor, in-30～50 ℃ scope accuracy reach ± 0.2%.2000, they began to supply to u s companys such as LCRA and CINERGY by the 362kV electronic current mutual inductor of development.
The researchist of domestic and international many scientific research institutions and universities and colleges just is being devoted to the research of new transformers such as photo-electricity mutual-inductor at present.There are Tsing-Hua University, the Central China University of Science and Technology, Shanghai University, Xi'an in the main research unit that is engaged in this respect with dimension company etc.Wherein, the Rogowski air core coil as power current transformer, with its outstanding advantage, has obtained numerous researchists' favor in conjunction with modern integrated electronic technology.The Central China University of Science and Technology that cooperates with the big treasure in Guangzhou Electro-optical Technology, INC. (US) 62 Martin Road, Concord, Massachusetts 017 just took up in the research work aspect the air core coil mutual inductor as far back as the seventies, by to its aspects such as high-voltage great-current, pulse high current, welding current should be used as the macromethod test, accumulated rich experience.
Recent international electrician association is the standard of distributing electronic formula voltage transformer (VT), and the standard of electronic current mutual inductor (sensor).The implication of electronic mutual inductor mainly comprises the photo-electric mutual inductor, also comprises other various voltage, current transformers that utilize the Electronic Testing principle.This proves absolutely, uses arrive the opportunity of photo-electric mutual inductor in electric system.
But no matter existing photo-electricity mutual-inductor is that active type or passive all exist obvious deficiency.This mutual inductor is by air core coil (Rogowski coil) induction current, with photoelectron technology and optical fiber technology electric current is transferred to terminal device from the higher-pressure region again.Since this coil-induced to electric current be output as voltage, so to need integrating circuit be electric current with voltage transitions in the rear end.As the optimal form of this mutual inductor should be passive, can reduce greatly like this higher-pressure region to the insulation requirement, mutual inductor will have lot of advantages, as volume is little, in light weight, reliability is high, safe, or the like.But the output voltage of Rogowski coil is very low, usually several millivolts between the hundreds of millivolt, can't directly drive existing photoelectric device, can't realize actually directly the output of coil being connected to terminal device by photoelectric technology.And the active type photo-electricity mutual-inductor is introduced power supply and ground in the higher-pressure region, is treatment circuit (comprising electronic circuit, photoelectric circuit etc.) power supply, and purpose is that the output voltage with coil is amplified to the amplitude that can carry out the electric light conversion.Owing to introduced power supply and ground in the higher-pressure region, just make whole device very complicated, the cost that cost a lot of money is carried out High-Voltage Insulation, this will influence photo-electricity mutual-inductor should have volume, weight, safety, reliably, the advantage of aspect such as electromagnetic compatibility.
Summary of the invention
Fundamental purpose of the present invention is to provide a kind of reflective sagnek interferometer all-fiber current transformator, adopt reflective Sagnac interference treatment technology, overcome the interference of various environmental factors such as temperature, vibration, electromagnetic interference (EMI), need not introduce power supply in the higher-pressure region; Induction optical fiber dynamic range is big, the linearity good, self have insulation characterisitic, and can improve measuring accuracy, reduces the volume and weight of mutual inductor.
Another object of the present invention is to provide a kind of reflective sagnek interferometer all-fiber current transformator, its reflectance coating, sensor fibre and quarter wave plate all can keep the advantage of easy realization on good anti-such environmental effects, the structure.
The object of the present invention is achieved like this:
A kind of reflective sagnek interferometer all-fiber current transformator is connected and composed by photovoltaic element and fibre-optic current sensing unit; Wherein, photovoltaic element is used to produce the light signal that is used to detect, and the fibre-optic current sensing unit utilizes this optical signal detecting to flow through electric current in the bus that its optical fiber winding twines, and returns this photovoltaic element sensed light signal is exported.
Above-mentioned photovoltaic element is connected and composed by light source, single-mode optical-fibre coupler, polarization maintaining optical fibre depolarizer, fibre optic polarizer, optical phase modulator, oscillation source, polarization maintaining optical fibre lag line and photoelectric detector at least; The light signal of light source output is given the polarization maintaining optical fibre depolarizer through the single-mode optical-fibre coupler forward transmitted; The light signal that leaves the polarization maintaining optical fibre depolarizer enters fibre optic polarizer; Fibre optic polarizer is given optical phase modulator respectively with the linearly polarized light that this light signal is divided into two quadratures; This optical phase modulator is exported to the fibre-optic current sensing unit through the polarization maintaining optical fibre lag line then according to from the modulation signal of oscillation source the linearly polarized light of two quadratures being carried out synchronous modulation; The light signal that returns from the fibre-optic current sensing unit arrives the interference of fibre optic polarizer generation Sagnac, and this interference light is given photoelectric detector through single-mode optical-fibre coupler reverse transfer; Photoelectric detector is exported detection signal.
Above-mentioned photovoltaic element also further is provided with the closed loop light phase modulation circuit of being made up of digital demodulator, feedback control circuit and optical phase modulator, is used to improve current transformer signal to noise ratio (S/N ratio) and stability; Wherein, photoelectric detector connects digital demodulator, is used for sending feedback control signal to optical phase modulator by feedback control circuit simultaneously through this digital demodulator output testing result.
When being AC signal, digital demodulator connects the wave filter that is used to exchange filtering high frequency interference when detecting, and this wave filter is that passband is the bandpass filter of 1Hz-10kHz when measured; And when measured when being direct current signal, described digital demodulator connects and is used for the wave filter that direct current detects, and this wave filter is that passband is the low-pass filter of 0-10kHz.
The fibre-optic current sensing unit is located at the higher-pressure region of current transformer, is made up of broadband optical-fibre wave plate, induction fiber optic coils and induction optical fiber coil-end face plating reflectance coating; Wherein, the linearly polarized light that broadband optical-fibre wave plate is used for the fine lag line of the polarisation of self-insurance in the future is converted to two circularly polarized lights, these two circularly polarized lights arrive the reflectance coating of end face through the induction fiber optic coils, this reflectance coating is this two circularly polarized light signals total reflection, and along the backpropagation of induction fiber optic coils.
The present invention adopts reflective Sagnac interference treatment technology, has overcome the interference of various environmental factors such as temperature, vibration, electromagnetic interference (EMI), need not introduce power supply in the higher-pressure region; The induction optical fiber dynamic range that the present invention adopts is big, the linearity good, self have insulation characterisitic, and can improve measuring accuracy, reduces the volume and weight of mutual inductor.The present invention adopts the fiber end face reflectance coating as reflecting surface, this reflectance coating plates reflectance coating again by after fiber end face is ground, grind back and the bonding reflecting body that constitutes of catoptron than traditional fiber end face, characteristics and its structure that reflectance coating of the present invention has bloated shrinkage of heat resistanceheat resistant and vibrations are easy to install, and can reduce manufacturing cost.Induction fiber optic coils of the present invention can adopt ultra-low birefringence fiber or common low-birefringence single-mode fiber, especially can adopt circular polarization to keep optical fiber, this circular polarization maintenance optical fiber can change traditional fiber and be subjected to defectives such as such environmental effects is big, the linear birefrigence fluctuating is big, and performance is improved.
Description of drawings
Fig. 1 is the principle of compositionality synoptic diagram of a specific embodiment of the present invention.
Embodiment
The present invention is described in further detail below in conjunction with accompanying drawing and specific embodiment:
Referring to Fig. 1, reflective sagnek interferometer all-fiber current transformator of the present invention comprises photoelectricity part and high pressure transducing part, and wherein, photoelectricity partly is technological core of the present invention.Light source 1 (can adopt the SLD[super-radiance light emitting diode], be characterized in that noise is little, light intensity is high, temperature stability is good) the output light signal give polarization maintaining optical fibre depolarizer 3 through 50: 50 single-mode optical-fibre coupler 2 forward transmitted, the effect of polarization maintaining optical fibre depolarizer 3 is intrinsic polarizabilities of eliminating from the light signal of light source 1, makes that light signal all presents in all polarization directions evenly, the character of constant amplitude; Then, light signal enters fibre optic polarizer 4, and fibre optic polarizer 4 is divided into the linearly polarized light signal of two quadratures with light signal, and gives optical phase modulator 7 along the x axle and the y axle of optical fiber respectively; Above-mentioned polarization maintaining optical fibre depolarizer 3 can integratedly be arranged among the fibre optic polarizer 4.The birefringent characteristic that optical phase modulator 7 utilizes optical fiber carries out synchronous modulation to the linearly polarized light of two quadratures, and modulation signal is from oscillation source 6, and the oscillation frequency of this oscillation source 6 is: f=1/4 τ, τ wherein are the time delay of polarization maintaining optical fibre lag line 8.Optical phase modulator 7 of the present invention adopts integrated optical modulator.Owing to there is parasitic cross polarization coupling in the described optical phase modulator 7, therefore one section polarization maintaining optical fibre can be set between fibre optic polarizer 4 and optical phase modulator 7 as depolarized 5, be used to suppress the cross polarization coupling.Can process the tail optical fiber of drawing for depolarized 5 in the conduct of the inside of optical phase modulator 7.Light signal after the modulation is given the fibre-optic current sensing part through polarization maintaining optical fibre lag line 8.
The fibre-optic current sensing part is positioned at the higher-pressure region of current transformer, is made up of quarter wave plate 9, induction fiber optic coils 10, induction optical fiber coil-end face plating reflectance coating 11.Quarter wave plate 9 wherein adopts optical-fibre wave plate to make, be characterized in: optical-fibre wave plate is wideer than the wave plate bandwidth of other kinds, the quality height of polarization converted, can better suppress to be converted to the ovality that causes in the circular polarization process by linear polarization, make light signal after the conversion near desirable circular polarization, and then reduce the current transformer measuring error; Owing to adopted optical fiber turn-knob technology, this optical-fibre wave plate has more the performance of resisting temperature, vibration effect than other wave plate, can improve the stability of current transformer.And wave plate is optical fibre device, and is easier with being connected of front and back optical fiber, is fit to industrialization.
Induction fiber optic coils 10 is ultra-low birefringence fiber or common low-birefringence single-mode fiber, twines some circles around high-tension current bus 12.The linearly polarized light of the fine lag lines 8 of quarter wave plate 9 self-insurance in the future polarisations is converted to circularly polarized light, and promptly the linearly polarized light of the x axle linearly polarized light that is converted to right-circularly polarized light, y axle is converted to left circularly polarized light.Two circularly polarized lights are through responding to the reflectance coating 11 that fiber optic coils 10 arrives end faces, and signal is by total reflection, and along 10 backpropagations of induction fiber optic coils, left circularly polarized light becomes right-circularly polarized light, right-circularly polarized light becomes left circularly polarized light.Quarter wave plate 9 is converted to linearly polarized light with the circularly polarized light of backpropagation, and promptly right-circularly polarized light is converted to x axis polarized light, left circularly polarized light is converted to y axis polarized light.During this period, the electric current in the high-tension current bus 12 makes phase differential of light signal generating of two polarization states by Faraday effect, and this phase differential satisfies following formula:
Δ φ=4VNI wherein,
V is the Verdet constant of optical fiber, and N is the number of turn of induction fiber optic coils 10, and I is the electric current in the high-tension current bus 12.
When the light signal of reverse transfer arrives fibre optic polarizer 4, producing Sagnac at these fibre optic polarizer 4 inner 45 ° of biasing interfaces that are provided with interferes, interference light is given photoelectric detector 13 through 50: 50 single-mode optical-fibre coupler 2 reverse transfer, and photoelectric detector 13 is converted to electric signal with the light intensity that detects and is:
Wherein,
I
dFor detecting light intensity, I
sBe the light intensity that light source provides, k is the loss of whole optical path, (t)=
mCos (ω
mT) be the modulation signal of optical phase modulator, V is the Verdet constant of optical fiber, and N is the number of turn of induction fiber optic coils.
The present invention both can be applicable to alternating current and had detected, and also can be applicable to direct current detection.When being used for exchange detecting, wave filter 16 adopts bandpass filter, passband from 1Hz to 10kHz, effectively filtering the temperature low-frequency disturbance and the extraneous high frequency interference of introducing that cause; When being used for the direct current detection, wave filter 16 is a low-pass filter, and passband is from the direct current to 10kHz.17 pairs of detected electric currents of processor amplify, proofread and correct, output exact current measured value.The present invention can provide analog-and digital-two kinds of output forms simultaneously according to the needs of metering of electric system terminal and protection equipment.
It should be noted that at last: above embodiment only in order to the explanation the present invention and and unrestricted technical scheme described in the invention; Therefore, although this instructions has been described in detail the present invention with reference to each above-mentioned embodiment,, those of ordinary skill in the art should be appreciated that still and can make amendment or be equal to replacement the present invention; And all do not break away from the technical scheme and the improvement thereof of the spirit and scope of the present invention, and it all should be encompassed in the middle of the claim scope of the present invention.
Claims (13)
1, a kind of reflective sagnek interferometer all-fiber current transformator, it is characterized in that: it is connected and composed by photovoltaic element and fibre-optic current sensing unit at least; Wherein, photovoltaic element is used to produce the light signal that is used to detect, and the fibre-optic current sensing unit utilizes this optical signal detecting to flow through electric current in the bus that its optical fiber winding twines, and returns this photovoltaic element sensed light signal is exported.
2, reflective sagnek interferometer all-fiber current transformator according to claim 1, it is characterized in that: described photovoltaic element is connected and composed by light source, single-mode optical-fibre coupler, polarization maintaining optical fibre depolarizer, fibre optic polarizer, optical phase modulator, oscillation source, polarization maintaining optical fibre lag line and photoelectric detector at least; The light signal of light source output is given the polarization maintaining optical fibre depolarizer through the single-mode optical-fibre coupler forward transmitted; The light signal that leaves the polarization maintaining optical fibre depolarizer enters fibre optic polarizer; Fibre optic polarizer is given optical phase modulator respectively with the linearly polarized light that this light signal is divided into two quadratures; This optical phase modulator is exported to the fibre-optic current sensing unit through the polarization maintaining optical fibre lag line then according to from the modulation signal of oscillation source the linearly polarized light of two quadratures being carried out synchronous modulation; The light signal that returns from the fibre-optic current sensing unit arrives the interference of fibre optic polarizer generation Sagnac, and this interference light is given photoelectric detector through single-mode optical-fibre coupler reverse transfer; Photoelectric detector is exported detection signal.
3, reflective sagnek interferometer all-fiber current transformator according to claim 2 is characterized in that: the oscillation frequency of the modulation signal that described oscillation source produces is observed following computing formula:
f＝1/4τ
Wherein, τ is the time delay of polarization maintaining optical fibre lag line.
4, reflective sagnek interferometer all-fiber current transformator according to claim 2, it is characterized in that: be provided with depolarized head between described fibre optic polarizer and the optical phase modulator, this depolarized head is made of polarization maintaining optical fibre, is used to suppress the cross polarization coupling.
5, arbitrary reflective sagnek interferometer all-fiber current transformator according to claim 2, it is characterized in that: described photovoltaic element also further is provided with the closed loop light phase modulation circuit of being made up of digital demodulator, feedback control circuit and optical phase modulator, is used to improve current transformer signal to noise ratio (S/N ratio) and stability; Wherein, photoelectric detector connects digital demodulator, is used for sending feedback control signal to optical phase modulator by feedback control circuit simultaneously through this digital demodulator output testing result.
6, according to claim 2 or 5 described reflective sagnek interferometer all-fiber current transformators, it is characterized in that: photoelectric detector is converted to electric signal according to following formula with the light intensity that detects:
Wherein,
I
dFor detecting light intensity, I
sBe the light intensity that light source provides, k is the loss of whole optical path, (t)=
mCos (ω
mT) be the modulation signal of optical phase modulator, V is the Verdet constant of optical fiber, and N is the number of turn of induction fiber optic coils.
7, according to claim 2 or 5 described reflective sagnek interferometer all-fiber current transformators, it is characterized in that: the signal voltage that described digital demodulator obtains after with the photoelectric detecting signal demodulation satisfies following formula:
V
Dm≈ J
1(
m) (4VNI) wherein,
V
DmBe signal voltage, J
1Be first-order bessel function, V is the Verdet constant of optical fiber, and N is the number of turn of induction fiber optic coils, and I is the electric current in the high-tension current bus.
8, reflective sagnek interferometer all-fiber current transformator according to claim 5, it is characterized in that: described digital demodulator further is connected with the wave filter that is used to exchange filtering high frequency interference when detecting, and this wave filter is that passband is the bandpass filter of 1Hz-10kHz.
9, reflective sagnek interferometer all-fiber current transformator according to claim 5, it is characterized in that: described digital demodulator further is connected with and is used for the wave filter that direct current detects, and this wave filter is that passband is the low-pass filter of 0-10kHz.
10, according to Claim 8 or 9 described reflective sagnek interferometer all-fiber current transformators, it is characterized in that: described wave filter also further is connected with detected electric current is amplified, proofreaies and correct, and the processor of output exact current measured value.
11, reflective sagnek interferometer all-fiber current transformator according to claim 1, it is characterized in that: described fibre-optic current sensing unit is located at the higher-pressure region of current transformer, at least form by λ/4 wave plates (wherein, λ is the wavelength of the light signal that transmits in the optical fiber), induction fiber optic coils and induction optical fiber coil-end face plating reflectance coating; Wherein, the linearly polarized light that λ/4 wave plates are used for the fine lag line of the polarisation of self-insurance in the future is converted to two circularly polarized lights, these two circularly polarized lights arrive the reflectance coating of end faces through the induction fiber optic coils, and this reflectance coating is this two circularly polarized light signals total reflection, and along the backpropagation of induction fiber optic coils.
12, reflective sagnek interferometer all-fiber current transformator according to claim 11, it is characterized in that: described λ/4 wave plates are broadband optical-fibre wave plate.
13, reflective sagnek interferometer all-fiber current transformator according to claim 11, it is characterized in that: described induction fiber optic coils is ultra-low birefringence fiber or common low-birefringence single-mode fiber or circular polarization maintenance optical fiber, and this optical fiber twines a circle at least around the high-tension current bus.
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Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100338449C (en) * | 2005-06-08 | 2007-09-19 | 北京航空航天大学 | Temperature sensor of polarization-preserving fiber in reflection type |
| CN102680763A (en) * | 2011-03-10 | 2012-09-19 | 株式会社东芝 | Photovoltage measuring device |
| CN102929323A (en) * | 2012-10-31 | 2013-02-13 | 上海康阔光通信技术有限公司 | Full fiber optic current sensor and current closed loop feedback correction method |
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