CN102539883A - Solenoid nesting type all-fiber current sensor - Google Patents
Solenoid nesting type all-fiber current sensor Download PDFInfo
- Publication number
- CN102539883A CN102539883A CN2011104327150A CN201110432715A CN102539883A CN 102539883 A CN102539883 A CN 102539883A CN 2011104327150 A CN2011104327150 A CN 2011104327150A CN 201110432715 A CN201110432715 A CN 201110432715A CN 102539883 A CN102539883 A CN 102539883A
- Authority
- CN
- China
- Prior art keywords
- solenoid
- solenoids
- sensing head
- fiber
- grin lens
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Abstract
The invention discloses a solenoid nesting type all-fiber current sensor, which comprises a light source, a polarizer, an optical fiber coupler, a sensing head, three self condenser lenses, a polarization analyzer and two optical detectors. The sensing head comprises two solenoids and sensing optical fibers located on the axes of the solenoids, the sensing optical fibers penetrate through the axes of the two solenoids so as to connect the two solenoids together, and the field directions in the solenoids along the optical wave transmission direction are identical. Each solenoid is 2000 turns, and galvanization is 1A. The two solenoids are connected together in parallel, and a distance between the two solenoids is 12cm. The core of the solenoid nesting type all-fiber current sensor is the two parallel-connected solenoids, and a coil winding mode is flexible. Therefore, compared with a fiber current sensor with a traditional optically-wound structure, the sensitivity is improved, the size of the sensing head is decreased, and due to the fact that bending radius of the optical fibers is increased, caused bending loss and bi-refraction effect are decreased.
Description
Technical field:
The invention belongs to power domain, relate to a kind of fibre-optic current (small-signal) sensing device, especially a kind of solenoid nested all-fiber current sensor.
Background technology:
At present; Widely used current transformer is an electromagnetic current transducer in electric system; Its sensor adopts electromagnetic induction principle; Under the different voltages with different grade,, supply metering, control and supervisory instrument use several amperes of primary sides several Ampere currents to the current transformation of several kiloamperes to zero potential state secondary side down.Electromagnetic current transducer simple in structure, so reliability is high, not fragile, this is its major advantage, also is its main cause that is able to generally use.But since the singularity of structure and service condition it also have following outstanding shortcoming:
A., the danger of generation systems inefficacy and catastrophic failure is arranged.Oil-filled electromagnetic current transducer ultra-high voltage environment have broken down cause shorted to earth or blast suddenly maybe, and if the mutual inductor secondary side open a way accidentally, will produce high pressure, controller switching equipment is worked the mischief even jeopardizes personal safety.
B. the magnetic saturation phenomenon possibly take place.When tested current anomaly increases, magnetic saturation will appear in transformer iron core, and accuracy of measurement is seriously descended.Under failure conditions such as short circuit, measurement data maybe complete failure especially.
C. frequency response is poor, can not correct response to the transient state process on the high-tension line.This is owing to induction current transformer is to process with iron core, and is relatively poor to the response characteristic of high-frequency signal.
D. electromagnetic interference (EMI) is serious.Because be in hyperbaric environment during electromagnetic current transducer work; For high pressure and extra-high voltage power station, floor area is all bigger, thereby transmission secondary side electric signal distance is also far away; Current signal will receive serious electromagnetic interference (EMI) when transmitting through lead, and accuracy of measurement is descended.
E. equipment is heavy, transportation and difficult installation.Electromagnetic current transducer mainly is made up of iron core, transformer oil, copper conductor and insulating medium; The volume and weight of these materials is all bigger, and equipment work requires between the high and low pressure end, to provide the electric insulation of complex and expensive in hyperbaric environment; Along with transmission and distribution network develops towards high voltage, high capacity direction; Not only make the electromagnetic current transducer of voltage levels become more and more heavier, price is more and more expensive, and brings difficulty for transportation and installation.
To these problems, fibre optic current sensor almost can overcome all shortcomings of traditional electromagnetic current transducer in theory, and its advantage is mainly reflected in following aspect:
A. good insulation preformance, cost is low.Close through the iron core lotus root between the high voltage bus of electromagnetic transformer and the secondary coil, complex structure involves great expense, and its price is the index rising with the growth of transmission voltage.The Fibre Optical Sensor material therefor mainly is a silica fibre, self is exactly insulator, and is simple in structure, and cost slightly increases with the increase of electric pressure.
B. do not contain iron core, do not have problems such as magnetic saturation, ferroresonance, thereby measurement range is big, the linearity is good, and frequency response range is wide, and accuracy of measurement is high.
C. with the light wave transmissions signal, anti-electromagnetic interference capability is strong, and low-pressure side do not exist that Keep Clear-High Voltage because of open circuit produces, and has also eliminated conventional electromagnetic transformer because of problem such as oil-filled generation is inflammable and explosive.
D. volume is little, and is in light weight.
E. the trend that adapts to digital, microcomputerization, robotization and the optical communication etc. of electric-power metering, protection.
F. range of dynamic measurement is big.Under the normal condition, the rated current of operation of power networks is also little, but short-circuit current is very big, and along with the increase of capacity, the failed shorted electric current is increasing.The current measuring range of electromagnetic current transducer is limited, can influence its accuracy during simultaneously big electric current.The fibre optic current sensor rated current can measure several kiloamperes, and momentary excess current can measure the hundreds of thousands ampere.
The device that optical current mutual inductor makes an experiment the earliest appears at U.S. sixties, is installed on the 230KV electrical network, and it has realized the signal transmission through glass waveguide.Contemporaneity, Japan utilizes the magneto-optic effect principle to carry out ultrahigh voltage power line current measurement Research.The research in this period is that preliminary theory and technology basis has been laid in the development of fibre optic current sensor.
The seventies in 20th century, the full fiber type current sensor has appearred in progressively perfect along with optic fibre manufacturing technology.Britain analyzes principle of full optical fiber current sensor in the electric power research centre the earliest, in the laboratory examination success.From the nineties,, make polarization metering type and phase modulation-type all obtain significant progress because the accuracy of measurement of temperature and vibration improves greatly.Wherein, Canadian NxtPhase company succeeds in developing the full fiber type current sensor, and class of accuracy reaches 0.2 grade, through various type approval tests, gets into the commodity production stage at present.Siemens is also at the similar all-fiber current transformator of research.The full fiber type current sensor of discovering afterwards causes birefringence easily, and wherein a part of scheme can not solve, and a part is brought new problem again.
The groundwork principle of fibre optic current sensor is to utilize the Faraday effect of fiber optic materials; Promptly be in the rotation that optical fiber in the magnetic field can make the polarized light generation plane of polarization that in optical fiber, transmits, length of fiber L is directly proportional in its anglec of rotation θ and magnetic field intensity H, the magnetic field:
θ＝VHL (1)
In the formula, V is a Verdet constant.Because the current carrying conductor magnetic field of space generation around satisfies Ampere circuit law, so have for long straight conductor:
In the formula, R representes the field circuit radius that electric current produces.Therefore, only measure θ, L, R just can by:
Obtain the electric current I in the long straight conductor.
As shown in Figure 1, the laser beam of sending from laser instrument becomes linearly polarized light through the polarizer, is coupled in the polymer optical fiber through fiber coupler and goes.Electric current through wherein in the current carrying conductor is I, produces Faraday magnetooptical effect in the optical fiber on the lead, makes the polarized light through optical fiber produce the rotation that an angle is the plane of polarization of θ.Emergent light is coupled to the coat Lars by fiber coupler and pauses in the prism.Be divided into the orthogonal two bundle polarized lights of direction of vibration to light beam through Wollaston prism, detector I at last makes a gift to someone respectively
1And I
2, and put calculating in order by data acquisition module.The function of output does
In the formula, I
1, I
2Be respectively two polarization light intensities.
Calculating shows, P and θ
fRelation be:
P＝2sinθ (5)
Because the angle θ of plane of polarization rotation in the general electric system
fAll very little, therefore have:
P≈2θ (6)
The advantage of this measurement current system is, measurement range is big, and is highly sensitive, contactless with high pressure, and electrical insulating property is good, is specially adapted to the measurement of high-voltage great-current, and measurement range is 0～1000A.Shortcoming is, the conductor surrounding magnetic field is less when measuring small-signal, and faraday's rotation angle is very little; The bending loss of optical fiber and bend birefringence effect are bigger.
Summary of the invention:
The objective of the invention is to overcome the shortcoming of above-mentioned prior art, a kind of solenoid nested all-fiber current sensor is provided, this all-fiber current sensor can be measured the Weak current signal, remedies the deficiency of this area research both at home and abroad.
Comprise light source, the polarizer, fiber coupler, Transmission Fibers, sensing head, first GRIN Lens, second GRIN Lens, the 3rd GRIN Lens, analyzer and photo-detector; Said light source is arranged on polarizer the place ahead, and fiber coupler is set behind the polarizer, and fiber coupler is connected with the input end of sensing head with first GRIN Lens through Transmission Fibers successively; The output terminal of said sensing head is connected with second GRIN Lens, Transmission Fibers and the 3rd GRIN Lens in turn; Be provided with analyzer in the 3rd GRIN Lens the place ahead, analyzer the place ahead is provided with two photo-detectors.
Said sensing head comprises two solenoids, be positioned at the solenoid axis uploads the sensitization fibre, and this sensor fibre passes the double solenoid axis and two solenoids are linked together, and the magnetic direction along the light wave transmissions direction in each solenoid is consistent; The sensing head sidewall is provided with reflectance coating.
Said light source is a semiconductor laser.The said polarizer is the Glan Taylor prism.Said analyzer is the logical prism in wet Lars.Said photo-detector is a PIN photodiode.
Said sensing head comprises two solenoids, be positioned at the solenoid axis uploads the sensitization fibre, and this sensor fibre passes the double solenoid axis and two solenoids are linked together, and the magnetic direction along the light wave transmissions direction in each solenoid is consistent.
Said solenoid is 2000 circles, galvanization 1A.Said two solenoids are connected in parallel, two solenoid spacing 12cm.Said two solenoids are cascaded, two solenoid spacing 12cm.Said solenoid is the copper cylinder of internal diameter 6cm, external diameter 8cm, long 10cm.
Apparatus of the present invention core is the double solenoid parallel connection; The coil canoe is flexible; So reduce with fibre optic current sensor specific sensitivity increase mutually, the sensing head size of traditional light, and because fiber bending radius increases, the bending loss and the birefringence effect that are caused reduce around electric structure.
Description of drawings:
Fig. 1 is a linear pattern all-fiber current sensor device synoptic diagram;
Fig. 2 is solenoid nested sensor construction figure;
Fig. 3 is the sensing head structural drawing
Fig. 4 is linear pattern current sensing head magnetic field mould result of calculation figure;
Fig. 5 is solenoid nested sensing head magnetic field calculation figure as a result;
Fig. 6 is the faraday rotation angle theoretical value and the tested current relationship figure of two kinds of sensing arrangements;
Wherein: 1 is light source; 2 is the polarizer; 3 is fiber coupler; 4 is Transmission Fibers; 5 is reflectance coating; 6 is sensing head; 7 is first GRIN Lens; 8 is second GRIN Lens; 9 is the 3rd GRIN Lens; 10 is analyzer; 11 is photo-detector; 12 is quartz glass.
Embodiment:
Below in conjunction with accompanying drawing the present invention is done and to describe in further detail:
Referring to Fig. 4; Tradition light around electric type current sensor during in measured current cable surrounding magnetic field intensity very little; In order to increase the magnetic field that tested electric current produces; Can the lead through tested electric current be turned to the solenoid form, the inner magnetic field of way solenoid can increase a lot of doubly (relevant with the lead number of turn of unit length).Sensor fibre is positioned on the solenoid axis, lets sensor fibre repeatedly pass coil, also encompasses solenoid structure, and faraday rotation angle will increase exponentially like this.Can also several solenoids be together in series, optical fiber passes successively, and symmetry is compact more to make structure, but should notice that the magnetic direction along the light wave transmissions direction should be consistent in each solenoid, otherwise faraday rotation angle can be cancelled out each other.Its synoptic diagram is as shown in Figure 3, temporarily this structure is called the solenoid nested structure.
This structure has improved the utilization factor in magnetic field greatly, and faraday rotation angle is greatly increased, and optical fiber formation closed circuit, and faraday rotation angle 0 does not receive the magnetic interference that foreign current produces in theory, and irrelevant with the particular location of optical fiber, according to Amp
θ＝V∫Hdl＝Vn
1n
2I (7)
In the formula:
n
1---the optical fiber number of turn
n
2---the telefault total number of turns that optical fiber surrounds
I---tested size of current
Can find out that by formula (7) compare with the linear pattern current sensor, the sensitivity of solenoid nested sensor has improved n
2Doubly, because the bending radius of optical fiber has increased a lot, bending loss causes birefringence and greatly reduces with bending simultaneously.
6, beneficial effect
Solenoid nested structure of the present invention has increased the sensitivity of fibre optic current sensor to a great extent, can well verify at experiment simulation.The faraday rotation angle theoretical value of two kinds of sensor constructions and the relation of tested electric current as shown in Figure 6; The remolding sensitivity tradition light of solenoid nested sensor is around high nearly thousand times of electric type (linear pattern) sensor in as can be seen from the figure testing; The adjustment solenoid is twined the number of turn and solenoid connected mode can the flexible transducer sensitivity, can obtain higher sensitivity
With COMSOL Multiphisics multiple physical field coupling Simulation software institute's traditional electrical has been carried out simulation calculation around light type and the electromagnetic field of solenoid nested sensor construction when measuring DC current, the parameter of each structure is all set with reference to the experiment actual conditions.Utilize formula θ=V ∫ Hdl the vector integration to be carried out in magnetic field then, calculated the ideal value of faraday rotation angle in each sensing arrangement along fiber path.
(1) linear pattern current sensor
It is the copper coin cylinder that cable is set, its diameter 1cm, long 1m, galvanization 1A; Be made as air in the right cylinder scope of radius 0.2m, high 1.4m on every side, outermost layer is made as the PML infinite element.The simulation calculation result in magnetic field is as shown in Figure 4, and the depth of color is represented the size of magnetic field mould among the figure.
If fiber path is a helix, its radius of spin is 1cm, and pitch is 4mm, totally 250 circles.The magnetic field simulation result is derived, and calculating magnetic field along light path the vector integration, the result is 251.6283A, is approximately equal to calculated value 250A.Suppose that used sensor fibre is a silica fibre, its Verdet constant is 4.68 * 10
-6Rad/A (wavelength is 633nm), then faraday rotation angle θ=V ∫ Hdl=4.68 * 10
-6* 251.6283=1.18 * 10
-3Rad.
(2) solenoid nested sensor
If two solenoid series connection, each solenoid 2000 circle, galvanization 1A.Because work as the solenoid number of turn more for a long time, grid dividing is crossed problems such as secret meeting causes that internal memory overflows, and therefore the solenoid structure equivalence is carried out emulation for cylinder.If solenoid is 2000 circles, galvanization 1A, with the copper cylinder of its equivalence for internal diameter 6cm, external diameter 8cm, long 10cm, two Cylindorical rod spacing 12cm are provided with current density, J=2 * 10 when setting up geometric model
6A/m
2, and the hoop of electric current is opposite in two cylinders, is set to air in the spheric region of radius 0.15m on every side.The simulation calculation result in magnetic field is as shown in Figure 5, and shade is represented the size of magnetic field mould value among Fig. 5 (a), and Fig. 5 (b) is the sectional view on yz plane, and shade is represented the z component (being the component of magnetic field along solenoid axis direction) in magnetic field.
Electromagnetic-field simulation result of calculation is derived; Along passing all approximately equals of two solenoidal closed circuit integral results arbitrarily; Integral result such as along the square path of the annular path of radius 7cm and length of side 12cm is respectively 4001.1A and 3999.3A, and 4000A is very approaching as a result with Theoretical Calculation.Getting the optical fiber number of turn is 50, adopts silica fibre as sensor fibre equally, and then faraday rotation angle is approximately θ=V ∫ Hdl=4.68 * 10
-6* 4000 * 50=0.936rad.
As shown in Figure 6, the relatively sensitivity of linear pattern current sensor and solenoid nested sensor, the latter is higher about 1000 times than the former.And solenoid nested sensor construction is simple, only needs the adjustment solenoid number of turn or SP solenoid number and structure to get final product the flexible system sensitivity.
The above only is preferred embodiment of the present invention, is not the present invention is done any pro forma restriction; Though the present invention discloses as above with preferred embodiment; Yet be not in order to limiting the present invention, anyly be familiar with the professional and technical personnel, in not breaking away from technical scheme scope of the present invention; When the method for above-mentioned announcement capable of using and technology contents are made a little change or be modified to the equivalent embodiment of equivalent variations; In every case be the content that does not break away from technical scheme of the present invention, to any simple modification, equivalent variations and modification that above embodiment did, still belong in the scope of technical scheme of the present invention according to technical spirit of the present invention.
Claims (5)
1. solenoid nested all-fiber current sensor is characterized in that:
Comprise light source, the polarizer, fiber coupler, Transmission Fibers, sensing head, first GRIN Lens, second GRIN Lens, the 3rd GRIN Lens, analyzer and photo-detector; Said light source is arranged on polarizer the place ahead, and fiber coupler is set behind the polarizer, and fiber coupler is connected with the input end of sensing head with first GRIN Lens through Transmission Fibers successively; The output terminal of said sensing head is connected with second GRIN Lens, Transmission Fibers and the 3rd GRIN Lens in turn; Be provided with analyzer in the 3rd GRIN Lens the place ahead, analyzer the place ahead is provided with two photo-detectors.
Said sensing head comprises two solenoids, be positioned at the solenoid axis uploads the sensitization fibre, and this sensor fibre passes the double solenoid axis and two solenoids are linked together, and the magnetic direction along the light wave transmissions direction in each solenoid is consistent; The sensing head sidewall is provided with reflectance coating.
2. solenoid nested full optical-fiber current sensing head according to claim 1, it is characterized in that: said solenoid is 2000 circles, galvanization 1A.
3. solenoid nested full optical-fiber current sensing head according to claim 1, it is characterized in that: said two solenoids are connected in parallel, two solenoid spacing 12cm.
4. solenoid nested full optical-fiber current sensing head according to claim 1, it is characterized in that: said two solenoids are cascaded, two solenoid spacing 12cm.
5. solenoid nested full optical-fiber current sensing head according to claim 1, it is characterized in that: said solenoid is the cylinder of internal diameter 6cm, external diameter 8cm, long 10cm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011104327150A CN102539883A (en) | 2011-12-16 | 2011-12-16 | Solenoid nesting type all-fiber current sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011104327150A CN102539883A (en) | 2011-12-16 | 2011-12-16 | Solenoid nesting type all-fiber current sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN102539883A true CN102539883A (en) | 2012-07-04 |
Family
ID=46347268
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011104327150A Pending CN102539883A (en) | 2011-12-16 | 2011-12-16 | Solenoid nesting type all-fiber current sensor |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN102539883A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111175557A (en) * | 2018-11-13 | 2020-05-19 | 北京自动化控制设备研究所 | High-precision optical fiber current transformer |
| CN112034229A (en) * | 2020-09-08 | 2020-12-04 | 东南大学 | All-fiber voltage transformer |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5434501A (en) * | 1994-04-29 | 1995-07-18 | The United States Of America As Represented By The Secretary Of The Navy | Polarization insensitive current and magnetic field optic sensor |
| WO2003042708A2 (en) * | 2003-02-14 | 2003-05-22 | Abb Research Ltd | Optic fiber current sensor, comprising several sensing heads |
| US20050156587A1 (en) * | 2004-01-16 | 2005-07-21 | Fieldmetrics Inc. | Current sensor |
| US20110060544A1 (en) * | 2009-09-04 | 2011-03-10 | Beijing Qi-Red Electric Power Technology Co., Ltd. | Optical fiber current transformer with optical fiber temperature acquisition and temperature compensation |
| EP2333498A1 (en) * | 2009-12-10 | 2011-06-15 | Kabushiki Kaisha Toshiba | Sagnac interferometer-type fiber-optic current sensor |
| WO2011080696A1 (en) * | 2009-12-29 | 2011-07-07 | Kuzin, Anton | Fiber optic current sensor |
-
2011
- 2011-12-16 CN CN2011104327150A patent/CN102539883A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5434501A (en) * | 1994-04-29 | 1995-07-18 | The United States Of America As Represented By The Secretary Of The Navy | Polarization insensitive current and magnetic field optic sensor |
| WO2003042708A2 (en) * | 2003-02-14 | 2003-05-22 | Abb Research Ltd | Optic fiber current sensor, comprising several sensing heads |
| US20050156587A1 (en) * | 2004-01-16 | 2005-07-21 | Fieldmetrics Inc. | Current sensor |
| US20110060544A1 (en) * | 2009-09-04 | 2011-03-10 | Beijing Qi-Red Electric Power Technology Co., Ltd. | Optical fiber current transformer with optical fiber temperature acquisition and temperature compensation |
| EP2333498A1 (en) * | 2009-12-10 | 2011-06-15 | Kabushiki Kaisha Toshiba | Sagnac interferometer-type fiber-optic current sensor |
| WO2011080696A1 (en) * | 2009-12-29 | 2011-07-07 | Kuzin, Anton | Fiber optic current sensor |
Non-Patent Citations (1)
| Title |
|---|
| 徐丽珊: "平面偏振光微小偏转角的精密测量", 《中国优秀硕士学位论文全文数据库 基础科学辑》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111175557A (en) * | 2018-11-13 | 2020-05-19 | 北京自动化控制设备研究所 | High-precision optical fiber current transformer |
| CN112034229A (en) * | 2020-09-08 | 2020-12-04 | 东南大学 | All-fiber voltage transformer |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Kuchanskyy et al. | Corona discharge power losses measurement systems in extra high voltage transmissions lines | |
| CN102565509B (en) | Multi-light-path reflecting optical fiber current sensor | |
| CN102967740B (en) | All-fiber current transformer and current measuring method | |
| CN103235167A (en) | Flexible optical current transformer | |
| CN106772133B (en) | Space magnetic field sensor based on micro-nano optical fiber and manufacturing method thereof | |
| CN114577245B (en) | Optical fiber sensing system capable of simultaneously measuring current and vibration | |
| CN211905488U (en) | Closed-loop demodulation all-fiber current transformer | |
| CN1252479C (en) | Reflection type 'Sage-qinke' interferometer type current transformer prepared from full optical fiber | |
| CN101620287A (en) | Method for manufacturing full-fiber quarter wave plate | |
| CN102539883A (en) | Solenoid nesting type all-fiber current sensor | |
| CN2638071Y (en) | Reflection type sagnek interferometer full optical fiber electric current mulual induction device | |
| Luo et al. | Broadband integrated optical waveguide current sensor based on a magneto-optical thin film | |
| CN202330519U (en) | Optical current mutual inductor for magneto-optic glass using interference close-loop detection | |
| CN203164257U (en) | Flexible optical current transformer | |
| Nedoma et al. | Measurement of electric current using optical fibers: A Review | |
| CN109342789A (en) | A kind of all-fiber current sensor and preparation method thereof | |
| CN102929323B (en) | Full fiber optic current sensor and current closed loop feedback correction method | |
| RU2720187C1 (en) | Ac and dc optical laboratory meter | |
| CN204964600U (en) | Fiber current sensor optical structure | |
| RU2663545C1 (en) | Optical measurement of variable and constant currents in high-voltage networks | |
| CN103472428A (en) | Method for testing accuracy of optical fiber current transformer | |
| CN102608380A (en) | Self-induced photoelectric mixed current transformer | |
| CN111562422A (en) | Passive electronic current transformer | |
| JP2001033490A (en) | Optical current transformer | |
| CN104237595A (en) | External current transformer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C12 | Rejection of a patent application after its publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20120704 |