WO2000040979A1 - Current measuring method and device - Google Patents
Current measuring method and device Download PDFInfo
- Publication number
- WO2000040979A1 WO2000040979A1 PCT/US1999/029779 US9929779W WO0040979A1 WO 2000040979 A1 WO2000040979 A1 WO 2000040979A1 US 9929779 W US9929779 W US 9929779W WO 0040979 A1 WO0040979 A1 WO 0040979A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- glass
- fluoride
- current
- composition
- glass fiber
- Prior art date
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C13/00—Fibre or filament compositions
- C03C13/04—Fibre optics, e.g. core and clad fibre compositions
- C03C13/041—Non-oxide glass compositions
- C03C13/042—Fluoride glass compositions
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/24—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices
- G01R15/245—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices using magneto-optical modulators, e.g. based on the Faraday or Cotton-Mouton effect
- G01R15/246—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices using magneto-optical modulators, e.g. based on the Faraday or Cotton-Mouton effect based on the Faraday, i.e. linear magneto-optic, effect
Definitions
- the invention relates broadly to measurement of large currents and production of devices for that purpose.
- Fiber optic, current sensors based on the Faraday effect, have a number of advantages for remotely measuring large electrical currents. These include wide dynamic range, fast response, immunity to electromagnetic interference, small size, and low cost. Consequently, a variety of fiber optic, current sensors have been investigated in recent years. Mainly, they have employed a single mode optical fiber (SMF) of clad silica. These sensors have not yet reached the stage of practical field use due to lack of accuracy and stability. This is mainly due to intrinsic and induced, linear birefringences that distort the Faraday rotation being measured. A particular problem arises from the inability of silica fibers to measure accurately large currents, such as surge or fault currents. Such currents are exceptionally large, as much as 180 kA under some circumstances. They generally occur due to some failure, such as a short circuit.
- SMF single mode optical fiber
- the Faraday effect is a phenomenon by which a linear, polarized light will rotate when propagating through a transparent material that is placed in a magnetic field in parallel to the magnetic field.
- H is the strength of the magnetic field (A/m)
- V is the Verdet constant of the material
- L is the path length over which the magnetic field acts (m).
- the magnetic field strength is measured in terms of Amperes (A) times turns (T) per unit length (AT/m) where m is meters). Since values are expressed in terms of one turn, this factor is usually implicit, rather than explicit. Hence, the strength is customarily given in amperes (A) or kiloamperes (kA) per unit path length in meters (m).
- Verdet constant is the angle of rotation divided by the magnetic field strength per unit length.
- the angle may be expressed in any of the customary units for angle measurement, but degrees are used here.
- Verdet constant values unless otherwise indicated, are given in terms of degrees divided by field strength expressed as (kA x T/m)m.
- I is the current
- U o is permittivity of free space
- a is the radial distance of the magnetic field from the conductor.
- the magnetic field is related to the magnetic induction by the simple relation:
- Birefringence arises primarily from stresses that result from bending, or otherwise distorting, a fiber in its disposition.
- the sources of linear birefringence in single mode fibers include residual stress from fabrication, bending, contact, and thermal stresses (Yamashita et al.,
- the stress-induced birefringence is quantified in terms of a coefficient, called the photoelastic constant (or the photoelastic coefficient).
- the photoelastic coefficient (B p ) may be defined as the coefficient relating the difference in the refractive indices in the stress direction (n(par)) and in the perpendicular direction (n(per)), to the magnitude of the applied stress:
- n(par) - n(per) B p ⁇
- phase shift measured in units of wavelength in nanometers (nm) per path length in centimeters (cm) divided by the stress in kilograms per square centimeter (kg/cm 2 ). The values then are in units of (nm/cm divided by kg/cm 2 ).
- An ideal glass fiber would have a photoelastic coefficient of zero, thereby nullifying any effect of stress-induced birefringence. However, this has proven difficult to obtain in conjunction with other desired properties. Therefore, a near-zero value, e.g., a value within a range of -0.2 to 0.2, has been considered adequate for some purposes.
- Another purpose is to provide a glass that is adapted to use in such improved method and device.
- a further purpose is to provide a method of producing a glass having a near-zero photoelastic coefficient in conjunction with a low Verdet constant.
- a still further purpose is to provide a method of reducing the photoelastic coefficient of a glass having a low Verdet constant.
- the present invention resides in part in a method of reducing the photoelastic coefficient of a fluoride glass that has a low Verdet constant at a wavelength suitable for measurement, and that contains zirconium fluoride as a primary component of its composition, the method comprising the step of incorporating a small amount of lead fluoride in the glass composition.
- the invention further resides in a method of determining the magnitude of a surge or fault current of up to about 200 kA which comprises: providing a glass fiber, current sensor, the glass having a composition composed predominantly of zirconium fluoride and containing up to about 3% lead fluoride, having a low Verdet constant at the wavelength used for measurement, and capable of causing an angular rotation of polarized light less than 0.45° per kA, per pass at that wavelength, passing a current through a conductor to create a magnetic field surrounding the conductor, positioning the current sensor within the magnetic field thus created, propagating polarized light into the glass fiber, current sensor, measuring the angle of rotation of the polarized light in the glass fiber sensor, and determining the magnitude of the current from the angle of rotation of the polarized light.
- FIGURE in the accompanying drawing is a device for carrying out the method according to the present invention.
- the present invention relates to a method and device for determining the magnitude of an exceptionally large current.
- the magnitude is determined by measuring the angle of rotation that the current creates in polarized light as the light is transmitted through a fiber in a magnetic field.
- the angle of rotation is less when the glass from which the fiber is drawn has a low Verdet constant.
- a fiber produced from a fluoride glass of the present invention will have a Verdet constant that is less than 0.45 degrees/kA. Therefore, when the fiber is exposed to a current up to at least 200 kA in magnitude, it will register an angle of rotation less than 90 degrees, and will accurately measure the current.
- Reference to a fiber signifies a clad fiber comprising essentially a fiber core and an outer cladding layer.
- the fiber core is the functional member for current measurement.
- a fiber core requires a cladding of lower refractive index to prevent loss of light from the core during transmission.
- a cladding glass will have the same composition as that of the core glass, except modified to impart a lower refractive index.
- Lead fluoride is added to a selected fluoride glass composition, in exchange for sodium fluoride (NaF), to produce a fiber core.
- Other exchanges such as for barium fluoride and/or zinc fluoride, may be made to lower the index for a cladding glass.
- NaF, or another alkaline earth metal fluoride, such as calcium or magnesium fluoride may be exchanged for barium or zinc fluoride to provide a lower refractive index.
- the two glasses may be melted, and a clad fiber drawn employing the well-known double crucible technique.
- Figure 1 illustrates an embodiment of the device of the present invention.
- a clad fiber 3 as described above, is utilized.
- any glass article such as a piece of bulk glass (not shown), can be used.
- Fiber 3 acts as a path for the polarized light.
- Conductor 4 carries the current to produce a magnetic field.
- fiber 3 is wrapped around conductor 4, as shown, to increase the length of the light path. Also, it is preferable that fiber 3 be insulated from the conductor.
- the device also includes a source of light rays 1 , the source being located such that light rays are directed to an input end of fiber 3.
- the source of light rays 1 is a laser.
- a polarizer 2 is located adjacent to source of light rays 1 such that the light rays are linearly polarized.
- An analyzer 5 is located at an output end of fiber 3.
- Analyzer 5 derives a rotatory, polarization component produced in proportion to the current flowing through the conductor 4. Also included is a means 8 for indicating the measured current corresponding to the output of analyzer 5. Typically, the means 8 is a light detector 6, and a display device 7. Light detector 6 receives and detects the output of analyzer 5. Device 7 receives the output of, and provides a display of, the output of the light detector 6.
- the analyzer may be a Wollaston prism, as described in Yamashita. Then, the light ray output from the fiber is broken into two orthogonal polarizations. Means 8 detects the output of each signal, and indicates the measured current corresponding to the output.
- Electrical current in a normal power station operation, can be determined by employing a glass current sensor, preferably in the form of a clad fiber.
- a glass current sensor preferably in the form of a clad fiber.
- the Verdet constant of the glass may then ordinarily be as large as possible to enhance the sensitivity of the determination. In measuring exceptionally large currents, as explained earlier, a low Verdet constant is now required. This avoids pushing the angle of rotation of the polarized light beyond 90°.
- fused silica has provided the smallest Verdet constant available in an inorganic glass, the value being 0.1 kA at 1150 nm.
- fused silica also has a large photoelastic coefficient, 3.5 (nm/cm)/(kg/cm 2 ) at 560 nm. This has led to a search for a glass of comparable Verdet constant and a low, near-zero photoelastic coefficient.
- fluoride glasses have relatively small photoelastic coefficients. Further, these glasses may also have small Verdet constants. Particular reference is made to a fluoride glass known by the acronym ZBLAN. This glass is reported to have a composition consisting of, in mole percent, 53 ZrF 4 , 20 BaF 2 , 4 LaF 3 , 3 AIF 3 and 20 NaF. Measurements on this glass show a desirably low Verdet constant of 0.22 kA at 633 nm., and a photoelastic coefficient of 0.34 (nm/cm)/(kg/cm 2 ) at 546 nm.
- ZBLAN fluoride glass known by the acronym ZBLAN. This glass is reported to have a composition consisting of, in mole percent, 53 ZrF 4 , 20 BaF 2 , 4 LaF 3 , 3 AIF 3 and 20 NaF. Measurements on this glass show a desirably low Verdet constant of 0.22 kA at 633 nm., and
- the glasses shown in TABLE I were prepared by mixing an appropriate batch of fluoride components, placing the batch in a covered, platinum crucible to retain fluorine, and melting at 800° C. for about 40 minutes. The crucible was then uncovered, and the melt was heat treated for 2-3 hours while being covered with gaseous sulfur hexafluoride. The melts were then poured into molds heated at 260° C. and the glasses annealed at that temperature. The annealed glasses were clear, and test pieces were prepared for measurements as recorded in TABLE I.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP99965273A EP1153306A1 (en) | 1999-01-05 | 1999-12-15 | Current measuring method and device |
AU31224/00A AU3122400A (en) | 1999-01-05 | 1999-12-15 | Current measuring method and device |
CA002357427A CA2357427A1 (en) | 1999-01-05 | 1999-12-15 | Current measuring method and device |
JP2000592647A JP2003525829A (en) | 1999-01-05 | 1999-12-15 | Method and apparatus for measuring current |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP99400016A EP1018492A1 (en) | 1999-01-05 | 1999-01-05 | Current measuring method and device |
EP99400016.4 | 1999-01-05 | ||
US11670699P | 1999-01-22 | 1999-01-22 | |
US60/116,706 | 1999-01-22 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2000040979A1 true WO2000040979A1 (en) | 2000-07-13 |
WO2000040979A9 WO2000040979A9 (en) | 2001-11-01 |
Family
ID=26153633
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1999/029779 WO2000040979A1 (en) | 1999-01-05 | 1999-12-15 | Current measuring method and device |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP1153306A1 (en) |
JP (1) | JP2003525829A (en) |
CN (1) | CN1332852A (en) |
AU (1) | AU3122400A (en) |
CA (1) | CA2357427A1 (en) |
WO (1) | WO2000040979A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102014219515A1 (en) * | 2014-09-26 | 2016-03-31 | Siemens Aktiengesellschaft | Optical current transformer |
DE102014219516A1 (en) * | 2014-09-26 | 2016-03-31 | Siemens Aktiengesellschaft | Optical current transformer |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE112011102080B4 (en) * | 2010-06-21 | 2020-06-18 | Schaeffler Technologies AG & Co. KG | Central clutch release |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4348587A (en) * | 1980-11-17 | 1982-09-07 | Hughes Aircraft Company | Fiber optic transducer for measuring current or magnetic field |
US4733938A (en) * | 1981-11-09 | 1988-03-29 | The Board Of Trustees Of The Leland Stanford Junior University | Magneto-optic rotator |
US5432806A (en) * | 1992-04-28 | 1995-07-11 | Rutgers University | Four level multiply doped rare earth laser system |
US5450006A (en) * | 1991-03-07 | 1995-09-12 | British Technology Group Limited | Apparatus and methods for measuring magnetic fields and electric currents |
US5856882A (en) * | 1995-02-15 | 1999-01-05 | Hoya Corporation | Optical fibers and optical fiber amplifiers |
-
1999
- 1999-12-15 AU AU31224/00A patent/AU3122400A/en not_active Abandoned
- 1999-12-15 WO PCT/US1999/029779 patent/WO2000040979A1/en not_active Application Discontinuation
- 1999-12-15 CA CA002357427A patent/CA2357427A1/en not_active Abandoned
- 1999-12-15 CN CN 99815423 patent/CN1332852A/en active Pending
- 1999-12-15 EP EP99965273A patent/EP1153306A1/en not_active Withdrawn
- 1999-12-15 JP JP2000592647A patent/JP2003525829A/en not_active Withdrawn
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4348587A (en) * | 1980-11-17 | 1982-09-07 | Hughes Aircraft Company | Fiber optic transducer for measuring current or magnetic field |
US4733938A (en) * | 1981-11-09 | 1988-03-29 | The Board Of Trustees Of The Leland Stanford Junior University | Magneto-optic rotator |
US5450006A (en) * | 1991-03-07 | 1995-09-12 | British Technology Group Limited | Apparatus and methods for measuring magnetic fields and electric currents |
US5432806A (en) * | 1992-04-28 | 1995-07-11 | Rutgers University | Four level multiply doped rare earth laser system |
US5856882A (en) * | 1995-02-15 | 1999-01-05 | Hoya Corporation | Optical fibers and optical fiber amplifiers |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102014219515A1 (en) * | 2014-09-26 | 2016-03-31 | Siemens Aktiengesellschaft | Optical current transformer |
DE102014219516A1 (en) * | 2014-09-26 | 2016-03-31 | Siemens Aktiengesellschaft | Optical current transformer |
Also Published As
Publication number | Publication date |
---|---|
CN1332852A (en) | 2002-01-23 |
WO2000040979A9 (en) | 2001-11-01 |
CA2357427A1 (en) | 2000-07-13 |
AU3122400A (en) | 2000-07-24 |
JP2003525829A (en) | 2003-09-02 |
EP1153306A1 (en) | 2001-11-14 |
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