Magneto-optical current sensor with optical media arranged with distinct verdet constant values and method for arranging said sensor

Abstract

Magneto-optical current sensor and method for arranging said magneto-optical current sensor are disclosed. An optical path is defined in the magneto-optical current sensor to pass an incoming beam of polarized light. The optical path is disposed about a conductor. Optical media is arranged in the optical path, and the optical media has regions defining at least two distinct Verdet constant values at a given reference wavelength of the light beam. The optical media may include at least two optical glass elements defining the at least two distinct Verdet constant values. The optical media may also be an optical fiber arranged with the regions that define the least two distinct Verdet constant values. Disclosed magneto-optical current sensors featuring at least two distinct Verdet constant values allow to inhibit rotation angles of the polarization plane leading to higher optical order modes and possibly increased measurement errors and further provide the ability to adjust a measuring range of the magneto-optical current sensor, a measuring sensitivity of the magneto-optical current sensor, or both.

Description

MAGNETO-OPTICAL CURRENT SENSOR WITH OPTICAL MEDIAARRANGED WITH DISTINCT VERDET CONSTANT VALUESAND METHOD FOR ARRANGING SAID SENSORBACKGROUND

[0001] Disclosed embodiments relate generally to the field of magneto-optics, and, more particularly, to magneto-optical sensors that may be arranged to sense, based on the magnetooptical Faraday effect, electrical current flowing in a current-carrying conductor.

[0002] The rising share of renewable energy sources, growing energy demands, especially electric energy involving high reliability and acceptable distribution losses, are each pushing for new power grids and for upgrade and renewal of existing power grids. This may involve a vast number of current sensors to, for example, efficiently handle the increased data flow between such power grids. Advantages of magneto-optic current sensors in comparison with traditional inductive current transformers are well understood. However, it is desirable to further improve the capabilities of magneto-optic current sensors. Respective examples of magneto-optical sensors that make use of the magneto-optical Faraday effect are disclosed in patent publications EP0831333A1 and EP0799426A1.BRIEF SUMMARY

[0003] In one aspect, a magneto-optical current sensor is disclosed. An optical path is defined in the magneto-optical current sensor to pass an incoming beam of polarized light. The optical path may be disposed about a conductor. Optical media is arranged in the optical path. The optical media has regions defining at least two distinct Verdet constant values at a given reference wavelength of the light beam. Each Verdet constant value is indicative of a respective strength of a magneto-optic effect that causes rotation of a polarization vector of the light beam as the light beam passes through the regions of the optical media in the presence of a magnetic field resulting from current flow in the conductor.

[0004] In another aspect, a method for arranging a magneto-optical current sensor is disclosed. The method allows defining in the magneto-optical current sensor an optical path to pass an incoming beam of polarized light. The optical path may be disposed about a conductor.The method further allows arranging optical media in the optical path. The optical media has regions defining at least two distinct Verdet constant values at a given reference wavelength of the light beam. Each Verdet constant value is indicative of a respective strength of a magnetooptic effect that causes rotation of a polarization vector of the light beam as the light beam passes through the regions of the optical media in the presence of a magnetic field resulting from current flow in the conductor.

[0005] The foregoing has broadly outlined some of the technical features of the present disclosure so that those skilled in the art may better understand the detailed description that follows. Additional features and advantages of the disclosure will be described hereinafter that form the subject of the claims. Those skilled in the art will appreciate that they may readily use the conception and the specific embodiments disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure in its broadest form.

[0006] Also, before undertaking the Detailed Description below, it should be understood that various definitions for certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases. While some terms may include a wide variety of embodiments, the appended claims may expressly limit these terms to specific embodiments.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a schematic view of one non-limiting embodiment of a disclosed magnetooptical current sensor involving optical glass elements that may define at least two distinct Verdet constant values and that may be arranged, without limitation, in a quadrilateral arrangement.

[0008] FIG. 2 is a schematic view of another non-limiting embodiment of a disclosed magneto-optical current sensor where the optical glass elements that define the distinct Verdet constant values may be arranged, without limitation, in a triangular arrangement.

[0009] FIG. 3 is a schematic view of yet another non-limiting embodiment of a disclosed magneto-optical current sensor where an optical fiber may be arranged with the regions that define the distinct Verdet constant values.DETAILED DESCRIPTION

[0010] Disclosed magneto-optical current sensors are based on Faraday's magneto-optical effect (discovered by Michael Faraday in 1845). This effect involves a rotation of the plane of polarization of linearly polarized light while passing through a medium in the presence of a magnetic field. As would be appreciated by one skilled in the art, the size of the angle of rotation 0, by which the polarization plane is rotated can be calculated using the following relationship:

[0011] 0= V*B*d (1)

[0012] where: V- Ver det constant,

[0013] B - magnetic flux density, and

[0014] d - length of path where the light and magnetic field interact.

[0015] The Ver det constant depends on the wavelength of the light, and it is an optical "constant" indicative of the strength of the Faraday-effect for a given material. A Verdet constant having a positive value corresponds to a counterclockwise angle of rotation 0 when the direction of propagation of the light beam is parallel to the magnetic field. Conversely, a Verdet constant having a negative value corresponds to a clockwise rotation when the direction of propagation of the light is anti-parallel to the magnetic field.

[0016] The inventors of the present invention have recognized that in certain known magnetooptical current sensing arrangements as the magnitude of the current being sensed increases, the angle of rotation 0 can eventually reach a value of, for example, 45° or 90°. As a result, the magneto-optical current sensor may no longer operate in a first optical order mode, but may operate in a higher optical order mode, such as in a second order optical mode, and this could affect stable detection by the sensor and associated sensor processing unit. That is, measurement errors may increase under large angle of rotations. A smaller Verdet constant thus may be desirable to inhibit rotation angles of the polarization plane leading to higher optical order modes and increased measurement errors. However, Verdet constants havingrelatively small values may not provide the desired sensitivity that may be required for certain applications.

[0017] At least in view of the foregoing considerations, the inventors of the present inventors propose sensing arrangement and techniques that permit disclosed magneto-optical current sensors to appropriately balance such counter-opposing considerations. One way to achieve a lower rotation of the polarization plane of the light beam may be reducing the length of the path d. However, in certain practical arrangements such length may not be easily changed, such as due to sensor packaging constraints and other electro-mechanical constraints that may be involved. One option featured in disclosed magneto-optical current sensors is appropriately arranging optical media having distinct Ver det constant values so that a resulting Verdet constant value of the optical media can be appropriately selected based on the needs of a given sensing application.

[0018] Thus, disclosed magneto-optical current sensors may involve an optical path that comprises optical media having regions that define at least two distinct Verdet constant values at a given reference wavelength of the light beam. The distinct Verdet constant values may involve Verdet constants having positive and negative values. The ability to appropriately configure the optical media with regions having distinct Verdet constant values can enable tailoring the measuring range of disclosed magneto-optical current sensors by appropriate selection of a combination of glass materials, for example. Moreover, the ability to appropriately configure the optical media with regions having distinct Verdet constant values can enable the manufacturing of magneto-optical current sensors that have a common topology that may be adapted to meet, cost-effectively and reliably, the varying needs of diverse sensing applications, such as may improve the measuring accuracy and / or the measuring range that may be needed in any given one of such diverse sensing applications.

[0019] Disclosed magneto-optical current sensors may be implemented by way of bulk optics, e.g., as may involve discrete optical glass elements selected to provide the distinct Verdet constant values; or may be implemented by way of fiber optics, as may include regions configured to provide the distinct Verdet constant values. For example, in certain embodiments, the optical glass elements may comprise a combination of glass types selected to provide the distinct Verdet constant values, and, for example, the measuring range of any given magneto-optical current sensor could then be adjusted as desired by selecting an appropriate combination of glass types.

[0020] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in this description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0021] Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0022] It should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “including,” “having,” and “comprising,” as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and / or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Furthermore, while multiple embodiments or constructions may be described herein, any features, methods, steps, components, etc. described with regard to one embodiment are equally applicable to other embodiments absent a specific statement to the contrary.

[0023] Also, although the terms “first”, “second”, “third” and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure.

[0024] In addition, the term “adjacent to” may mean that an element is relatively near to but not in contact with a further element or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard is available, a variation of twenty percent would fall within the meaning of these terms unless otherwise stated.

[0025] FIG. 1 is a schematic view of one non-limiting embodiment of a disclosed magnetooptical current sensor 10 involving optical glass elements that may define at least two distinct Verdet constant values and that may be arranged, without limitation, in a quadrilateral arrangement.

[0026] In one non-limiting embodiment, an optical path 14 is defined in the magneto-optical current sensor to pass an incoming beam of polarized light 16, such as linearly polarized light. Optical path 14 may be disposed about a conductor 17 that in operation carries a flow of electrical current having properties, such as magnitude of the current flow, to be sensed by the magneto-optical current sensor 10.

[0027] In one non-limiting embodiment, optical media is arranged in the optical path, and the optical media include regions 18 defining at least two distinct Verdet constant values at a given reference wavelength of the light beam. The regions 18 of the optical media may comprise at least two optical glass elements 20 defining the at least two distinct Verdet constant values. In this embodiment, without limitation, the number of optical glass elements 20 is three and thenumber of distinct Ver det constant values, without limitation, may be three (Fy, Vz, V3) or could be two. For example, two of the optical glass elements 20 could have Verdet constant values Vi and the third one of the optical glass elements 20 could have a Verdet constant value Vz. It will be appreciated by one skilled in the art, that each Verdet constant value is indicative of a respective strength of a magneto-optic effect that causes rotation of a polarization vector of the light beam as the light beam passes through the regions of the optical media in the presence of a magnetic field resulting from current flow in the conductor 17.

[0028] FIG. 2 is a schematic view of another non-limiting embodiment of a disclosed magneto-optical current sensor where the optical glass elements 20 that define the distinct Verdet constant values may be arranged, without limitation, in a triangular arrangement about conductor 17 in lieu of the quadrilateral arrangement shown in FIG . 2. That is, in this embodiment, without limitation, the number of optical glass elements 20 is two and the number of distinct Verdet constant values, without limitation, in this example is two, (Fy, Vz).

[0029] It will be appreciated that the embodiments illustrated in FIGs. 1 and 2 should be construed in an example sense and not in a limiting sense since the concepts embodied in disclosed magneto -optical current sensor are not limited to: any particular geometry and could be configured in the form of a glass ring, or in the form of a linear rod; any particular number of optical glass elements 20; or any specific number of distinct Verdet constant values so long as there is a minimum of two distinct Verdet constant values.

[0030] As may be appreciated FIGs. 1 and 2 the optical glass elements 20 may be spaced apart relative to one another. The glass types for the optical glass elements 20 may be selected to inhibit birefringence. Without limitation, the optical glass elements may comprise respective prisms, such as may include dove prisms or similar optical elements. It will be appreciated that the inlet optical surface that respectively passes the light beam into a given magneto-optical current sensor and the outlet optical surface that outputs the light beam from such magnetooptical current sensor need not be beveled at a given beveling angle, such as 45°, and may be designed as respective end faces perpendicular to the respective prism to which such surfaces are optically coupled to. This feature is conducive to inhibiting input and exit optical losses.

[0031] FIG. 3 is a schematic view of yet another non-limiting embodiment of a disclosed magneto-optical current sensor 30 where an optical fiber 32 may be arranged with the regionsthat define the distinct Verdet constant values. In this embodiment, a first fiber region (schematically represented by a dashed line) may have a Verdet constant value Vi,), and a second fiber region (schematically represented by a dotted line) may have a Verdet constant value (IV), where Vi, and V represent distinct Verdet constant values.

[0032] In any of the foregoing embodiments, by way of appropriately selecting the values of the at least two distinct Verdet constant values, one can adjust at least one of the following: a measuring range of the magneto-optical current sensor, and a measuring sensitivity of the magneto-optical current sensor. Concurrently, in any of the foregoing embodiments, by way of appropriately selecting the values of the at least two distinct Verdet constant values, one can inhibit the magneto-optical current sensor from operating in a higher optical order mode, and thereby inhibit measurement errors.

[0033] In operation, disclosed magneto-optical current sensors featuring at least two distinct Verdet constant values allow to appropriately balance counter-opposing considerations, such as the desire to inhibit rotation angles of the polarization plane leading to higher optical order modes and possibly increased measurement errors while providing the ability to adjust a measuring range of the magneto-optical current sensor, a measuring sensitivity of the magnetooptical current sensor, or both. In one example high voltage / high current application, a circuit breaker may be equipped with one or more disclosed magneto-optical current sensors. In another high voltage / high current example application, disclosed magneto-optical current sensors may be used for sensing current, without limitation, in extra-high or ultra-high voltage transmission lines and / or for sensing current in electrical equipment associated with any such transmission line. Yet in another example high voltage / high current application a magnetooptic current transformer may be equipped with one or more disclosed magneto-optical current sensors.

[0034] For the sake of illustration, let us presume a magneto-optical current sensor involving a total of four prisms: arranged in one example case with two prisms made up of F N11 glass and with two prisms made up of SF 6 glass; and in a second example case arranged with two prisms made up of F N11 glass and with two prisms made up of LF 3 glass. It can be shown that either of the foregoing example cases involving a mix of different glass types (involving different Verdet constants) would provide improved measurement performance, such as a substantially uniform accuracy over a given measurement range compared to, for example, asensor arrangement where the four prisms are made up of just a singular type of glass, such as F N11. It should be appreciated that aspects of disclosed embodiments are not limited to the example glass types listed above, which should be interpreted in an example sense and not in a limiting sense.

[0035] Although at least one exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the scope of the disclosure in its broadest form.

[0036] None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope. The scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words "means for" are followed by a participle.

Claims

CLAIMSWhat is claimed is:

1. A magneto-optical current sensor comprising: an optical path defined in the magneto-optical current sensor to pass an incoming beam of polarized light, the optical path disposed about a conductor, optical media arranged in the optical path, the optical media having regions defining at least two distinct Verdet constant values at a given reference wavelength of the light beam, wherein each Verdet constant value is indicative of a respective strength of a magneto-optic effect that causes rotation of a polarization vector of the light beam as the light beam passes through the regions of the optical media in the presence of a magnetic field resulting from current flow in the conductor.

2. The magneto-optical current sensor of claim 1, wherein the regions of the optical media comprise at least two optical glass elements defining the at least two distinct Verdet constant values.

3. The magneto-optical current sensor of claim 2, wherein the at least two optical glass elements are spaced apart relative to one another.

4. The magneto-optical current sensor of claim 2, wherein the at least two optical glass elements comprise glass types selected to inhibit birefringence.

5. The magneto-optical current sensor of claim 2, wherein the at least two optical glass elements comprise respective prisms.

6. The magneto-optical current sensor of claim 5 wherein the respective prisms comprise dove prisms.

7. The magneto-optical current sensor of claim 1, wherein the optical media comprises an optical fiber arranged with the regions that define the at least two distinct Verdet constant values.

8. The magneto-optical current sensor of claim 1, wherein the at least two distinct Verdet constant values include positive and negative values.

9. The magneto-optical current sensor of claim 1, wherein, by way of a selection of the values of the at least two distinct Verdet constant values, at least one of the following is adjustable: a measuring range of the magneto-optical current sensor, and a measuring sensitivity of the magneto-optical current sensor.

10. The magneto-optical current sensor of claim 1, wherein, by way of a selection of the values of the at least two distinct Verdet constant values, the magneto-optical current sensor is inhibited from operating in a higher optical order mode, and thereby inhibiting measurement errors over a measuring range of the magneto-optical current sensor.

11. A circuit breaker including the magneto-optical current sensor according to any of the preceding claims.

12. A high-voltage or extra-high voltage transmission line including the magnetooptical current sensor according to any of claims 1 -10.

13. Electrical equipment operatively coupled with a high-voltage or extra-high voltage transmission line, the electrical equipment including the magneto-optical current sensor according to any of claims 1-10.

14. A method for arranging a magneto-optical current sensor, the method comprising: defining in the magneto-optical current sensor an optical path to pass an incoming beam of polarized light, the optical path disposed about a conductor, and arranging optical media in the optical path, the optical media having regions defining at least two distinct Verdet constant values at a given reference wavelength of the light beam, wherein each Verdet constant value is indicative of a respective strength of a magneto-optic effect that causes rotation of a polarization vector of the light beam as the light beam passes through the regions of the optical media in response to a magnetic field resulting from current flow in the conductor.

15. The method of claim 14, wherein the regions of the optical media comprise at least two optical glass elements defining the at least two distinct Verdet constant values.

16. The method of claim 15, selecting glass types of the at least two optical glass elements to inhibit birefringence.

17. The method of claim 14, wherein the optical media comprises an optical fiber, and the method further comprises arranging in the optical fiber the regions that define the at least two distinct Verdet constant values.

18. The method of claim 14, by way of selecting the values of the at least two distinct Verdet constant values, adjusting at least one of the following: a measuring range of the magneto-optical current sensor, and a measuring sensitivity of the magnetooptical current sensor.

19. The method of claim 14, by way of selecting the values of the at least two distinct Verdet constant values, inhibiting the magneto-optical current sensor from operating in a higher optical order mode, and thereby inhibiting measurement errors.

Images