Magneto-optical current sensor having optical media arranged with different wielder constant values and method for arranging said sensor

Abstract

A magneto-optical current sensor and a method for arranging the magneto-optical current sensor are disclosed. An optical path is defined in the magneto-optical current sensor to pass an incident beam of polarized light. The optical path is disposed around the conductor. An optical medium is arranged in the optical path, and the optical medium has a region defining at least two different Vierd constant values at a given reference wavelength of the light beam. The optical medium may include at least two optical glass elements that define at least two different Vild constant values. The optical medium may also be an optical fiber arranged with regions defining at least two different Weidet constant values. The disclosed magneto-optical current sensor characterized by at least two different Vild constant values allows the rotation angle of the plane of polarization that results in higher order optical modes and possibly increased measurement errors to be suppressed, and also provides the ability to adjust the measurement range of the magneto-optical current sensor, the measurement sensitivity of the magneto-optical current sensor, or both.

Description

Technical Field

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

[0002] The increasing share of renewable energy and the growing demand for energy, particularly electricity with high reliability and acceptable distribution losses, are driving the development of new power grids as well as the upgrading and modernization of existing ones. This can involve a large number of current sensors, for example, to efficiently handle the increased data flow between these grids. The advantages of magneto-optical current sensors over conventional inductive current transformers are well known. However, further improvements in their performance are desired. Patent publications EP0831333A1 and EP0799426A1 disclose various examples of magneto-optical sensors that utilize the magneto-optical Faraday effect. Summary of the Invention

[0003] In one aspect, a magneto-optical current sensor is disclosed. In the magneto-optical current sensor, an optical path is defined for passing an incident beam of polarized light. The optical path can be disposed around a conductor. An optical medium is disposed in the optical path. The optical medium has a region defining at least two different Verdet constant values at a given reference wavelength of the light beam. Each Verdet constant value represents a corresponding strength of a magneto-optical effect that causes a rotation of the polarization vector of the light beam when the light beam passes through the region of the optical medium in the presence of a magnetic field generated by a current in the conductor.

[0004] In another aspect, a method for arranging a magneto-optical current sensor is disclosed. The method allows for defining an optical path in the magneto-optical current sensor to pass an incident beam of polarized light. The optical path can be arranged around a conductor. The method also allows for arranging an optical medium in the optical path. The optical medium has a region defining at least two different Verdet constant values at a given reference wavelength of the light beam. Each Verdet constant value represents a corresponding strength of a magneto-optical effect that causes a rotation of the light beam's polarization vector when the light beam passes through the region of the optical medium, given a magnetic field generated by a current in the conductor.

[0005] The foregoing has summarized 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 present disclosure that form the subject matter of the claims will be described below. Those skilled in the art will appreciate that they can readily use the disclosed concepts and specific embodiments as a basis for modifying or designing other structures for achieving the same purposes of the present disclosure. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of the present disclosure in its broadest form.

[0006] Additionally, before proceeding with the following detailed description, it should be understood that various definitions of certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that these definitions apply in many, if not most, instances to prior and future uses of these defined words and phrases. Although 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] Figure 1 is a schematic diagram of a non-limiting embodiment of the disclosed magneto-optical current sensor, which includes optical glass elements that can define at least two different Verdet constant values and can be arranged in a non-limiting quadrilateral arrangement.

[0008] Figure 2 is a schematic diagram of another non-limiting embodiment of the disclosed magneto-optical current sensor, wherein optical glass elements defining different Verdet constant values may be arranged in a non-limiting triangular arrangement.

[0009] Figure 3 is a schematic diagram of yet another non-limiting embodiment of the disclosed magneto-optical current sensor, wherein an optical fiber may be arranged to have regions defining different values of the Verdet constant. DETAILED DESCRIPTION

[0010] The disclosed magneto-optical current sensor is based on the Faraday magneto-optical effect (discovered by Michael Faraday in 1845). This effect involves the rotation of the polarization plane of linearly polarized light as it passes through a medium in the presence of a magnetic field. As will be understood by those skilled in the art, the magnitude of the rotation angle β of the polarization plane can be calculated using the following relationship:

[0011] β=V*B*d (1)

[0012] Where: V – Verdet constant,

[0013] B – magnetic flux density, and

[0014] d – the path length of the interaction between light and magnetic field.

[0015] The Verdet constant, an optical constant that indicates the strength of the Faraday effect for a given material, depends on the wavelength of light. When the light beam propagates parallel to the magnetic field, a positive value of the Verdet constant corresponds to a counterclockwise rotation angle β. Conversely, when the light beam propagates antiparallel to the magnetic field, a negative value of the Verdet constant corresponds to a clockwise rotation.

[0016] The inventors of the present invention have recognized that in certain known magneto-optical current sensing arrangements, as the magnitude of the sensed current increases, the rotation angle β may 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 a second optical order mode, and this may affect the stable detection of the sensor and the associated sensor processing unit. That is, at large rotation angles, the measurement error may increase. Therefore, a smaller Verdet constant may be desirable to suppress the rotation angle of the polarization plane, thereby resulting in higher optical order modes and increased measurement errors. However, a Verdet constant with a relatively small value may not provide the desired sensitivity that may be required for certain applications.

[0017] In light of at least the foregoing considerations, the present inventors have proposed sensing arrangements and techniques that allow the disclosed magneto-optical current sensor to appropriately balance these opposing considerations. One way to achieve a lower rotation of the beam's polarization plane can be to reduce the length of the path d. However, in certain practical arrangements, such a length may not be easily varied, for example due to sensor packaging constraints and other electromechanical constraints that may be involved. One option for the disclosed magneto-optical current sensor features the appropriate arrangement of optical media having different Verdet constant values, such that the resulting Verdet constant value of the optical media can be appropriately selected based on the needs of a given sensing application.

[0018] Thus, the disclosed magneto-optical current sensor can involve an optical path including an optical medium having regions defining at least two different Verdet constant values at a given reference wavelength of the optical beam. The different Verdet constant values can include Verdet constants having both positive and negative values. For example, by appropriately selecting a combination of glass materials, the ability to appropriately configure the optical medium having regions with different Verdet constant values can enable customization of the measurement range of the disclosed magneto-optical current sensor. Furthermore, the ability to appropriately configure the optical medium having regions with different Verdet constant values can enable the manufacture of magneto-optical current sensors having a common topology that can be adapted to cost-effectively and reliably meet the different requirements of different sensing applications, for example, to improve the measurement accuracy and / or measurement range that may be required in any given one of such different sensing applications.

[0019] The disclosed magneto-optical current sensor can be implemented using bulk optics, for example, including discrete optical glass elements selected to provide different Verdet constant values, or can be implemented using optical fibers, which can include regions configured to provide different Verdet constant values. For example, in certain embodiments, the optical glass elements can include a combination of glass types selected to provide different Verdet constant values, and the measurement range of any given magneto-optical current sensor can be adjusted as desired by selecting an appropriate combination of glass types.

[0020] Before explaining any embodiments of the present invention in detail, it should 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 specification or illustrated in the following drawings. The invention is capable of other embodiments and can be practiced or carried out in various ways. Furthermore, it should be understood that the phraseology and terminology used herein are for descriptive purposes only and should not be considered as limiting.

[0021] Various techniques related to systems and methods will now be described with reference to the accompanying drawings, in which 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 merely exemplary and should not be construed as limiting the scope of the present disclosure in any way. Those skilled in the art will appreciate that the principles of the present disclosure can be implemented in any suitably arranged device. It should be understood that the functions described as being performed by certain system elements can be performed by multiple elements. Similarly, for example, an element can be configured to perform the functions described as being performed by multiple elements. Many innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0022] It should be understood that, unless expressly limited in some examples, the words or phrases used herein should be interpreted broadly. For example, the terms "including," "having," and "comprising," and their derivatives, mean inclusion without limitation. The singular forms "a," "an," and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. In addition, the term "and / or," as used herein, refers to and includes 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 with" and their derivatives may mean including, contained within, interconnected with, containing, contained within, connected or connected with, coupled or coupled with, communicating with, cooperating with, intertwining, juxtaposed, proximate, bound or bound with, having, having characteristics, etc. In addition, although multiple embodiments or configurations may be described herein, any features, methods, steps, components, etc. described with respect to one embodiment are equally applicable to other embodiments unless specifically stated otherwise.

[0023] In addition, although the terms "first," "second," "third," etc. may be used herein to refer to various elements, information, functions, or actions, these elements, information, functions, or actions should not be limited by these terms. On the contrary, these numerical adjectives are used to distinguish different elements, information, functions, or actions. For example, without departing from the scope of this disclosure, a first element, information, function, or action may be referred to as a second element, information, function, or action, and similarly, a second element, information, function, or action may be referred to as a first element, information, function, or action.

[0024] Additionally, the term "adjacent" can mean that one element is relatively close to but not in contact with another element, or that the element is in contact with the other element, unless the context clearly indicates otherwise. Furthermore, the phrase "based on" is intended to mean "based at least in part on" unless explicitly stated otherwise. The terms "approximately" or "substantially" or similar terms are intended to encompass variations in values within normal industry manufacturing tolerances for that dimension. If no industry standard is available, a variation of 20 percent would be considered within the meaning of these terms unless otherwise indicated.

[0025] Figure 1 is a schematic diagram of one non-limiting embodiment of the disclosed magneto-optical current sensor 10 comprising optical glass elements that can define at least two different Verdet constant values and that can be arranged in a non-limiting quadrilateral arrangement.

[0026] In one non-limiting embodiment, an optical path 14 is defined in the magneto-optical current sensor to pass an incident beam of polarized light 16, such as linearly polarized light. The optical path 14 can be disposed around a conductor 17 that, when in operation, carries a current having a characteristic sensed by the magneto-optical current sensor 10, such as a magnitude of the current.

[0027] In one non-limiting embodiment, an optical medium is disposed in an optical path, and the optical medium includes a region 18 defining at least two different Verdet constant values at a given reference wavelength of the optical beam. The region 18 of the optical medium may include at least two optical glass elements 20 that define at least two different Verdet constant values. In this embodiment, without limitation, the number of optical glass elements 20 is three, and the number of different Verdet constant values is not limited and may be three (V1, V2, V3) or may be two. For example, two optical glass elements 20 may have a Verdet constant value of V1, and a third optical glass element 20 may have a Verdet constant value of V2. Those skilled in the art will appreciate that each Verdet constant value represents a corresponding strength of a magneto-optical effect that, in the presence of a magnetic field generated by the current in the conductor 17, causes the polarization vector of the optical beam to rotate as the optical beam passes through the region of the optical medium.

[0028] Figure 2 is a schematic diagram of another non-limiting embodiment of the disclosed magneto-optical current sensor, wherein optical glass elements 20 defining different Verdet constant values may be arranged in a triangular arrangement around the conductor 17, without limitation, instead of Figure 2 That is, in this embodiment, without limitation, the number of optical glass elements 20 is two, and the number of different Verdet constant values is not limited, which is two (V2, V1) in this example.

[0029] It should be understood that Figure 1 and Figure 2 The embodiments shown in should be understood in an illustrative sense and not in a limiting sense, as the concepts embodied in the disclosed magneto-optical current sensor are not limited to: any particular geometry, and may 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 particular number of different Verdet constant values, as long as there are at least two different Verdet constant values.

[0030] from Figure 1 and Figure 2As can be seen in FIG, the optical glass elements 20 can be spaced apart from each other. The glass type of the optical glass element 20 can be selected to suppress birefringence. Without limitation, the optical glass elements can include respective prisms, for example, can include dove prisms or similar optical elements. It should be understood that the entrance optical surface that transmits the light beam into a given magneto-optical current sensor and the exit optical surface that outputs the light beam from such magneto-optical current sensor do not need to be inclined at a given oblique angle (e.g., 45°), and can be designed to be perpendicular to the corresponding end faces of the corresponding prisms to which such surfaces are optically coupled. This feature helps to suppress input and output light losses.

[0031] Figure 3 FIG2 is a schematic diagram of another non-limiting embodiment of the disclosed magneto-optical current sensor 30, in which the optical fiber 32 can be arranged to have regions defining different Verdet constant values. In this embodiment, a first optical fiber region (schematically represented by a dashed line) can have a Verdet constant value (V1), and a second optical fiber region (schematically represented by a dashed line) can have a Verdet constant value (V2), where V1 and V2 represent different Verdet constant values.

[0032] In any of the aforementioned embodiments, by appropriately selecting at least two different Wildt constant values, at least one of the following can be adjusted: a measurement range of the magneto-optical current sensor and a measurement sensitivity of the magneto-optical current sensor. Furthermore, in any of the aforementioned embodiments, by appropriately selecting at least two different Wildt constant values, the magneto-optical current sensor can be prevented from operating in a higher optical order mode, thereby suppressing measurement errors.

[0033] In operation, the disclosed magneto-optical current sensor characterized by at least two different values of the Verdet constant allows for the appropriate balancing of opposing considerations, such as the desire to suppress rotation angles of the polarization plane that result in higher-order optical modes and potentially increased measurement errors, while providing the ability to adjust the measurement range of the magneto-optical current sensor, the measurement sensitivity of the magneto-optical current sensor, or both. In one example of a high voltage / high current application, a circuit breaker may be equipped with one or more of the disclosed magneto-optical current sensors. In another example of a high voltage / high current application, the disclosed magneto-optical current sensor may be used to sense current in an ultra-high voltage or ultra-high voltage transmission line, without limitation, and / or for sensing current in electrical equipment associated with any such transmission line. In another example of a high voltage / high current application, a magneto-optical current transformer may be equipped with one or more of the disclosed magneto-optical current sensors.

[0034] For illustrative purposes, let's assume a magneto-optical current sensor includes a total of four prisms: in one example, two prisms are made of FN11 glass and two prisms are made of SF6 glass; and in a second example case, two prisms are made of FN11 glass and two prisms are made of LF3 glass. It can be seen that any of the aforementioned example cases involving a mix of different glass types (involving different Verdet constants) will provide improved measurement performance, for example, substantially consistent accuracy over a given measurement range, compared to, for example, a sensor arrangement in which the four prisms are composed of only a single type of glass (e.g., FN11). It should be understood that aspects of the disclosed embodiments are not limited to the exemplary glass types listed above, which should be interpreted in an exemplary, rather than a restrictive, sense.

[0035] Although at least one exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will appreciate that they can make various changes, substitutions, alterations, and improvements as disclosed herein without departing from the scope of the disclosure in its broadest form.

[0036] Nothing in this application should be construed as implying that any particular element, step, act, or function is essential to the scope of the claims. The scope of patented subject matter is defined solely by the allowed claims. Furthermore, none of the claims is intended to invoke a means-plus-function claim construction unless the exact word "means" is followed by a participle.

Claims

1. A magneto-optical current sensor, comprising: an optical path defined in the magneto-optical current sensor for passing an incident light beam of polarized light, the optical path being arranged around a conductor, an optical medium arranged in the optical path, the optical medium having a region defining at least two different values of the Verdet constant at a given reference wavelength of the optical beam, Each value of the Verdet constant represents the corresponding strength of the magneto-optical effect, which causes the polarization vector of the light beam to rotate when the light beam passes through a region of the optical medium when the current in the conductor generates a magnetic field.

2. The magneto-optical current sensor according to claim 1, wherein: The region of optical medium includes at least two optical glass elements, and the at least two optical glass elements define the at least two different values of the Verdet constant.

3. The magneto-optical current sensor according to claim 2, wherein: The at least two optical glass elements are spaced relative to each other.

4. The magneto-optical current sensor according to claim 2, wherein: The at least two optical glass elements comprise a glass type selected to suppress birefringence.

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

6. The magneto-optical current sensor according to claim 5, wherein: The respective prisms include dove prisms.

7. The magneto-optical current sensor according to claim 1, wherein: The optical medium comprises an optical fiber arranged with regions defining the at least two different values of the Verdet constant.

8. The magneto-optical current sensor according to claim 1, wherein: The at least two different Wildt constant values include positive values and negative values.

9. The magneto-optical current sensor according to claim 1, wherein: By selecting the values of the at least two different Verdet constants, at least one of the following is adjustable: a measurement range of the magneto-optical current sensor and a measurement sensitivity of the magneto-optical current sensor.

10. The magneto-optical current sensor according to claim 1, wherein: By selecting the at least two different values of the Wildt constant, the magneto-optical current sensor is suppressed from operating in a higher optical order mode, thereby suppressing measurement errors within a measurement range of the magneto-optical current sensor.

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

12. A high voltage or ultra-high voltage transmission line, comprising the magneto-optical current sensor according to any one of claims 1 to 10.

13. An electrical device capable of being operatively coupled to a high voltage or extra-high voltage power transmission line, the electrical device comprising the magneto-optical current sensor according to any one of claims 1 to 10.

14. A method for arranging a magneto-optical current sensor, the method comprising: defining an optical path in the magneto-optical current sensor to pass an incident beam of polarized light, the optical path being disposed around the conductor, and providing an optical medium in the optical path, the optical medium having a region defining at least two different values of the Verdet constant at a given reference wavelength of the optical beam, wherein each value of the Verdet constant represents a respective strength of a magneto-optical effect that causes a rotation of the polarization vector of the light beam as the light beam passes through a region of the optical medium in response to a magnetic field generated by the current in the conductor.

15. The method according to claim 14, wherein The region of optical medium includes at least two optical glass elements, and the at least two optical glass elements define the at least two different values of the Verdet constant.

16. The method of claim 15, wherein the glass type of the at least two optical glass elements is selected to suppress birefringence.

17. The method according to claim 14, wherein: The optical medium comprises an optical fiber, and the method further comprises arranging in the optical fiber a region defining the at least two different values of the Verdet constant. 18 . The method of claim 14 , wherein at least one of the following is adjusted by selecting the at least two different values of the Wildt constant: a measurement range of the magneto-optical current sensor and a measurement sensitivity of the magneto-optical current sensor.

19. The method of claim 14, wherein the magneto-optical current sensor is inhibited from operating in a higher optical order mode by selecting the at least two different values of the Wildt constant, thereby inhibiting measurement errors.

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