MONOLITHIC GLASS RING AND METHOD FOR OPTICAL CURRENT MEASUREMENTS

Description

[0001] The invention relates to a glass ring for current measurements and a method for optical current measurement, comprising a glass body that can be arranged around an electrical conductor and has a light entry surface and a light exit surface. The glass ring is designed to allow light entering the glass body through the light entry surface to circulate completely around the conductor within the glass body by reflection on the outer sides of the glass body, with the light exiting the glass body at the light exit surface.

[0002] An electric current, for example, is measured resistively via a voltage drop across a resistor. An alternating current generates an electromagnetic field around a current-carrying conductor, which can be measured inductively, for example, via a measuring transformer, and / or optically using the Faraday effect. High currents, particularly in the range of several hundred amperes, are advantageously measured using induction and / or the Faraday effect, as these methods do not increase the resistance in the current-carrying conductor or primary conductor. To measure current using the Faraday effect, polarized light is guided around a current-carrying conductor. Polarization-maintaining optical fibers or, for example, a glass ring are used for this purpose. In this case, glass with a Verdet constant other than zero is used.

[0003] The magnetic field of the current-carrying conductor leads to an additional rotation of the polarization plane of the incident light in the glass, which can be measured using various methods and is directly proportional to the current in the conductor. Compared to optical fibers, the glass rings used exhibit significantly lower temperature and vibration effects, but have not yet been manufacturable without glass bonding. Such glass rings are known, for example, from US Pat. No. 4,564,754. One glass ring used comprises four corners and is essentially rectangular. At each of the four corners of the rectangular glass ring, the light beam is reflected by two surfaces tilted at 90 degrees to avoid changing the polarization plane. This partially determines the glass ring geometry. A second boundary condition is the possibilities of a grinding and polishing process during the production of such a glass ring.Only entire surfaces without any steps can be polished.

[0004] The boundary conditions mean that the glass ring produced in this way does not allow 360-degree light circulation around the conductor, or that light cannot be coupled in or out. The production of such glass rings, which allow light to be coupled in and out and also allow light to 360-degree circulation around the conductor, requires the polarization-maintaining glass ring to be assembled from several parts. The parts are then assembled and glued together. This avoids the limitations of the polishing process. In order to avoid inducing mechanical stresses into the glass body of the glass ring through the bonding points, which could lead to stress birefringence and polarization effects, glass adhesive systems in this case require very long setting times. The adhesives used can only be used in certain application temperature ranges. If the temperature range is exceeded, the mechanical parameters change.The adhesive can degrade and show color changes, which leads to measurement drifts and unacceptable measurement deviations in an optical measuring system.

[0005] The application areas of a bonded glass ring composed of several monolithic glass bodies are therefore limited. Its use for current measurement is limited, as degradation and / or discoloration of the adhesive and / or mechanical stresses do not allow for a long-term stable measuring system. Measurements with a bonded glass ring lead to measurement errors, particularly after calibration, which increase over time. Furthermore, the adhesive causes mechanical problems, especially at temperatures outside the permissible temperature range. The production of bonded glass rings is complex, time-consuming, and costly. Other glass rings are known from DE 43 42 409 A1 and EP 0 088 419 A1.

[0006] The object of the present invention is to provide a glass ring for current measurements and a method for optical current measurement that solve the problems described above. In particular, the object is to provide a glass ring that is long-term stable, easy to manufacture and inexpensive to manufacture, produces no or minimal measurement errors in optical current measurements, and is mechanically stable, particularly over a wide temperature range and long periods of time.

[0007] The stated object is achieved according to the invention by a glass ring for current measurements having the features according to claim 1 and / or by a method for optical current measurement, in particular with a glass ring described above, according to claim 4. Advantageous embodiments of the glass ring for current measurements according to the invention and / or of the method for optical current measurement, in particular with a glass ring described above, are specified in the subclaims. Subject matter of the main claims can be combined with each other and with features of subclaims, as well as with features of the subclaims.

[0008] A glass ring for current measurements according to the invention comprises a glass body that can be arranged around an electrical conductor and has a light entry surface and a light exit surface. The glass ring is designed to allow light entering the glass body through the light entry surface to circulate completely around the conductor within the glass body by reflection on the outer sides of the glass body, with the light exiting the glass body at the light exit surface. According to the invention, the glass ring is formed from a monolithic glass body.

[0009] By forming the glass ring from a monolithic glass body, without adhesives, any optical change in the light caused by an adhesive is excluded. Aging effects of an adhesive on light in the glass ring are eliminated, and temperature effects on the stability of the glass ring, e.g., due to critical changes in mechanical stability at temperatures outside a given temperature range, are eliminated. The optical behavior of the monolithic glass ring according to the invention is long-term stable, and such a glass ring, which maintains polarization for light and enables coupling and decoupling of light as well as 360-degree circulation for light around an electrical conductor, is simple, mechanically stable, and can be manufactured without great effort, particularly by polishing side surfaces.

[0010] The glass ring comprises two opposite sides, in particular a fifth and a sixth side. In particular, it comprises two flat, opposite sides arranged parallel to one another, which each have exactly four corners. The glass ring has a continuous, circular-cylindrical opening, which in particular extends through the two sides. An electrical conductor can be guided through the opening, in particular arranged with a longitudinal axis perpendicular to the two parallel, flat, opposite sides. This enables a current measurement of the current in the electrical conductor via the electromagnetic field of the conductor, which projects into the glass ring. A change in the polarization of light in the glass ring occurs depending on the electromagnetic field and thus depending on the current strength in the conductor, in particular proportionally.

[0011] The glass ring can be designed so that the polarization of the light is essentially completely preserved as it circulates around the conductor. This makes it possible to measure the current in the conductor, since the change in polarization of the light is not caused by the glass ring itself, but only by the conductor's electromagnetic fields. Circulating light around the conductor allows sufficient interaction of the light with the electromagnetic field of the current-carrying conductor, so that a measurable change in polarization of the light can occur due to the current-carrying conductor's electromagnetic field. This makes it possible to measure the current in the conductor using the glass ring.

[0012] The light entry surface is a third side of the glass ring, which comprises two adjacent partial surfaces tilted relative to each other at an angle, one partial surface being particularly triangular in shape. The inclined or angled partial surface, particularly in a triangular shape, ensures sufficient area for light entry and / or exit, thus enabling light to be coupled into and out of the glass ring.

[0013] Adjacent to the third side of the glass ring is a second side, which adjacent to the sixth side comprises a first, in particular trapezoidal, planar partial surface. Adjacent to the fifth side, the second side comprises a trapezoidal partial surface, which is composed of two mutually tilted, in particular triangular, surfaces, a second and third partial surface of the second side. Tilting the in particular triangular surfaces, the second and third partial surfaces of the second side, repositions a light beam such that it leaves the glass ring at the light exit surface. This enables light to exit the glass ring, and it is possible to measure outside the glass ring the change in polarization of the light in the glass ring caused by the electromagnetic field of the current-carrying conductor, with the advantages described above.

[0014] The third partial surface of the second side is tilted by an angle of just a few degrees, namely 2 degrees, relative to the second partial surface of the second side. A tilt of just a few degrees, namely 2 degrees, results in the advantages described above.

[0015] In particular, adjacent to the second side, a fourth side is included, which is composed of two adjacent, mutually tilted partial surfaces, each partial surface being particularly trapezoidal in shape. The partial surfaces, in particular one partial surface, reflect a light beam along a circuit in the glass ring toward the fifth side or onto a first partial surface of the first side. This enables a closed circuit without a change in polarization through the glass ring or glass body itself, with the advantages described above.

[0016] Adjacent to the third side is a first side, which is composed of two adjacent, mutually tilted partial surfaces, each partial surface being particularly trapezoidal in shape. The partial surfaces, in particular one partial surface, reflect a light beam along a circuit within the glass ring toward the second side or onto a first partial surface of the second side. This enables a closed circuit without a change in polarization through the glass ring or glass body itself, with the advantages described above.

[0017] The glass body can comprise a glass with a Verdet constant greater or less than zero and / or be made of a glass with a Verdet constant greater or less than zero. The Verdet constant represents a material property that indicates the strength of the Faraday effect in a particular material. The value depends on the wavelength of the light and is positive for a material, i.e. .This is particularly true for glass, which has a counterclockwise rotation when light propagates parallel to the magnetic field lines. Due to a non-zero Verdet constant of the glass from which the glass body or glass ring is made, an electromagnetic field acts on the light and changes the polarization of the light depending on the magnitude of the field or the current in the current-carrying conductor. Since the glass does not change the polarization of the light in the glass ring, or essentially does not change it, without an electromagnetic field, a current in the current-carrying conductor can be measured or determined via the change in polarization in the glass ring.

[0018] A method according to the invention for optical current measurement, in particular with a glass ring as described above, comprises that a current flow in an electrical conductor generates an electromagnetic field around the conductor, via which the polarization of a light beam in a glass ring which is arranged around the conductor, in particular with a plane perpendicular to the longitudinal axis of the conductor, is changed as the light beam circulates around the conductor.

[0019] The light beam can pass through a monolithic glass body as it travels around the conductor, with changes in direction of the light beam occurring via reflection on the outer sides of the glass body, in particular on a third partial surface of the second side that is tilted relative to a second partial surface of the second side, in particular tilted by an angle of 2 degrees, and / or on a partial surface of the third side of the glass ring that is tilted by a few degrees, in particular in a triangular shape. The partial surface of the third side of the glass ring that is tilted by a few degrees, in particular in a triangular shape, together with the other partial surface of the third side, enables sufficient surface area for light to enter and, in conjunction with the sixth side, sufficient surface area for light to exit the glass ring in order to couple light into or out of the glass ring.The third partial surface of the second side is tilted relative to the second partial surface of the second sides, in particular tilted by an angle of 2 degrees, and enables the light to exit, in particular by repositioning the light beam in the glass ring, at a light exit surface, which in particular comprises parts of the sixth side, adjacent to the light entry on the third side.

[0020] The tilted surfaces described above, which can be produced easily and inexpensively by cutting, grinding and / or polishing the glass body or glass ring, make it possible to produce a high-temperature optical measuring device for large currents that is long-term stable and does not show signs of aging such as changes in transmission and / or coloration due to components in the light beam path.

[0021] The light can enter the glass body through the light entry surface and exit the glass body through the light exit surface. The light can enter the glass body, in particular, via the third side of the glass ring, in particular via two adjacent partial surfaces tilted at an angle to each other, and / or exit the glass body on the sixth side of the glass ring, in particular at an angle of substantially 90 degrees to the incoming light.

[0022] The advantages of the method according to the invention for optical current measurement, in particular with a previously described glass ring, according to claim 10 are analogous to the previously described advantages of the glass ring according to the invention for current measurements according to claim 1 and vice versa.

[0023] In the following, an embodiment of the invention is shown schematically in the Figures 1 and 2 shown and described in more detail below.

[0024] The Figure 1 schematically shows in oblique view an arrangement for optically measuring a current 3 in an electrical conductor 2 by means of a glass ring 1 according to the invention, and Figure 2 schematically shows the shape or geometry of the glass ring 1 of the Figure 1 .

[0025] In Figure 1 is a schematic oblique view of an arrangement for optically measuring a current 3, in particular in the range of up to several hundred amperes, in an electrical conductor 2 using a glass ring 1 according to the invention. The electrical conductor 2, e.g., a copper conductor and / or cable, is, for example, cylindrical. A current 3 flows in the direction of the arrow in Figure 1 . A glass ring 1 is arranged around the conductor 2, which completely encircles the conductor 2. The glass ring 1 is provided with a plane, in particular a parallel top and bottom side corresponding to Figure 1, arranged perpendicular to the longitudinal axis of the cylindrical conductor 2. The glass ring 1, with its essentially rectangular base and top surface, or in particular parallel top and bottom, has a continuous, circular-cylindrical opening in the center through which the conductor 2 is guided.

[0026] The glass ring 2 has six sides, in particular a parallel top and bottom side and four lateral sides corresponding to the Figure 1 , wherein the sides delimit the glass body, ie, the glass material of the glass ring 2, from the outside, ie, in particular from the ambient air or the ambient gas. The glass or glass material of the glass ring 1 is, for example, a glass for optical applications, with low impurities and a Verdet constant, in particular greater than zero. The glass is, for example, high-temperature resistant.

[0027] Light or a light beam, in particular light of a specific optical wavelength matched to the glass material and its refractive index as well as absorption behavior, which is provided, for example, via a laser or via a light source with optical components such as lenses, enters the glass ring 1, for example, via a lateral side. The light is radiated, for example, perpendicular to the longitudinal axis of the conductor 2 or parallel to the parallel top and bottom of the glass ring 1 into the glass ring 1. The center point or the central axis of the light beam is directed towards an area of the light entry side, which is adjacent to a corner of the glass ring 1, for example in Figure 1 the front lower right corner. After reflections on the sides or side surfaces of the glass ring 1, whereby the light beam in the glass ring 1 completely circles the conductor 2 once, the light beam or the light exits on the light exit side, in Figure 1 the underside of the glass ring 1.

[0028] The area in which the light emerges from the glass ring 1 is in the embodiment of the Figure 1 on the underside adjacent to the corner of the glass ring 1, adjacent to which the light enters on the light entrance side. The light entrance side and the light exit side are adjacent, with an angle to each other of substantially 90 degrees, wherein the light exit side is an underside of the glass ring according to Figure 1 and the light entrance side is a lateral side. As the light circulates around the current-carrying conductor 2, the light changes its polarization essentially only depending on the electromagnetic field of the current 3 in the conductor 2. After calibration, a measurement of the change in polarization of the light yields the current in the conductor 2, e.g., in amperes.

[0029] In Figure 2 is the geometry of the glass ring 1 of the Figure 1with its outer boundary sides in detail. From the perspective of the Figure 2 Visible edges are marked with solid lines, while hidden edges are marked from the perspective of the Figure 2 are marked with dashed lines. The upper side or the upper boundary surface of the glass ring 1 according to Figure 2 is designated as the fifth side 10. The lower side or the lower boundary surface of the glass ring 1 according to Figure 2 is designated as the sixth side 11. The fifth and sixth sides 10, 11 are arranged parallel to each other and planar. In the middle, both sides 10 and 11 are pierced by the continuous, circular-cylindrical opening, ie they have circular openings through which the conductor 2 is guided, which for the sake of simplicity is Figure 2 is not shown.

[0030] Four sides of the glass ring 1, the first side 6, the second side 7, the third side 8, and the fourth side 9, close off the glass ring 1, with two sides 6 and 7 as well as two sides 8 and 9 facing each other. The third side 8 is the light entry side. The third side 8 has two partial surfaces, the first partial surface 8' of the third side 8 having the shape of a triangle. One edge of the triangle is a common edge with the sixth side 11 and another edge is a common edge with the second side 7. By dividing the third side 8 into two partial surfaces, e.g. created by grinding from one surface, light can be coupled into the glass ring 1 on the third side 8 with sufficient intensity and coupled out on the sixth side 11. The two partial surfaces of the third side 8 are connected to one another via a common, in particular straight, edge and enclose an obtuse angle with one another.

[0031] The third side 8 is opposite the fourth side 9, which is composed of two, in particular, trapezoidal partial surfaces. The two partial surfaces of the fourth side are connected to each other via a common, in particular straight edge, and enclose an obtuse angle with each other. A partial surface that is Figure 2 upper part of the surface forms with the second part of the surface, which Figure 2 The lower surface is a hipped roof-shaped structure. The upper surface is arranged at a right angle to the fifth side 10, for example, and the lower surface is created from the surface, for example, by an oblique cut.

[0032] The first side 6 is constructed analogously to the fourth side 9, only with reversed partial surfaces. The two partial surfaces of the first side are connected to each other via a common, in particular straight edge, and enclose an obtuse angle with each other. A partial surface 6', which in Figure 2upper part forms with the second part 6", which in Figure 2 The lower partial surface is a hipped roof-shaped structure. The lower partial surface 6'' is arranged, for example, at a right angle to the sixth side 11, and the upper partial surface 6' is created, for example, by oblique grinding from the surface.

[0033] The second page 7 is structured analogously to the first page 6, only with a Figure 2 upper part, which is further divided into two parts 7' and 7". The lower part in Figure 2is arranged, for example, at a right angle to the sixth side 11, and the upper partial surfaces 7' and 7" are created from the surface by oblique grinding. The two upper partial surfaces 7' and 7'' are each triangular in shape, with a common edge. The partial surface 7'' repositions the light beam as it circulates through the glass ring 1, whereby after reflection at the partial surface 6' the light beam can exit the glass ring 1, in particular perpendicular to the sixth side 11.

[0034] The light beam thus enters the third side 8, adjacent to the front lower corner in Figure 2 , over both partial surfaces of the third side 8 into the glass ring 1, is inserted at the Figure 2 lower partial surface of the fourth side 9 is reflected to the first partial surface 6' of the first side 6, from there the light beam is reflected to the first partial surface 7' of the second side 7 and further reflected to the Figure 2lower part of the fourth side 9. From the Figure 2 lower partial surface of the fourth side 9, the light beam is reflected to the first partial surface 8' of the third side 8, and from there further to the second partial surface 7'' of the second side 7, whereby reflection to and at the first partial surface 6' of the first side 6 to the sixth side 11 leads to the light beam exiting the glass ring 1 via the sixth side 11. The light beam has thereby completely circulated the conductor 2 once and has essentially retained its polarization through reflection at the glass sides. Changes in polarization occur in particular exclusively through the electromagnetic field of the conductor 2 in the glass ring 1 when current 3 flows in the conductor 2. The value of the current flow 3 can be determined in this way by measuring the degree of the change in polarization.

[0035] The previously described embodiments can be combined with one another and / or can be combined with the prior art. For example, glasses with a positive or negative Verdet constant can be used for the glass ring 1. The glass ring 1 can be manufactured from a cuboid-shaped body, which is produced by cutting the glass, via ground surfaces. Alternatively or additionally, beveled and / or tilted surfaces can be produced directly by cutting the glass or by polishing. The through opening in the glass ring 1 can be circular-cylindrical or, for example, depending on the shape of the conductor 2, in the case of rail-shaped conductors 2 in particular, it can be square, T-shaped, or double-T-shaped. The glass of the glass ring 1 or the glass body can be made of Corning glass, for example, or comprise other optical glasses.Devices for generating light, particularly for light of a single wavelength, which are not shown in the figures for the sake of simplicity, may include lasers and / or lamps with lenses and / or polarization filters. Devices for analyzing light, particularly for light of a wavelength with altered polarization, which are also not shown in the figures for the sake of simplicity, may include polarization filters, lenses, and / or interferometers.

[0036] The glass ring 1 can be produced from a cuboid, which is produced in particular by glass cutting. The beveled partial surfaces, in particular at an angle of 135 degrees to the respective cuboid surface or ground or beveled by 45 degrees, e.g., the partial surfaces 6', 7' and the lower partial surface according to Figure 2The fourth side 9 can be produced, for example, by glass cutting and / or grinding. The partial surface 7", which is beveled by 2 degrees relative to the partial surface 7', can be produced, for example, by grinding and / or polishing. The partial surface 8' can also be produced by cutting and / or grinding, whereby all surfaces can be finally polished. Further processing methods of the glass ring 1 can include drilling, milling, and / or, for example, laser processing. List of reference symbols

[0037] 1Glass ring 2Electrical conductor 3Direction of current flow 4Light entry surface 5Light exit surface 6First side, front boundary surface 6'First partial surface of the first side, upper front boundary surface 6"Second partial surface of the first side, lower front boundary surface 7Second side, rear boundary surface 7'Second partial surface of the second side, first upper rear boundary surface 7"Third partial surface of the second side, second upper rear boundary surface 8Third side, right lateral boundary surface 8'First partial surface of the third side, lower right lateral boundary surface 9Fourth side, left lateral boundary surface 10Fifth side, upper boundary surface 11Sixth side, lower boundary surface

Claims

1. A glass ring (1) for current measurements, having a glass body that is arrangeable around an electrical conductor (2) and has a light entry surface (4) and a light exit surface (5), wherein the glass ring (1) is configured to allow light entering the glass body through the light entry surface (4) to completely circulate around the conductor (2) in the glass body due to reflection at external sides of the glass body, wherein the light exits the glass body at the light exit surface (5), and wherein the glass ring (1) is formed from a monolithic glass body, wherein the light entry surface (4) is a third side (8) of the glass ring (1), which comprises two adjacent partial surfaces that are tilted through an angle with respect to one another, wherein a partial surface (8') has a triangular shape, wherein, the glass ring (1) comprises a fifth (10) and a sixth (11) side, which are arranged mutually opposite and in parallel, each having exactly four corners, and the glass ring (1) has a circular cylindrical through-opening, which extends in particular through the fifth (10) and the sixth (11) side, wherein, adjacent to the third side (8) of the glass ring (1), a second side (7) is arranged comprising, adjacent to the sixth side (11), a first, trapezoidal planar partial surface, and comprising, adjacent to the fifth side (10), a trapezoidal partial surface that is composed of two triangular surfaces (7', 7") that are tilted with respect to one another, a second (7') and a third (7") partial surface of the second side (7), wherein the third (7") partial surface of the second side (7) is tilted through an angle of 2 degrees, with respect to the second (7') partial surface of the second side (7), wherein, adjacent to the second side (7), a fourth side (8), which is constructed from two mutually adjacent partial surfaces that are tilted with respect to one another, with each partial surface having a trapezoidal shape, is comprised, wherein, adjacent to the third side (8), a first side (6), which is constructed of two mutually adjacent partial surfaces (6', 6") that are tilted with respect to one another, with each partial surface having a trapezoidal shape, is comprised. wherein the first partial surface (8') of the third side (8) is arranged, to reflect a light beam coming from the fourth side (9) further to the second partial surface (7'') of the second side (7), wherein the reflection to and at the first partial surface (6') of the first side (6) leads to the sixth side (11), to an exit of the light beam from the glass ring (1) via the sixth side (11).

2. The glass ring (1) as claimed in claim 1, characterized in that the glass ring (1) is configured such that, in the case of a circulation of light around the conductor (2) without any flow of current, the polarization of the light is substantially completely maintained.

3. The glass ring (1) as claimed in one of the preceding claims, characterized in that the glass body comprises a glass having a Verdet constant that is greater or smaller than zero and / or consists of a glass having a Verdet constant that is greater or smaller than zero.

4. A method for optically measuring currents with a glass ring (1) as claimed in one of the preceding claims, characterized in that a flow of current (3) in an electrical conductor (2) generates an electromagnetic field around the conductor (2), via which the polarization of a light beam in the glass ring (1), which is arranged around the conductor (2), in particular with a plane perpendicular to the longitudinal axis of the conductor, is changed during a circulation of the light beam around the conductor (2).

5. The method as claimed in claim 4, characterized in that, during a circulation around the conductor (2), the light beam travels through a monolithic glass body, wherein changes in directions of the light beam are realized via reflection at external sides of the glass body, in particular at a third partial surface (7") of the second side (7) that is tilted, in particular through an angle of 2 degrees, with respect to a second (7') partial surface of the second side (7).

6. The method as claimed in either of claims 4 and 5, characterized in that the light enters the glass body through the light entry surface (4) and exits the glass body at the light exit surface (5), and / or the light enters the glass body in particular via the third side (8) of the glass ring (1), in particular via two adjacent partial surfaces tilted by an angle with respect to one another and / or exits the glass body on the sixth side (11) of the glass ring (1), in particular at an angle of substantially 90 degrees relative to the entering light.