Devices and methods for electro-optic double crystal voltage sensors

Abstract

An optical voltage measurement system may include a pick-off rod, a thread, and optical components. The pick-off rod is electrically connected to a power line and configured to generate an electric field proportional to the energy of the power line. The thread can align and maintain the optical components in a predetermined orientation relative to the pick-off rod. The optical components may include a double RTP crystal assembly.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority from U.S. Provisional Application No. 63 / 498,769, filed on April 27, 2023, the entire disclosure of which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to the technical field of optical components. More particularly, the technology relates to an assembly for aligning and constructing high - precision optical sensors based on the Pockels effect for detecting and measuring electric fields and voltages in utility high - voltage power lines and distribution networks.

Background Art

[0003] The ability to detect electric fields is important in several industries. In the utility industry, for example, the detection of electric fields is necessary for measuring voltage potentials and currents. In addition to measuring electrical properties, the detection of electric fields is important in important industrial deployments where ensuring that the power supply of a system is turned off is for safety. In such environments, it is not always important that the absolute value of the electric field (e.g., voltage) is measured, but only that the presence of the electric field is accurately detected.

[0004] Electric field detection is most important in the electric utility industry, and voltages and currents must be monitored at the source, transmission grid, distribution grid, and final electrical circuits. Detecting and measuring electric fields at these locations is of utmost importance in ensuring that electricity is transmitted through the grid to end - users at the correct voltage. In addition to measuring electric fields for the delivery of electricity, there is a need within the utility industry to detect electric fields in harsh climate and weather conditions. In such conditions, the environment or air temperature can vary greatly.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Historically, medium voltage measurements in distribution substations have been achieved using iron-core ferromagnetic instrument transformers. However, such techniques still disrupt the electromagnetic field (EMF) inherently associated with medium voltage transmission measurements, actively interfering with the voltage to be determined and thereby indirectly impairing the voltage measurement. These conventional measuring devices have also been associated with risks and hazards of arc discharge, flash, partial discharge, explosion, and catastrophic failure. [Means for solving the problem]

[0006] The embodiment may include an optical voltage measurement system. The system may include a pick-off rod, a thread, and optical components. The pick-off rod is electrically connected to a power line and configured to produce an electric field proportional to the energy of the power line. The thread can align and maintain the optical components in a predetermined orientation relative to the pick-off rod. The optical components may include a double RTP crystal assembly.

[0007] Embodiments may include a ground cage. The ground cage is configured to increase the intensity of the electric field generated from the pick-off rod at the location of the optical component. The distal end of the pick-off rod (i.e., the end opposite to the end connected to the power line) can be hemispherical.

[0008] In embodiments, the thread may include a ceramic thread body having a central chamber for holding optical components. The thread may be made of alicyclic epoxy. The thread may include an input port for receiving light rays and an output port for transmitting light rays. The input and output ports may be collinear along the light ray path. A thread cover is configured to mate with the ceramic thread body and / or seal the central chamber. The central chamber may have a flat surface parallel to the light ray path.

[0009] In another embodiment, the double RTP crystal assembly may include a first crystal aligned along the ray path, a quarter-wave plate aligned along the ray path, a second crystal aligned along the ray path, and / or a half-wave plate aligned along the ray path.

[0010] Another embodiment may include a line post insulator. The insulator may be a hollow barrel having a cavity. A ground cage is configured within the cavity to increase the electric field intensity from the pick-off rod affecting and through the optical components. The ground cage may be a metal liner positioned in the inner portion of the line post insulator. The line post insulator is configured to provide environmental protection to the thread.

[0011] The embodiment may include optical fibers for carrying light to and / or from optical components positioned within the thread.

[0012] Another embodiment may include an optical detector. The detector may be, for example, a photodiode. The optical component is configured to physically sense voltage and / or electric field. For example, light from an external optical fiber may change its characteristics as it passes through the optical component based on the voltage and / or electric field detected by the optical component. The optical detector can detect the change resulting from the characteristics and output a signal correlated with the change in characteristics. The output signal may be received by, for example, an analog-to-digital converter, which can output the digital signal to a processor or digital signal processor, which can provide measurement data.

[0013] The present invention will be further described in the following detailed description with reference to several drawings shown as non-limiting examples of specific embodiments of the invention, in which similar numbers throughout several figures of the drawings represent similar elements. [Brief explanation of the drawing]

[0014] [Figure 1] This is an isometrically reconstructed assembly diagram of an opticmechanical ceramic thread having optical components including an RTP crystal, an optical waveplate, and a polarizing collimator. [Figure 2] This is a front view of the ceramic thread body. [Figure 3] This is an isometric view of the ceramic thread body. [Figure 4] These are isometric and assembly diagrams of a ceramic thread having optical components. [Figure 5] This is a simulation diagram of the optical components drawn within the electric field generated from the pick-off rod inside the sensor body. [Figure 6] This is a diagram of idealized electric field lines incident on optical components contained within an opticmechanical ceramic thread assembly in the base of a line-hanging voltage sensor body. [Figure 7a] This is a diagram of the line-hanging sensor body clamped to a high-voltage power line. [Figure 7b] This diagram shows a cross-section of the line-hanging sensor body and the optical-mechanical ceramic thread assembly contained inside. [Modes for carrying out the invention]

[0015] A detailed description of the apparatus, systems, methods, and exemplary embodiments of the present invention is provided below. Numerous specific details are described to provide a complete understanding of the embodiments of the present invention. Nevertheless, embodiments of the present invention will be understood by those skilled in the art to be practiced without these specific details. In other examples, well-known methods, procedures, and components are not described in detail so as not to obscure the invention. The exemplary embodiments described, shown, and / or disclosed herein are not intended to limit the claims in any way, but rather to teach those skilled in the art about various aspects of the present invention. Other embodiments can be practiced and / or implemented without departing from the scope and spirit of the present invention.

[0016] Due to the inherent challenges of electromagnetic voltage measurement technology, optical sensors are used for medium and high voltage environments as well as for low voltage applications. Such sensors are unaffected by electromagnetic and radio frequency interference and have no inductive or galvanic coupling between the sensor head on high-voltage lines and the electronic equipment of the transmission substation. The wide bandwidth of optical sensors can provide high-speed fault and transient current detection as well as power quality monitoring and protection. Optical sensors can be easily installed or integrated into existing substation infrastructure and equipment such as circuit breakers, insulators, or bushings, resulting in significant space savings and reduced installation costs, with no environmental impact.

[0017] Optical voltage sensors utilize the Pockels effect, also known as the linear electro-optic effect, and may include a polarizer at the input and a beam splitter at the output. Traditionally, such devices can function well at constant temperatures. Nevertheless, significant temperature, humidity, and environmental weather changes can affect the accuracy of these devices. Therefore, environmental stability, depending on the temperature and humidity of the environment surrounding the optical system or assembly, can affect the reliability of these optical voltage sensors, particularly in terms of sensitivity.

[0018] Before and without introducing light into a system associated with the functional use of an optical assembly, passive optical and optomechanical alignment techniques are used to align a series of small and miniaturized optical components, such as optical fibers, lenses and collimators, and crystal elements. Using passive alignment methods can significantly reduce manufacturing time and cost by avoiding the complex procedures required for power supply or introduction of light and monitoring of light output or signals for the functional use of the optical assembly in actively aligned methods or systems. Moreover, in such a hybrid optical element system including crystal and polarization directions of light involving projections onto crystal axes and planes, the passive optical alignment method for fixing and firmly fixing the optical elements in the optomechanical assembly is essential to ensure the functional performance of the optical assembly with respect to the temperature when actively powered. Such thermal performance is achieved only when the optical elements are fixed and firmly fixed at a given starting temperature (e.g., room temperature) and then do not subsequently move or change their position and orientation with respect to the crystal optical axis and the beam direction of light.

[0019] Using conventional transformer-based methods to detect and measure the high voltage of a power supply also requires challenging trade-offs and compromises against the physical size and installation limits that generally must optimize important safety limit scale attributes, such as creepage, clearance distances, and the basic insulation level (BIL).

[0020] Optical voltage sensors can minimize and eliminate the problems associated with traditional transformer-based voltage sensors. Optical voltage sensors based on the Pockels effect can also be used with electro-optic crystals for the purpose of achieving stability against temperature and related environmental conditions. This advantageous configuration is achieved by utilizing a double crystal that cancels out the additional doubly refractive Pockels effect by the precise orientation of the crystal axis with respect to the optical axis of the crystal and the direction of light propagation. An example of such an optical assembly is described in U.S. Provisional Patent Application No. 63 / 338,223 (''Reference 1''), which is incorporated herein by reference in its entirety.

[0021] Optomechanical mounting and sealing techniques are advantageously utilized to provide stable performance over operating temperature and environmental conditions. Such hermetic type sealing further prevents the ingress of moisture, water condensation, and other harmful contaminants that can affect sensitive polarization-based optical performance.

[0022] Optical voltage sensors can utilize complex polarization diversity schemes with various optical components dedicated to phase and rotational polarization manipulation. Typically, such polarization components such as waveplates, retarders, and beam splitters are fragile and vary greatly with temperature and environmental conditions, which can change the phase of the optical beam and the resulting signal.

[0023] FIG. 1 illustrates an optomechanical diagram of an exemplary optical electric field sensor assembly (100). The input fiber-coupled polarization collimator (101) can define a light propagation path that is incident on the first crystal (102) and further passes through the second crystal (103). The output polarization collimator (104) acts as an analyzer after the second crystal (103) receives light and is coupled to the output fiber.

[0024] The input polarization, as set by the input polarizer (101), and the output polarization, as analyzed by the output polarizer (104), are optimally oriented with respect to the crystal axis, as described in Reference 1. The input polarizer (101) and output polarizer (104) used in this illustrative embodiment as a polarizing collimator (i.e., polarizers coupled to a collimator lens) are described in U.S. Patent No. 10,175,425 ("Reference 2"), which is incorporated herein by reference as a whole. As those skilled in the art will recognize, alternative embodiments are possible, and other types of polarizer and collimator combinations are used in other examples, achieving substantially similar functions without loss of generality and without departing from the spirit of the invention. For example, the device may include optical fibers, fiber ferrules, collimating lenses, polarizer elements, and housings. The device may include other types and numbers of elements or components in other configurations, including, but only as an example, additional optical systems such as lenses, prisms, or filters. For example, additional optical systems are used to redirect, focus, collimate, or filter the wavelength of light within the device.

[0025] The temperature dependence of the Pockels effect in the first and second crystals 102 and 103 is substantially linear. Nevertheless, the temperature dependence is obscured by birefringence in the first and second crystals (102, 103) due to the change induced by the coefficient of thermal expansion (CTE) and the associated temperature-dependent stress.

[0026] The combined optical phases of polarized light in the direction of propagation through the first and second crystals (102 and 103, respectively) are generally given by Γ = β + φ, where β is the birefringence phase and φ is the Pockels effect phase. The technique described and illustrated herein as an example conveniently eliminates the temperature-dependent birefringence phase β by orienting the crystal axis such that the accumulation of the Pockels effect phase φ of the crystal is additive and the birefringence phase is subtractive, as described in detail in Reference 1.

[0027] The first and second crystals (102, 103) can conveniently contain rubidium titanyl phosphate (RbTiOPO4) (RTP).

[0028] In a preferred embodiment (100), the ceramic thread holder (105) can hold and align a series of optical components for use, for example, in a laser system. The ceramic thread body is designed to securely hold and align RTP crystals (102, 103) and waveplates (106, 107) to manage the polarization diversity and optical phase of light propagation. The ceramic thread body is made from a high-strength ceramic material that is both durable and resistant to thermal stress. The ceramic material is selected to have a low coefficient of thermal expansion that can ensure the thread body maintains its shape and alignment even when subjected to temperature changes.

[0029] In the embodiment shown in Figure 1, the components of the embodiment are assembled directly on the ceramic thread body. Each RTP crystal and waveplate may have a small air gap between them and their neighboring optical components extending along the optical axis. The air gap can reduce thermal stress on the RTP crystal and waveplate by allowing thermal expansion and contraction without contact with neighboring optical components. The air gap can accommodate slight differences in the dimensions of the RTP crystal and / or waveplate.

[0030] The RTP crystal (102, 103) is a matched pair with an optical crystal axis aligned with the direction of light propagation. In this preferred embodiment, the crystal dimensions are 10 mm × 4 mm × 5.3 mm, and light propagation is along the 5.3 mm axis. Waveplates are included in the assembly to control the polarization diversity and orientation of the crystal toward the electric field, so that the Pockels optical phase sensing the electric field across the crystal and the associated voltage drop across both ends of the crystal is maximized. The RTP crystal is conveniently coated with metal along the surface defining the voltage effect, as depicted in Reference 1, to further maximize the optical phase sensing of the electric field spreading across the RTP crystal (102, 103) and the associated voltage drop across both ends of the crystal.

[0031] The ceramic thread body may further include a probe (108) and / or other sensing devices for measuring temperature. The probe can be optical fiber based. As will be understood by those skilled in the art, several types and configurations of optical fibers and waveguides are available, depending on the application and wavelength range of interest of the light. Examples include index-guiding glass, ceramic, or plastic fibers with a core and cladding. Stepped, continuous, or multi-refractive index cladding is used for optical fibers. Furthermore, glass, ceramic, plastic, and metal hollow core fibers, photonic bandgap, or photonic crystal fibers are used as part of optical fibers. Optical fibers can include single-mode optical fibers, but multimode fibers are also employed. According to one example, the use of multimode fibers for optical fibers can allow multiple modes of light to propagate within the optical fiber. This can allow for the selection of substantially random or partially polarized light, and its conversion to linearly polarized light.

[0032] The ceramic thread body (105) is sealed by a thread cover (109). The thread cover may be, for example, ceramic and / or resin. The body and cover are semi-bonded and / or fitted together via bolts. A gasket (not shown) is used to maintain an airtight seal. A sleeve (110) is used to cover the thread body and thread cover. The sleeve is semi-bonded to the body and cover.

[0033] Figure 2 depicts a front view of an illustrative embodiment of an opened thread holder (200). The engraved surface (201) shown in the image represents a flat surface extending parallel to the optical axis of the crystal axis and the direction of light and through the waveplate. All optical components are adhered to a shaded surface which can serve as passive alignment data for the optical components. The crystal may have its respective optical axis aligned to an angular displacement of preferably 10 mins or less. The adhesion accuracy of the rectangular optical components to the ceramic thread surface parallel to the direction of light propagation and the optical axis of the crystal can ensure that the beam passes through the optical surface almost perfectly perpendicularly.

[0034] Figure 3 illustrates an isometric view of the thread body (300). The shaded surface (301) illustrates a collimator holder machined using a single drilling method. By using one drilling method for the collimator bore, the optical axes of both bores are made collinear. The shaded surface shown in the image represents a flat surface extending parallel to the optical axis of the crystal and the direction of light. Optical components such as the crystal, waveplate, and collimator are mounted using ultraviolet (UV) curing adhesive. The optical components are cut to precise dimensions to ensure that their non-optical surfaces are within 10 minutes perpendicular to the optical surfaces. Precision is important to ensure passive alignment to avoid variations or tolerance deviations due to, for example, thermal or environmental deviations.

[0035] Figure 4 illustrates isometric exploded view (400) and assembled view (401) of a ceramic thread with optical components. This figure shows all the optical components assembled within the ceramic thread, with the RTP crystal and waveplate attached to the shaded surface using UV-reactive adhesive. The collimator is inserted into a machined collimator holder within the ceramic thread body.

[0036] While the above discussion primarily focuses on preferred ceramic thread bodies, other materials such as metals or plastics can be utilized. Nevertheless, it is important to note that the material used for the thread body should possess sufficient thermal stability and rigidity to ensure the precise alignment of the optical components. Furthermore, while RTP crystals and waveplates are specifically discussed, other types of optical components such as lenses, prisms, or mirrors can be used instead. The specific selection of optical components will depend on the particular application and the desired performance characteristics.

[0037] Regarding the assembly of optical components to the thread body, alternative mounting methods such as mechanical fasteners and / or thermal couplings are used instead of UV-reactive adhesives. The choice of mounting method will depend on the specific requirements of the application. There are several types of UV adhesives used to adhere optical components to the thread body. For example, acrylic UV adhesives have a fast curing time and form a strong bond that is resistant to shock and temperature changes. Epoxy UV adhesives have a longer curing time but form a strong and durable bond that can withstand high temperatures and harsh environments. Silicone UV adhesives have a flexible bond that absorbs stress and vibration, making them ideal for applications where the thread and optical components will be exposed to movement or mechanical stress. Polyurethane UV adhesives are strong and durable adhesives that are resistant to shock and temperature changes, making them suitable for applications with uneven terrain. Cyanoacrylate UV adhesives have a fast curing time and form a strong bond that is resistant to shock and temperature changes. The specific type of UV adhesive to be chosen will depend on the specific requirements of the application, such as curing time, bond strength, temperature resistance, and flexibility.

[0038] Furthermore, the shape and size of the thread body and optical components are modified to suit different applications. For example, the thread body is made larger or smaller to accommodate different numbers or sizes of optical components. Similarly, the shape and size of the optical components themselves are modified to achieve specific optical properties.

[0039] Coatings and / or surface treatments, such as anti-reflective coatings on optical components to improve optical throughput, or coatings on threads to modify or optimize thermal conductivity for an application, are applied to components and thread bodies to enhance performance characteristics. The specific choice of coating will depend on the desired performance characteristics and operating environment of the device. The dielectric constant or relative permittivity of materials, including ceramic threads, is also selected to optimize the electric field that affects and penetrates the RTP crystal of the optical component within the thread body, in order to maximize the sensitivity and determination of voltage on high-voltage distribution lines.

[0040] The opposite surface of the RTP crystal is oriented such that the normal to the surface has a projection perpendicular to the direction of light propagation through the crystal. Similarly, all lines existing within the plane of the surface have a projection parallel to the direction of light.

[0041] Figure 5 shows an electrodynamic simulation using Coulomb electrodynamic software of a drawn optical component in the electric field generated from the pick-off rod within the sensor body. The optical assembly and its constituent optical components (501) are shown near the end of the pick-off rod, which extends backward and is attached to a clamping mechanism for a high-voltage power line. Electric field strength and direction are shown as well as contour lines of equal potential. A ground cage (503) is advantageously used to concentrate the contour lines of potential and adjust them to maximize the electric field affecting and through the optical crystal element, thereby maximizing the voltage drop across the crystal surface perpendicular to the direction of light propagation.

[0042] Figure 6 shows a cross-section of an optical assembly contained within a ceramic thread (601) installed in a cavity (602) near a high-voltage pick-off rod (603) having an idealized potential line (604) formed by a ground cage. The idealized electric field line is incident on optical components and crystals contained within the opticmechanical ceramic thread assembly in the base portion of a line-hanging voltage sensor body, which is conveniently made of resin, plastic, ceramic, or other non-metallic material, for example, alicyclic epoxy in this embodiment. An optical fiber cable works for the tube from the outside of the sensor body through the base for light propagation to a launch polarizing collimator.

[0043] Here, the Pockels effect phase is determined by the time-varying voltage V(t) on the high-voltage power line being measured. The output polarizer collimator in the optical assembly is configured to resolve and superimpose polarization components that exhibit an optical phase difference. This produces light having an optical phase amplitude that will exhibit time-varying optical intensity modulation detected by a device or unit, such as a modular optical device or unit, or a remotely installed device or unit, such as U.S. Patent No. 10,623,099 ("Reference 3") incorporated herein by reference as a whole, on an electro-optical photodiode via an exit fiber optic cable.

[0044] The representation of light transmission through an optical voltage assembly due to the Pockels effect phase is expressed as a transverse Pockels cell modulator. With respect to the direction of light through a crystal that detects the electro-optic Pockels effect, as described in the optical assembly, the optical intensity in an exit polarization collimator, which functions as an optical analyzer, is given by the following equation: T=sin 2 (V / V π +φ) Here, V πV is a half-wavelength voltage, V is the voltage drop between the opposite surfaces of the RTP crystal to which the electric field is incident, and φ is an arbitrary phase factor calculated by an external optical telemetry device or unit in a time-varying optical modulation detection scheme.

[0045] The optical voltage assembly is connected by an optical fiber cable to one or more detectors (e.g., photodiodes) as part of an optical telemetry unit. In particular, the optical fiber light output, electro-optically detected using the optical telemetry unit (reference 2), is converted into an electrical signal to which sophisticated digital signal processing (DSP) algorithms are applied to improve accuracy.

[0046] Figure 7a shows the entire sensor body (700) attached to a high-voltage power line (701) using a clamp (702) that securely fastens the alicyclic sensor body to a base plate suspended below. Figure 7b shows a cross-section of the suspended sensor body with a pick-off rod having an attachment securely fastened to the base plate, and a hemispherical endpoint near the embedded optical voltage assembly in an exploded insert as shown in Figure 6. The hemispherical endpoint of the pick-off rod will therefore be at the same voltage and potential as the high-voltage power line and will act as a source of an electric field that affects and penetrates the optical voltage assembly, which includes a double electro-optic crystal.

[0047] Although the methods and devices described herein focus on line-hanging sensor embodiments, the sensor systems described herein are equally applicable without loss of generality to line posts, platforms, underground, and other similar sensors. As those skilled in the art will recognize, the sensor systems described herein are used in conjunction with a computer system to produce measurement data. For example, the sensor output is coupled to an analog detector such as a photodiode. The analog signal is converted by an analog-to-digital converter, etc. The resulting digital signal is fed to a processor or digital signal processor capable of providing digital measurement data for downstream practical use.

[0048] The above discussion is intended to illustrate the principles and various embodiments of the present invention. With full understanding of the above disclosure, numerous variations and modifications will become apparent to those skilled in the art. The following claims are intended to be construed to encompass all such variations and modifications.

Claims

1. An optical voltage measurement system: A pick-off rod electrically connected to a power line and configured to generate an electric field proportional to the energy of the power line; A thread for aligning and maintaining the optical components in a predetermined orientation relative to the pick-off rod; Includes, Here, the optical components include a double RTP crystal assembly, which is part of the optical voltage measurement system.

2. Furthermore, the optical voltage measurement system according to claim 1 includes a ground cage for increasing the electric field intensity affecting the optical components.

3. The thread includes a ceramic thread body having a central chamber for holding optical components, an input port for receiving light rays, and an output port for transmitting light rays; The optical voltage measurement system according to claim 1, wherein the input port and output port are on the same line along the optical ray path.

4. The optical voltage measuring system according to claim 3, further comprising a thread cover configured to engage with the ceramic thread body and to seal the central chamber.

5. The optical voltage measurement system according to claim 4, wherein the central chamber has a flat surface parallel to the light ray path.

6. The optical voltage measurement system according to claim 1, wherein the double RTP crystal assembly includes a first crystal aligned along the ray path, a quarter-wave plate aligned along the ray path, a second crystal aligned along the ray path, and a half-wave plate aligned along the ray path.

7. The optical voltage measurement system according to claim 1, wherein the thread comprises an alicyclic epoxy.

8. Furthermore, a line pole insulator having a cavity; The optical voltage measuring system according to claim 6, comprising a ground cage configured to increase the electric field intensity affecting the optical components, wherein the ground cage includes a metal liner positioned inside the linepost insulator.

9. Furthermore, the optical voltage measurement system according to claim 1 includes an optical fiber cable for transmitting light to the thread.

10. The optical voltage measuring system according to claim 1, wherein the pick-off rod has a distal end of a power line, and the distal end is hemispherical.

11. The optical voltage measuring system according to claim 8, wherein the line post insulator is configured to provide environmental protection to the thread.

12. Furthermore, it includes an optical detector; The optical components are configured to physically sense voltage and electric fields; The optical detector is configured to detect voltage and electric field. The optical voltage measurement system according to claim 3.

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