Optical Voltage Sensor Research Articles

Open-loop optimization method based on the GRU and dual-grating demodulation principle for a PZT based optical voltage sensor

Distributed online monitoring of grid voltage is crucial for ensuring power quality, providing a foundational data layer for effective grid management. Piezoelectric grating optical voltage sensing presents a cost-effective solution with high bandwidth and long-distance transmission capabilities. This paper introduces an open-loop optimization approach that leverages the gate recurrent unit (GRU) and dual-grating demodulation principles to enhance the real-time response accuracy and extend the measurement range of piezoelectric-based optical voltage sensors. Experiments conducted within a 2.8 kV sensing range analyze the voltage response and spectral characteristics. After applying corrections, the sensor achieves a linearity of 99.93%, with a maximum deviation of 2.07% and a maximum hysteresis of 3.33%. This method significantly enhances real-time response accuracy and optimizes the utilization of the sensor’s nonlinear measurement range, advancing the application of optical voltage sensors in power grids.

Half-wave voltage controllable optical voltage sensor with arbitrary electric field direction modulation*

Abstract An optical voltage sensor with an arbitrary electric field direction modulation (AEFDM) mode is proposed to increase the half-wave voltage. The mode is realized by heterogeneous electrodes arranged in a center-symmetric way, and generates an electric field with a direction at an arbitrary angle to the light propagation direction. The finite element method and coupling wave theory are used to design and optimize the electrodes and field distribution. The experimental results show that heterogeneous electrodes and AEFDM mode are able to regulate the sensor’s half-wave voltage in a range from 1 to 30 times (47–1409 kV), with 0.5 class accuracy and 99.99% linearity. This novel AEFDM method proposes a new electrode shape and position, reducing temperature drift to 50% compared to solid-state voltage divider method.

Real-time monitoring method for power system voltage based on optical voltage sensors

Abstract A real-time monitoring method for power system voltage based on optical voltage sensors is proposed to obtain transient voltage signals and achieve real-time tracking of instantaneous changes in electrical parameters of the power system accurately and effectively. Analyzing the topology principle of power system transformers clarifies the installation location of optical voltage sensors. By combining the measurement principle of optical voltage sensors, the electrical, optical modulation, and optical-electrical conversion of voltage signals are achieved, and the voltage signal of the power system is output. Using the short-time Fourier transform method to perform temporal processing on the output signal and obtaining a voltage signal sliding window based on wavelet packet decomposition, we set the normal range threshold of the voltage signal in the sliding window, combined with information entropy theory to extract key features of the voltage signal and achieve real-time monitoring of the power system voltage. The experimental results show that the proposed method can effectively obtain transient voltage signals of the power system, with an average detection accuracy of 92.61%, and the output voltage can be adjusted promptly to reflect the instantaneous changes in the power system voltage.

Effect of device coupling mode on output characteristics in piezoelectric grating voltage sensor

Sensor networks provide a physical foundation for distributed data acquisition. Monitoring voltage signals at nodes allows real-time assessment of grid operation. Piezoelectric grating voltage sensors offer advantages of smaller size, lower cost, strong electromagnetic shielding, and easy network integration, appropriating for intelligent voltage sensing. This study investigates the relationship between device coupling mode and output characteristics of these sensors to improve their performance and advance sensor network applications. Using solid mechanics theory, a device coupling mechanical model is established for a temperature-independent piezoelectric grating voltage sensor employing dual-grating spectral overlay demodulation. Then, a flexible structure with variable stiffness is designed to couple the PZT and FBG. Results show linear voltage sensing in the range of 0–6 kV and 0–1500 N using the flexible coupling structure, with a reduction of spectral shift by 50.86–87.82% through structural design. This research provides insights for enhancing sensor performance and improving the application of optical voltage sensors.

Analysis of the Influence of Incident Light Polarization on Measurement Accuracy for RPOVS

Nowadays, the optical voltage sensor (OVS) has become the best practical solution for the high voltage measurement in modern smart grid. And the polarization of the incident light greatly influences the sensor's measurement accuracy. In this paper, taking the radial polarization optical voltage sensor (RPOVS) as an example, its practical optical model is established by using the theory of polarized optics. The formula of the measurement relative error is obtained, and the influences of the ellipticity and extinction ratio on sensor performance are analyzed in detail. Then the suggestions are given and verified by simulations and experiments, which show the measurement error brought by the polarizer parameters to RPOVS is reduced by about 0.2%, promoting the sensor's realization of 0.2 accuracy class from the aspect of optical path. In addition, this study has certain reference value for other types of OVS and optical polarization measurement. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Fiber Optic Voltage Sensor Based on Capacitance Current Measurement With Temperature and Wavelength Error Correction Capability

Traditional optical voltage transformers (OVTs) based on electro-optical and inverse piezoelectric effects are gradually exposing their accuracy and reliability issues. In contrast, fibers for measuring electricity have unique properties and significant advantages in the high-voltage power industry, especially fiber optic current sensor (FOCS), which has been widely used in the field of high-voltage measurement. As a result, a novel fiber optical voltage sensor (FOVS) is proposed, which uses FOCS to measure the current flowing through the capacitive voltage divider (CVD) and then calculates the primary voltage proportional to it. In order to solve the inherent temperature- and wavelength -dependent errors and achieve high accuracy, a novel closed-loop signal processing method, which aims to minimize the influence of temperature-sensitive components such as CVD, quarter waveplate, and sensing fiber on the measurement accuracy of the system, is presented. A 110-kV FOVS prototype with a rated voltage of 110/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$({3})^{1/2}$ </tex-math></inline-formula> kV and a rated frequency of 50 Hz is developed and tested. The results show that after temperature and wavelength correction, the accuracy reaches the metering class of 0.2% and protection class of 3P specified in GB/T20840.7-2007

An optical fiber voltage sensor based on self-mixing interference

An optical voltage sensor based on self-mixing interference (SMI) and on the converse piezoelectric effect of a piezoelectric ceramic (PZT) is proposed and demonstrated. A single-mode fiber is coiled around the PZT, and when an AC voltage is applied, the deformation of the PZT modulates the phase of the light propagation in the fiber. Light reflected at the fiber end back into the laser cavity forms SMI, and the voltage is obtained by demodulating the output signal with the reverse point recognition algorithm. Experimental results show that the sensor has good linearity, and the scheme has a relative error of ±2 %, which meets the standard IEC 60044-7.

Design of Novel Resonant Optical Voltage Sensor Based on Pockels Effect

A novel resonant optical voltage sensing scheme based on Pockels effect with less optical elements is proposed to pave the way for the miniaturization of voltage sensors in a high-voltage power grid, which can improve the voltage detection accuracy by using the multiple propagation of light in the resonator composed of Bi4Ge3O12 (BGO) crystal and reflector. Based on the multiple beam interference theory, the optical sensing model is analyzed to explore the influence of the key parameters such as the propagation loss and the resonator reflectivity on the performance of resonant optical voltage sensor. Considering the propagation loss and reflectivity, a resonator is designed to promote the limit sensitivity of the resonant optical voltage sensor. Also, based on the theoretical analysis results, we obtained that the design parameters (propagation loss <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> and reflectivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${r}$ </tex-math></inline-formula> ) of the resonator are, respectively, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \le0.5$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${r} \ge0.83$ </tex-math></inline-formula> . Finally, the experimental equipment of the novel resonant optical voltage sensor is built, and the measured resonator finesse shows that the limit sensitivity of the resonant optical voltage sensor can achieve <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.689\times 10^{-{5}}$ </tex-math></inline-formula> V. Furthermore, the experimental results of the resonant optical voltage sensor demonstrate that the resonant frequency of the resonator is linear with the applied voltage. The proposed resonant sensing scheme has the potential to lay the foundation for the miniaturization of high-precision optical voltage sensors in the future.

Construction and Evaluation of an Optical Medium Voltage Transducer Module Aimed at a 132 kV Optical Voltage Sensor for WAMPAC Systems.

This paper reports on the construction and characterization of an optical voltage transducer module for applications in the field of wide-area monitoring, protection, and control (WAMPAC). The optical medium voltage transducer (MVT) module was designed to be combined with a capacitive voltage divider (CVD) to form a voltage sensor intended for 132 kV high voltage (HV) networks. The MVT module comprises a combination of a piezoelectric transducer (PZT) and a fiber Bragg grating (FBG) as a core optical sensing element. Changes in the input voltage across the PZT translate into strain being detected by the FBG. The resultant FBG peak wavelength can be calibrated in terms of the input voltage to obtain a precise voltage measurement. The module was experimentally evaluated in the laboratory, and its performance was assessed based on the requirements specified by the IEC standards for electronic voltage transformers and low power voltage transformers. The results of accuracy tests demonstrate that the MVT module is free from hysteresis, within the experimental error, and is capable of simultaneously meeting the requirements for 0.1 metering and 1P protection classes specified by the IEC 60044-7 and IEC 61869-11 standards.

Identification of Railway Power Supply Voltage Sag Source Using Optical Fiber Voltage Sensor

With the construction of the smart grid and the continuous improvement of voltage levels, the traditional voltage sensor can no longer meet the development needs of the modern power system. There is an urgent need for a new high-quality voltage sensor to replace it. Aiming at the problems of complex structure, difficult adjustment, poor temperature stability, large optical power loss and inconvenient voltage introduction of the existing optical fiber voltage sensor, an optical fiber voltage sensor based on full polarization state detection without polarizer and analyzer is proposed. The sensor only contains three main components: Grin Lens, BGO crystal and total reflection mirror. It has few devices, simple structure and easy alignment. Moreover, the polarization state evolution and high voltage on the transmission line of Pockels effect of BGO crystal are analyzed. The voltage sag simulation model of the electrified railway is established. The sample data of different disturbance sources are obtained with the assistance of the designed optical fiber voltage sensor. S-transformation and Radial Basis Function (RBF) neural networks are introduced and combined with the prototype of electrified railway power quality detection and analysis device to identify voltage sag sources. The designed optical fiber voltage sensor is suspended. There is no electrode or grounding on the sensor, which saves expensive insulators and increases the sensor’s measuring range. The sensor has a good linear relationship in the power frequency AC voltage range of 0~10 kV at room temperature. It is proved that the design is effective. The working condition analysis of the actual railway power supply reveals that it can detect the voltage sag amplitude and disturbance time, and identify the type of voltage sag disturbance source.

Optical voltage sensor based on a piezoelectric thin film for grid applications.

Continuous monitoring of voltages ranging from tens to hundreds of kV over environmental conditions, such as temperature, is of great interest in power grid applications. This is typically done via instrument transformers. These transformers, although accurate and robust to environmental conditions, are bulky and expensive, limiting their use in microgrids and distributed sensing applications. Here, we present a millimeter-sized optical voltage sensor based on piezoelectric aluminum nitride (AlN) thin film for continuous measurements of AC voltages <350kVrms (via capacitive division) that avoids the drawbacks of existing voltage-sensing transformers. This sensor operated with 110μW incident optical power from a low-cost LED achieved a resolution of 170mVrms in a 5kHz bandwidth, 0.04% second harmonic distortion, and a gain deviation of +/-0.2% over the temperature range of ~20-60°C. The sensor has a breakdown voltage of 100V, and its lifetime can meet or exceed that of instrument transformers when operated at voltages <70kVrms with capacitive division. We believe that our sensor has the potential to reduce the cost of grid monitoring, providing a path towards more distributed sensing and control of the grid.

Low error of garnet optical sensor induced by spin Hall effect

The Polarization properties of a linearly polarized laser beam reflected from garnet/Au, Ta/Nd2Fe14B/Ta/garnet/Au are studied by a Thorlabs PAX 5710 IR3 polarimeter undser external magnetic and direct current (DC) electric fields. The Nd2Fe14B, Ta and Au films are prepared by a DC magnetron sputtering method. The magnetic domains of the garnet films are obtained by a polarized light microscope. The magnetic domains in different garnet films show different distributions. The error of the Stokes parameter S1 is used to characterize the results. The S1 of the linearly polarized laser beam reflected from garnet/Au and Ta/Nd2Fe14B/Ta/garnet/Au shows different trends with the magnetic and electric fields. The maximum error S1 of garnet/Au is 0.005%, while the maximum error S1 of Ta/Nd2Fe14B/Ta/garnet/Au is 0.003%, when the external DC voltage increases from 0 to 2.5V, and the magnetic field increases from 0 to 100Oe. The low error may be induced by the spin Hall effect of garnet and Au. It is very important for the manufacture and design of optical current and voltage sensors.

Opto-mechanical modeling and experimental implementation of an FBG-based piezoelectric bimorph actuator for high voltage sensing applications

This paper proposes a highly simplified optical voltage sensor by using a piezoelectric bimorph and a Fiber Bragg Grating (FBG) that can be used for high voltage applications with a relatively good accuracy and stability. In this work the theoretical framework for the whole opto-mechanical operation of the optical sensor is detailed and compared to experimental results. In the analysis, a correction term to the electric field is derived to account for the linear strain distribution across the piezoelectric layer improving the designing equations and giving more criteria for future developments. Finally, some experimental results from a laboratory scale optical-based high voltage sensing setup are discussed, and shown to be in excellent agreement with theoretical expected behavior for different voltage magnitudes.

Vibration Characteristics of Quartz Crystal and Analysis of System Error in Fiber Optic Voltage Sensor

The additional deformation of the quartz crystal under the vibration stress disturbance greatly affects the measurement accuracy of the fiber optic voltage sensor. In this paper, the influence of different vibration directions on quartz crystal deformation is analyzed by the finite element method based on the analysis and derivation of the system error mathematical model of the quasi-reciprocal reflected fiber optic voltage sensor. Furthermore, the effect of additional quartz crystal deformation on the output precision of the system is calculated. The results show that the vibration stress along the axial direction mainly causes the quartz crystal to deform in height, and the vibration stress along the radial direction mainly causes the quartz crystal to deform the circumference. Among them, the deformation of the crystal radial circumference is the main reason to influence the system output accuracy. In addition, the size and deformation parameters of the quartz crystal are related to the output error of the sensor system. This paper provides the parameter optimization and design guidance for improving the anti-mechanical vibration performance of the sensor head of the fiber optic voltage sensor and provides a theoretical basis for the suppression method of the system error.

Optical Phase Detection Method for Measurements and Calibration of Pockels Cell-Based Sensors

Nowadays, the most successful optical technique developed for measuring high voltages in 50-/60-Hz electric power lines utilizes the bulk lithium niobate Pockels cell, constituting the so-called optical voltage sensor (OVS). However, unlike the area of vibrometry, where there are ISO standards based on reliable and simple interferometric methods for calibrating the sensors, there is still no standardized procedure for measuring Vπ (half-wave voltage) of Pockels cells or for calibrating OVSs. As the Pockels cell-based OVSs can be considered as a polarimetric interferometer, and inspired by the ISO 16063-41 standard (for the calibration of vibration and shock transducers), specifically the technique called signal coincidence method (SCM), this work presents a new digital and real-time method for optical phase detection tailored for the measurement of Vπ in OVSs. Measurements were made in order to demonstrate the effectiveness of the new technique by applying a voltage signal to the OVS, composed by the superposition of a 60-Hz sinusoidal voltage, with amplitude equal to the reference value of Vπ (4.068 kV in this case) and a dc voltage high enough to provide a 90° bias static phase shift, as specified by SCM, proving that the method can recover the value of Vπ in accordance with the estimated value. However, it is well known that the adjustment of the bias phase in a polarimetric interferometer can undergo undesired variations from time to time, due to drifts in ambient temperature and other external disturbances, taking the OVS out of its optimal operating point and thus not attending the ISO standard. As an advantage, experiments have shown that the new method is tolerant to variations in the 90° bias static phase (ranging from 60° to 120°), as well as to variations in the amplitude of the voltage applied to the OVS, varying ±25% in relation to the 4.068-kV reference voltage. The Vπ values were accurately detected, with a maximum percentage error of 0.2% and, therefore, satisfying the specification of the ISO 16063 standard.

Simulation and Research of Light Path Optical Wave Field of Optical Voltage Sensor Based on Pockels Effect

This paper introduces the development status of optical voltage sensor based on Pockels effect at home and abroad. A research scheme of optical voltage sensor with optical path reciprocity is proposed and its reciprocity mechanism is expounded. Comsol Multiphysics, a multi-physical field coupling simulation software, is used to simulate the fluctuation of the transmission of incident polarized light in the electro-optic crystal, thus realizing the three-dimensional fluctuation simulation of the light wave field, which provides a new research idea and theoretical reference for analyzing and designing the optical path component unit of the optical voltage sensor.

Research on Thermal Stress Birefringence of Longitudinal Modulated OVS

Thermal stress birefringence is a key factor affecting the stability of optical voltage sensors. The study of thermal stress birefringence is of great significance for the development of optical voltage sensors. In this regard, this article first analyzes the thermal stress birefringence theory systematically based on the theory. Then, by adopting finite element method, ANSYS software is used to establish a model of the longitudinal modulation optical voltage sensor, and the thermal stress in the BGO crystal is simulated and analyzed. Finally, the distribution and change law of stress birefringence in crystal are obtained by combining theory and simulation. The results show that the average linear birefringence on the central clear path is 4.8004×10−7, and the resulting phase delay is 0.0476 (2.7273deg). When the clear path is off-center, the birefringence will increase, and increasing the spot size also increase the birefringence.

Near-Infrared Voltage Nanosensors Enable Real-Time Imaging of Neuronal Activities in Mice and Zebrafish.

Optical voltage sensors with the ability to monitor neuronal activities are invaluable tools for studying information processing of the brain. However, the current genetically encoded voltage indicators usually require high-power visible light for excitation and are limited to genetically addressable model animals. Here, we report a near-infrared (NIR)-excited nongenetic voltage nanosensor that achieves stable recording of neuronal membrane potential in intact animals. The nanosensor is composed of a Förster resonance energy transfer (FRET) pair, the outer membrane-anchored upconversion nanoparticle (UCNP), and the membrane-embedded dipicrylamine (DPA). The negative charge of DPA allows membrane potential fluctuation to affect the distance between the DPA and UCNP, therefore changing the FRET efficiency. Consequently, the emission intensity of the nanosensor can report the membrane potential. Using the nanosensor, we monitor not only electrically evoked changes in the membrane potential of cultured cells but also sensory responses of neurons in intact zebrafish and brain state-modulated subthreshold activities of cortical neurons in intact mice.

Analysis and suppression of nonreciprocal phase shift error of the optical voltage sensor based on the converse piezoelectric effect

Abstract In the reflected all-optical voltage sensor (RAOVS) based on the converse piezoelectric effect, the influence of ambient temperature on the system output cannot be ignored when the length of sensing fiber and compensating fiber is asymmetric. In this study, the nonreciprocal error model of the RAOVS due to the asymmetric fiber length is originally established, according to the polarization optics theory. Then, the influence of temperature fluctuation and asymmetric fiber length on the output error is investigated with the condition of different voltage levels. Finally, a method for suppressing the nonreciprocal error is presented from the sensing fiber performance. Results show that the increase of nonreciprocal phase shift is proportional to the asymmetric fiber length and it is hardly avoided in the assembly process. And the magnitude of nonreciprocal error is influenced by ambient temperature fluctuation. Interestingly, the nonreciprocal error can be reduced by ~75 times with employing polarization-maintaining photonic crystal fiber (PM-PCF) as sensing fiber. This study can provide a theoretical basis for suppressing the nonreciprocal phase shift error of RAOVS in practically.

Concept of control and data acquisition system for modern digital power substation

The article deals with the issue of standardization of approach to definition of modern digital substation is considered. The approaches proposed and partially implemented by equipment manufacturers are described, such as data collection and processing by means of relay protection and automation with the use of proprietary algorithms, wireless and optical current and voltage sensors, etc. The authors propose the use of a unified system for collecting and processing data generated and used in the operation of an electric substation. The structure of the signal transmission system for the main groups of electrical power equipment is described, the requirements for the predictive diagnostics system that allows maintaining the equipment based on its technical condition are described.