Optical Voltage Transformers Research Articles

Research on Traveling Wave Detection Performance Based on Optical Voltage Transformer

Traditional transformers cannot effectively transmit high-frequency traveling wave signals, which leads to the fact that traditional voltage transformers cannot fully reflect the panoramic information of fault traveling waves and ensure fault location accuracy. This paper mainly analyzes the working principle of optical voltage transformers. The Jones matrix models the optical path system and its optical components, and the output model of the optical path system is obtained. The principle of photoelectric signal conversion is analyzed. The test principle, experimental method, and data results are studied and analyzed by power frequency, withstand voltage, lightning impulse, and arc tests. The transmission effect of fault traveling wave signal is verified, which provides the theoretical and experimental basis for the fault location of the distribution network.

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

Optical Voltage Transformer Based on FBG-PZT for Power Quality Measurement.

Optical Current Transformers (OCTs) and Optical Voltage Transformers (OVTs) are an alternative to the conventional transformers for protection and metering purposes with a much smaller footprint and weight. Their advantages were widely discussed in scientific and technical literature and commercial applications based on the well-known Faraday and Pockels effect. However, the literature is still scarce in studies evaluating the use of optical transformers for power quality purposes, an important issue of power system designed to analyze the various phenomena that cause power quality disturbances. In this paper, we constructed a temperature-independent prototype of an optical voltage transformer based on fiber Bragg grating (FBG) and piezoelectric ceramics (PZT), adequate to be used in field surveys at 13.8 kV distribution lines. The OVT was tested under several disturbances defined in IEEE standards that can occur in the electrical power system, especially short-duration voltage variations such as SAG, SWELL, and INTERRUPTION. The results demonstrated that the proposed OVT presents a dynamic response capable of satisfactorily measuring such disturbances and that it can be used as a power quality monitor for a 13.8 kV distribution system. Test on the proposed system concluded that it was capable to reproduce up to the 41st harmonic without significative distortion and impulsive surges up to 2.5 kHz. As an advantage, when compared with conventional systems to monitor power quality, the prototype can be remote-monitored, and therefore, be installed at strategic locations on distribution lines to be monitored kilometers away, without the need to be electrically powered.

A temperature-independent optical voltage transformer based on FBG-PZT for 13.8 kV distribution lines

Abstract Instrument Optical Voltage Transformers (OVTs) have been presented by the electric power industry as an alternative to the conventional iron and copper inductive instrument transformers from the last years. OVTs based on fiber Bragg gratings and piezoelectric (PZT) crystals present two well know limitations: maximum voltage that can be applied on the PZT due to their limited electric field and the cross-sensitivity of the FBG on temperature that influence measurement accuracy. This paper presents an FBG-PZT based OVT with a novel thermally compensated method, capable to measure and monitor distribution voltages of 13.8 kV class. The presented results show that the developed system satisfies the 0.2 Accuracy Class of IEC standards, meaning a 0.2% accuracy.

Studies in electromagnetic compatibility of optical and digital current and voltage transformers

The use of microprocessor devices for relay protection and automation, devices for measuring and determining electric power quality permits the introduction and development of digital circuits leading from primary current and voltage transformers. The use of optical channels for digital circuits addresses the problem of offsetting electromagnetic interference and voltage shift. Creating optical and digital current and voltage transformers with digitization of signals already at high measuring transformer voltage is the best solution for the above problem of mechanical engineering in the field of electromagnetic compatibility of high voltage measuring transformers. However, a difficulty arises in ensuring electromagnetic compatibility of sensors and microelectronic equipment adjoining live parts. The present study is devoted to examining the impact of electromagnetic fields on sensors and solving the problems of electromagnetic compatibility of optical and digital current and voltage transformers.

Research on the Error Characteristics of a 110 kV Optical Voltage Transformer under Three Conditions: In the Laboratory, Off-Line in the Field and During On-Line Operation

Optical voltage transformers (OVTs) have been applied in power systems. When performing accuracy performance tests of OVTs large differences exist between the electromagnetic environment and the temperature variation in the laboratory and on-site. Therefore, OVTs may display different error characteristics under different conditions. In this paper, OVT prototypes with typical structures were selected to be tested for the error characteristics with the same testing equipment and testing method. The basic accuracy, the additional error caused by temperature and the adjacent phase in the laboratory, the accuracy in the field off-line, and the real-time monitoring error during on-line operation were tested. The error characteristics under the three conditions—laboratory, in the field off-line and during on-site operation—were compared and analyzed. The results showed that the effect of the transportation process, electromagnetic environment and the adjacent phase on the accuracy of OVTs could be ignored for level 0.2, but the error characteristics of OVTs are dependent on the environmental temperature and are sensitive to the temperature gradient. The temperature characteristics during on-line operation were significantly superior to those observed in the laboratory.

Optimization for Dynamic Performance of the Fiber Optical Voltage Transformers

Concerning the effect of the parameter uncertainty caused by environmental temperature, we present a robust control algorithm for the fiber optical voltage transformer (FOVT) to achieve optimized dynamic performance. The principle of the FOVT based on closed-loop detection is analyzed and the system model is established. Based on the system model and the optimized dynamic performance index, the robust controller is investigated to suppress the effect of the forward gains variation. Furthermore, we give a design criterion in terms of linear matrix inequality (LMI) for the proposed control. Finally, the experimental results show that the control has strong robustness against parameter uncertainty for improving the dynamic performance of the FOVTs.

Optical High Voltage Measurement Technique Using Pockels Device

This paper describes a new optical high voltage measurement technique to realize optical voltage transformers (optical VTs) through which high voltages up to 400 kV can be directly measured. A prototype of an optical VT using Pockels device in a multi-segmented arrangement is designed based on the numerical calculation of the electric field distribution. The response characteristics of the developed prototype are examined for ac, dc, and lightning impulse voltages, and these experimental results showed good agreement with theoretical estimations. An oscillatory component appearing on the output signal of the sensor for the impulse voltage application is successfully eliminated using a fast Fourier transform (FFT) digital filter. It is also found that the sensor can respond to fast transients with a rising time of 40 ns, which defines the frequency response bandwidth of the system from dc to several MHz.

72kV三相一括形GIS用光変成器の開発

We developed optical voltage and current transformers (PT and CT) for 72kV three-phase in one enclosure type Gas Insulated Switchgears (GIS). We used Bi12GeO20and flint glass as device material used in the optical PT and CT, respectively. We also designed an optical PT unit with a pin hole type grounded electrode and intermediate electrode in the pin hole and an optical CT located at the ground level with optical transmission by an optical fiber instead of free space light propagation. We assembled the optical PT and CT into GIS and conducted withstand voltage test, ratio error characteristic test, and other-phase influence test, obtaining good assessment results. Finally, we suggested that the developed optical PT and CT have a possibility of practical use.

Development and field test evaluation of optical current and voltage transformers for gas insulated switchgear

An optical current transformer (CT) based on the Faraday effect and an optical potential divider (PD) based on the Pockels effect, for application to electric power systems, are described. This optical CT is suitable for highly reliable gas insulated switchgear (GIS), and has free space light transmission parts among the optical fiber signal transmission lines. The developed optical CT and PD were built into 77/ square root 3 kV 1200 A single-phase prototype GIS. Their basic characteristics of current and voltage measurement conformed well with the standards of the JEC (Japan Electrotechnical Commission) 1201 for instrument transformers. A long-term field test of the prototype GIS was carried out at a substation for 20 months, during which time no significant variation of current and voltage measuring characteristics was observed. >