Some 175 years ago Michael Faraday discovered magnetic circular birefringence, now commonly known as the Faraday effect. Sensing the magnetic field through the influence that the field has on light within the fiber optic sensor offers several advantages, one of them fundamental. These advantages find application in the measurement of electric current at high voltages by measuring the induced magnetic field, thus warranting application for this kind of fiber optic sensor (FOS) in future smart grids. Difficulties in designing and manufacturing high-performance FOSs were greatly alleviated by developments in optical telecommunication technology, thus giving new impetus to magnetometry based on the Faraday effect. Some of the major problems in the processing of optical signals and temperature dependence have been resolved, yet much effort is still needed to implement all solutions into a single commercial device. Artificial structures with giant Faraday rotation, reported in the literature in the 21st century, will further improve the performance of FOSs based on the Faraday effect. This paper will consider obstacles and limits imposed by the available technology and review solutions proposed so far for fiber optic sensors based on the Faraday effect.

Fiber Optic Sensors Based on the Faraday Effect.

Fractional calculus is a 300 years topic, which has been introduced to real physics systems modeling and engineering applications. In the last few decades, fractional-order nonlinear chaotic systems have been widely investigated. Firstly, the most used methods to solve fractional-order chaotic systems are reviewed. Characteristics and memory effect in those method are summarized. Then we discuss the memory effect in the fractional-order chaotic systems through the fractional-order calculus and numerical solution algorithms. It shows that the integer-order derivative has full memory effect, while the fractional-order derivative has nonideal memory effect due to the kernel function. Memory loss and short memory are discussed. Finally, applications of the fractional-order chaotic systems regarding the memory effects are investigated. The work summarized in this manuscript provides reference value for the applied scientists and engineering community of fractional-order nonlinear chaotic systems.

Solutions and memory effect of fractional-order chaotic system: A review

High reliability and measurement accuracy are the premises and foundations of the practical use of optical transformer in power systems. Based on the theory of power optic sensor and model structure, the implementation plans for magneto-optical glass type as well as all-fiber type current transformer and electro-optic crystal type as well as all-fiber type voltage transformer are classified and compared, the advantages and disadvantages in the aspects of detection algorithms and manufacturing processes are also pointed out. Finally, the problems associated with the practical use of optical sensing technology and research directions are discussed.

Study and comment of the optical transformers in power system

The invention discloses a closed-loop control device and method for a subway/coal stray current fiber sensor and can realize low cost non-contact measurement of the subway/coal stray current. The device is composed of a broadband light source, a fiber circulator, a polarization modulator, a delay fiber, a sensing fiber, a fiber mirror, a fiber framework, a photoelectric detector and a control unit. The closed-loop control method based on the device is characterized in that a rotation angle formed by the polarization modulator for the input line polarized light is equal to a rotation angle formed by the measured current, the directions are opposite, linearity of the sensor is improved, the dynamic range of the sensor is broadened, the cost of the sensor is reduced, the optical path structure of the sensor is optimized, and advantages of strong anti-electromagnetic interference capability and intrinsic explosion-proof insulation are realized.

Closed-loop control device and method for subway/coal stray current fiber sensor

The paper introduces fundamental principles and main characteristics of the fiber optical current transformer(FOCT),compares in detail with the Rogowski coil type CT and magneto-optical CT,analyzes the advantages preferable to relay protection by using FOCTFacing the main problems in the engineering application of FOCT,the paper suggests solving measures

The Fiber Optical Current Transformer(FOCT) Technology and It's Engineering Application

The fiber optic current sensor (FOCS) is susceptible to external temperature in actual operation, which will lead to its accuracy deviation, even malfunction. In order to improve the temperature stability of FOCS’s ratio error, a temperature compensation method based on RBF neural network is established by taking the temperature as input and the ratio error as output to the network. Compared with BP neural network, the simulation results show that the temperature compensation model based on RBF neural network has better accuracy whose prediction error is less than 3%. At the same time, the experimental results show that the drift deviation of ratio error can remain as low as ±0.1% in the range of -40 °C to 70°C, and the 0.2S-level accuracy of GBT20840.8 standard can be achieved.

Fiber optic current sensor temperature compensation through RBF neural network

The invention provides a combined optical transformer for a novel GIS. An all-fiber current transformer sensing ring is mounted at one end of a flange body covered by a flange cover board, and an optical voltage transformer sensing head is embedded into a chamber of the flange body; the all-fiber current transformer sensing ring is connected with an external all-fiber current transformer electric unit through a polarization-maintaining fiber; the optical voltage transformer sensing head is connected with an external optical voltage transformer electric unit through a single-mode fiber and a polarization maintaining fiber; the one end of the flange body covered by the flange cover board is mounted at one end of the external GIS through the flange cover board in an abutting mode, the other end of the flange body is mounted at the other end of the external GIS in an abutting mode; parts in the all-fiber current transformer sensing ring, such as the flange body and the flange cover board are separated by employing insulation rings to block ring current, the mounting part is sealed by employing an O-type sealing ring. The combined optical transformer for the novel GIS has advantages of compact structure, insulative, simple and reliable performance, flexible mounting and good sealing performance.

Combined optical transformer for novel GIS

The engineering application number of fiber optic current sensor (FOCS) is decreasing year by year since 2012 in China due to its reliability problems. However, the researchers and related enterprises have also made some constructive attempts on the study of fault diagnosis of FOCS. In this paper, the application status and the common fault modes of FOCS are analyzed. Three ways to diagnosing the soft and hard fault of FOCS are reviewed, including based on analytical model, on signal processing and on knowledge. Finally, the research direction of FOCS fault diagnosing is prospected. It is concluded that the diversified and intelligent fault diagnosis method based on knowledge has more advantages compared with the other two methods. In addition, the development of FOCS for integrated optical path is of great help in improving its reliability and will be a research hotspot in the future.

Fault diagnosing methods of fiber optic current sensor: a review

The invention provides an electrified analysis system for electronic transformers, which is composed of multiple electronic transformers, merging units, a fault wave recording and network recording analysis device and an upper computer, wherein the electronic transformers are connected with the merging units respectively; the merging units are connected with the fault wave recording and network recording analysis device; the fault wave recording and network recording analysis device is connected with the post-end upper computer; the electronic transformers acquire data, the data are transmitted to the fault wave recording and network recording analysis device through the merging units, the fault wave recording and network recording analysis device stores a large-capacity storage hard disk,the acquired data are subjected to data format conversion through programmed software, and the data are subjected to offline analysis processing through a wavelet analysis algorithm based on Labviewanalysis software and a neural network based on depth learning. Detection on at least two electronic transformers in aspects of precision, harmonic detection performance and bandwidth performance stability and long-time electrified contrast examination can be realized.

Electrified analysis system for electronic transformers

The present invention discloses a novel optical path sensing unit for a low-voltage optical current sensor. The unit comprises a light source, an optical fiber isolator, an optical fiber depolarizer, an optical fiber coupler, a photoelectric detector and a second unit. The light source, the optical fiber isolator, the optical fiber depolarizer, the optical fiber coupler and the second unit are connected with each other through the optical fiber. The photoelectric detector is connected with the optical fiber coupler, the second unit is connected with a conductor, the optical axis direction of the second unit is perpendicular to the current direction of the conductor, and the second unit includes an optical fiber collimator, a polarizer, a magneto-optical crystal, a Faraday rotator and a reflector. The novel optical path sensing unit for the low-voltage optical current sensor solves the problems that the optical path structure of the current optical current sensor is complex, many kinds of optical devices are required the technology realization difficulty is big, the engineering installation difficulty is big and the product cost is high. In addition, the measurement sensitivity is ensured.

Novel optical path sensing unit for low-voltage optical current sensor

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