Optical fiber technologies are very appropriate for using in high voltage equipment due to their excellent characteristics, mainly, immunity to electromagnetic interferences and electrical isolation. After the Smart Grid initiative, the focus for medium voltage (13.8 to 34 kV) smart meters leveraged the development of optical sensors for distribution application. This work provides a historical overview of optical technologies used in power quality monitoring, discussing technological, economics, standards and practical installation aspects. The sensors technologies analyzed in this work are the well-known optical Pockels cells and Faraday Effect, the fiber Bragg grating (FBG) and power-over-fiber (PoF).
Distributed sensors based on phase-optical time-domain reflectometry (phase-OTDR) are suitable for aircraft health monitoring due to electromagnetic interference immunity, small dimensions, low weight and flexibility. These features allow the fiber embedment into aircraft structures in a nearly non-intrusive way to measure vibrations along its length. The capability of measuring vibrations on avionics structures is of interest for what concerns the study of material fatigue or the occurrence of undesirable phenomena like flutter. In this work, we employed the phase-OTDR technique to measure vibrations ranging from some dozens of Hz to kHz in two layers of composite material board with embedded polyimide coating 0.24 numerical aperture single-mode optical fiber.
João P. Fracarolli, João Rosolem, Elias Tomiyama, Claudio Floridia, Rivael Penze, Rodrigo Peres, Danilo Dini, Claudio Hortencio, Paulo I. Dilli, Erlon da Silva, Marcéu dos Santos, Fabiano Fruett
We propose a passive optical sensor for online magnetic field monitoring in large hydrogenerators, based on FBG (Fiber Bragg Grating) technology and a magnestostrictive material (Terfenol-D). The objective of this sensor is to detect faults in the rotor windings due to inter turn short-circuits. This device is packaged in a novel rod-shaped enclosure, allowing it to be easily installed on the ventilation ducts of the stator of the machine. This sensor was developed and tested in laboratory and it has been evaluated in a field test on a 200 MVA, 60 poles hydrogenerator.
Joao Rosolem, Claudio Hortencio, Claudio Floridia, Danilo Dini, Rivael Penze, Bruno Aires, Fabio Bassan, Rodrigo Morbach, Eduardo da Costa, Felipe Salgado, Rodrigo Peres, João Paulo Fracarolli, Marcus Vinícius Santana, Augusto Cezar Gregatti, Guilherme Muniz, Gerson Amadeo, Gilson Carvalho, Fernando Pertile, Luis Fernando Melegari, Heloisa Herreros, Marcelo Kurokawa, Luis de Avila
This paper presents the results of a field test of a multi-parameters' monitoring network using FBGs adapted directly in the conventional instruments of two dams which are in full operational capability. We presented the details of the design and tests of the sensor’s network, such as, the sensors adaptation, the resolution comparison between the conventional instruments and the FBGs, the network topology, the spectral occupancy distribution considering the parameters optical bandwidth and also the temperature compensation for FBGs, the number of sensors by fiber and the performance of the FBGs sensors compared with the conventional instruments used in the Dams.
A high-speed FBG interrogation method for magnetic field sensing is proposed. A FBG attached to a magnetostrictive material (Terfenol-D) was used to show the output invariance when increasing the attenuation on the optical link. This was achieved by computing the ratio between the sensing and the reference signals, both generated using different DFB lasers properly tuned. The output remained invariant to attenuations up to 12 dB. Also, the system’s interrogation speed was tested and compared to a commercial solution. While the commercial model was limited by its 6 kHz sampling frequency, this method provided responses up to 60 kHz.
In this work we present a comparison between simplex coded and optical amplified simplex coded Raman based Distributed Temperature Sensing (DTS). An increase in performance is demonstrated using erbium doped fiber amplifier (EDFA) with proper gain control scheme that allows a DTS operates with simplex code. Using 63-bit simplex code and gain controlled EDFA we demonstrated the temperature resolution and dynamic range improvement in 16 °C @ 10 km and 4 dB, respectively.
In this work we proposed the use of free-space-optics (FSO) to transmit and receive the optical signals from optical fiber placed in ground potential to the FBG fiber optics at high voltage potential, using a pair of optical collimators. The technique evaluation was performed in a prototype for the study of sensitivity to optical alignment and in an external environment using emulated sensing systems for both bus bar and overhead transmission line with real isolator chain. It has been shown that the FSO system allows collimators operate at distances of 500 mm to 2.000 mm. This range of distances is similar to the length of insulator’s chain up to 230 kV. It was also shown that the proposed system can be used in real external environment for bus bar temperature monitoring in substations, where, even if the time out of the system is of 45%, with major interruption time of almost 15 hours, the majority of the interruption time was less than 18 minutes long. On the other hand, system has to be improved in order to be used in overhead transmission line. As tested for a real isolator chain the system shown a time out of 80.3%, with significant number of events of interruption acquisition time greater than 150 minutes. It is believed that for overhead power lines, system must be installed in rigid surge arresters or in a line post where it is expected to have similar results as in substation bus bars monitoring.
An electro-optical sensor system for monitoring synchronous compensators in the electrical distribution network is presented. The fiber-optic sensor system is based on two main technologies: optical bend loss sensors for monitoring the brush wear and, free-space optics to determine the dust accumulation from brush wear. Both techniques are characterized to monitor the parameters by means of simple optical power readings. In order to avoid optical power fluctuations in the fiber optics link from interrogation system to the synchronous compensators, bend-loss insensitive fibers are used. The low-cost interrogation system consists on one laser, optical splitters and 80 photodetectors to independently monitor each one of the synchronous compensators’s brushes. This setup ensures an ease installation and avoid cascaded fault that a serial configuration could originates, thus increasing reliability of the sensor system.
We propose a fiber optic sensor array based on bend loss assessed by optical time domain reflectometry (OTDR). The
sensor mechanism is based on optical fiber bending loss compressed by external pressure. An elastomeric surface is
applied to the sensor in order to communicate external pressure to the fiber coil and also, this make sensor able to deal
with degradation coming from aggressive environments. The sensing system proposed is able to monitor liquid or gas
pressure in different environments, such as water, oil, alcohols, some diluted acids and others, depending only of
elastomeric membrane choice. In order to protect the sensor stage against environmental degradation a plastic packaging
was chosen. Bend loss measurements is taken concerning the number of fiber loops involved in the sensor, pump signal
wavelength and temporal width. This long for the best parameters in the sensor construction. The specific case of the
sensor applied to water percolation monitoring from embankment damns is detailed in this paper; for this application the
sensor array have a number of at least six stages totally independent each other, in such a way that each stage can be
developed to monitor a specific environment. Sensors have shown good performance in field tests, reaching work range
from 0.1 to 0.6 atm with 0.05 atm of precision.
In this work we present the results of a passive optical sensor for monitoring lightning strikes on overhead power lines,
which can also be used for several other applications. The optic sensor is very simple and cheap and basically consists in
the use of an antenna connected directly to a semiconductor laser. No batteries and solar panels are necessary to
implement this sensing system in power lines towers. It was tested in laboratory and showed a good performance.
In this work we propose an asynchronous FBG interrogation system for rotating machines. The method was developed to
monitor temperature and deformation on hydrogenerator rotors, but can be easily used to monitor any other rotating
machine. The proposed scheme relays in a simplified interrogator, which need not be synchronized with the optical
collimation system. The system was tested successfully for various rotating velocities from 0 to 800 RPM.
We present a hydrogenerator partial discharge sensing system based in RF/Optical technology developed to obtain non-intrusive
and large bandwidth characteristics. It was tested using hydrogenerator stator bars and showed a very good
performance.
A numerical model based on Mueller matrix formalism is developed to include depolarization effects in the statistics of Polarization-Dependent Loss (PDL) in recirculating loops. The model shows that depending on the degree of depolarization introduced at each round trip, the maximum value of PDL is limited to lower values when compared with completely polarized light. First experimental evidence of this effect is also reported with estimation of the degree of polarization, DOP, introduced in the system, mainly due to spontaneous emission noise of the optical amplifiers.
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