RESUMEN
In this work, we present the design, laboratory tests, and the field trial results of a power-over-fiber (PoF) low power instrument transformer (LPIT) for voltage and current measurements in the medium voltage distribution networks. The new proposed design of this power-over-fiber LPIT aims to overcome the drawbacks presented by the previous technologies, such as the continuous operation (measuring and data transmission) for a wide current range conducted in the medium voltage transmission lines, damage due to lightning strikes, accuracy dependency on vibration, position and temperatures. The LPIT attends the accuracy criteria of IEC 61869-10 and IEC 61869-11 in terms of current and voltage accuracy and it attends the practical criteria adopted by Utilities companies including voltage measurements without removing the coating of the covered conductors. The PoF based LPIT was developed to be applied at 11.9 kV, 13.8 kV, and 23.0 kV phase-to-phase nominal voltages, and in two current ranges 1.25-30 A and 37.5-900 A. The digital data transmission of current, voltage, and temperature from the sensing unit to the processing unit uses a special synchronism technique and it is performed by two 62.5 µm multimode fibers in 850 nm. The optical powering in 976 nm is also performed by one 62.5 µm multimode fiber from the processing unit to the sensor unit. We presented all details of the sensor design and its laboratory characterization in terms of accuracy and temperature correction. We also presented the results of field tests of the sensor made in two different conditions: in a standard distribution network and an experimental hybrid fiber/power distribution network. We believe that these studies aim to incorporate optical fiber and devices, digital technologies, communications systems in electrical systems driving their evolution.
RESUMEN
In this work, we developed a new measurement system which includes a Wireless Instrumented Sphere (WIS) and a Graphical User Interface (GUI) software, called Real Time Analysis (RTA). This system is able to acquire, process and visualize the three axis acceleration of the WIS allowing the identification and measurements of rotations, vibrations and impacts in real time. The aim of this instrument is to help the fruit producers to reduce food wasting and improve quality, especially in Brazil, one of the major agricultural countries in the world, whose losses could surpass 20% along the post-harvesting handling chain. Additionally, a data Post Processing Analysis software (PPA) provided of a video synchronization option was developed to determine the impact magnitude, position and even the cause of the impact itself (drop, fruit-to-sphere impact, etc.). Both GUIs presented graphics of the three axis acceleration vectors, acceleration magnitude and velocity, as well as the calculations of the number of impacts (peak detection), maximum, minimum and average impact magnitude. The WIS board was encapsulated in the middle of a spherical transparent polyurethane elastomer. It was also intended to be a small, simple, robust and low cost instrument. Its final diameter of approximately 63 mm, 160 g weight and 1.1 relative density. The RTA reduces the time for testing and is suitable for a fast feedback and allows the user to make adjustments in the experiment setup, packing system or even monitor any process along the post-harvesting handling chain, with an immediate response. The PPA with video synchronization option, proved to be a unique tool, relating the acceleration information with the video position.