Search results for "high voltage"
showing 10 items of 78 documents
Effect of Polarity Reversal on the Partial Discharge Phenomena
2020
In the field of High Voltage Direct Current (HVDC) transmission, the space charge accumulation phenomenon and the Partial Discharges (PD) phenomena are considered the main causes of dielectric ageing. During the years, the degradation effect of both phenomena under constant DC stress has been widely studied by several researchers. In case of polarity reversal, typically carried out to control bi-directional power flow between interconnected High Voltage transmission systems, the space charge movement may not synchronously follow the electric field polarity. This could make the moment of reversing polarity a very critical one, where space charge injected during preceding polarity produces hi…
SiC Based Latching Current Limiter for High Voltage Space Power Distribution Systems
2018
This study presents a novel Latching Current Limiter topology, based on a N-channel Silicon Carbide (SiC) MOSFET as the main switching element. The design has been carried out using only discrete components, without digital controllers. This design has been validated by simulation and with a prototype. Tests have been performed at 1000V, modifying the limitation times, current-limiting values and eventually checking the proper operation of the system.
High resistance measurement circuit for fiber materials: Application to moisture content estimation
2018
Abstract Measuring very high resistance values is a difficult task since low voltage or currents are present and thus, noise and amplification must be carefully done, especially when low resistance values are required to be measured using the same circuit, too. This work proposes a novel and accurate measurement instrument for a wide range of resistance values oriented to portable applications, i.e. low power and low supply voltage (5 V) for battery operated equipment, with a small circuit design including analog sensing, digital interface (data reading and control) using a microcontroller and external communication. The proposed circuit includes an inverter attenuator with layout and confi…
Effect of low amount of nanosilica on dielectric properties of polypropylene
2010
This paper presents the results of the dielectric properties measurements conducted on Silica-Polypropylene (PP) nanocomposites. According to prior investigations by the authors silica nanoparticles have improved the performance of the dielectric material considering capacitor applications. Especially breakdown strengths with ac and dc voltages and resistance against surface degradation have increased. The relative permittivity and dielectric losses have also been comparable to reference PP. In this paper the results of the dielectric measurements conducted on composites with 1-2 wt-% silica are compared with reference PP. Silica dispersion in PP was confirmed with transmission electron mic…
Performance Evaluation of a Three- Phase Five-Level Quasi-Z-Source Cascaded H-Bridge for Grid-Connected Applications
2018
In the field of the PV generation, Quasi-Z-source cascaded H-bridge (qZS-CHB) inverters are promising due to their features of modularity and high voltage conversion ratio. Thus, new topology structures and innovative modulation techniques are continuously being developed to improve the performance in terms of voltage stress and harmonic content. This paper proposes an innovative modulation technique that allows reducing the voltage stress and a specially designed grid-connected control strategy is also introduced. Through simulations in MATLAB, it has been validated that the performance of a three-phase five-level qZS-CHB is improved with the proposed solution.
Methodologies for the Exploitation of Existing Energy Corridors. GIS Analysis and DTR Applications
2018
The exploitation of power lines currently in operation has now become a common practice among electric system operators. The construction of new power lines requires taking economic, political and social problems into consideration. This paper considers two methodologies adopted by the Italian Transmission System Operator (TSO), Terna S.p.A.: Dynamic Thermal Rating (DTR) and Laser Imaging Detection and Ranging-Geographic Information System (L-GIS). DTR systems dynamically calculate the real transport capacity of a power line. The L-GIS system allows, after the geo-referencing of the power line, the management of any interference between the line and the nearby obstacles, permitting the opti…
New High Voltage Interconnections with Islands in the Mediterranean Sea: Malta and Sicily. Analysis of the Effects on Renewable Energy Sources Integr…
2018
The present paper shows the benefits coming from the operation of the recent electrical high voltage (HV) interconnections between Sicily, Malta and mainland Italy. These new interconnections allow zonal prices of electricity considerably lower than in the past, ensuring greater flexibility to the system and a better integration of Renewable Energy Sources (RES). After briefly illustrating the two high-voltage electrical systems (Sicily and Malta), and having provided a description of the interconnection cable with Malta and its protection devices, the authors hypothesized two modes of operation (Sicily-Malta system islanded or interconnected to the rest of Europe). For the first case (isla…
Electromagnetic Full-Wave Simulation of Partial Discharge Detection in High Voltage AC Cables
2019
Partial discharge (PD) activity in the insulation system of an electrical equipment can determine the failure of the whole apparatus. PD sensors are widely used in high-voltage electrical systems as the main elements of a detecting system oriented to real time monitoring. Recently, non-invasive sensors have been proposed in industrial applications for cable and other sensitive electrical parts: they are based both on capacitive and on the electromagnetic radiating coupling. In order to assess the real performance of a new sensor produced by a high voltage AC cables manufacturer, the paper proposes electromagnetic fullwave simulation results.
Circuit proposals for high-voltage latching current limiters
2019
This work discusses some ideas to adapt existing low voltage Latching Current Limiter (LCL) circuits to high voltage operation to provide a basis for future designs. Component selection, driver and ancillary power supply are key issues discussed which eventually provides a high-voltage LCL proposal. Experimental validation of two different prototypes (380Vdc and 1kVdc) is included as well as some digital techniques to enhance LCL capabilities.
Impact of pulsed electric fields and high voltage electrical discharges on extraction of high-added value compounds from papaya peels
2014
Abstract Extraction of the nutritionally valuable and antioxidant compounds from papaya peels using conventional aqueous extraction (E) (at 20 °C, 50 °C, and 60 °C) and extraction assisted by pulsed electric field (PEF) or by high voltage electrical discharges (HVED) was studied. Increase of extraction temperature or extraction in basic media (pH = 11) not always resulted in an increase of the yields or TEAC values. E.g., the concentration of proteins and TEAC values at pH = 7 and pH = 11 were noticeably smaller at 60 °C as compared to those measured at 50 °C. HVED-assisted technique showed a higher extraction efficiency of high-added value compounds compared to PEF-assisted extraction. E.g…