Search results for "Cables"
showing 10 items of 27 documents
Space charge accumulation in undersea HVDC cables as function of heat exchange conditions at the boundaries – water-air interface
2020
Transmission lines with undersea HVDC cables are an interesting technological solution for the supply of electrical energy to islands. The accumulation of space charge inside the dielectric layer of a HVDC cable is one of the most important element to consider in its design and during operation. The formation of space charge is due to various factors including the high dependence on the temperature of the electrical conductivity of the insulation and the establishment of a thermal gradient under load conditions. This research is focused on the space charge accumulation phenomenon around a section of a HVDC cable half dipped in water and half in air. Due to the high difference in thermal con…
Critical issues in the PD testing methodology for XLPE-insulated MV cables: An experimental case
2017
This paper describes some critical issues arising during the partial discharge (PD) testing of a 500m delivery length of an XLPE-insulated MV cable. At first, conventional PD measurements were performed on the whole length by using a standard acquisition system; PDs activity was detected, but the system allowed the operator to localize the PDs only on a length of 70 m. A visual inspection of this section highlighted the presence of an excoriation in the outer sheet. Aiming at a more accurate pin-pointing of the defect, more measurements were carried out in the proximity of the outer defect using a portable PD detection system. These measurements showed PDs activity, whose source was located…
Review of the PEA Method for Space Charge Measurements on HVDC Cables and Mini-Cables
2019
This review takes into account articles and standards published in recent years concerning the application of the Pulsed Electro Acoustic (PEA) method for space charge measurement on High Voltage Direct Current (HVDC) cables and mini-cables. Since the 80s, the PEA method has been implemented for space charge measurements on flat specimens in order to investigate space charge phenomena and to evaluate the ageing of dielectrics. In recent years, this technique has been adapted to cylindrical geometry. Several studies and experiments have been carried out on the use of the PEA method for full size cables and HVDC cable models. The experiments have been conducted using different arrangements of…
Could malaria and dengue reappear in Spain?
2010
El aumento de la inmigración durante los últimos años en España ha facilitado la importación de numerosas enfermedades tropicales. Entre ellas, las de transmisión vectorial son algunas de las más complicadas de estudiar por la complejidad que conlleva la participación de diversos hospedadores en los ciclos de transmisión, así como por la necesidad de conocer todos los parámetros fisiológicos, bioecológicos y biogeográficos relacionados con el organismo vector para poder inferir las posibilidades reales de la emergencia o la reemergencia de las enfermedades pertinentes. En estas circunstancias, el presente trabajo aporta información acerca de enfermedades importadas de incuestionable interés…
¿Pueden la malaria y el dengue reaparecer en España?
2010
ResumenEl aumento de la inmigración durante los últimos años en España ha facilitado la importación de numerosas enfermedades tropicales. Entre ellas, las de transmisión vectorial son algunas de las más complicadas de estudiar por la complejidad que conlleva la participación de diversos hospedadores en los ciclos de transmisión, así como por la necesidad de conocer todos los parámetros fisiológicos, bioecológicos y biogeográficos relacionados con el organismo vector para poder inferir las posibilidades reales de la emergencia o la reemergencia de las enfermedades pertinentes. En estas circunstancias, el presente trabajo aporta información acerca de enfermedades importadas de incuestionable …
¿Pueden la malaria y el dengue reaparecer en España? Could malaria and dengue reappear in Spain?
2010
El aumento de la inmigración durante los últimos años en España ha facilitado la importación de numerosas enfermedades tropicales. Entre ellas, las de transmisión vectorial son algunas de las más complicadas de estudiar por la complejidad que conlleva la participación de diversos hospedadores en los ciclos de transmisión, así como por la necesidad de conocer todos los parámetros fisiológicos, bioecológicos y biogeográficos relacionados con el organismo vector para poder inferir las posibilidades reales de la emergencia o la reemergencia de las enfermedades pertinentes. En estas circunstancias, el presente trabajo aporta información acerca de enfermedades importadas de incuestionable interés…
The effect of the axial heat transfer on space charge accumulation phenomena in HVDC cables
2020
To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating …
Ground-Fault Current Transfer at the Transition Station of a Combined Overhead-Cable Line. A Parametric Analysis
2007
When a substation is fed by a combined overhead-cable transmission line, a significant part of the ground fault current flows through the grounded cable sheaths and discharges into the earth at the transition station, where cables are connected to the overhead line. If the transition station is a dead-end steel pole structure, the local ground electrode, small and of high resistance, could be inadequate to maintain the ground potential rise within safety limits in case of a fault to ground at the receiving end substation. Based on a circuit model approach, the paper presents a parametric analysis of the fault current distribution between the faulted substation and the transition station, ta…
A statistic approach of cables ageing in MV lines on thermal and electrical combined stress
2006
The paper introduces a methodology that through a probabilistic characterisation of load for MV network, and implementing a life model for combined electric and thermal stresses, simulates the process of ageing of the insulating materials evaluating the expected life time of the cable. Such evaluation is necessary to the possibility of assuming less restrictive thermal overloading limits on electrical cables, with the consequential increase on reserve that cables could offer. A numerical example is reported to better explain the methodology
Elevation Cable Modeling for Interactive Simulation of Cranes
2008
In this paper, the way to simulate hoisting cables in real time is addressed. We overcome instability in such simulation by considering a two-layered model: a model for the dynamics of a cable passing through a set of pulleys and an oscillation model based on the classical one-dimensional wave equation. The first layer considers the interaction between the cable and pulleys with the elevation equipment, while the second layer simulates cable oscillation. Numerical instability is avoided by suspending the oscillation layer when required. Due to the system properties, this can be carried out in such a way that does not cause significant loss in the system quality. It considers the oscillation…