Feasibility of Space Charge Measurements on HVDC Cable Joints

This review article aims at illustrating the starting of the activities carried out by the Study Group from the viewpoint of the assessment of the state of the art in the measurement of SC in HVDC extruded cable system joints

Validation of Mechanical Features of HPTE Insulation for EHV DC Land Cable Systems

HVAC and HVDC extruded cable systems present a series of operational and logistic constraints that should be taken into account. Reliability and on-time-delivery demand a fine tuning of all the steps of the project, from the cable manufacturing to the system installation. Innovative projects on large scale, such as the HVDC 525 kV German Corridors [1], require an accurate verification of the system performances, not only from an absolute point of view, but also relatively to the environmental constraints and the system design linked to the single projects. As regards HVDC cable accessories, the interface between the premoulded sleeve and the cable requires investigations from both the thermomechanical and the electrical point of view. This study aims at evaluating all these constraints

The Effect of ambient thermal properties on transient electric field distribution and life estimation in HVDC cable insulation

Innovative cable designs have recently achieved high rated temperatures. Cable environment properties are getting more attention to guarantee thermally stable operation and reduced loss-of-life of the HVDC cable at all possible weather conditions. This paper aims at studying the effect of different resistivities and seasonal temperatures of the laying environment on the electric field distribution inside the insulation of HVDC cables subjected to the type test load cycles according to CIGRÉ Technical Brochure 496. Five different conditions of the laying environment are considered, set according to IEC 60287, i.e., soil saturated with water, very moist, moist, partially dry, and dry; different temperatures of the laying environment are also taken accordingly. The results show that the greater the thermal resistivity and/or the temperature of the laying environment, the shorter the life of the cable insulation

Investigation on Online Fault Location Techniques During Factory Testing on Manufactured Cable Lengths

The operational constraints for the supply and exercise of HV extruded cable systems requires a fast and reliable localization of possible faults in cable insulation. Methods are available in the literature for offline fault location for both underground and (long) submarine cables installed in the field. The main method used is Time Domain Reflectometry (TDR), which works well when the fault impedance is low, but other methods are also available for relatively high fault impedances. However, such methods require a subsequent fault pin-pointing that works well offline and in the field. On the other side, there is the need of an effective and extremely-accurate localization method that can be applied on factory tests as well as on site. The purpose of this work is to get insights on such effective online fault localization technique in factory-tested cables, based on the analysis of the fault curve and on its comparison to different offline fault localization methods

Temperature enhancement of zinc and iron separation from chromium(III) passivation baths by emulsion pertraction technology

This work reports the influence of the temperature on the selective removal of zinc and iron from a chromium(III) passivation bath by emulsion pertraction technology using Cyanex 272 as extractant and hollow fiber membrane contactors. The results indicate that the kinetics of the separation was largely influenced by the temperature in the range 10-40 °C. The viscosity of the organic liquid phase was measured at different temperatures and extractant concentrations, and the results were fitted to the Riedel and Grunberg and Nissan correlations. The improvement observed from 20 to 40 °C was explained by the increase in the diffusion coefficient of the zinc and iron organometallic complexes through the liquid membrane. However, the remarkably slower zinc and iron separation rates observed at 10 °C in comparison with those at 20-40 °C were attributed to a shift in the driving force due to an endothermic change of the interfacial extraction reaction. The equilibrium parameters at 10 and 20-40 °C were estimated by fitting the experimental kinetic results to the proposed mathematical model. Thus, this work addresses the thermal character of equilibrium and its relevant influence on the separation kinetics of reactive membrane systems. © 2012 American Chemical Society.Peer Reviewe

Evidences of the effect of GO and rGO in PCL membranes on the differentiation and maturation of human neural progenitor cells

The effect of doping graphene oxide (GO) and reduced graphene oxide (rGO) into poly(ε‐caprolactone) (PCL) membranes prepared by solvent induced phase separation is evaluated in terms of nanomaterial distribution and compatibility with neural stem cell growth and functional differentiation. Raman spectra analyses demonstrate the homogeneous distribution of GO on the membrane surface while rGO concentration increases gradually toward the center of the membrane thickness. This behavior is associated with electrostatic repulsion that PCL exerted toward the polar GO and its affinity for the non‐polar rGO. In vitro cell studies using human induced pluripotent cell derived neural progenitor cells (NPCs) show that rGO increases marker expression of NPCs differentiation with respect to GO (significantly to tissue culture plate (TCP)). Moreover, the distinctive nanomaterials distribution defines the cell‐to‐nanomaterial interaction on the PCL membranes: GO nanomaterials on the membrane surface favor higher number of active matured neurons, while PCL/rGO membranes present cells with significantly higher magnitude of neural activity compared to TCP and PCL/GO despite there being no direct contact of rGO with the cells on the membrane surface. Overall, this work evidences the important role of rGO electrical properties on the stimulation of neural cell electro‐activity on PCL membrane scaffolds

Evidences of the effect of GO and rGO in PCL membranes on the differentiation and maturation of human neural progenitor cells

The effect of doping graphene oxide (GO) and reduced graphene oxide (rGO) into poly(ε‐caprolactone) (PCL) membranes prepared by solvent induced phase separation is evaluated in terms of nanomaterial distribution and compatibility with neural stem cell growth and functional differentiation. Raman spectra analyses demonstrate the homogeneous distribution of GO on the membrane surface while rGO concentration increases gradually toward the center of the membrane thickness. This behavior is associated with electrostatic repulsion that PCL exerted toward the polar GO and its affinity for the non‐polar rGO. In vitro cell studies using human induced pluripotent cell derived neural progenitor cells (NPCs) show that rGO increases marker expression of NPCs differentiation with respect to GO (significantly to tissue culture plate (TCP)). Moreover, the distinctive nanomaterials distribution defines the cell‐to‐nanomaterial interaction on the PCL membranes: GO nanomaterials on the membrane surface favor higher number of active matured neurons, while PCL/rGO membranes present cells with significantly higher magnitude of neural activity compared to TCP and PCL/GO despite there being no direct contact of rGO with the cells on the membrane surface. Overall, this work evidences the important role of rGO electrical properties on the stimulation of neural cell electro‐activity on PCL membrane scaffolds