진학프로석·박사 채용 접수 플랫폼

Electrical energy is an indispensable commodity in our daily lives. Before consuming the energy, it is necessary to transport it from the power plant. Although the transport of electrical energy seems simple in the collective consciousness, just a few electrical wires, this does not correspond at all to the challenges of today and tomorrow. Indeed, the need for electric energy is continuously increasing, losses are no longer acceptable in the context of global warming and, to a lesser extent, neither the overhead line corridors through our countryside. Dielectric losses can be eliminated by using from alternating (ac) to continuous (dc) voltage. Since the power carried is the product of the voltage and the current, increasing the voltage reduces the current for a given power and as well the Joule effect losses. However, as it is not possible to increase the voltage indefinitely, Joule losses remain significant and prevent large distance from power plant to consumption place.

One way to drastically reduce the Joule effect losses is to use superconducting material instead of copper to conduct the current. Superconducting materials conduct the current without resistance and therefore without Joule effect. However, superconducting materials only work at low temperatures, which requires cooling the conductor and therefore spending energy. Within the framework of the European BESTPATHS project, it has been demonstrated that beyond a hundred kilometers, superconducting cables consume less energy than conventional cables, but above all, they are capable of transporting much more energy with an environmental footprint that is almost ten times smaller. This would allow the construction of energy transmission highways across continents, taking advantage of the abundant winds in northern countries or off the coasts and the abundant sunshine in the deserts near the equator. If superconducting materials are able to conduct a lot of current, they must be brought to a high enough voltage to carry enough energy. However, under high voltage, insulators are far from perfect, and charges can be injected into them and become permanently trapped. The electric field produced by these charges is then superimposed on the applied field; the total field is therefore likely to exceed the dielectric breakdown field and thus lead to the breakdown of the insulator, rendering the installation out of order. Knowing that an exceeding electron over a billion molecules can produce this effect, it is absolutely essential to study and characterize the insulation material of a power transmission line to ensure operational sustainability and safety over very long period, at least 40 years.

One of the objectives of the European CABLEGNOSIS project is to analyze the lifetime of the insulating part of the superconducting cable by various experiments. In one of the experiment, it is necessary to test insulating samples by recording all events appearing before the breakdown voltage. These data will be then analyzed with artificial intelligence (AI) for generating a model of lifetime for the tested material. As lifetime tests are very long and thus cannot be done twice, it is absolutely necessary to completely check the test bench before. The instrumentation group of the LPEM of ESPCI is at the forefront in the field of instrumentation. In particular, it has developed many specific high voltage instruments in cryogenic environment and many methods of signal analysis, especially for breakdown tests. In the framework of his work, the postdoc will mount a small test bench mimicking the real one, for testing the reliability of data acquisitions, specially when breakdown occurs. The test bench will be controlled by a computer and the measured data (drift current, impedance spectrometry, partial discharge and breakdown strength) will be stored on a server for sharing among the project partner.

This is an experimental physics position with a design and signal processing parts. An experience is required in high voltage measurement systems (between 30 kV to 70 kV), insulating material characterization, instrument interfacing from a remote computer.