Characteristics of creeping discharges along epoxy surface in fluoronitrile/co2 gas mixture under lightning impulse

2019-08-26T08:55:10+02:00August 26th, 2019|High Voltage Substation Equipment, Publications|

This paper deals with creeping discharges propagating over solid insulator samples in presence of a fluoronitrile mixture consisting of 10% of fluoronitrile and 90% of CO2, under positive and negative standard lightning impulse voltages, in point-plane geometry. The solid samples used are disks made of filled epoxy resin used for real GIS insulators. The experimental results are compared with those obtained with SF6 at pressure ranging 0.1 to 0.3 MPa, while the pressure of fluoronitrile mixture is chosen to match an equivalent dielectric strength of SF6. Different characteristic parameters are investigated namely the maximum length of creeping discharges versus the gas/mixture pressure and voltage polarity. In SF6, two regimes of discharges that depend on the voltage polarity are evidenced. Under positive impulse, the mixture presents similar properties as SF6. However, under negative polarity the maximum discharge length in SF6 is much longer than in the fluoronitrile mixture.

SuperGrid Institute hosts the 11th Quarterly review of NanocompEIM 2

2019-07-25T17:33:19+02:00July 25th, 2019|High Voltage Substation Equipment, HVDC Cable Systems|

Since October 2016, SuperGrid Institute has been involved in the NanocompEIM 2 project. The goal of the project is to develop nanocomposites (Nanocomp) for electrical insulation materials (EIM) in order to reduce CO2 emissions and improve system reliability and availability. Financed at 50% by Innovate UK, a government organisation dedicated to research and innovation in the United Kingdom, the overall budget of the project is around 1M£ (1.1M€).

Phd Priscillia DANIEL “Electrical properties study of cross-linked polyethylene insulated cables in presence of gaseous cavities aged under DC or DC with harmonic voltages”

2019-07-09T16:00:23+02:00July 5th, 2019|High Voltage Substation Equipment, HVDC Cable Systems, Phd|

This study aims to examine possible impact of these harmonics in presence of microcavities. Depending on their size and on the electrical field, partial discharges (PD) can occur in these microcavities. Two types of cables have been aged: a medium voltage AC (MVAC) cable with millimetric cavities induced artificially and a model cable with an HVDC XLPE grade.

SuperGrid Institute involved with the National Congress of Dielectric Spectroscopy

2019-08-08T10:37:07+02:00June 18th, 2019|High Voltage Substation Equipment, HVDC Cable Systems|

The national congress of dielectric spectroscopy (SDM2) took place at LyonTech on the 6th and 7th of June at the La Doua academic campus. A number of our materials experts attended to present some of the innovative studies that are under way at SuperGrid Institute.

Comparaison de mesures de conductivité obtenues par spectroscopie diélectrique et mesure de courant sous tension continue sur une résine époxy

2019-06-24T15:37:19+02:00June 6th, 2019|High Voltage Substation Equipment, HVDC Cable Systems, Publications|

De par sa facilité d’utilisation et sa capacité à isoler la permittivité complexe représentant les pertes dans un matériau tout en faisant un balayage fréquentiel, la spectroscopie diélectrique semble être une méthode de choix pour obtenir la valeur de conductivité ohmique d’un matériau. Cette méthode pourrait permettre de s’affranchir des temps conséquents de stabilisation généralement associés aux mesures de conductivité issues de courbes courant-tension effectuées suivant la norme IEC 62631-3. Par l’intermédiaire d’une comparaison entre ces 2 méthodes, les auteurs vont revenir sur les limites de chacune d’entre elle.

New challenges for High voltage transmission

2020-01-21T16:48:50+01:00May 15th, 2019|High Voltage Substation Equipment, Publications|

In able to fully integrate renewable energies and to stop to use fossil energy and nuclear power, there is a need to evolve the current electric grid in a new one called the supergrid. This new grid will be based on a mix of High Voltage AlternativeCurent (HVAC) and High voltage Direct Current (HVDC) junctions highly meshed with Gas Insulation Substation (GIS) as nodes. While HVAC GIS technologies are well mastered, HVDC ones are still at the beginning. One weakness of the equipment being dielectric insulators, industries may have to conceive new dielectric formulations or improved ones. This paper presents a list of properties and values to target for future dielectrics formulation. At the end, it highlights as well, the importance of health and environnement and how their consideration have to be at the same level of attention than the final properties of the dielectrics.

A New Energy Management Control of Modular Multilevel Converters for Coping with Voltage Stress on Sub-Modules

2019-06-10T16:33:04+02:00April 24th, 2019|High Voltage Substation Equipment, Publications|

This paper investigates the impact of the operating condition on the SM voltage ripples. In particular, it is revealed that under the classical control scheme where the Modular Multilevel Converter internal energy varies naturally with the DC grid voltage, the traditional sizing approach based on the analytical expression of instantaneous SM voltage may fail to respect the SM voltage constraint. To tackle this problem, this paper presents a solution by incorporating the advantages of the explicit energy management and the developed analytical expressions of the SM voltage ripple, which achieves a better utilization of the converter asset.