//High Voltage Substation Equipment

Liquid spray injection in the expansion volume of a CO2 high voltage circuit breaker

2019-09-06T14:02:18+02:00September 6th, 2019|High Voltage Substation Equipment, Publications|

Most high voltage gas circuit breakers (HVCB) in operation use SF6 as the arc interruption medium because of its high dielectric strength and good arc interruption properties. However, SF6 also displays a high global warming potential which motivates the investigation of possible alternatives to this gas.

Numerical modelling and influence of defects on space charges in epoxy resin under HVDC stresses

2019-09-02T15:14:31+02:00August 29th, 2019|High Voltage Substation Equipment, Publications|

Space charge accumulation on High Voltage Direct Current Gas Insulated Substations can produce electrical field reinforcements in the insulation that need to be taken into account in the equipment design. The TSM (Thermal Step Method) is one of the experimental techniques allowing to determine space charge distributions in insulating materials. However localized defects (i.e. microvoids, delaminations etc) cannot usually be detected by this technique. A new numerical approach to study the influence of structural defects on Thermal Step Method currents is proposed. The method is based on a Finite Element numerical simulation allowing to simultaneously solve electrical and thermal equations. The effect of three different defects were studied. It results that ring defects, with diameters smaller than 0.4 mm, produce less than 10% of change on TSM current signals. This confirms the difficulty to detect small defects by this method. It was also observed that delaminations can produce variations in signal as high as 70%, and even generate signals of opposing sign from the case without defect.

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.