Studies on the aging processes of polymers in electrical systems

Mayoux, C.

doi:10.1002/(sici)1522-9505(19981201)261-262:1<143::aid-apmc143>3.0.co;2-#

Cited by 6 publications

(1 citation statement)

References 51 publications

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“…Treeing is related to sporadic discharges that are intermittent and not steady like corona discharge. The mechanism of treeing is very similar to electric breakdown, because both start in the regions with the highest and most divergent electrical stresses [6,8,11,12]. In fact, as it can be inferred from above, the electric breakdown phenomenon of insulating materials is a very complex problem due to the large quantity of variables which are involved.…”

Section: Introductionmentioning

confidence: 97%

Study of dielectric strength in EPDM by nondestructive dynamic mechanical analysis in high electrical field

Bonifacich

Giordano

Lambri

et al. 2017

IEEE Trans. Dielect. Electr. Insul.

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In the present work the value of the degree of the area swept by the polymer chain due to an electrical force for a given mesostructure was related to the corresponding value of the dielectric strength. This value was deduced from the electric inclusion formalism applied to dynamic mechanical analysis (DMA) studies conducted under high electric field, which were performed in commercial ethylene-propylene-diene M-class rubber (EPDM); used for the housing of polymeric electrical insulators. EPDM samples with different arrangements of the polymer chains and crystalline degree, promoted by controlled neutron irradiation were studied. Several characterization techniques, as infrared absorption spectroscopy (IR), differential scanning calorimetry (DSC), positron annihilation lifetime spectroscopy (PALS) and dielectric strength (DS) were also used. The relationship between the DS and the degree of movement of polymer chains promoted by electrical forces coming from the electric field applied in a non destructive test as the DMA was successfully established. In fact, a larger empty space in the sample leads to larger areas swept by the polymer chains during bending under the application of the field strength in the dynamic mechanical analysis tests. Therefore, an increase in the capability of movement of charges occurs, corresponding to smaller dielectric strength values. Crystallinity improves the dielectric strength due to the increase in the internal stresses which decreases the capability of movement of the polymer chains and electric carriers by electric forces.

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Section: Introductionmentioning

confidence: 97%

Study of dielectric strength in EPDM by nondestructive dynamic mechanical analysis in high electrical field

Bonifacich

Giordano

Lambri

et al. 2017

IEEE Trans. Dielect. Electr. Insul.

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Mechanical energy losses in commercial crosslinked low‐density polyethylene in the temperature range between 200 and 400 K

Lambri

Bonifacich

Garcı́a

et al. 2019

J of Applied Polymer Sci

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Aging treatments in water and in air and controlled neutron irradiation were performed on commercial crosslinked lowdensity polyethylene (XLPE) for promoting different mesostructural arrangements of crystallites and crosslinking degree. Infrared spectroscopy, differential scanning calorimetry, differential thermal analysis, thermogravimetry, and dynamic mechanical analysis were used as characterization techniques. The relaxation peak related to the mobility of the grain boundaries from crystalline zones in XLPE was identified at around 260 K (at 7 Hz), involving an activation energy of 90 AE 4 kJ mol −1 . The usual equation for describing the grain boundary mobility in metals involving the movement of grain boundary dislocations was adapted for studying the mobility of the boundaries among the crystalline zones, successfully. In addition, a new mechanical relaxation peak that appears at around 300 K (at 7 Hz), which involves an activation energy of 94 AE 5 kJ mol −1 , was found. The driving force controlling this peak was determined as the dragging of the polymer chains at the amorphous zones adjacent to the crystals controlled by the mobility of the crystallites boundaries. The chains movement was done with break away from the physical pinning points.

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Inception of vented water trees in high voltage XLPE cable insulation: Effect of inorganic contaminations inside the semiconductive material

Hårberg,

Wenner,

Hvidsten

et al. 2024

J of Applied Polymer Sci

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Wet‐design AC subsea power cables are currently rated up to a maximum voltage of 72.5 kV. These high voltage (HV) cables are cost‐effective alternatives to subsea cables kept dry by a protective lead sheath and exhibit superior properties for dynamic applications. However, several vented water trees, degradation phenomena reducing the cable lifetime, are observed in a HV XLPE insulated cable subjected to wet aging in the laboratory. The water trees initiate from a smooth and clean XLPE insulation/semiconductive screen interface. In this paper, we show that voids in the range 15–150 μm are observed in the conductor screen, 50–320 μm from the water tree inception sites. Degradation of the semiconductive material is observed, in the form of porous regions that connect the voids to the water tree inception sites. NaCl impurities are detected on the void surfaces and in the porous regions. These features are proposed to be the pre‐requisites for the formation of the vented water trees observed in this type of cable. The mechanism responsible for the formation of the void and porous regions in the semiconductive cable screen is discussed based on the observations.

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Studies on the aging processes of polymers in electrical systems

Cited by 6 publications

References 51 publications

Study of dielectric strength in EPDM by nondestructive dynamic mechanical analysis in high electrical field

Study of dielectric strength in EPDM by nondestructive dynamic mechanical analysis in high electrical field

Mechanical energy losses in commercial crosslinked low‐density polyethylene in the temperature range between 200 and 400 K

Inception of vented water trees in high voltage XLPE cable insulation: Effect of inorganic contaminations inside the semiconductive material

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