No abstract

No abstract

International audienceThis paper describes the assessment of the resistance to tracking of various polymers after (i) flashover voltage (FOV) and flashover gradient (FOG); and (ii) partial discharges (PDs) measurements in dry, clean and salt fogs on one insulator model using standardised electrodes; the aim being the development of optimised methods based on flashover and PDs to the conception of new generation of piercing connectors. The investigated materials belong to two distinct classes widely used in the electrical industry: thermoplastics (namely polyphenylene sulfide and high density polyethylene) and thermosetting cycloaliphatic epoxy resins namely one unfilled material (UnCEP) and another unfilled and hydrophobic resin (UnHCEP). FOV measurements are based on the electro-geometrical parameters of each specimen and the resistance to tracking, both may be assessed through the slope of FOV curves against the leakage distance as an indicator of surface damages. Regarding PDs, the suggested technique is devoted to clean and salt fogs and provides quicker and more accurate information about PDs effects on materials deteriorations rather than IEC60109 where the exposition time to discharges is much longer at lower voltage levels by using only liquid contaminants such as sulfuric or nitric acids or ammonium chloride as described in IEC60587 or ASTM D2303

No abstract

International audienceThis work deals with a comparative study of AC breakdown voltage (BDV) of various polymeric samples. The investigated materials cover thermoplastics (namely polyamide 6 (PA6/50), fireproofed polyamide 66 (PA66/50), polyarylamide (PARA/50), polycarbonate (PC/40), polyethylene (HDPE) and polyphenylene sulfide (PPS/65)); and two EPDM based elastomers (namely unfilled EPDM (EPDM) and fireproofed EPDM (EPDM V0)). We mainly analyze: (i) the effect of electrodes shape (namely cylindrical and spherical); (ii) thermal ageing at high temperatures (100, 130 and 150°C); and (iii) hydrothermal ageing in salt fog conditions. It is shown that obtained BDV with spherical electrodes exhibits the highest values because of small surface contact of electrodes with polymeric surfaces; materials such as PEHD and EPDM show the highest BDV. It is found that thermal ageing affects seriously BDV of EPDM based materials. PPS/65 depicts the lowest BDV but is less affected by thermal ageing because of its high thermal stability. Hydrothermal ageing reveals that the moisture absorption is the main reason of the significant decrease of BDV for polyamides