Materiais isolantes: análise do comportamento elétrico sob corrente contínua

Abstract

In electrical transmission cables and accessories, controlling the behavior of the insulation system is a key point in order to ensure the reliability of these cables. Low voltage electrical power cables are generally composed of two components: a conductor, the purpose of which is to conduct electricity; and an insulator, the purpose of which is to insulate the conductor and the electricity it carries from its surroundings. The main subjects of study are to characterize the electrical properties of insulating materials for low and medium voltage direct current in order to improve their electrical performance under continuous electric field. In general, the purpose of the study is the electrical investigation of halogen free flame retardant (HFFR) materials under DC for ranking and comparison to AC; study the influence of bubbles in poly(vinyl chloride) (PVC) material under DC; evaluation of the electrical threshold under DC in ethylene propylene diene rubber (EPDM) insulation system between ohmic and SCLC behavior, to know if space charge is present in MVDC application; evaluation of non-linear behavior of silicone material as a function of temperature under DC. Electrical characterizations allowed analyzing the DC conductivity, AC and DC breakdown voltage and DC lifetime of HFFR, PVC, EPDM and silicone materials. The measurements have already made it possible to classify HFFR and PVC under direct current and analyze the differences of this behavior in relation to alternating current, as well as understanding the behavior of EPDM and silicone for the use of accessories for electrical transmission in DC.