Understanding the Incipient Discharge Activity with Epoxy/MoS2 Nanocomposites

Epoxy resin is basically a high-performance material and is used as an insulant in all high voltage power apparatus because of its high electrical, thermal and mechanical properties. With the advancement of nano materials, its use as filler has provided greater advantage to achieve required electrical, thermal and mechanical properties [1, 2]. Carbon nanotubes (CNT) and graphene have good application to use as an electric fi eld grading material [3]. Recently, MoS2 material is gaining popularity because of its inherent characteristics of high band gap which will not impart electrical conductivity and the world over researchers have indicated that addition of it as filler content can enhance mechanical and thermal properties of the material [4]. In power apparatus, surface discharge activity is one of the mechanisms by which the solid insulation fails. The surface resistivity and hydrophobicity of the material play an important role on life of insulating material. The surface charge accumulation can enhance the tangential electric field, leading to surface discharge activity and poor hydrophobicity of the material, which lead to thinning of water droplet causing inception of corona activity near the water droplet edge. The characteristic variation in degradation of insulating material occurs due to enhancement of local electric fi eld and hence it has become important to ensure the surface free from charge accumulation/electric field enhancement in the insulating material. Conventionally, the inorganic fillers, namely, silicon carbide material is used as a fi ller material in epoxy resin, which can relieve the accumulated charge, because of its semiconducting properties. In recent times, the molybdenum di-sulphide material, is gaining importance because of its inherent material properties and can be alternative material because of its semi-conductive nature [5]. Under normal operating conditions, the insulating material may expose to electrical discharges due to surface discharges or degradation of insulating materials due to corona activity. These discharges in turn can cause degradation of the insulating material over a period thereby alternating the fundamental properties of insulating material thereby reducing the life of the equipment [6]. Therefore, there is a strong need for developing electrical insulating materials possessing good discharge resistant characteristics. Recently, CIGRE working group has indicated development of non-standard materials for improved performance [7]. Epoxy resin with silicon carbide reinforcement exhibits good partial discharge resistance characteristics [8]. In the electric power sector, it is generally utilized as stress grading substance for high voltage electrical machines [9, 10]. Many studies have reported the use of non-linear dielectrics in power apparatus operating at normal ambient temperatures [11]. A major problem with insulating material is moisture condensation forming water droplet. If a water droplet is sitting on the top of insulating material, under high electric field, corona activity incepts followed with surface discharge activity, causing surface temperature rise followed Understanding the Incipient Discharge Activity with Epoxy/MoS2 Nanocomposites