Dielectric characterisation of epoxy nanocomposite with barium titanate fillers
Romana Zafar, Nandini Gupta
Abstract
High permittivity materials are currently in use for mitigation of electrical stress in high‐voltage apparatus and energy storage systems. In this work, epoxy‐based high permittivity nanocomposites with Barium titanate (BaTiO 3 ) nanofillers are considered, for the purpose of stress mitigation. Uniform dispersion of the fillers in the polymer up to 10% by volume is achieved. Apart from the use of as‐received fillers, the effect of using surface‐functionalised nanoparticles (with 3‐glycidoxypropyltrimethoxy‐silane) before use is also investigated. The nanocomposite is characterised in terms of its complex permittivity, DC conductivity, short‐term AC breakdown strength and space charge accumulation, to gauge its suitability for use in high‐voltage insulation. Complex permittivity is measured using broadband dielectric spectroscopy over a broad frequency range of 1 mHz to 1 MHz. DC conductivity is studied from polarisation–depolarisation current measurements. Short‐term AC breakdown strength tests are performed at power frequency (50 Hz). Space charge density along the sample thickness is obtained using pulsed electro‐acoustic technique. A computational case‐study is presented to show the feasibility of using the high permittivity nanocomposite for electric stress control in high‐voltage equipment (viz., at mounting flanges of 69 kV bushings).