Equilibrium electrification parameters inferred from Couette charger terminal measurements

The authors consider the use of a compact Couette charger of coaxial cylinders to measure basic parameters in flow-induced electrification of oil/pressboard models of transformer insulation. They describe a method for obtaining both the turbulent core and wall charge densities by measuring either the terminal current in the short-circuit connection or the terminal voltage in the open-circuit connection between inner and outer metal cylinders. Theoretical considerations and experimental results are presented. Results obtained with the proposed technique are compared with those from the absolute charge sensor technique for measuring the charge density at the oil/cylinder interface