A set-up to apply very-fast transients in power transformers

This paper presents the development of a device capable of generating very fast transient signals typically found in SF6 Gas Insulated Substations (GIS), originated from disconnector switchings or the occurrence of disruptive discharge to ground. Substations where power transformers are coupled to GIS, such signals are presented as a potential source of failure as a function of dielectric request imposed. This device is basically a variable "gap" made of special spheres, inserted in a pressurized SF6 compartment between a SF6/Air passing bushing and a 6power transformer. Using this set-up, triggered by self discharge, associated an adequate procedure; it is possible to test the supportability of bushings and transformers to dielectric requests of steep and fast front waves.