The performance decrease of disc insulator with RTV coating under steep-front impulse shows that it is urgent to study the steep-front discharge process. In order to explore the development process and the discharge speed of steep-front impulse

we constructed a discharge observation platform based on ICCD ultra fast photography

providing the means to catch the steep-front impulse discharge process. The synchronous scheme of discharge capturing and steep-front impulse voltage measurement was designed and realized. The timing analyses of discharge circuit and optical shooting circuit were carried out on the observation platform

and the moments of discharge were successfully corresponded to the steep-front impulse voltage waveform. Based on the results of the discharge observations obtained on this platform

the dis

charge process and the microscopic discharge mechanism of the steep-front impulse were described qualitatively. In order to prove that the platform can play an important role in researching the steep-front impulse

the steep-front impulse discharge velocity over different dielectric surfaces under different polarities were calculated based on the measurement.The steep-front impulse discharge velocity has the order of magnitude of 10

-2

～10

-1

cm/ns

and can be slowed down by RTV coating.