To obtain the impulse impedance characteristics for grounding device of UHV 1 000 kV transmission tower

a small and portable instrument is used as the incident current source to the grounding device.It can stably output the 8/20 μs and 10/350 μs standard lightning currents with simultaneous measurement of the response transient voltage from the grounding device

which simulates the currents of direct and indirect lightning strikes

respectively.Firstly

tests are made to some given standard resistances

and the results show that the function satisfy the veracity need of on-site application.Then

tests and date recording are done to a typical tower of UHV 1 000 kV An-Tong line in Shanghai Area under two conditions

shunt currents and without shunt currents through grounding lines.Results show that the instrument is stable

the testing method is simple

and the test results can accurately reflect the basic physical properties of the grounding device of transmission tower.Anyhow

this method shown in this paper is fit for the on-site test to obtain impulse impedance characteristics for grounding device

which provides a foundation for lightning protection evaluation of the UHV 1 000 kV transmission tower.