The influence of floating electrodes in the results of impulse tests

When testing high voltage set-ups for searching for the critical flashover voltage the value of the associated standard deviation, as stated in technical standards, is usually assumed as lower than 3%. Normally, high values of standard deviation indicate problems in the accomplishment of the test. This work deals with the influence of floating electrodes close to the region of the formation of the electrical field on the values of standard deviation of the critical flashover. The presented results are based in tests carried out in a 15 kV spacer system and in rod-rod gaps.