The corona effect in thepower system has a dominant role in reducing the efficiency of the high-voltagelines. In this study, the current and voltage impulses, which are important incorona determination, have been examined in frequecy spectrogram base from testresult. The frequency spectrogram graphs have been obtained from thecurrent-time and voltage-time variation by Matlab program. With these graphs,frequency values have been found to provide an important clarification of theinsulation performance of electrical equipment for reliable and accuratediagnosis. These values have been observed according to different conditionslike pressure, polarity, and insulation ambient. This spectrogram analysis canbe used to find the characteristic frequencies and eliminate the disturbanceeffect. The time between corona steps decrease when Sulphur hexafluoride (SF6)gas pressure is increased. The time of second corona is close to leader'sdischarge time. Corona starts early when SF6 amount is decreased in gasmixtures. The corona currents are large in the low SF6 gas mixtures, thissituation is related to the high insulation of the SF6 gas. A feature which isdependent the frequency is not found.