Transient Earth Voltage(TEV) gets more and more used in live detection of distribution networks switchgears due to high sensitivity, anti-interference ability and non-invasive, et al. This article has independently developed four typical defect models which are insulated air discharge, creeping discharge, floating potential discharge and corona discharge based on fully analysis of fault cases of actual operating switchgear and the actual detection effect of TEV worked out by State Grid provincial companies. TEV sensors and TEV handheld tester are used. Analysis of time-domain waveform and PRPD maps of different defects shows that: the sensitivities of TEV on different discharge are different; the discharge capacity, discharge waveform, TEV time-domain waveform and PRPD maps of four types of PD defects has a good identification; when the detection position is different, it shows a certain regularity of the results detected by TEV sensors and TEV handheld tester. It is studied by simulation of CST and tests. Contents of this paper have greater significance on the switchgear periodic general detection and theoretical research of TEV methods.