In rail transit

contact-type tester is used to detect the power outage condition of the contact network in the power outage operation of the contact network so to assure the correct operation and safe maintenance of the ground wire. The contact electrode

as an important component of contact-type tester

affects directly the collection of electrical testing signals. For studying the influence of the contact electrode structure on the results of the contact-type tester

type GSY-II 27.5 kV AC tester and type ZGD 1 500 V DC tester are taken as examples

their working principles are analyzed

and the influence of variation of shape and length of the contact electrodes on the inspection results is simulated and studied. The simulation results show that for AC tester

the shape of the contact electrode is changed into round hood type and V shape

the variation of voltage of induction signal of the internal circuit is 3.1% and 2.3% respectively

and the influence of such variation on the inspection result is less; While

the length increase of the contact electrode improves induction signal voltage and thus enhances the test sensitivity. For the DC tester

in case of variation of shape and length of its contact electrode

the signal voltage of internal circuit remains unchanged

therefore the shape and length of the contact electrode will not affect the inspection result. The simulation results provide a reference for the design and optimization of the structure of the inspection device.