Ping-Pong type protection for ground fault in field winding is widely used for its merits. However

there are still some problems in protection applications. One of those is that the improper choice of component parameter in switch circuit can have a great impact on the protection precision

and another is that the accuracy of protection operation will be influenced by the change of ground resistance value. To solve the first problem

this paper studies some factors that can affect the protection precision

and proposes a simulation model to verify the analytical results

then obtains the rule of component parameter selection. For the solution of the second problem mentioned above

the influence of different change trends of ground resistance on protection are analyzed

and the related methods are provided such that the adverse influence of the change of ground resistance value on protection is reduced.