Thanks!
Currently there are no filter & lightening protection circuit in our system, we use metal box, and have linked to the earth ground.
It seems that on the moutaintop, the grounding is not so good. because in the other place, the system works properly.
another problem I encountered is when we did the testing in the lab with surge from L to Ground(4KV), we found that the microcontroller sometimes was latch-up with the metal box, if we remove the metal box, the microcontroller can automatically reboot. Does it mean we need to do something with the mechanical side on the box?
anyway I will try your circuit first.
Thank you again for your help.