Hi...
I am facing a problem, looking for a suitable Solution.

In our Plant DCS system, i am facing a problem of reverse voltage. ie Our DCS System is feeding +24V DC to Field, Once the contact is closed at field, the Same voltage is fed back to card. In case if there is any 230 V AC Induction in to the Cable from the Field, its affecting the system. Looking for a solution to protect my system. Using of Relay is not solving the problem as we need to use external supply for Field signals, if there is any reverse voltage in the cable, it affects the total Power supply modules connected in the system.

looking for a solution...

 

Series polyswitches and shunt tranzorbs may help.
Why does it have power both ends?
Can you post a circuit of your setup please to clarify what you are meaning?