Keep signal wires away from power cables, which should be in their own conduit or duct. This will minimize resistive and capacitive currents. Keep signal wires inside a metal shield grounded at one point only. Magnetic Interference Placing signal wires inside a ground metal sheath will divert resistive and capacitive currents. Changing magnetic fields from external equipment can link the signal wiring.
Conductive shielding is ineffective against it, and even magnetic shielding is of limited use.
Again, separation of signal and power wiring is the best measure. Using twisted pair signal wiring may help as it acts by successive twisted loops to cancel each other's pick up of magnetically induced voltages, reducing mutual inducance. In the case of DC interference, prevention by good isolation is the only remedy because you cannot filter out DC from a DC signal. AC interference can be further reduced by low-pass filters. The filters can be combinations of capacitors and inductors in the signal lines, or they can be digital filters built into the controller's electronics.