A system to minimise induction between conductors.
Best design: Two cables seperated by several inches, one for power/control valve, another for feedback or whatever.
Otherwise, if you are locked into a single cable:  ALWAYS use twisted-pairs for this sort of application, the more twists/m the better.  The best suppression comes from having a floating load and grounding one of the wires at the source if possible.  The suppression is typically 10-20dB better when the pair is also shielded, shield connected at each end, to the conductor which is grounded.  If the load is not floating then suppression is much poorer. 
The induced voltage is mostly due to the magnetic field surrounding the power conductor coupling transformer-wise into adjacent conductors.  Twisted pairs greatly reduce the coupling.
Next: In all cases, suppress any inductive switching transients directly at the load.  This reduces the high frequency component along the line and hence the induced voltage.

MORE NEWS