Consider the following 2 use cases:
- Fully electric vehicle with 2 different insulated voltage systems: 1 high voltage @1000V DC insulated from chassis and 24VDC system with minus pole (-) at chassis. Would PE cable (connected to chassis) need to be shielded? If yes, then why?
- Single phase house supply system. Would the PE cable need to be shielded? If yes, then why?
In my opinion there is no need for shielding as these cables' sole purpose is to protect the people from indirect contact should any live part came into contact with metal exposed parts (that can be touched by people).
In short, these conductors are not meant to carry any signal/current (if not for brief periods < 1s), I don't see any reason for EM shielding.
In question 1, the the chassis is ground (as in "return path") only for 24V system while metal parts of chassis of high power loads are connected to the chassis with a PE cable (as in "Protective Earth").
In question 2, consider a TT system, the PE cable is grounded.