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Consider the following 2 use cases:

  1. 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?
  2. 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.

Short clarification:

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.

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  • \$\begingroup\$ Doesn't the PE cable (connected to chassis) carry all the return current back to the batter? \$\endgroup\$
    – SteveSh
    Commented Dec 3, 2019 at 18:51
  • \$\begingroup\$ What do you mean by the PE cable? \$\endgroup\$
    – SteveSh
    Commented Dec 3, 2019 at 18:52
  • \$\begingroup\$ I guess Protective Earth \$\endgroup\$
    – Huisman
    Commented Dec 3, 2019 at 18:54
  • \$\begingroup\$ PE = Protective Earth as Huisman said. @SteveSh For 24V loads (or signals) it is frequent to have grounding to chassis. For high power loads (such as the inverters feeding the motors) that would be a bad choice. \$\endgroup\$
    – mickkk
    Commented Dec 3, 2019 at 18:58
  • 2
    \$\begingroup\$ There may be a reason to shield from moisture corrosion \$\endgroup\$ Commented Dec 3, 2019 at 19:08

3 Answers 3

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I see no reason to shield the grounding (return) that is connected to chassis.

As standard design practice, we twist the supply (hot) line with its return.

If there is a need for an overall shield around that twisted pair bundle, then the shield is connected to chassis at both ends. The only reason for the shield is if you were to have some conducted emissions (CEs) flowing as common mode currents on your twisted pair supply+return cable, that would then become radiated emissions (REs) from an unshielded cable.

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The problem with shielding any sort of safety grounding is what do you shield it with?

I mean, you're out of groundy things. You have vehicle chassis or your local earthing rods, where do you get a better ground than that? You don't.

If your PE shield needs shielding, then what you really need is for the PE shield to be a better one than it is.

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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?

The reason for shielding cables is to prevent electromagnetic radiation from leaving or entering the cable. Since the ground is tied to the chassis, the cable and chassis can be considered as being the same potential. The chassis also acts like a shield because the impedance between cable and chassis will be very low and short out almost all emissions from high frequency electric fields inside of the vehicle.

Single phase house supply system. Would the PE cable need to be shielded? If yes, then why?

Not ever, grounding systems in houses are very low impedance and can be considered as ground and being at earth potential. There is very little radiation emitted from grounding systems in a house.

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