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Electrical Vehicle Charging Points - True earth on solid floor

Apostolos
Good afternoon.

The problem with EVC Points in a few words is that it introduces the PME (the MET in reality) voltage on the metallic car body. Then, if someone touches the car (under PME voltage) and stands on the ground touching the TRUE EARTH potential he will be introduced to a high voltage in case of an open PEN incidence. 

There are some gross guidlines ( https://www.electricvehiclechargepoint.com/ev-resources/earthing )that say

-If the EVC is outside then TT is needed (the person touches the true earth)

-If the EVC is inside and no charging happens on the outside then PME can be used (the person does not touch the true earth)

Then my question is:
WHAT IS THE POTENTIAL OF A CONRETE FLOOR IF THE EVC POINT IS INSIDE THE BUILDING????

Why do we assume that the concrete floor inside the building is on PME potential and so the EVC can be on PME?

If it is a metal building then I can see somehow that the concrete floor is in touch with the metal skeleton which is bonded to the MET so the concrete floor could be assumed to be on PME potential (correct me please if I am wrong)

If the building is concrete, how on earth this solid concrete floor is considered to be at PME potential????

 


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  • 0

    OMS:




    Apostolos Kasinalis:


    I think you can see why I am a bit reluctant to use PME on the EVC points although it is inside the building.


     




    OK - if you decide to go for a TT supply to the EVC's how do you segregate the TT electrode from the earthy frame of the building which has PME for all the other services.


    Consider if it would be safer making arrangements to connect the rebar under the vehicle areas to the MET and retaining PME to supply the EVC  - what potentials would exist between the vehicle body and the floor slab that a person might actually bridge between hand and foot in either case


    Regards


    OMS


     


     




    If a driver drops their car keys onto the concrete floor and reaches to retrieve them, they may be in contact with the metal keys on the floor with one hand, and the car as they steady themselves with the other bare hand.


    Z.

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  • 0

    OMS:




    Apostolos Kasinalis:


    I think you can see why I am a bit reluctant to use PME on the EVC points although it is inside the building.


     




    OK - if you decide to go for a TT supply to the EVC's how do you segregate the TT electrode from the earthy frame of the building which has PME for all the other services.


    Consider if it would be safer making arrangements to connect the rebar under the vehicle areas to the MET and retaining PME to supply the EVC  - what potentials would exist between the vehicle body and the floor slab that a person might actually bridge between hand and foot in either case


    Regards


    OMS


     


     




    If a driver drops their car keys onto the concrete floor and reaches to retrieve them, they may be in contact with the metal keys on the floor with one hand, and the car as they steady themselves with the other bare hand.


    Z.

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