Earthing Rod

[Mike.J]

All very interesting, but how do you prevent any of this happening? Especially if you have no gas and polypropylene water pipes, TNCS system, underground copper oil pipes between the tank and boiler all bonded to the CU, my brain hurts.

If it matters a full RCBO board.

 

[Andy™]

All very interesting, but how do you prevent any of this happening? Especially if you have no gas and polypropylene water pipes, TNCS system, underground copper oil pipes between the tank and boiler all bonded to the CU, my brain hurts.

If it matters a full RCBO board.

the biggest risk of high current is shared conductive services, gas pipes etc. if your services are plastic then they wont be extraneous and can't introduce any high currents through anything, it'll jsut be your neutral & earth voltages that are high with reference to ground. rod will help but potentially not by much

you can't prevent a broken neutral happening, however if you make the system TT and you can reduce the risk - a neutral failure will still result in a high voltage neutral to ground, however the earth voltage will remain at/similar to ground as it doesn't have any link between it and the neutral

also worth noting that if you do have a neutral failure and your earth voltage does rise enough to give you a shock if your touching ground, your RCD will do nothing as it wont detect any fault to be able to trip (some RCBO's may trip because of the voltage difference line to neutral/earth though but not because of an imbalance)

 

[Joules]

the biggest risk of high current is shared conductive services, gas pipes etc. if your services are plastic then they wont be extraneous and can't introduce any high currents through anything, it'll jsut be your neutral & earth voltages that are high with reference to ground. rod will help but potentially not by much

you can't prevent a broken neutral happening, however if you make the system TT and you can reduce the risk - a neutral failure will still result in a high voltage neutral to ground, however the earth voltage will remain at/similar to ground as it doesn't have any link between it and the neutral

also worth noting that if you do have a neutral failure and your earth voltage does rise enough to give you a shock if your touching ground, your RCD will do nothing as it wont detect any fault to be able to trip (some RCBO's may trip because of the voltage difference line to neutral/earth though but not because of an imbalance)

Relating to this is content by John Ward Earthing systems, EV charging connection options and open PEN detection devices it’s his recommendation at the end of the video that deals with ground spikes and supplemental earths. John is saying that for EV Chargers 70V is the max permissible voltage. No one appears to have mentioned that TNCS is not allowed for portable buildings. Under a fault condition touching the metal work on the car or caravan should not result in a voltage exceeding 70V. The TNCS supply cable is plastic sheathed, single core with a metal braiding. Its when the braiding disconnects from the neutral-earth bond that presents the greatest danger as metal casings connected to earth become live. The ground spike mitigates this but only if the touch voltage can be <= 70V.