IEC 60364 Table 48A

AJJewsbury:

ProMbrooke:

AJJewsbury:

There's also a trade-off between conductor size and cost.

Indeed. The simplest (but most expensive) solution would simply to make the c.p.c.s (all the way back to the transformer) 5x the size of the line conductors - that way touch voltages remain below 50V even during a fault (or 10x and 25V if you prefer).


   - Andy.

Thats just one of two other factors. Speed and transformer output drop also play a role in protection. 

My point was by arranging the potential divider keeping touch voltages below 50V (or 25V) during faults you design out the need for any reliance at all on disconnecton times, or indeed voltage droop.


   - Andy.

My mistake, you would correct. However, one still has the issue of incident energy at the fault point.


The beauty of high conductance is faster disconnection and more voltage sag on the trafo's output.  


I've long proposed discarding the emphasis/focal point of earthing and bonding and rather creating a new, third central pillar of source loop conduction theory, which rooted in admittance on the basis of protecting life and property rather than having earth electrodes and connecting metal things to one another.

AJJewsbury:

ProMbrooke:

AJJewsbury:

There's also a trade-off between conductor size and cost.

Indeed. The simplest (but most expensive) solution would simply to make the c.p.c.s (all the way back to the transformer) 5x the size of the line conductors - that way touch voltages remain below 50V even during a fault (or 10x and 25V if you prefer).


   - Andy.

Thats just one of two other factors. Speed and transformer output drop also play a role in protection. 

My point was by arranging the potential divider keeping touch voltages below 50V (or 25V) during faults you design out the need for any reliance at all on disconnecton times, or indeed voltage droop.


   - Andy.

My mistake, you would correct. However, one still has the issue of incident energy at the fault point.


The beauty of high conductance is faster disconnection and more voltage sag on the trafo's output.  


I've long proposed discarding the emphasis/focal point of earthing and bonding and rather creating a new, third central pillar of source loop conduction theory, which rooted in admittance on the basis of protecting life and property rather than having earth electrodes and connecting metal things to one another.