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Table 41.1 Assumed Touch Voltage
Former Community Member
I am a bit confused by this. Why do the disconnection times in Table 41.1 appear to be based on a touch voltage of 100 volts rather than a touch voltage of 125 volts?
For example, 110% of 230= 253 volts. Assuming L and PE are of the same size and material, indirect contact touch voltage is 126.5 volts. Would 0.33 seconds not appear more realistic?
The disconnection time needs to be a fraction of a heartbeat period to significantly reduce the risk of fibrillation.
Animals with faster heartbeats, like mice and lab rats can be killed by shorter current impulses than humans..
The fact I say 'current' and not 'voltage' is significant. Skin resistance of 5k-50k ohms per square cm of skin means that only a large area contact will get anywhere near the 30mA of the RCD threshold, in turn based on the lethality date. Shock current in terms of contact resistance is the single biggest variable in all this.
The fast disconnection will work with fuse or MCB, if the fault path is mostly metallic and the human is in parallel with some of that 'wire wound' resistance all will be well, RCD or not. The time an RCD is most useful is when the the human is in series with the fault path, or something else limits the current, like a liquid path rather than a metal one, as in that case the fault current will be utterly incapable of operating even the smallest fuse or breaker.
M.
Well, perhaps. AC-3 in Figure 1 of IEC-61200 does not indicate ventricular fibrillation, 5% at curve c2.
The disconnection time needs to be a fraction of a heartbeat period to significantly reduce the risk of fibrillation.
Animals with faster heartbeats, like mice and lab rats can be killed by shorter current impulses than humans..
The fact I say 'current' and not 'voltage' is significant. Skin resistance of 5k-50k ohms per square cm of skin means that only a large area contact will get anywhere near the 30mA of the RCD threshold, in turn based on the lethality date. Shock current in terms of contact resistance is the single biggest variable in all this.
The fast disconnection will work with fuse or MCB, if the fault path is mostly metallic and the human is in parallel with some of that 'wire wound' resistance all will be well, RCD or not. The time an RCD is most useful is when the the human is in series with the fault path, or something else limits the current, like a liquid path rather than a metal one, as in that case the fault current will be utterly incapable of operating even the smallest fuse or breaker.
M.
Well, perhaps. AC-3 in Figure 1 of IEC-61200 does not indicate ventricular fibrillation, 5% at curve c2.
