You can no longer post new replies to this discussion. If you have a question you can start a new discussion
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?
A very similar curve is in the older editions too. However the pinhole breakdown mechanism is thermal, and takes a some tens of milliseconds to occur - by then an instant RCD should be thinking about de-latching, if it has not already done so, I'd be nervous about relying on anything with a much longer disconnection time. Note that this hot spotting seems to be a feature of smaller contact areas only.
I agree the figures need to be taken with a pinch of salt, or perhaps not, if your hands are wet ?.
Also it is not clear which body parts this relates to, and skin thickness varies quite a bit, palms of hands can be over 1mm to 1.5mm thick, while more delicate bits are less than half mm (ref)
Mike.
Curve 3 is the square cm or so of contact, on this subject between 2 and 3 k ohms at 250V, and more like 10-20k at the sort of touch voltage you see in a TN system.
A very similar curve is in the older editions too. However the pinhole breakdown mechanism is thermal, and takes a some tens of milliseconds to occur - by then an instant RCD should be thinking about de-latching, if it has not already done so, I'd be nervous about relying on anything with a much longer disconnection time. Note that this hot spotting seems to be a feature of smaller contact areas only.
I agree the figures need to be taken with a pinch of salt, or perhaps not, if your hands are wet ?.
Also it is not clear which body parts this relates to, and skin thickness varies quite a bit, palms of hands can be over 1mm to 1.5mm thick, while more delicate bits are less than half mm (ref)
Mike.
Curve 3 is the square cm or so of contact, on this subject between 2 and 3 k ohms at 250V, and more like 10-20k at the sort of touch voltage you see in a TN system.
