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Disconnection time 120 volts Uo vs 150 volts Uo
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<blockquote data-quote="Sidewinder" data-source="post: 491452" data-attributes="member: 9512"><p>OK, IEC standards are not concerned with actual measured voltages, they are based on the nominal voltage as stated in the supply characteristics from the supply "authority".</p><p></p><p>If you are going to take on the liability for designing outside the specified disconnection times, then your RA had better be pretty robust as well as your PII able to take a good kicking to keep you out of trouble if things go wrong!</p><p></p><p>To start with both fault voltages are classed as lethal in IEC documents.</p><p></p><p>However, you will need to look at the body model and apply the calculations for the fault current, then apply this to the statistical model for human body resistances in the most onerous conditions you expect then calculate the current likely to flow through the body of the person, then assess the physiological affect on said person from that current flow, then refer back to the model to look at what percentile of the population are likely to be harmed or killed.</p><p></p><p>Then you an try and justify your deviation for elongating the disconnection time.</p><p></p><p>Good luck.</p><p></p><p>Oh &amp; btw, this isn't a fully formed answer, it's just a suggestion as to how you may estimate this.</p><p></p><p>If you want to follow this through and develop a whole formal risk assessment to justify this action, this post isn't adequate for that.</p><p></p><p>It can be done &amp; I can advise, but not on an internet forum.</p><p></p><p>Do I think it's a good idea to stretch the disconnection time, no, would I recommend it or say that it is acceptable, never.</p></blockquote><p></p>
[QUOTE="Sidewinder, post: 491452, member: 9512"] OK, IEC standards are not concerned with actual measured voltages, they are based on the nominal voltage as stated in the supply characteristics from the supply "authority". If you are going to take on the liability for designing outside the specified disconnection times, then your RA had better be pretty robust as well as your PII able to take a good kicking to keep you out of trouble if things go wrong! To start with both fault voltages are classed as lethal in IEC documents. However, you will need to look at the body model and apply the calculations for the fault current, then apply this to the statistical model for human body resistances in the most onerous conditions you expect then calculate the current likely to flow through the body of the person, then assess the physiological affect on said person from that current flow, then refer back to the model to look at what percentile of the population are likely to be harmed or killed. Then you an try and justify your deviation for elongating the disconnection time. Good luck. Oh & btw, this isn't a fully formed answer, it's just a suggestion as to how you may estimate this. If you want to follow this through and develop a whole formal risk assessment to justify this action, this post isn't adequate for that. It can be done & I can advise, but not on an internet forum. Do I think it's a good idea to stretch the disconnection time, no, would I recommend it or say that it is acceptable, never. [/QUOTE]
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Disconnection time 120 volts Uo vs 150 volts Uo
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