The DNO network system categorised as Hot site or Cold site (430V or 650V ~ in case operating voltage of 33kV with sensitive earth faults cleared within 200ms). My submission is the standard always talks about the voltage (i.e pressure) or 30mA ELCB limits in case of housing earth leakage protection(i.e current). I presume either voltage or current are not alone cause for safety hazard. It is the product i.e voltage*current or V*I*t which causes burns on human body. Hence may i suggest in this forum to review this and consider the subject resistivity+ time aspects while calculating the "Step & touch power / energy" rather than "Step & touch voltage" as is being mentioned in the earthing standards. The additional variables of resistivity& time would help us to choose the appropriate insulating materials and relay settings and enhance human safety. Happy to discuss further, to bring this idea to shape and benefit wider community.
The greatest unknown is always the resistance of the particular path through the human body - this defines the current that flows for a given shock voltage, in turn the resistance is defined by the area of contact and the thickness of skin on that part of the body that makes the contact, and other factors such as water, sweat or blood that may lower the resistance. Where skin is removed a far lower voltage will drive a lethal shock current. As this thread shows, how disconnection times are decided is an involved topic.
For a given current, the disconnection times for given survival likelihoods relate to the period of the human heartbeat - a far higher current can be withstood if the shock is very small fraction of a heartbeat long, while a shock that is much more than a heartbeat long may as well be forever.
The greatest unknown is always the resistance of the particular path through the human body - this defines the current that flows for a given shock voltage, in turn the resistance is defined by the area of contact and the thickness of skin on that part of the body that makes the contact, and other factors such as water, sweat or blood that may lower the resistance. Where skin is removed a far lower voltage will drive a lethal shock current. As this thread shows, how disconnection times are decided is an involved topic.
For a given current, the disconnection times for given survival likelihoods relate to the period of the human heartbeat - a far higher current can be withstood if the shock is very small fraction of a heartbeat long, while a shock that is much more than a heartbeat long may as well be forever.
