continues heading Elettricoplus, whom I thank for their hospitality, and in my blog the battle for greater safety of electrical installations and for the professionalism and expertise of fellow designers and freelance technical departments of installation firms . Schneider Electric
published and perhaps it is still an invaluable guide to the Low Voltage system, the page from which I, suggest that attached to your attention. In it for the processors to normal losses, low leakage and resin are given for those values \u200b\u200bof resistance at 75 ° C for short circuit and the equivalent impedance of a short circuit always at 75 degrees. I ask colleagues to calculate the corresponding power factor, short circuit, with the simple division that allows it (by dividing the resistance to the corresponding impedance).
You will find that almost all the calculated values \u200b\u200bare lower than those for which they have enabled the circuit breakers that have a breaking capacity up to now considered appropriate for use after the transformer under consideration.
Thus, if the connection cable between the transformer and main switchboard does not produce a decrease in the value of the short circuit current and / or an increase of the power factor (very likely the first and the second unlikely) to make the appropriate 'switch, we can state that default all the plants are not safe.
What to do? We continue to navigate in water unsafe?
Manufacturers of equipment should not stop now to the new reality? Why
the Italian Electrotechnical Committee, which should provide clear benchmarks for security, does not comment on that? It would be enough time to enter in accordance with a new article, the content of which maximum could be as follows: the power circuit-breakers must be appropriate in reference to the power factor of the short-circuit current and power factor to a minimum, to which the power of circuit-breakers is guaranteed by the manufacturer.
For many years we do not act? The problem is that perhaps we should declare unsafe, as they are officially the most important sections of the plants achieved so far? We do not know how to get out? Even considering the fact that my first officially reported in the journal AEIT goes back many years ago (n February 1999)? Look
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