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Electrical fires victims USA vs. France 1

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North American vs. French:






Summary of changes in the distribution of electricity in France.
The neutral to the ground schematic.


Initially in North America and France, voltages were similar (115 Volts / 230 Volts):







Following the Second World War, French distribution networks were devastated but to cope with increased demand for electrical energy during the rapid growth years known as the "30 glorious years" it was decided during the 1960's years to increase the voltage to 220-380 Volts (currently 230-400V).






In doing so, the French reduced the intensity (amperage), which resulted in substantial savings in copper costs. This raised the issue for better protection of persons against inadvertent contact of an energized phase conductor to its grounded metal chassis (typically found with domestic appliances). The neutral-to-ground schematic (TT) was adopted.

This schematic requires significant use of these differential devices at the head of the installation associated with main-breakers: In this schematic a differential is necessarily placed at the beginning of the circuits, and all protective earth conductors or Grounds are connected to an independent Ground for each installation, and not common with the neutral as in North America.


Example for a Single Phase Connection:




Example for a 3 Phase+Neutral Connection:




The function is simple, it is the same function as a GFCI, however placed in the electrical panel. In the case of an insulation failure, the "leak" is cleared to ground independently and through the neutral. The differential device detects this difference, like a GFCI, and instantly cuts the current however for the entire house:


Protection against indirect contacts (Parallel Arcs Phase to Ground) since the 60's and before the 1980's



1 - Insulation fault (parallel arcs).
2 - The independent ground electrode evacuates a quantity of current resulting from the insulation fault.
3 - The differential associated with the main breaker detects the difference and cuts off power in an instant, by a value of 230 Volt x 0.500 Ampere = 115 Watts.



This neutral to ground schematic TT was made mandatory for all dwellings.


However, for private institutions, the final current transformer could be owned by the consumer-operator. In this case the choice of the ground schematic can be determined by the owner of the transformer, except in special cases.


Also in France, there are several grounding schematics that have been in operation for decades:

TT:



IT:



TN-C:



TN-S:



TN-C-S:
(Similar to US homes)




Concerning this basis, significant improvements have been made over the years.
...

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