Régime de neutre (neutral systems)

• Definition of neutral systems :

In Electricity , an earthing system defines how the earth is connected on the side of the voltage source (eg a distribution transformer EDF, a generator, a wind ... ) and on the side of the masses of the user (washing machine , dishwasher ... ) . That is to say how the metal skeletons of your devices (eg washing machine , oven ... ) are connected to ground. There are several earthing systems , the most used:

The neutral system TT: The first " T " indicates that the neutral of the system is grounded on the generator side and the second "T" indicates that the masses ( metal skeletons ) are grounded.

The neutral regime TN : The first letter "T " indicates that the neutral of the installation is connected to the generator side and ground the "N" indicates that the masses ( metal skeletons ) are connected to neutral.
The neutral IT : The first letter "I" indicates that the neutral of the installation is isolated from ground (so no connection) generator side and the "T" indicates that the masses ( metal skeletons ) are connected to the Earth.

• TT neutral regime :

                               cabling :

                During the installation of a neutral system TT , the neutral of the source is grounded and the user side masses are also connected to ground (see diagram below ) .

This system is used in France for individuals. On the other hand , households are equipped with an overall differential set to 500mA .

Other differentials, generally rated at 30mA , are cascaded to each of the circuits . This allows electrically cut only a defaulting party ( this is called "selectivity" ) .

 

In case of default

In case of failure (eg L1 power cable of the washing machine was disconnected due to vibration and touch the metal casing ) . The current arriving in this phase passes through the carcass, which is conductive , to finish in the ground wire . Thus , the differential is a device taking the difference between the current entering through the phases and the current flowing out through the neutral . If this difference is zero then nothing happens . In our case a little current flows through the earth (called leakage current ) involving a difference between the current phase and neutral. If this difference exceeds 30 mA ( our control ) then the differential freaks .