TT system
Türkçe: TT sistemi
The source and the consumer have independent earthings; because fault current returns through the ground an RCD is essential.
// EXPLANATION
In a TT system the consumer has its own electrode and fault current returns to the source through the earth resistance. That path is high-impedance, so the current may never be large enough to blow a fuse; protection is therefore provided by a residual-current device. It is common in rural and detached buildings.
// ALSO KNOWN AS
TT systemTT earthing
// RELATED TERMS
TN-S systemThe source neutral is solidly earthed and the neutral (N) and protective conductor (PE) run separately throughout the installation.
IT systemA system whose source is isolated from earth (or earthed through a high impedance); the first earth fault does not cause an outage and insulation is monitored.
Residual-current deviceA safety device that watches the difference between line and neutral currents and opens the circuit within a fraction of a second when that difference exceeds a threshold.
Earth resistanceThe resistance an electrode presents to the surrounding soil; the lower it is, the more easily fault current flows into the ground.
