Earthing Systems Flashcards
(18 cards)
How many types of earthing systems are there?
There are 5.
What does T stand for?
Earth, as in the french word Terre.
What does N stand for?
Neutral.
What does S stand for?
Separate.
What does C stand for?
Combined.
What does I stand for?
Isolated.
List the types of earthing systems?
TT, TN-S, TN-CS, TN-C and IT.
What does the 1st letter represent?
The supplier’s earthing method.
What does the 2cd letter represent?
The consumer’s earthing method.
What does the 3rd letter represent?
The supplier’s E-N method.
What does the 4th letter represent?
The consumer’s E-N method.
Which earthing system is the most common in Ireland?
TN-CS.
Which one is uncommon and requires an exemption from the Electrical Safety Regulation bodies? How come?
TN-C because RCDs can not detect Earth fault currents because E and N are combined on both the consumers and the suppliers’ side. This makes them dangerous.
Which one is not permitted for low voltage public supply because the source is not directly earthed?
IT.
What is TN-CS also known as?
PME: Protective Multiple Earthing.
What is the max speed of automatic disconnection for TN arrangements?
0.4 seconds.
What is the max speed of automatic disconnection for TT arrangements?
0.2 seconds.
What voltage value is Earth considered to be at any point?
0 volts.
