Earthing System Types – TN-S, TN-C-S, TT, and IT Explained

Earthing systems provide safety by preventing electric shocks and equipment damage. Different international systems exist depending on how neutral and earth are connected. Here we explain TN-S, TN-C-S, TT, and IT earthing systems.

1. TN-S System

Separate neutral (N) and protective earth (PE) conductors from the source to the load.

• Safe and reliable
• Common in industrial installations

2. TN-C-S (PME) System

Neutral and earth combined in part of the system, then separated at consumer premises.

• Economical
• Widely used in residential supply

3. TT System

Consumer provides their own earth electrode, independent of utility.

• Common in rural areas
• Requires RCD protection

4. IT System

Neutral is isolated or connected via high impedance, with equipment earthed locally.

• Used in hospitals and mines
• Allows operation even with single fault

Comparison Table

System	Neutral	Earth	Applications
TN-S	Separate	Separate	Industries
TN-C-S	Combined then split	Shared	Homes
TT	Utility	Own electrode	Rural
IT	Isolated	Local earth	Hospitals

FAQs

1. Which earthing system is safest?

TN-S is considered the safest as PE and N are separate throughout.

2. Why is TT system used in rural areas?

Because utility earth may be unavailable, consumers must provide their own earthing.

3. Where is IT system preferred?

In hospitals, mines, and continuous process plants where uninterrupted power is critical.