Comparison of Earthing Systems
| TT | IT | TN-S | TN-C | TN-C-S | |
|---|---|---|---|---|---|
| Earth fault loop impedance | High | Highest | Low | Low | Low |
| RCD preferred? | Yes | No | Yes | No | No |
| Need earth electrode at site? | Yes | Yes | No | No | No |
| PE conductor cost | Low | Low | Highest | Least | High |
| Risk of broken neutral | No | No | No | Highest | High |
| Safety | Safe | Less Safe | Safest | Least Safe | Safe |
| Electromagnetic interference | Least | Least | Low | High | Low |
| Safety risks | High loop impedance (step voltages) | Double fault, overvoltage | None | Broken neutral | Broken neutral |
| Advantages | Safe and reliable | Continuity of operation, cost | Safest | Cost | Safety and cost |
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