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The system earthing arrangement must be properly selected to ensure the safety of life and property. The behaviour of the different systems with respect to EMC&nbsp;considerations must be taken into account. '''Figure R1 '''below presents a summary of their main characteristics.<br>European standards (see EN 50174-2 § 6.4 and EN 50310 § 6.3) recommend the TN-S system which causes the fewest EMC problems for installations comprising information-technology equipment (including telecom equipment). 

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{| style="width: 794px; height: 207px" cellspacing="1" cellpadding="1" width="794" border="1"
|-
| valign="top" bgcolor="#0099cc" | &nbsp;&nbsp; 
| bgcolor="#0099cc" | '''TT''' 
| bgcolor="#0099cc" | '''TN-S''' 
| bgcolor="#0099cc" | '''IT''' 
| bgcolor="#0099cc" | '''TN-C'''
|-
| valign="top" | Safety of persons 
| Good<br>RCD mandatory 
| colspan="3" | Good<br>Continuity of the PE conductor must be ensured throughout the installation
|-
| Safety of property 
| Good 
| Poor 
| Good 
| Poor
|-
| 
| valign="top" | Medium fault current<br>(&lt; a few dozenamperes) 
| valign="top" | High fault&nbsp; current<br>(around 1 kA) 
| valign="top" | Low current for first fault <br>(&lt; a few dozen mA),<br>but high for second fault 
| valign="top" | High fault current<br>(around 1 kA)
|-
| Availability&nbsp;of&nbsp;energy 
| Good 
| Good 
| Excellent 
| Good
|-
| valign="top" | EMC behaviour 
| valign="top" | Good<br>- Risk&nbsp;of&nbsp;overvoltages&nbsp;&nbsp;&nbsp;&nbsp; <br>- Equipotential problems<br>- Need to manage <br>devices with high leakage currents 
| valign="top" | Excellent<br>- Few equipotential&nbsp;problems<br>- Need to manage devices with high leakage currents<br>- High fault currents <br>(transient disturbances) 
| valign="top" | Poor (to be avoided)<br>- Risk of overvoltages<br>- Common-mode filters and surge&nbsp;&nbsp;&nbsp; arrestors must handle the phase- to-phase voltages <br>- RCDs subject to nuisance tripping if common-mode capacitors are present<br>- Equivalent to TN system for second fault 
| Poor <br>(should never be used) <br>- Neutral and PE are<br>the same<br>- Circulation of disturbed<br>currents in exposed<br>conductive parts (high<br>magnetic-field radiation)<br>- High fault currents<br>(transient&nbsp;disturbances)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
|}

'''''Fig. R1:''' Main characteristics of system earthing''

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When an installation includes high-power equipment (motors, air-conditioning, lifts, power electronics, etc.), it is advised to install one or more transformers specifically for these systems. Electrical distribution must be organised in a star system and all outgoing circuits must exit the main low-voltage switchboard (MLVS).
Electronic systems (control/monitoring, regulation, measurement instruments, etc.) must be supplied by a dedicated transformer in a TN-S system.
'''Figure R2''' below illustrate these recommendations.
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'''''Fig. R2:''' Recommendations of separated distributions''