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) allowing:
communications).
c anticipation of maintenance (prediction), The IT earthing system offers the most
c quicker tracking of the first insulation faults advantages and best meets operators’
(automation), or even remote tracking (remote requirements with such specific features as: supervision via digital connections),
c better EMC (interconnection of frames and in c preparation of troubleshooting (remote theory a single earth connection),
diagnosis).
c minimum fire and explosion hazards (low first fault currents).
Cahier Technique Schneider Electric no. 178 / p.26
6.4 In short
Our readers now understand the importance of is essential at this point: this is the purpose of properly listing the requirements relating to figure 28 .
equipment used, the environment and the study NB: The installation cost is not included in this conditions of the installation and subsequent table as the possible additional cost of an IT
modifications, before choosing the earthing system (PIM, fault tracking system) must be system for an electrical distribution network.
compared with the financial loss generated by A brief reminder of the advantages and
unexpected downtime on the first fault… this disadvantages inherent in each earthing system must be evaluated for each activity.
TT TN-C TN-S
IT Safety of persons (perfect installation) c c c
c c c
c c c
c c c
Safety of equipment
c against the fire hazard
c c c
v
v v
c c c
c for machine protection on an insulation fault c c c
v
v
c c c
Availability of electrical power
v v
v v
v v
c c c c
Electromagnetic compatibility
v v
v
v v
v v
For installation and maintenance
c skill
c c
c c c c
c c c c
c c c
c availability
v
v v
v v
c c c
c c c c excellent
c c c good
v v average
v poor
Fig. 28 : summary of the advantages and disadvantages of the various earthing systems.
Cahier Technique Schneider Electric no. 178 / p.27
Bibliography
Standards and decrees c IEC 60364: Electrical installations of buildings.
c IEC 60479-1: Effects of current on human beings and livestock.
c IEC 60947-2: Low voltage switchgear and controlgear - Part 2: Circuit-breakers.
c IEC 60950: Safety of information technology equipment.
c IEC 61000: Electromagnetic compatibility.
c IEC 61557, NF EN 61557: Electrical safety in low voltage distribution systems up to 1,000 V AC
and 1,500 V DC - Equipment for testing, measuring or monitoring of protective measures -.
Part 8: Insulation monitoring devices for IT systems.
c NF C 15-100: Installations électriques à basse tension.
Schneider Electric’s Cahiers Techniques c Neutral earthing in an industrial HV network.
F. SAUTRIAU, Cahier Technique no. 62
c Residual current devices.
R. CALVAS, Cahier Technique no. 114
c EMC: Electromagnetic compatibility.
F. VAILLANT, Cahier Technique no. 149
c Harmonics in industrial networks.
N. QUILLON, P. ROCCIA,
Cahier Technique no. 152
c Calculation of short-circuit currents.
B. De METZ-NOBLAT, G. THOMASSET,
R. CALVAS and A. DUCLUZAUX,
Cahier Technique no. 158
c Earthing systems in LV.
R. CALVAS, B. LACROIX,
Cahier Technique no. 172
c Earthing systems worldwide and evolutions.
R. CALVAS, B. LACROIX,
Cahier Technique no. 173
c Perturbations des systèmes électroniques et schémas des liaisons à la terre.
R. CALVAS, Cahier Technique no. 177
c LV surges and surge arresters - LV insulation co-ordination -.
Ch. SERAUDIE, Cahier Technique no. 179
c Intelligent LV switchboards.
A. JAMMES , Cahier Technique no. 186
c Cohabitation of high and low currents.
R. CALVAS, J. DELABALLE,
Cahier Technique no. 187
Cahier Technique Schneider Electric no. 178 / p.28
Electric
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Service Communication Technique
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