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5
Installation and Operating Instructions
A number of different power distribution systems are employed
in various countries around the world. It is important to
identify the distribution system in use prior to installation of
the SRF, and confirm that the SRF is the model recommended
by the manufacturer for that distribution system. To identify
the distribution system in use, consult reputable and
knowledgeable sources such as:
• The local power supply authority
• Local electrical engineers
• Applicable regulatory bodies or standards associations
Alternatively, confirm the type of distribution system used by
personal inspection. By visually tracing the neutral and earthing
conductors from the load equipment or sub-distribution
point back to the point of entry (and perhaps to the supply
transformer), the type of distribution system should be
identifiable with the aid of the following diagrams (figures 2-6).
These are prescribed in local regulations and describe the
relationship between the source, exposed or conductive parts
of the installation and earth. Amongst these, the TN-C, TN-S,
TN-C-S and TT systems are most commonly encountered.
Note that supplies such as those used in industry and mining
may often use a different distribution system to that of the local
supply authority.
4 IDENTIFY THE DISTRIBUTION SYSTEM
Regulations differ between countries. Check compliance with appropiate authorities
Figure 2. TN-C system: In this system, the neutral and protective earth conductor combine in a single conductor
throughout. All exposed conductive parts are connected to the PEN conductor.
