There are three different
types system recognized.
Second letter -
relationship exposed conductive parts the installation earth:
T direct connection exposed parts earth, independent the earthing any point of
the supply system,
N direct electrical connection the exposed conductive parts the earthed point the
supply system (in a. These types differ from each other according the arrangement
of neutral and protective conductors, follows:
TN-S system: having separate neutral and protective conductors throughout the system;
TN-C system: which the neutral and protective functions are combined single
conductor throughout the system;
TN-C-S system: whitch the neutral and protective functions are combined single
conductor part the system.
The codes used for these systems have the following meanings:
First letter -
relationship the supply system earth:
T direct connection one point power supply system earth,
I all live parts isolated from earth, one point power supply system connected earth
through impedance.
The meaning the letters used the symbols:
PEN stands for conductor with protective (PE) and neutral (N) functions. Alphanumeric
notations for particular conductors applied following figures:
.FUNDAMENTAL RULES FOR PROTECTION AGAINST ELECTRIC SHOCK 39
other but shifted one from another third period. systems the earthed point normally the neutral point).
The mostly used system the Czech Republic the system. can see the line voltages the Figure
5.
Subsequent letters -
arrangement neutral and protective conductors: separate (S) and combined (C) are the
words from which the letters are derived. The line voltages are voltages between courses phase voltages.
For types system earthing following classification applied:
- system;
- system;
- system.c.3 well.2
