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− First letter: relationship of the power distribution system to earth;
{3 J% _' W* }1 `T means direct connection of one pole to earth,. G, I9 o' k4 [/ K8 [, O0 K
I means system isolated from earth, or one point connected to earth through an1 x2 B# X9 |6 ~
impedance.
% {- ]1 I! e3 h' ]4 S− Second letter: earthing of the equipment;# N, R- H% S& g, f: ^5 K% V
T means direct electrical connection of the equipment to earth, independently of the
7 O0 h& I& ?) h* E! p% K+ Y- {earthing of any point of the power distribution system,9 b m& k* Y/ a/ ?& M( V) W8 E. q
N means direct electrical connection of the equipment to the earthed point of the power5 R! Z: X- c/ h# ? A1 I
distribution system (in a.c. systems, the earthed point of the power distribution system
4 q6 V# Z+ _$ x1 `is normally the neutral point or, if a neutral point is not available, a phase conductor).1 h0 N1 r2 j! p) o8 I* \0 T
− Subsequent letters if any: arrangement of neutral and protective conductors;& \ i! c4 Y, U" B4 Y. ~ H
S means the protective function is provided by a conductor separate from the neutral or5 ]! n; N1 ]" y% T) D) i) L
from the earthed line (or in a.c. systems, earthed phase) conductor,& a9 n: t, J5 z! ]% }
C means the neutral and protective functions are combined in a single conductor
2 y* N* Q1 _5 }2 L; m5 ](PEN conductor).! a E- ?" i$ j# E1 Q3 x8 l& P
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