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− First letter: relationship of the power distribution system to earth;
/ p$ \0 U4 @& `2 M/ l9 ]T means direct connection of one pole to earth,* {. L" s* H6 ?+ m4 Y3 Y
I means system isolated from earth, or one point connected to earth through an9 J3 \& \2 N' y# `, y& i7 I
impedance." j" F& A; d1 r! y" K
− Second letter: earthing of the equipment;$ S" ^, o' G! y# Z# [
T means direct electrical connection of the equipment to earth, independently of the
4 }2 y* A% J8 E0 p2 W' L$ Q1 hearthing of any point of the power distribution system,' p1 e# G8 Y3 p# B2 N, `/ B
N means direct electrical connection of the equipment to the earthed point of the power
0 r5 h3 c) L2 `" A9 Vdistribution system (in a.c. systems, the earthed point of the power distribution system
3 d/ ]- b- M8 x) H0 V% r( {) d) N: His normally the neutral point or, if a neutral point is not available, a phase conductor).
2 U; W. z0 \3 M G− Subsequent letters if any: arrangement of neutral and protective conductors;& c9 r" @4 x6 H
S means the protective function is provided by a conductor separate from the neutral or/ v Z7 L* [8 ?: e) z
from the earthed line (or in a.c. systems, earthed phase) conductor,4 }7 z, ]" R- u2 p
C means the neutral and protective functions are combined in a single conductor
1 t: Y1 z; m! U0 o! I9 F( s(PEN conductor).$ i0 r) N* f# `3 {% Q
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