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− First letter: relationship of the power distribution system to earth;+ u( A) C) C; t% E' Y3 X+ R
T means direct connection of one pole to earth,* B$ q3 q7 C4 ?7 G" g# q
I means system isolated from earth, or one point connected to earth through an
. z% j+ j6 T( Gimpedance.
1 R$ s, ]7 P( ~( s( `− Second letter: earthing of the equipment;
5 w+ J5 \: X. z. n4 TT means direct electrical connection of the equipment to earth, independently of the
8 w) w: U* f" r+ |1 nearthing of any point of the power distribution system,. j8 R/ h/ y- D9 G
N means direct electrical connection of the equipment to the earthed point of the power9 w$ w8 S1 c1 [* \, H/ M( ~
distribution system (in a.c. systems, the earthed point of the power distribution system
4 N7 j. F1 y& W( Mis normally the neutral point or, if a neutral point is not available, a phase conductor).- E3 r% K% c. F' s
− Subsequent letters if any: arrangement of neutral and protective conductors;; Y: d' n$ l' [6 p8 f
S means the protective function is provided by a conductor separate from the neutral or, ?3 C/ _# M6 ?$ m
from the earthed line (or in a.c. systems, earthed phase) conductor,
" R9 g9 I7 v- o& c# f2 eC means the neutral and protective functions are combined in a single conductor) l/ |/ z( M2 T7 E9 [* i* A) E, P
(PEN conductor).* V# b6 y! [0 P* Q1 N
--`,,`````,,,````,,`,,,``,,,,,`-`-`,,`,,`,`,,`--- |
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