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− First letter: relationship of the power distribution system to earth;4 B& T7 n6 G/ p, W- w
T means direct connection of one pole to earth,
# L% X" V! E* b7 CI means system isolated from earth, or one point connected to earth through an
. E2 K* T( i8 h1 `* S- y: Z5 o/ D1 }$ Nimpedance.
7 o" h8 Y8 R) N5 d! d2 B# ?− Second letter: earthing of the equipment;
1 E4 m3 E; c4 o+ G$ \# F8 yT means direct electrical connection of the equipment to earth, independently of the! r! C' s6 x( g% |" m" L$ y+ Y
earthing of any point of the power distribution system,6 j9 F+ I$ n2 ^; N0 d( a
N means direct electrical connection of the equipment to the earthed point of the power
7 [ m5 @" O0 b) k$ `- {distribution system (in a.c. systems, the earthed point of the power distribution system8 V1 ]) f6 C# b3 y4 ^
is normally the neutral point or, if a neutral point is not available, a phase conductor).
. Z! d% n) q( X# c, K* ?$ ]& {− Subsequent letters if any: arrangement of neutral and protective conductors;
8 e) a) ?* c5 R+ ~5 xS means the protective function is provided by a conductor separate from the neutral or0 f8 C. a/ o+ |4 u+ @# |
from the earthed line (or in a.c. systems, earthed phase) conductor,
5 ]9 ~+ z# H- |9 g) M; u5 K& b% \9 fC means the neutral and protective functions are combined in a single conductor
& C1 B, ^! A1 `/ j R6 b7 Q(PEN conductor).
2 G6 s8 k$ {. j v: j" P--`,,`````,,,````,,`,,,``,,,,,`-`-`,,`,,`,`,,`--- |
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