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− First letter: relationship of the power distribution system to earth;; f$ I0 k) g. {" z L7 {. K! F
T means direct connection of one pole to earth,/ t, Q# \/ w2 ^4 D
I means system isolated from earth, or one point connected to earth through an& e! w2 S( p9 B# d1 k; \
impedance.
. `# a; X: N1 F1 }" l1 T− Second letter: earthing of the equipment;
" p4 t& F. ^# a. lT means direct electrical connection of the equipment to earth, independently of the
0 B( K& x4 P9 Z; {7 }* l$ Eearthing of any point of the power distribution system,
) N. H6 K- K% l7 E' j+ I VN means direct electrical connection of the equipment to the earthed point of the power0 Z5 p# }- m( o* W1 ~
distribution system (in a.c. systems, the earthed point of the power distribution system0 s, b ~/ O* s3 P# W
is normally the neutral point or, if a neutral point is not available, a phase conductor).+ x" v0 N" M4 f! Y& c- E8 j' \
− Subsequent letters if any: arrangement of neutral and protective conductors;
. |; {6 m4 w4 V. |: O# vS means the protective function is provided by a conductor separate from the neutral or) ~7 e9 B) _8 G8 ~; m1 n0 j2 r
from the earthed line (or in a.c. systems, earthed phase) conductor,/ ~5 ?9 h- i# l5 S9 b/ Z
C means the neutral and protective functions are combined in a single conductor
" j4 I# r+ u0 ~4 _- w+ b* D) W(PEN conductor).
$ B3 o2 a7 j. U1 c1 e4 S--`,,`````,,,````,,`,,,``,,,,,`-`-`,,`,,`,`,,`--- |
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