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附件是CTL decision sheet 416，大家讨论。5 ?8 } c( m0 T' C/ G
Question:) W8 h7 Q! N w* b
EQUIPMENT may contain floating circuits which under the definition 2.1.10 would not be) O7 }2 I, U, G Z6 r$ F
considered as LIVE, since contact with these parts could not result in excessive leakage9 \5 i' S$ \ R1 u \, Z
currents to earth or to other ACCESSIBLE PARTS. There would therefore appear to be no
" @% N! A4 ]8 B. B6 i! N/ prequirements for safety separation between these circuits and ACCESSIBLE PARTS or
6 B& s# h" z1 ]+ @5 P# ] e9 ~/ B# EAPPLIED PARTS. But voltages within these circuits or in conjunction with other circuits may4 @1 y6 |' R9 H: i6 F- S! W# P
lead to currents exceeding the values given in Table IV.
( A1 G; @1 I: ^. ?- G$ ~Decision:, b8 h+ V: b* s( h
If the failure of insulation of such isolated circuits is likely to lead to a SAFETY HAZARD, such/ F0 ]( t$ P8 V2 k( v; i
insulation should be short-circuited before determining whether a part is LIVE. This shortcircuit. G' Q6 y/ {' X$ f
should not be treated as a SINGLE FAULT CONDIT ION unless the insulation- l: Q) t0 k% Q) e, C. f: ]% S: l& V- G6 B
concerned satisfies the requirements for BASIC or SUPPLEMENTARY INSULATION
* j$ Q: G: H' O* c$ h* Z. {( V% Onecessary for the voltages within the isolated part.+ ?5 G# u' X9 ?. g" J) l
Explanatory notes:$ v8 d7 v4 {# d6 a8 S. [( v& R
There are two possibilities for solving this problem. One is to change the definition of LIVE and
& n" V+ d* I" A$ G$ badopt the requirements for insulation accordingly. The second is to treat the separation of the
3 k' @/ |* U/ @isolated circuits as subject to failure.
/ [! W3 E9 ~: @3 \If one pole of the isolated circuit is short-circuited to earth (failure of insulation) then the other: K8 i" K! X( `( s+ E
pole becomes LIVE and the adequacy of the separation of this LIVE part under these8 V% r* O1 u( L2 ~# K
conditions may be assessed. If that separation is inadequate then it should be short-circuited
, R* m/ |% O* l' j4 X. f3 hin turn to assess the separation on the other pole.
" S0 Q/ V, u4 H6 t; K1 a# ^Since for an isolated circuit there may be two separate protective insulations (on either pole),. y0 B* w/ @: K) V0 l
each of these can be BASIC INSULATION rather than BASIC and SUPPLEMENTARY& f1 d! x% r4 _& i+ u7 t ~" }
INSULATION. Of course other combinations may be used although if the insulation of one
6 o8 Z# x2 V% `0 q% Fpole is less than BASIC INSULATION then the other pole must have DOUBLE or
2 x/ x: F" N& Y* ~REINFORCED INSULATION. |
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