|
附件是CTL decision sheet 416,大家讨论。7 g& ]3 U$ E) E+ R( f& O( C
Question:
9 z) x) x1 {/ a; u1 fEQUIPMENT may contain floating circuits which under the definition 2.1.10 would not be( U+ t( @) Y2 R. |% R
considered as LIVE, since contact with these parts could not result in excessive leakage8 |$ I4 C& }3 S% f
currents to earth or to other ACCESSIBLE PARTS. There would therefore appear to be no" C3 l7 L! E1 q+ @7 K
requirements for safety separation between these circuits and ACCESSIBLE PARTS or% h1 {( z6 g: R- J
APPLIED PARTS. But voltages within these circuits or in conjunction with other circuits may1 E3 i1 K$ ^" M) |; b
lead to currents exceeding the values given in Table IV.
" M$ H" o5 G7 g. `% L2 {. qDecision: `* C( a( ^9 u# A. k+ h, H: M
If the failure of insulation of such isolated circuits is likely to lead to a SAFETY HAZARD, such
9 k4 M$ ?' s4 Pinsulation should be short-circuited before determining whether a part is LIVE. This shortcircuit
, v, d8 z! `8 ?1 s0 E8 X' C9 fshould not be treated as a SINGLE FAULT CONDIT ION unless the insulation5 e: k3 x* R, K: C6 O
concerned satisfies the requirements for BASIC or SUPPLEMENTARY INSULATION* z" n9 Q0 D( Z: y) n
necessary for the voltages within the isolated part.
1 i- T$ a/ L6 v: ]6 TExplanatory notes:
& f1 D6 {* D: P0 i/ u' o5 w( F1 uThere are two possibilities for solving this problem. One is to change the definition of LIVE and+ k" `& k7 H, X4 X" P1 j+ O
adopt the requirements for insulation accordingly. The second is to treat the separation of the$ ^0 k8 a8 _6 F2 ^& e
isolated circuits as subject to failure.1 l: j2 H3 A2 E$ U! I
If one pole of the isolated circuit is short-circuited to earth (failure of insulation) then the other/ ] O9 n' a5 }$ z* T/ B. T8 c
pole becomes LIVE and the adequacy of the separation of this LIVE part under these
0 g2 {. q: A4 x/ vconditions may be assessed. If that separation is inadequate then it should be short-circuited
' Y) P" o$ X- Y* u, Hin turn to assess the separation on the other pole.
% h/ U7 e7 f0 X2 ~* ~( D e; hSince for an isolated circuit there may be two separate protective insulations (on either pole),/ k7 c: _; |2 |5 j# L
each of these can be BASIC INSULATION rather than BASIC and SUPPLEMENTARY
2 S& ?7 \* I* m6 m. ^7 C9 l! HINSULATION. Of course other combinations may be used although if the insulation of one
! d+ H* e/ A; K; d' ^* `1 Spole is less than BASIC INSULATION then the other pole must have DOUBLE or
6 z! X0 J4 ^/ {* ~4 Q4 uREINFORCED INSULATION. |
本帖子中包含更多资源
您需要 登录 才可以下载或查看,没有账号?注册安规
x
|